Effect of Exogenous Enzymes in Plant-Based Diets on Growth of Nile Tilapia Fingerlings
Various vegetable ingredients are being used or have been proposed to replace ingredients like fishmeal to enhance the cost-effectiveness of aquafeeds. However, the cell walls of cereals and legumes currently used in tilapia feeds are widely known to impair the nutritive value of the feed, resulting in a negative impact on the growth performance and health of the fish. Specifically, vegetable ingredients possess antinutritional factors that interfere with the absorption or hinder the bioavailability of nutrients, such as phytate and non-starch polysaccharides (NSP), which reduce their nutritive value. As alternatives to vegetable ingredients, exogenous [of external origin] enzymes – including phytase, xylanase, and β-glucanase – have been proposed to enhance the nutritive value of plant-based aquafeeds.Phytate is the main form of unavailable phosphorus in legumes and cereals. The enzyme phytase increases the availability of phosphorus and other nutrients such as protein, starch, and cationic minerals. In contrast, NSPs, which are mainly composed of cellulose [an important structural component of the primary cell wall of green plants], arabinoxylans [dietary fiber found in cereal grains], and β-glucans [sugars found in the cell walls of fungi, bacteria, yeasts, algae, lichens and plants], increase intestinal viscosity and decrease the activity of digestive enzymes and digestibility.Also read: Enhanced Biodiversity of Gut Flora, Feed Efficiency in Nile Tilapia Under Reduced-frequency FeedingTherefore, the presence of non-starch polysaccharides and phytate exerts negative impacts on nutrient utilization and, consequently, the growth performance of fish. In addition, the high levels of unabsorbed nutrients, mainly phosphorus, induce eutrophication, which is the proliferation of cyanobacterial algae responsible for giving fish an off-flavor.To overcome this problem, the addition of phytase and exogenous carbohydrases [enzymes that turn carbohydrates into simple sugars] has been proposed to increase the nutritional value of plant-based diets and reduce the output of nitrogen and phosphorus from aquaculture operations. Thus, this study evaluated the growth performance of Nile tilapia (Oreochromis niloticus) fingerlings fed extruded diets based on wheat bran and soybean meal, supplemented with a liquid blend of exogenous phytase and xylanase-β-glucanase.Study setupAll experimental procedures for fish were performed following the guidelines of the State University of Ponta Grossa Animal Care and Use Committee (Protocol No. 132808/2019). Fish were anesthetized (100 mg/L) and euthanized (600 mg/L) with tricaine methanesulfonate (MS-222).A control diet based on soybean meal was supplemented with 341 g/kg crude protein, 14.4 MJ/kg of digestible energy, 9 g/kg calcium, and 7 g/kg total phosphorus (dry matter basis). From the control diet (CON), three different experimental diets were created by adding phytase (PHY; 1,000 phytase units, FTU, per kg and xylanase-β-glucanase, XB; 1,120 xylanase units, TXU, per kg xylanase and 500 thermostable glucanase units, TGU, per kg of β-glucanase). Phytase units, FTU; xylanase units, TXU; and thermostable glucanase units, TGU are used to measure and describe the activity of these enzymes under very specific conditions. The third diet was created by combining PHY and XB. Liquid phytase (Natuphos®E), and a blend of xylanase and β-glucanase (Natugrain®) exogenous enzymes (BASF, Ludwigshafen am Rhein, Germany) were used. The enzymes were dissolved in soybean oil and sprayed onto the tops of the extruded diets.This study was carried out in a completely randomized design with four treatments and four replicates of 17 fish. Fish (n = 272; initial body weight 22.52 ± 0.20 grams) were distributed into 16-200-liter fiberglass tanks. The water temperature and dissolved oxygen were maintained at 27.2 ± 1.3 degrees-C and 5.85 ± 0.51 mg/L. Furthermore, the fish were hand-fed six times daily for 42 days. At the end of the feeding experiment, fish were weighed and assessments of whole-body composition (four fish per tank) and vertebral mineral content (two fish per tank) were made.Exogenous enzymesThis study evaluated the effect of exogenous enzymes in plant-based diets on the growth of Nile tilapia fingerlings.Additionally, feces were collected daily from each experimental tank to determine the apparent digestibility of protein (N × 6.25) and phosphorus. The resulting data were then entered into ANOVA and, in case of statistical difference, the means were compared by Tukey’s test (p < 0.05).Results and discussionThe growth performance of the Nile tilapia fingerlings is shown in Table 1. The final body weight (g), body weight gain (percent), and feed conversion ratio were optimized in fish fed PHY, XB, and PHY+XB diets when compared to the control group (CON); while there was no difference among fish groups fed PHY, XB, and PHY+XB diets (p < 0.05).Macêdo, exogenous enzymes, Table 1Table 1: Performance of Nile tilapia fingerlings fed diets based on soybean meal with supplementation of enzymes phytase and a xylanase/β-glucanase complex.CON, control diet with no enzyme application; PHY, phytase-supplemented diet; XB, xylanase and β-glucanase supplemented diet; PHY+XB, phytase, xylanase, and β-glucanase supplemented diet; SEM, pooled standard error of the mean.The means are of four replicate groups and values with the same column with different letters are significantly different (p < 0.05). Also read: Combining Yucca Extract and Yeast in Tilapia FarmingThe whole-body proximate composition and the vertebral ash content are shown in Table 2. Whole-body moisture and crude protein content were not affected by dietary treatments (p > 0.05). Conversely, fish fed a diet supplemented with a combination of phytase, xylanase and β-glucanase (PHY+XB) showed higher whole-body lipids, ash, and vertebral ash contents, than those fed the CON diet (p < 0.05). However, there was no difference in whole-body and vertebral ash between fish fed PHY and PHY+XB diets.Table 2: Whole-body composition of Nile tilapia fingerlings fed diets based on soybean meal with supplementation of enzymes phytase and a xylanase/β-glucanase complex.CON, control diet with no enzyme application; PHY, phytase-supplemented diet; XB, xylanase and β-glucanase supplemented diet; PHY+XB, phytase, xylanase, and β-glucanase supplemented diet; SEM, pooled standard error of the mean.The means are of four replicate groups and values with the same column with different letters are significantly different (p < 0.05). The combination of phytase, xylanase, and β-glucanase revealed a synergic effect, reducing phosphorus and nitrogen excretion in the fish. Compared to the control (CON), fish fed the PHY+XB diet showed reduced phosphorus and nitrogen excretion by 50.9 percent and 30.3 percent, respectively.Overall, phytase and xylanase-β-glucanase blends, individually or in combination, improved the growth performance of Nile tilapia fingerlings. Moreover, the combination of phytase, xylanase and β-glucanase exerted synergistic effects on reduced phosphorus and nitrogen excretion and can thus contribute to sustainable aquaculture, in addition to their positive growth performance effects.Also read: Influence Of Diet Type on Gut Microbiome, Nutrient Assimilation in GIFT TilapiaPerspectivesThe results of this study support the hypothesis that the addition of phytase, xylanase and β-glucanase would improve the growth performance of Nile tilapia that are fed all-vegetable diets. These exogenous enzymes play an important role in reducing potentially harmful phosphorus and nitrogen in the aquatic environment.It is important to note that exogenous liquid enzymes are affected by high-temperature conditions during the grinding, extrusion, and drying processes involved in producing fish feed. For this reason, liquid enzymes may be top-coated after the drying process, providing a high residual level on the extruded pellets. Source: Global Aquaculture Alliance ...
Effects Of Carbohydrate Sources on A Biofloc Shrimp Nursery
Biofloc technology is a resource-efficient aquaculture production system that supports better use of basic natural resources, such as fresh water and land, and aquafeeds. The addition of organic carbohydrate (CHO) to the biofloc system provides an energy source for microbial organisms to convert ammonia or nitrate into microbial biomass. This process helps to lower ammonia and nitrite levels, thereby reducing the need for water exchange. At the same time, the generated microbial biomass serves as natural food for the cultured species and increases feed use efficiency. Biofloc systems also benefit immunological responses of Pacific white shrimp (Litopenaeus vannamei) against infectious agents.Potential CHO sources may include simple ones such as molasses, glycerol and glucose, and complex ones such as flours and starches. Different CHO sources result in different nutritional values of the biofloc. In addition, they have varying effects on the composition of the microbial community in the biofloc, the production, and the immunity of the cultured fish and shrimp. The underlying mechanism for some of these differences may lie in the complexity of CHO structure. These results altogether indicate the importance of selecting a suitable CHO for a successful biofloc technology system.In biofloc technology, feed and CHO represent major sources of organic material entering the system. Following feeding, the oxygen consumption and ammonia excretion by fish significantly increase, creating high fluctuations in ammonia concentration on a daily basis. It is currently unknown how the carbon and nitrogen inputs are accumulated in different compartments (e.g. shrimp, biofloc, water) of the biofloc culture of L. vannamei, and further research on nutrient recycling in biofloc systems is still needed.This article – adapted and summarized from the original publication [Tinh, T.H. et al. 2021. Effects of carbohydrate sources on a biofloc nursery system for whiteleg shrimp (Litopenaeus vannamei). Aquaculture, Volume 531, 30 January 2021, 735795] – investigated how the addition of corn starch or molasses affected water quality, biofloc and periphyton [complex mixture of algae, detritus, cyanobacteria and heterotrophic microbes attached to submerged surfaces in most aquatic ecosystems] proximate composition, shrimp production parameters, diurnal fluctuations and distribution of carbon and nitrogen in a L. vannamei shrimp nursery system.Also read: Biofloc Systems, Tilapia by Product may Support Cheaper Shrimp ProductionStudy setupThe experiment was carried out at the animal research facility of Wageningen University (Carus), the Netherlands. L. vannamei (0.075 ± 0.006 grams) juveniles were obtained from CreveTec in Ternat, Belgium, and stocked at the density of 250 shrimp per square meter into tanks in an indoor nursery system. The tanks had continuous aeration, temperature control, a 12-hour/12-hour dark/light regime and established biofloc.The animals were fed twice per day with 34 percent commercial protein feed (CreveTec) at the feeding level of 8 percent body weight (BW) per day, and an assumed feed conversion rate of FCR of 0.7, reaching a maximum feeding rate of 43 grams per cubic meter per day. After feeding, corn starch and molasses were added immediately to their respective treatments. For each kilogram of shrimp feed fed, 0.6 kg of corn starch or 1.1 kg of molasses were added to maintain an input C:N ratio of 12.Shrimp samples were collected as a composite sample at the beginning and separately from each tank at the end of the experiment for determination of average body weight and survival rate. Biofloc samples were collected at the beginning of the experiment and the end of weeks 1, 3 and 5. Other samples were also collected at various times during the experiment.For detailed information on the experimental design and system, and animal husbandry; sample collections and analyses; and data analyses, refer to the original publication. Results and discussionOverall, results of the study showed that both corn starch and molasses addition treatments resulted in low ammonium nitrogen levels in the water. The total suspended solids and volatile suspended solids in both treatments increased over time and were not significantly different among treatments. The protein content in the dry matter of the biofloc varied from 34 percent to 48 percent, being higher in the molasses treatment. The same was observed for the protein content in the dry matter of the periphyton which ranged between 16 percent and 26 percent.The corn starch treatment resulted in significantly higher shrimp growth rate, production, average body weight and lower FCR compared to molasses addition. Water quality was stable on a daily basis, but changed over the weeks. Carbon and nitrogen accumulations in the system were not significantly different among treatments.The survival percentage (90 to 96 percent) and specific growth rate (SGR), the increase in cell mass per unit time (8 to 10 percent body weight, BW, per day) of shrimp in this study were high and comparable to previous studies on L. vannamei shrimp nursery. We used a carbon:nitrogen (C:N) ratio of 12 for both treatments, and recommended for biofloc culture of L. vannamei shrimp.The addition of corn starch yielded significantly better shrimp production, probably due to the more stable environmental conditions in the corn starch treatment, in particular the dissolved organic carbon and nitrogen compared to the molasses treatment (Fig. 1). Stable water quality reduces stress and improves growth and survival of cultured shrimp. Lower and more stable organic carbon and nitrogen concentrations in the water of the corn starch treatment suggest that the microbial community in the experimental system differed in composition and was more efficient than in the molasses treatment.Also read: Ten Easy Steps Towards Biofloc Production of Shrimp or TilapiaFig. 1: Weekly changes of dissolved nitrogen (N) and carbon (C) in water by treatment (carbohydrate source). Values are means (±SD) of three replicate tanks per sampling time in each treatment. The asterisks (*) indicate weeks with significant difference among treatments (P < .05).The two carbohydrate sources used in this research differed significantly in mineral content, especially in potassium. Previous research also reported that iron, potassium and manganese concentrations in molasses were approximately 17, 50 and 70 times, respectively, higher than in starches. Phosphate concentrations in the molasses treatment was also higher than in the corn starch treatment and previously reported values in conventional shrimp pond. But it is not clear if these differences contributed to the difference in shrimp growth among treatments. Overall, in addition to maintaining a suitable C:N ratio, the choice of CHO source is of major importance in biofloc technology, as different CHOs have different effects on biofloc nutritional content, microbial diversity and production of the cultured animals.Biofloc protein content was higher than 390 g/kg dry weight in both treatments. The average biofloc concentration reached 434 mg per liter, presenting an extra source of nutrients for the cultured shrimp. The higher biofloc protein content observed in the molasses treatment likely resulted from the fact that molasses contains more protein on a dry weight basis (8.5 percent) than corn starch (0.3 percent), which was directly available to biofloc.We observed that as the biofloc concentration increased, its protein content increased, while its ash content decreased. This may be due to changes in the biofloc microbial composition. At high biofloc concentration, the bacteria part in biofloc became dominant over the algal content. In our study, in the system was outcompeted from week 3 onwards, showing a decrease in chlorophyll a concentration when biofloc concentration reached 403 mg per liter in the corn starch and 417 mg per liter in the molasses treatments. A balanced biofloc system where neither algae nor bacteria is dominant is more beneficial for shrimp, and biofloc concentrations of 400 to 600 mg per liter are reported as suitable for L. vannamei shrimp culture.Periphyton production in our trial reached 22 to 46 grams DW per tank at the end of the experiment, with protein contents ranging from 19 percent to 24 percent. Periphyton protein content, similarly to biofloc protein content, was significantly higher in molasses treatment. There are few studies on the effects of carbohydrate type on periphyton, but periphyton nutritional values have been shown to be dependent on substrate type. The periphyton protein level in our study was comparable to the 25 percent reported by researchers for L. vannamei ponds and represented an extra source of nutrients for the animals.The direct contribution of periphyton to intensive culture of L. vannamei shrimp has not been studied, but scientists have shown that promoting periphyton growth by substrate addition increased L. vannamei shrimp production in less intensive systems. We observed that shrimp grazed on periphyton, which in our system mostly grew on the tank wall at the water-air interface, so that maintaining a constant culture water level may increase the availability of periphyton for the shrimp.Also read: Evaluating Compensatory Growth in Pacific White Shrimp in a Biofloc SystemFig. 2: Carbon and nitrogen distributions in different compartments of the culture system, and total nutrient input from feed and carbohydrates. Values are means of three replicate tanks by treatment (carbohydrate source).Our data demonstrated that only 15 to 17 percent of carbon and 28 to 43 percent of nitrogen input remained in the system at the end of the experiment. The nitrogen accumulated in shrimp in the corn starch treatment of this research is comparable to that reported by other researchers. However, the total 43 percent of the nitrogen input accumulated in the tank was slightly more than half of the 80 percent accumulation of the nitrogen input reported elsewhere. The other 20 percent was assumed to be lost through denitrification and volatilization. From other researchers working in conventional culture ponds without CHO addition, 23 percent of carbon and 35 percent of nitrogen inputs (i.e. from feed and fertilizer) were reportedly assimilated in shrimp, indicating that our system was less efficient in carbon use compared to more conventional shrimp production systems.PerspectivesOur results show that the choice of organic carbon source plays an important role in the success of a biofloc system. Corn starch was superior to molasses for enhancing the growth of L. vannamei shrimp juveniles. Once the biofloc is established, nitrogen waste can be efficiently controlled, resulting in relatively little diurnal fluctuation of nitrogen and carbon in culture water. However, the nutrient loss in biofloc systems, especially carbon loss is high, and ways to reduce carbon losses from culture systems should be explored. Also, further research is needed on improving nutrient use efficiency, either directly by the cultured animals or indirectly by trapping nutrients and making them available for other uses. Source: Global Aquaculture Alliance ...
Polyculture Of Pikeperch Juveniles in Recirculating Aquaculture Systems
Recirculating aquaculture systems (RAS) are mainly used to intensively produce a single species (monoculture), and predominantly fish species that have high commercial value such as Atlantic salmon, flatfishes and others. RAS technology has many well-known advantages, including reduced water use, minimal footprint, greater control, high production and limited environmental impacts, among others. Also, RAS operations can be very restrictive for fish that are subject to stress through handling, containment and high-density conditions.Although monoculture is the predominant approach in RAS, polyculture (production of more than one species) could theoretically overcome some of the limitations of this production system. Polyculture has been proved to be a valuable option to increase the efficiency and the sustainability of production systems. Polyculture can improve the system operation by taking advantage of coexistence and interactions between different species, supporting better feed resource utilization and limiting feed losses, less waste through recycling and optimal utilization of culture space.Very few studies have evaluated polyculture implementation in RAS operations. To help generate pertinent information, we carried out the first multi-trait assessment of RAS polyculture of several fish species, comparing survival rates, growth performance and behavior of pikeperch (Sander lucioperca), a freshwater carnivorous species in monoculture or in polyculture with two other species – sterlet (Acipenser ruthenus) and tench (Tinca tinca). We chose these species because their polyculture could improve pikeperch RAS productions.Also read: Benefits of Recirculating Aquaculture SystemsPikeperch is a valuable freshwater mainly produced in RAS monoculture. This production strategy faces two main challenges: steady supply of good-quality water and fish stress reduction. As pikeperch does not take the feed on the bottom of the production tanks, its monoculture impacts water quality. Therefore, associating pikeperch with bottom-feeder species such as sterlet and tench could improve the water quality and therefore the fish production.Moreover, pikeperch is very sensitive to stress in rearing systems. Although no scientific assessment is available to date, fish farmers commonly add tench during transportation of other fish species because of their known calming effect on other fish. Therefore, co-rearing of tench and pikeperch could mitigate the pikeperch stress issue. Although pikeperch and sterlet co-rearing in RAS has already been investigated by other researchers, its production potential and any behavioral issues are not documented.This article – adapted and summarized from the original publication (Thomas, M. 2020. The effects of polyculture on behavior and production of pikeperch in recirculation systems. Aquaculture Reports Vol. 17, July 2020, 100333) – compared survival rates and growth and behavior of pikeperch reared alone and with other fish species in a RAS system.Study setupThe experiment was carried out at the Experimental Platform for Aquaculture of the UR AFPA lab, Faculty of Sciences and Technologies, University of Lorraine (France). Juvenile pikeperch (58 ± 10 grams) were reared in our facilities, whereas juvenile sterlet (17 ± 4 grams) and tench (40 ± 6 grams) were obtained from the Fisheries Cooperative Györ (Hungary).Before the beginning of the experiment, fish were transferred into indoor aquaria, each an independent RAS. Water quality parameters were maintained within acceptable levels and controlled during the acclimation and experimental periods. Fish were fed manually with a commercial diet and aquaria were cleaned once a week. Rearing conditions followed established fish farmer practices and scientific literature.Four treatments – pikeperch monoculture (P); pikeperch and sterlet polyculture (PS); pikeperch and tench (PT); and pikeperch, sterlet and tench (PST) – were tested, each in triplicates (Fig. 1). The total initial biomass differed between aquaria, but we chose to work with a fixed number of fish per aquarium instead of uniform biomass because the number of fish could influence their behavior, and particularly their relationships. Fish growth and survival data were collected and analyzed.Fig. 1: Description of the experimental design. Four treatments were tested in triplicate: one treatment in monoculture: P (pikeperch) and three treatments in polyculture: PS (pikeperch and sterlet), PT (pikeperch and tench) and PST (pikeperch, sterlet and tench). The initial fish number was 36 (with an adjustment of fish number by species according to the treatment).For detailed information on the experimental design and environment; production parameters; behavioral assessments, interindividual interactions and group structures; and statistical analyses, refer to the original publication.Also read: Feeding Systems for Fish Farms and RASResults and discussionThe survival rate for pikeperch in our study was 100 percent after one month in all experimental treatments. At the beginning of the experiment, pikeperch weights were similar between the four treatments, but the mean final weights between the four treatments were significantly different. Pikeperch alone had lower weight than those pikeperch with tench, and those with both tench and sterlet (treatment P: 75.7 ± 2.7 grams; treatment PT: 85.7 ± 8.1 grams; treatment PST: 90.3 ± 1 6.4 grams). Moreover, the weight of juvenile pikeperch was lower when fish were reared with sterlet than for pikeperch reared with both tench and sterlet (PS: 80.1 ± 3.2 grams).After one month, there was no difference in the coefficient of variation, CV [a measure of uniformity of size distributions] between the pikeperch in the four treatments. Pikeperch biomass gain (BG) also differed between the four treatments after one month. The pikeperch alone had lower BG than those pikeperch reared with tench and those reared with both sterlet and tench (P: 25.2 percent; PS: 38.3 percent; PT: 50.1 percent; PST: 51.5 percent).Our results show that RAS polyculture of pikeperch positively affects juvenile fish rearing performance without significantly affecting their behavior. Indeed, although the number of contacts between pikeperch juveniles was lower under monoculture than under polyculture conditions, we detected no aggressive behavior between conspecifics [of the same species].We observed an increase in pikeperch weight from 25 percent in monoculture to 51 percent in polyculture. The better growth rate measured in our study could result from using different pikeperch individual densities between the four treatments. In contrast, pikeperch individual densities were similar in monoculture and polyculture treatments in a previous study by other researchers, because density can change feed availability and/or intraspecific relationships for individual pikeperch.Pikeperch consumed feed mostly in the water column, with a very low percentage of the pellets eaten at the bottom. Therefore, even though feed quantities were lower when pikeperch juveniles were associated with the other species due to the lower biomass of these species, pikeperch benefited from the total feed amounts for all the species while feed was in the water column. This meant that there could have been less competition between pikeperch, as they had larger amounts of food per individual and consumed the feed before the other two species. This was also supported by the results from the behavioral analysis, which revealed lower cohesion and homogeneity of the pikeperch group when they were reared alone compared to the polyculture treatments.Also read: A successful Case of Split Pond Recirculation Aquaculture System (SP-RAS) for Snakehead Fish Farming in Andhra Pradesh of IndiaIntraspecific competition is a known key characteristic of the social life in pikeperch, and generally leads to the establishment of hierarchy with dominant fish. Since this social relationship depends on the fish density (i.e., dominance increases at higher density), the loss of feed due to intraspecific competition and subsequent lower growth is more likely in the pikeperch alone treatment.Additional attention should be given to the limits of our experiment before projecting our results to an economic scale. We used low fish densities (∼7 kg per cubic meter in the treatment pikeperch alone and lower in the treatments with the other two species), which is quite lower from the RAS pikeperch monoculture industry conditions (i.e. 80 to 100 kg per cubic meter). Since the fish density could directly influence the growth through the interindividual competition for food, our results could not be transposable to industrial fish farming contexts. And our trial lasted only 30 days, while the rearing period of juveniles is one year in the pikeperch industry. However, the growth parameters we measured in our study can be projected over the entire juvenile growing period since juvenile growth is a continued function during this early life stage.Our results suggest that the implementation of polyculture in RAS could be an interesting option for the rearing of juvenile pikeperch. In general, we believe our results should be considered as a first step, showing the feasibility and the potential of RAS polyculture for fish production. It opens up great prospects for future studies on RAS polyculture with conditions closer to commercial scale aquaculture, in order to provide a comprehensive assessment of the potential of polyculture in intensive indoor fish farming.PerspectivesOur results show the positive effects on growth and only a few behavioral changes in pikeperch, indicating that RAS polyculture is a relevant alternative option for the rearing of juvenile pikeperch compared to monoculture. Our research opens up new prospects for the production of high-value species such as pikeperch and support the need to move towards more efficient and sustainable aquafarming systems. Source: Global Aquaculture Alliance ...
Global Trends in Antimicrobial Use in Aquaculture
Increasing use of antimicrobials in humans and food producing animals is driving antimicrobial resistance, which is amongst this era’s defining global health challenges. Rising incidence of antimicrobial resistant pathogens of animal production significance also increase treatment failure rates, undermining sustainable food animal production and animal welfare.Globally, rising demand for animal source nutrition is being met with a transition to increasingly intensive animal production systems. This transitional period is typically characterized by an emphasis on production volume that precedes the adoption of farm biosecurity, hygiene and management standards. In this context, non-therapeutic antimicrobial use may serve to increase growth and substitute for good animal husbandry practices. The current estimate of antimicrobial use in terrestrial food producing animals substantially exceeds human use, and is expected to grow considerably by 2030, particularly in countries with fast-growing economies like Brazil, Russia, India, China and South Africa (BRICS).In aquaculture, production intensification and increasing incidence of aquatic animal pathogens are similarly driving antimicrobial use and antimicrobial resistance across a diversity of farmed aquatic species. Compared with antimicrobial use in terrestrial food animal production, application of antimicrobials in aquaculture provides a potentially wider environmental exposure pathway for drug distribution through water with important ecosystem health implications. Antimicrobial residues in the aquatic environment alter the environmental microbiome and, consequently, ecosystem regulatory, provisioning and supporting capacities.Further, aquaculture settings utilizing antimicrobials may serve as reservoirs for antimicrobial resistance genes, providing routes for human and animal exposure to antimicrobial resistant bacteria. However, the levels and patterns of antimicrobial use in aquaculture globally remain largely undocumented, limiting application of targeted interventions and policies promoting sound antimicrobial stewardship in a high-growth industry.This article – adapted and summarized from the original publication (Schar, D. et al. Global trends in antimicrobial use in aquaculture. Sci Rep 10, 21878 2020.) – presents an analysis of global antimicrobial consumption trends in aquaculture, estimating current antimicrobial use and project use to 2030 by combining species-specific antimicrobial use coefficients from a systematic review of point prevalence surveys with aquaculture production volumes. These trends are then compared with previously published data on antimicrobial use in humans and terrestrial food producing animals. The resulting estimates provide an initial foundation upon which future studies will be able to build and refine in directing iterative enhancements in antimicrobial stewardship policies.Also read: Research Collaboration Reveals New Antiviral Function in Sense of Smell in FishStudy setupWe estimated global trends in antimicrobial use in aquaculture in 2017 and 2030 to help target future surveillance efforts and antimicrobial stewardship policies. Baseline antimicrobial consumption and projected growth through 2030 were calculated by application of species-specific antimicrobial use coefficients to current and projected aquaculture production by species.A systematic review of peer-review and grey literature was carried out for antimicrobial use point prevalence surveys in aquaculture between 2000 and 2019, using three primary search term categories: “antimicrobial” (antimicrobial; antibiotic; veterinary medicine); “use” (use; usage; consumption; amount; quantity); and “aquaculture” (aquaculture; aquatic; fish; shellfish; marine; freshwater).We identified 25 studies representing 12 countries constituting 146 biomass-adjusted use rates, and from which species-specific mean antimicrobial use coefficients in milligrams per kilogram of aquatic animal biomass were obtained. Antimicrobial use coefficients by drug class were similarly obtained for analysis of use trends by class.Antimicrobial use intensity (mg/kg) was estimated for six species groups though a systematic review of point prevalence surveys, which identified 146 species-specific antimicrobial use rates. Antimicrobial use in each country was projected by combining mean antimicrobial use coefficients per species group with OCD/FAO Agricultural Outlook and FAO FishStat production volumes.For detailed information on the information sources and methods used in this study, refer to the original publication.Also read: Antioxidants Protect Tilapia From The Toxin MycotoxinResults and discussionAt current rates, global antimicrobial consumption in aquaculture is expected to increase 33 percent between 2017 and 2030. These estimates are associated with considerable uncertainty and relatively wide uncertainty intervals due to the scarcity of point prevalence surveys on antimicrobial use in aquaculture. Global trends in antimicrobial use in aquaculture are heavily influenced by the expansion of aquaculture in Asia, and particularly in China (Fig. 1). Since 1991, China alone has accounted for more annual farmed fish output by weight than all other countries combined.Fig. 1: Projected antimicrobial use (tons) in aquaculture by species by 2030 in the five highest-consuming countries. The China panel y-axis is broken at 8,000 and resumes at 20,000 tons. Error bars represent the 95 percent uncertainty intervals for the annual total use.At a country-level, few estimates of antimicrobial use in aquaculture have been produced. Although this limits comparisons of our estimates with country-level use, our antimicrobial use estimates for aquaculture are within the range of a 2013 domestic consumption estimate from China, and approximately 40 percent of the low bound from a 2002 estimate in the United States.Collectively, the five countries with the largest projected relative increase in antimicrobial consumption between 2017 and 2030 account for only 11.5 percent of global antimicrobial consumption in 2030, indicating that, with the exception of Indonesia, the countries with the fastest antimicrobial consumption growth will remain the minority contributors to global consumption projected by 2030.By 2030, global antimicrobial use from human, terrestrial and aquatic food producing animal sectors is projected to reach 236,757 tons annually (95 percent uncertainty interval, UI 145,525 to 421,426). Proportion of use across sectors remains relatively consistent through 2030, when human use (48,608 tons), terrestrial food producing animal use (174,549 tons), and aquatic food producing animal use (13,600 tons) represent 20.5, 73.7, and 5.7 percent of global consumption, respectively.Fig. 2: Global antimicrobial consumption, 2013 to 2030. Dotted lines represent the 95 percent uncertainty interval for fish.Regarding drug classes and species, the most commonly used antimicrobial classes observed in this study – quinolones, tetracyclines, amphenicols and sulfonamides – were consistent with a previous review of antimicrobials used in the 15 highest aquaculture-producing countries. Countries with export-oriented production largely follow the regulatory structures and maximum residue limits (MRLs) established by the European Union and United States.The four countries with the highest antimicrobial consumption identified in this study (China, India, Indonesia and Vietnam), for example, have adopted European Union MRLs to meet export requirements. Notably, enforcement of regulations remains a challenge in many countries, and parallel production systems serving domestic and export markets may encourage differing use practices.All of the classes of antimicrobials identified in our systematic review of point prevalence surveys are classified by the World Health Organization as important for human medicine. Classes assigned to the top two classification tiers — highly important and critically important antimicrobials for human medicine — collectively represented 96 percent of all use). This finding is of particular concern given that few alternatives to these drug classes exist. It further raises the prospect of antimicrobial use in aquaculture driving resistance trends in aquatic environments, with implications for transfer of resistance genes across bacterial species. Such transfers are ecological in nature and are thus challenging to document.Also read: A Targeted Alternative to Antibiotics?Several countries have experienced dramatic reductions in antimicrobial use rates following introduction of vaccination and improved management and husbandry programs, serving as important antimicrobial stewardship models. Future strategies aimed at strengthening aquaculture production without pharmaceutical interventions may leverage advancements in bacteriophage therapy, prebiotics and probiotics, and CRISPR-Cas genome editing. Identifying solutions that can be implemented and economically self-sustaining in low- and middle-income country settings currently representing the substantial majority of aquaculture production is imperative.Our study has some limitations. In the absence of comprehensive, standardized antimicrobial use data, our study relies upon a relatively limited collection of antimicrobial use point prevalence surveys. Despite a Chinese language search of the China National Knowledge Infrastructure (CNKI) database, surveys on antimicrobial use in China are underrepresented in our study, constituting an important knowledge gap on antimicrobial use in the world’s largest aquaculture producing nation. This limitation is particularly acute for some of the most commonly farmed fish species, such as the freshwater Cyprinidae family of species that includes carp.Our antimicrobial consumption projections are subject to wide uncertainty intervals that likely reflect both the limited availability of surveys, from which projections were generated, and the diversity of global aquaculture production systems, practices and species. The diversity of farmed aquatic animal species greatly exceeds terrestrial food animal producing species. In 2016, 558 distinct aquatic animal species items were commercially farmed worldwide.Although a smaller subset of 27 species groups accounted for 90 percent of global aquaculture production in 2016, by comparison, only three species groups – chickens, pigs and cattle – contributed to an equivalent level of terrestrial food animal production. Such a diversity of farmed aquatic species – compounded by polyculture production systems – presents substantial variability and challenges documentation of antimicrobial use. Currently, antimicrobial use is poorly documented even for those species of greatest production significance.Despite these and other limitations, our estimates provide a starting point to help frame a discussion outlining near-term priorities to enhance antimicrobial use data collection.Also read: Dr Loc’s Key Steps to Antibiotic-Free Shrimp ProductionPerspectivesOur study underscores the urgent need for standardized antimicrobial use surveillance in the aquaculture industry. Experience from countries implementing antimicrobial stewardship initiatives cite the establishment of antimicrobial use surveillance structures as the foundation for identifying risk and targeting interventions.Robust surveillance data (1) facilitates identification of sectors and production contexts where either inappropriate use or lack of access would benefit from rebalancing; (2) enables the establishment of time-bound, measurable consumption targets and monitoring progress toward achieving these targets; and (3) when paired with resistance data, generates additional insight into the association between patterns of consumption and antimicrobial resistance trends.A tiered approach to surveillance of antimicrobial consumption permits utilization of existing sales channel data to direct enhanced stewardship policies while structures are developed to produce iteratively more granular, farm-level consumption data. As a function of potentially higher rates of off-label use of antimicrobials in aquaculture – particularly in developing country contexts – sales data, however, may currently under-represent consumption. Labelled indications for therapeutic use in primary aquaculture species will improve attribution to – and characterization of – aquaculture use.Our study uses current evidence to draw a first assessment of the global trends in antimicrobial use in aquaculture. Aquaculture-associated antimicrobial consumption remains a minority share of total global consumption through 2030. However, high industry growth rates, shifting dietary preferences and transitions to intensified production without corresponding management changes may drive increasing antimicrobial use in aquaculture relative to other sectors. Increases in use may be particularly significant in geographies with nascent antimicrobial consumption surveillance, regulatory and enforcement capacities.Our findings call for urgent strengthening of surveillance for antimicrobial consumption and enhanced understanding of antimicrobial resistance transmission risk across the aquatic animal-environment-human interface, with application of targeted policies and regulatory structures promoting antimicrobial stewardship and antimicrobial efficacy as a shared global resource.Source: Global Aquaculture Alliance ...
Pacific White Shrimp Responses to Low Salinity Temperature Fluctuations
The Pacific white shrimp ( Litopenaeus vannamei ), with its wide range of tolerance to salinity, rapid growth and several other characteristics appropriate for intensive aquaculture, has become the most important cultured shrimp species in the world. However, a variety of environmental factors can affect shrimp growth, such as changes in pH, salinity, dissolved oxygen (DO), temperature, and also chemical compounds such as nitrite, ammonia, and sulfur.The annual cold wave affecting the shrimp industry in southern China during the winter months (November to January) causes significant economic losses to the L. vannamei aquaculture industry . However, little information is available on the physiological responses of shrimp during the process of gradual cooling and warming of temperature.For shrimp, researchers have reported on the histology [the study of the microscopic anatomy of tissues and cells from animals and plants] of their hepatopancreas as a tool to monitor the impact of environmental stressors that can cause ultrastructural alterations at the onset of stress. . For example, environmental stresses such as changes in pH can cause changes or damage to the cells of the hepatopancreas. However, for temperature fluctuations, so far there is no definitive information on any changes in the hepatopancreas.This article, adapted and summarized from the original publication (Wang, Z. et al. 2019. Physiological Responses of Pacific White Shrimp Litopenaeus vannamei to Temperature Fluctuation in Low-Salinity Water. Front. Physiol., August 13, 2019) - reports on a study that investigated various physiological responses in juvenile L. vannamei subjected to temperature fluctuations (28 to 13 to 28 degrees-C) in low salinity water.Also read: Supplementing Rotifers to Reduce Stress for White ShrimpStudy setupJuveniles of L. vannamei (average weight 5.4 ± 0.7 grams) from a commercial farm in Panyu (Guangdong, China) were transported to the laboratory and acclimatized in tanks of filtered and aerated seawater for several days before the experiment. During the acclimatization stage, the salinity of the water and the temperature in the tanks were consistent with those of the farm's culture ponds (salinity 5 ppt, pH 8.3 ± 0.1 and temperature 28 ± 1 degrees-C) where the prawns. The shrimp were fed commercial feed twice a day at 5 percent of their body weight.From these shrimp, the selected healthy individuals were randomly divided into three replicate tanks and placed in an artificial climate incubator. The water temperature was reduced from the acclimatization temperature (AT, 28 degrees-C) to 13 degrees-C with a cooling rate of 7.5 degrees-C per day (2.5 degrees-C every 8 hours). After 13 degrees-C for 24 hours, the water temperature was increased back to 28 degrees-C at the same rate.At various temperature points (28, 23, 18, 13 and 13 degrees-C for 24 hours during the cooling process and at 18 and 28 degrees-C during the heating process), whole hepatopancreas from experimental animals were dissected and preserved. for several hours. analysis.For detailed information on experimental design and animal husbandry; collection and preservation of tissue samples; histology, RNA and DNA extractions, real-time polymerase chain reaction (qPCR) and other tests; and statistical analysis, see the original publication.Also read: Transcriptomic Analysis of Pacific White Shrimp in Response to AHPNDResults and DiscussionIn this study, we investigated various physiological responses, including histological changes in the hepatopancreas, concentrations of plasma metabolites, expression of various genes, and other processes, in juvenile L. vannamei exposed to fluctuations in water temperature (28 to 13 to 28 degrees-C). All these responses and processes were affected as temperatures decreased, but in general they recovered during the reheating stage and showed that L. vannamei shrimp can adapt to a certain level of temperature fluctuations.The crustacean hepatopancreas is a vital organ involved in excretion, molting, various metabolic activities, and storage of energy reserves. The results of our study showed that the number and volume of certain cells (B cells) in the tubules of the hepatopancreas increased significantly after the shrimp underwent cold stress. This may be related to the fact that B cells are the main site of absorption and digestion of nutrients. It is possible that the high rate of synthesis and release of digestive enzymes in B cells accelerated the mobilization of nutrients in the tubules of the hepatopancreas, which would help the shrimp better adapt to temperature stress.In shrimp, the hepatopancreas is known to have a high self-healing capacity. For example, researchers have reported that L. vannamei can repair hepatopancreas lesions after prolonged exposure to low zinc levels and low pH. And that the weight of the hepatopancreas of L. vannamei decreased significantly after fasting, but then increased immediately after the animals began to feed again. In our study, the histological damage of the hepatopancreas was reversed after the animals returned to higher water temperatures, confirming this reported capacity for self-repair.Also read: Evaluating Plant Protein Sources Replacing Fishmeal In Juvenile White Shrimp DietsRegarding changes in shrimp plasma [liquid portion in shrimp blood, the hemolymph] during temperature fluctuations, our results showed that lipids and proteins in L. vannamei plasma responded more quickly to fluctuation temperature, while glucose levels were stable before the temperature of the experimental water reached 13 degrees-C, and it recovered to acclimatization levels after the temperature rose again to 28 degrees-C.The hepatopancreas is typically lipid-rich and appears to be the primary site for gluconeogenesis [a metabolic pathway that generates glucose from certain non-carbohydrate carbon substrates] in decapod crustaceans, those with five pairs of walking legs, such as prawns. Therefore, combined with our observed hepatopancreas histology and plasma results, we conclude that the increase in B cells in the hepatopancreas facilitates gluconeogenesis to synthesize glucose from proteins and lipids, through which shrimp supply the demand for glucose under experimental cold stress. However, after the water temperature dropped to 13 degrees-C, the rupture of the tubules of the hepatopancreas causes lipids and proteins to enter the hemolymph,Non-specific immunity plays an important role in the immune defense of aquatic animals. Shrimp like L. vannamei rely entirely on cellular and humoral immunity to prevent external injury. The enzyme alkaline phosphatase (ALT) is directly involved in several metabolic pathways and plays an important role in the immune system of shrimp against various pathogens, probably because it can help protect the hepatopancreas and hemolymph from damage caused by cold.Analysis of plasma metabolite concentration also showed that ALT enzyme activity reached its highest level at 13 degrees-C; ALT activity in plasma is inversely proportional to the health of the hepatopancreas. This finding is consistent with previous studies and confirms the self-healing capacity of shrimp L. vannamei . Furthermore, the expressions of many genes that we evaluated in our study, as well as the number of hemocytes [type of cell involved in the invertebrate immune system], reached their highest level in the hepatopancreas at 13 degrees-C.Also read: Effect of Streptomyces Probiotics on Gut Microbiota of Pacific White ShrimpPerspectivesThe results of our study showed that proteins and lipids were the main source of energy for L. vannamei during temperature fluctuations. During the rewarming stage, all overall assessed histopathological symptoms reversed and all plasma metabolite concentrations and gene expressions returned to acclimatization temperature levels. Overall, the results suggest that L. vannamei can adapt to a certain level of temperature fluctuation, but the detailed adaptation mechanism in this shrimp species still needs further study.Source: Aquaculture Alliance ...
Modeling Microalgae Production Cost in Aquaculture Hatcheries
The use of microalgae in aquaculture has increased in the past decade, because of the importance of microalgae as the primary source of nutrition for all stages of filter-feeder bivalves and the larval and juvenile stages of fish and shrimp. The quality of feed is linked to survival and mortality rates of larval stages, development rate, egg viability and other performance parameters of the species cultured.For a constant supply of fresh microalgae, aquaculture hatcheries generally have an in-house microalgae production facility, generally small in scale and up to 100 square meters in area. In the early 1990s, maintaining a microalgae production facility was estimated by researchers to account for an average of 30 percent, and up to 60 percent of the total budget of aquaculture hatcheries and nurseries, and the cost of microalgae biomass in aquaculture hatcheries was estimated at $50 to $400 (U.S.) per kg dry weight (DW) depending on the applied scale.Despite the high cost prices, no effort has been described in literature to determine the cost price of microalgae in detail and highlight strategies for cost reduction. Microalgae production systems in aquaculture are typically not selected or optimized for cost efficient production. Most relevant studies available in the literature on microalgae for aquaculture applications focus on the nutritional value of the algae only.A techno-economic analysis of small-scale algae production facilities – such as the systems used in aquaculture – is not available, as these analyses for microalgae production are typically performed on much larger scales, focusing on the production of bulk chemicals and commodities such as biofuels.This article – adapted and summarized from the original publication [Oostlander, P.C. et al. 2020. Microalgae production cost in aquaculture hatcheries. Aquaculture, Volume 525, 30 August 2020, 735310] – evaluated the production costs and cost distribution of microalgae production in aquaculture hatcheries, and provides guidelines for cost reduction strategies.Study setupWe developed a techno-economic analysis for small scale microalgae production facilities (25 to 1500 square meters) to determine the cost-price and cost-distribution of microalgae production facilities in the Dutch aquaculture industry and to identify the most efficient cost reducing strategies. We used data from commercial microalgae facilities in the Netherlands to model reference scenarios describing the cost price of microalgae production with state-of-the-art technology in aquaculture for a biomass production capacity of 125 kg/year.Commercially available reactors commonly used in aquaculture were compared; tubular photobioreactors (TPBR) and bubble-columns (BC) in two placement possibilities, using artificial light in an indoor facility (AL) and utilizing sunlight in a greenhouse (GH) under Dutch climate conditions.Fig. 1: Schematic representation of the four reference scenarios applied in the model. AL: Artificial light, GH: Greenhouse, TPBR: Tubular photobioreactor and BC: Bubble-column.For detailed information on study design; reactor type and placement; reference scenarios; biomass yield on light; sensitivity analysis; and effect of scale, refer to the original publication.Results and discussionThe results of cost price and biomass capacity for the reference scenarios in the techno-economic analysis are shown in Fig. 2. The lowest overall production cost for two placement options, greenhouse (GH) and artificial light (AL) is found with the tubular photobioreactor (TPBR) scenarios in both settings.A cost price of €290/kg ($343.07/kg) is found for the AL-TPBR scenario and €329/kg ($389.20/kg) for the GH-TPBR scenario. These results clearly show a cost price advantage for the TPBR systems over the bubble-column (BC) systems in the reference scenarios. The BC scenarios result in a cost price of €587/kg ($694.40/kg) for the AL-BC and €573/kg ($677.63/kg) for the GH-BC scenarios, respectively. These cost prices are in the order of 100 times higher than numbers described by other researchers but describe algae production on a much smaller scale than number described by these other scientists.Fig. 2: Cost price of microalgae production, divided over 10 categories. Left half: four reference scenarios. Right half: combined scenarios from the sensitivity analysis excluding the effect of scale (bars: primary axis, €/kg microalgae). Total biomass capacity of each scenario (kg microalgae/year) is represented by the diamonds (secondary axis). Presented at scales of 20 to 50 square meters. AL: Artificial light, GH: Greenhouse, BC: Bubble-column and TPBR: Tubular photobioreactor.Regarding sensitivity analysis, the results show the effect of each input parameter on the cost price. The results of cost price reduction (in percent from the reference scenarios) are presented in Fig. 3.Fig. 3: Results of the sensitivity analysis: the effect on cost price, as a percent in cost reduction from the reference scenarios for changes made to the scenarios. AL = Artificial light, GH = Greenhouse, BC = Bubble-column and TPBR = Tubular photobioreactor. Yx,ph = biomass yield on light.The results in Fig. 3 show that additional artificial light has a large impact on the cost price for all systems. A cost price reduction in biomass production is found for all four scenarios with additional artificial light. Doubling the artificial light in AL scenarios doubles the total biomass production per year while adding costs for the lights in both capital expenditure, CAPEX [funds spent by an organization to maintain, buy or improve its fixed assets, such as buildings, equipment, vehicles or land] and operating expenses, OPEX [ongoing costs for operating a business, product or system].The addition of artificial light can be regarded as an easy to implement and cost-effective method for cost price reduction in existing microalgae production for aquaculture facilities if the reference cost price is higher than the cost of additional light. The further use of highly efficient light sources – such as Light-Emitting Diodes, LEDs [semiconductor light sources that emits light when current flows through it] – will make the use of artificial light even more economically interesting for small scale algae production than is shown in our results.We only tested the temperature range for the GH scenarios. In the AL scenarios, a constant temperature of the indoor facility is assumed and cooling requirements are based on heat production by the artificial lights. For the GH-BC scenario, reactors are not actively controlled for temperature and a change in the temperature range does therefore not affect the cost price. In the GH-TPBR scenario the temperature of the systems is actively controlled. The larger temperature range results in a reduced cost price, but only by a very small percentage of around 0.36 percent.The cost price reductions between the different scenarios and the differences observed could be attributed to actual temperature range differences, location (solar input, wind speeds, etc.), electricity cost, reactor geometry and more. The cost reduction in our calculations vs. those of other researchers is smaller due to the much higher cost price for biomass used as reference. Algae growth at temperatures other than the optimal growth temperatures will result in a negative effect on the biomass on light. Therefore, we conclude that to be more cost efficient on these small scales, efforts should target optimizing temperature control to maximize biomass yield on light (Yx,ph), rather than on energy reduction.The biomass yield on light (Yx,ph) has a large effect on the cost price, as this directly impacts the total amount of biomass produced. The same effect of biomass yield on light is found for all systems: by increasing the biomass yield on light, the total amount of biomass produced is increased without adding costs in our calculations. These results show the importance of operating a microalgae facility using optimized growth parameters and maximizing the biomass yield on light. The value we determined, 0.22 to 0.32 g/mol [a mol is the unit of measurement for amount of substance in the International System of Units, SI] for the monitored systems is much lower than values available in literatureBiomass production cost is a function of the total biomass capacity (kg) and total cost (€, U.S.$) of a production facility. Increasing biomass yield on light should only be the aim if it leads to a larger total biomass production without substantially increasing operational cost. Research focused on understanding the algal species used in aquaculture application and optimizing the applied growth parameters for most cost-efficient production is, therefore, one of the most promising cost reduction methods for small scale microalgae production but requires more effort than other cost reduction strategies.Labor is the largest cost price component for all reference scenarios, representing between 46 and 65 percent of total cost. More reactor capacity results in a larger labor requirement and therefore a larger effect of labor reduction. In practical applications, reduced labor costs would typically be obtained by the implementation of more automation, for example, for harvesting, for nutrient addition and with artificial light systems, among others, typically linked to higher CAPEX. A breakeven point between additional automation and labor reduction could be determined using the presented model and would be different for each scenario.Considering seasonal production, the scenarios in greenhouses under the Dutch climate show a very low biomass productivity in the winter months due to low light availability. The scenarios simulated with no production in winter show a reduction of the microalgae production costs of 12.6 percent and 7.9 percent for the GH-BC and GH-TPBR scenarios, compared to production during all days of the year.Regarding the effects of scale, in an algae production facility it has a large impact on the cost price. The total effect of scale on the cost price for each scenario is compared by comparing scenarios at equal floor area. The results for the effect of scale are summarized in Fig. 4, showing the cost price as a function of total biomass capacity (kg microalgae/year) for each of the scenarios.Fig. 4: Cost price of biomass (€/kg in y-axis, logarithmic scale) represented over the total biomass production (kg year-1 x-axis) of 9 different scenarios for six scales (25-100-250-500-750-1,500 square meters), each subsequent marker represents the next scale size. Solid lines represent reference scenarios, dotted lines show scenarios described as combined scenarios of the sensitivity analysis. BC = bubble-columns (circles), TPBR = Tubular photobioreactors (squares), AL = artificial light (black), GH = Greenhouse (grey). GH-TPBR-NoAL represents the same scenarios as GH-TPBR with combined scenarios of the sensitivity analysis but without the addition of artificial light. For combined scenarios, some scales produce more biomass than the maximum represented 10,000 kg microalgae/year.The results related to scale are highly dependent on the selected inputs from the starting reference scenario. Therefore, and because it is a parameter with a high impact, the effect of scale was analyzed in more detail for a total of nine scenarios. This analysis shows the potential cost price reduction that could be achieved when producing algae for multiple aquaculture facilities in one centralized algae production facility. Four scenarios show the cost price at different scales for the reference scenarios (solid lines in Fig. 4). The scenarios with combined optimization of the sensitivity analysis (1 through 5) are used for a future outlook on biomass cost price at larger scales (dotted lines in Fig. 4). Additionally, a GH-TPBR scenario using the combined cost reduction methods from the sensitivity analysis is modelled without the addition of artificial light (GH-TPBR-NoAL) in order to indicate the breakeven point for the use of artificial light in a GH-TPBR scenario.The overall lowest biomass production cost for the scenarios studied is found for the GH-TPBR scenarios not utilizing artificial lights (GH-TPBR-NoAL) on the largest scale (1,500 square meters) producing 6,892 kg microalgae/year at €23.47/kg (US$). The addition of artificial lights on a larger scale under more optimized conditions yields higher biomass cost price while producing much more biomass (11,822 kg/year at €26.35/kg for the GH-TPBR scenario). This shows that when moving to larger scales the addition of artificial light will not always result in a cost price reduction as it does for the small scale. At the 1,500-square-meter scale the cost of artificial light exceeds the relatively low-cost price of biomass, supporting the results as described for the sensitivity analysis on additional artificial light.Optimizing the scale of a microalgae production facility shows a big potential for cost reduction. The results show that, for the reference scenarios, the cost price could be reduced by 21 to 24 percent for BC scenarios and by 55 to 65 percent for TPBR scenarios by simply increasing the operation from the reference scenarios of 25 to 40 square meters to 250 square meters, and much further when moving up to 1,500 square meters in production area. However, most aquaculture facilities do not require the amount of biomass that is produced at these larger scales. But a specialized algae facility providing biomass for multiple aquaculture applications could produce at a larger scale, reaching much lower production prices than the smaller individual systems.The scenarios describing the lowest biomass production cost in this comparison, GH-TPBR-NoAL at €23,47/kg ($27.76) and GH-TPBR at €26,35/kg ($31.16), produce 55-100X the biomass capacity as described in the reference scenarios for aquaculture. More realistic near-term prediction can be found in the result for GH-TPBR-Base at 250 square meters. This scenario describes a facility producing 762 kg/year at €123/kg (US$145.46) without further improvements of state-of-the-art technologies other than a scale increase.PerspectivesUsing a techno-economic analysis, we evaluated the cost price of small-scale, industrial microalgae production facilities as presently used in the aquaculture industry. Modelled scenarios based on current commercial standards showed that microalgae biomass cost prices are currently between €587/kg microalgae ($694.66/kg) and €290/kg ($343.20/kg). Two of the most applied commercial systems were compared (bubble-columns vs. tubular reactor systems), showing a significant price advantage for the tubular reactor systems in all tested scenariosThe potential for cost price reduction based on state-of-the-art technology and operation can be significant: our results show that up to 90 percent cost reduction can be achieved from the reference scenarios. From the tested scenarios, the addition of artificial light, increasing biomass yield on light (Yx,ph) and reducing labor requirements showed the largest potential for cost price reduction when not changing the scale of the production facility.For existing production facilities the easiest strategy for cost price reduction is the addition of artificial light, yielding a cost reduction of 35 to 36 percent for all tested scenarios. Other cost price reducing strategies should focus on higher efficiency of the available production methods, thereby increasing the biomass yield on light. This could be achieved by optimizing growth parameters for the produced strains by optimizing temperature, light, pH, nutrient availability and harvesting strategies in the applied systems. Changes in temperature should focus on improved growth rather than cost reduction for energy consumption.The size of the facility shows the largest impact on the cost price of microalgae, but a larger scale could be difficult to implement in most existing facilities due to a lack of biomass requirements. A centralized microalgae production facility providing high quality microalgae for multiple aquaculture applications could decrease the cost price by 60 to 80 percent when producing 762 kg/year at €123/kg ($145.56/kg) on a 250-square-meter scale, compared to the 125/kg/year in the reference scenarios. This larger scale is still considered to be a very small production facility but does show a large reduction of overall biomass production cost.On an even larger scale (1,500 square meters), a cost price of €43/kg ($50.89/kg) is feasible with state-of-the-art technology, and future improvements can reduce this to €26.40/kg ($31.24) on the large 1,500-square-meter scale utilizing TPBR-systems. The large cost reduction that could be achieved in such a facility could have a large impact on aquaculture production processes in the future.Source: Global Aquaculture Alliance ...
Green Mussel Culture Using Longlines and Traditional Stake Methods in Indonesia
The green mussel (Perna viridis) is an excellent source of protein, fat and carbohydrates and a popular source of food for local communities throughout Southeast Asia, including Indonesia.Because the mussel reproduces throughout the year, requires no supplemental food input, grows to harvestable size in about six months and requires no mangrove removal for pond construction, it is particularly promising as a sustainable aquaculture product for culture in erosion‐sensitive mangrove coasts. Additionally, mussel culture does not require highly sophisticated techniques, knowledge or equipment, which makes it particularly suitable for use in small‐scale artisanal settings.Indonesia lags far behind in the culture of molluscs and little recent work has been done on mussel culture in Indonesia. Green mussel culture in the country takes place in sheltered marine mangrove waters and traditionally only involves the use of bamboo stakes. In the Demak Regency, northeast of Semarang on the northern coast of central Java, negative impacts from shrimp farming have promoted interest in mangrove‐friendly alternatives.Also read: Renewable Energy Could Transform Offshore AquacultureThis article – adapted and summarized from the original publication [Rejeki, S. et al. 2020. Increased production of green mussels (Perna viridis) using longline culture and an economic comparison with stake culture on the north coast of Java, Indonesia. Aquaculture Research, 2020; 00:1-8.] – reports on feasibility trials to develop green mussel culture as an alternative livelihood for the impoverished coastal fishing communities of Demak, Java. The green mussel is already being harvested from man‐made structures in the surrounding areas and, as is the case with several other bivalves, is a well‐established local food.Study setupThe study was carried out in Morosari Village, on the northern coast of Central Java, Indonesia, just 2 km northeast of Semarang in the coastal zone of the Demak Regency. The area was selected based on its physical suitability for aquaculture and the absence of potential interference from other fishing activities.The experimental site had an average depth of 0.77 meters, temperature of 29.8 to 30.2 degrees-C, salinity 27.7 to 38.4 ppt and current speed of 8.0 to 15.0 cm per second. Dissolved oxygen was 5.4 to 6.2 mg/L and pH was 7.1 to 7.8, while average ammonia and phosphate concentrations were 0.105 ppm and 0.590 ppm, respectively. The site was connected to the open sea through several canals of about 20 meters in width.In our study, we compared spat settlement, survival and growth to market size between longline rope culture technique used elsewhere and the traditional stake (rompong) method (Fig. 1). In the stake method, culture takes place using 200-cm long bamboo stakes stuck into the sediment 60 cm apart in water depths of 40 to 70 cm (Fig. 1a). The spat collectors consisted of 100-cm pieces of natural palm fiber rope, one cm in diameter (surface area: 314 square cm).Also read: Feeding Systems for Fish Farms and RASThey were suspended from their middle from the longlines or stakes, and total settlement was assessed for two months. In the grow‐out experiment, one mussel stocking was attached at both ends vertically to each stake, approximately 30 to 40 cm from the bottom. Longlines consisted of 7.5-mm diameter natural palm fiber rope. The rope was suspended between two stakes along the water surface. The longlines were three meters, but effective area submerged was about 2 meters. Five mussel stockings were suspended from the longline approximately 30 to 40 cm from the bottom and 30 to 50 cm apart (Fig. 1b). Four of these units were used in the same area and simultaneously with the 20 stakes.Fig. 1: The bamboo stake method (a) and the longline method (b) used in the experiment to support the mussel stockings used for culture trials.Spat collection involved 20 units of both bamboo stakes and longlines, while the grow‐out experiment involved four treatments and six replications for each of the two methods. After approximately 30 days, the spat (average 4.3 grams each) was removed from the bamboo stakes and longlines and was placed in mussel stockings, and then attached to the structures so that the mussels were constantly submerged. The mussel stockings were gunny sack, woven, 25-cm plastic nets with a width of 20 cm and a mesh size of ± 1.5 mm, obtained free of charge as waste packaging. During the grow-out cycle, there was no possibility for the mussel to escape the stockings.Our use of mussel stockings in conjunction with longlines differs from the practice elsewhere where the mussels are typically attached to 1-meter long suspended ropes instead. Mussel stockings were filled with 20, 30, 40 or 50 individuals spat per stocking and left for 75 days after which they were retrieved. Data on mussel survival, weight and other parameters were collected and analyzed.Also read: Growing Fish on Land Will Exacerbate Climate Change For detailed information on the experimental design; experimental culture units; and statistical analyzes, refer to the original publication.Results and discussionSpat settlement densities (± 1 standard deviations, SD) for longlines averaged 213 ± 109 individuals per settlement rope or 6,786 ± 3,476 individuals per square meter, while bamboo stakes collected significantly fewer for an average of 76 ± 15 individuals per settlement rope and 2,412 ± 484 individuals per square meter (Fig. 2).Fig. 2: Spat settlement density (individuals per square meter ± 1 SD) on collectors suspended from longlines and bamboo stakes.The method of spat collection had no effect on the average biomass per individual spat, and individual spat had an average weight of 4.3 grams on both the longline and bamboo stake collectors. Mussel survival during growout was comparably high for both methods (90 to 92 percent) and did not differ significantly (Fig. 3a). Weight gain per mussel was significantly higher for longlines (mean = 24.3g) than for bamboo stakes (mean = 22.9 grams; Fig. 3b). Therefore, the cultivation method also significantly affected the specific growth rate, SGR (86 percent/month for longlines; 83 percent/month for the stakes; Fig. 3c) and relative total weight gain of the mussel stockings (751 percent for the longline and 707 percent for the stake method; Fig. 3d). Mussels in the lowest density showed a significantly higher average weight gain (Fig. 3b). However, differences in stocking density did not significantly affect relative weight gain per mussel stocking SGR (Fig. 3c), or the total mussel biomass per stocking (Fig. 3d).Fig. 3: Comparison of measurements on mussels grown in stockings at different initial stocking densities on longlines and on bamboo stakes (N = 6; ± 1 SD). (a) Average percent survival of mussels. (b) Average weight gain of individual mussels. (c) Monthly specific rate of weight increase (SGR) per mussel stocking (percent/month). (d) Average weight gain per stocking during grow-out.Spat settlement onto artificial surfaces is highly dependent on shape and structure, so generalizations across areas, species and differing environmental conditions are difficult. Other researchers reported settlement densities for the Mediterranean mussel (Mytilus galloprovincialis) in the Black Sea of 3,450 ± 126 individuals per square meter. In India, where mussel culture has grown rapidly in recent years, the practice is based on natural spat fall on intertidal rocks, which is then collected as seed, and previous studies showed typical spat densities of 6,225 individuals per square meter on natural intertidal rocks in India. Therefore, our results indicate clearly suitable spat settlement densities for the establishment of mussel culture in Demak.Our site had relatively high current velocities which may influence settlement success in green mussels. We also found that spat collection was significantly higher with spat collector ropes suspended from longlines than when suspended from stakes. We speculate that the greater level of movement and water exposure might be the reason why collector ropes were more effective when hung from longlines.Also read: Researchers Succeed in Fortifying Oysters with VitaminsOur results also indicate higher growth rates and resulting weight yields for mussels grown in longline culture compared with mussels grown in stake culture. The only difference in culture conditions between the two methods was that the mussels grew in stockings attached to a stationary support with stake culture, while with longline culture they grew in a stocking that can move and turn with water currents, wind and wave action. Mussel growth obtained from the experiment was 24.3 grams and 22.9 grams for 75 days (2.5 months) of cultivation, respectively, for longlines and stakes. Therefore, average weight increments per mussel were 9.72 grams per month and 9.16 grams per month, respectively. These results were significantly higher than the mussel growth rates documented by other researchers.Density of mussel stocking numbers did have a significant effect on the growth but not on survival rate of individual mussels. It is common that higher stocking density leads to both lower average body weight and lower survival rate. However, in our study we did not observe lower survival rates. We speculate that general growth conditions under all examined stocking densities were so favorable that the mussels were not affected strongly enough to influence their survival.The differences in stocking density (20 to 50 mussels per stocking) did result in different growth rates for individual mussels but not in the total weight yield achieved by the mussel stockings. Low stocking density simply yielded fewer larger mussels, while higher stocking densities yielded more but smaller mussels for a similar total weight yield. Thus, it probably was not the filtering capacity of the mussels that ultimately limited weight yield but the total amount of water that the mussels were effectively exposed to. This should be a combined function of water flow, stocking size and shape, and any possible constraints caused, for example, by the use of the small‐meshed stockings.Also read: Innovation Award 2020 Finalist: Aquaterra from NuseedThe most recent review on the status of mangroves worldwide concluded that integrating human livelihood needs in mangrove conservation is necessary to achieve long‐term sustainability for mangrove forests. There is a great need to develop viable yet mangrove‐compatible livelihood alternatives for communities inhabiting mangrove areas. Such alternatives may include livelihoods based on mangrove‐supported fisheries, ecotourism or a multitude of other sustainable uses of mangrove products and resources. Unfortunately, very few of these alternatives have yet been developed beyond a purely artisanal level and the need for mangrove livelihood innovation and development has been stressed by several authors.Our results show that mussel culture using longlines for both spat collection and grow‐out at densities of 50 mussel seeds per stocking is a simple, low‐cost and easily adopted source of income for households in areas where other means of income generation have been lost or are limited. Culture of the species in other countries in the region has proven profitable and has developed into important sources of income and food for coastal communitiesAs an aquaculture practice, longlines are a mangrove‐friendly alternative livelihood as it does not require mangroves to be removed for pond construction. They can be placed alongside mangrove channels, in lagoons, inside abandoned ponds and in shallow marine areas seawards from the mangrove forests without any need to cut mangroves or excavate ponds. In fact, longline culture is even considered ideal for unprotected open‐sea culture conditions. Thus, mussel culture can serve as an economic incentive to preserve mangroves so the latter can be left intact to fulfil their many other important ecosystem functions.Environmental contamination is known to be a problem for shellfish in heavily populated areas along the north coast of Java. For Semarang and the area of concern, the situation is less clear, but at least two studies suggest that contamination levels are low enough for safe consumption. However, even though the coastal area of Demak is still largely rural and probably less contaminated, the issue of contamination deserves close attention.PerspectivesOur results showed that longlines present a feasible, more sustainable and more profitable alternative to stake mussel culture for mussel farmers in the Demak region in Central Java. Innovation towards a more significant mussel culture industry in Indonesia is long overdue and we believe that additional research towards methods of scaling up production, improved site selection and greater efficiency in the market value chain could further improve green mussel culture profitability, and thereby make it even more effective as a mangrove‐friendly alternative, livelihood option for the inhabitants of economically strained coastal communitiesSource: Aquaculture Alliance ...
Electrochemical Detection of WSSV With Disposable Electrode
The White Spot Syndrome Virus (WSSV) infects shrimp and causes White Spot Disease (WSD), which is considered one of the most lethal and costly virus pathogens in the cultured shrimp industry globally. Vaccination is always the most useful method for solving any viral infection, and a few attempts to induce an immune response and protect shrimp from WSSV infection have already been reported. But the results of these vaccination attempts are still poor considering their practical use. To avoid the risk of WSD in shrimp farming, it is important to have the means to quickly identify any infected shrimp.Current methods for detecting WSSV rely on polymerase chain reaction (PCR, a method widely used to rapidly make millions to billions of copies of a specific DNA sample) techniques using viral DNA or protein assays using a specific antibody, with a limit of detection, LOD (the lowest quantity of a substance that can be distinguished from the absence of that substance with at a confidence level of generally 99 percent) of a few hundred DNA copies per mL within four to 12 hours. Diagnostic PCR assays for use in aquaculture are limited by their cost and requirement of highly skilled operators. Other WSSV detection methods include other sophisticated techniques like dot blots, lateral flow assay and enzyme-linked immunosorbent assay (ELISA).Also read: Shrimp Aquaculture and Competitive Exclusion Of PathogensNanomaterials [materials with a single unit sized – in at least one dimension – between 1 and 100 nanometers (a unit of length in the metric system equal to one billionth of a meter, or 0.000000001 meter)] with unique physical, optical and electrochemical properties have been successfully used for high-sensitivity detection of various viruses. Electrochemical impedance spectroscopy (EIS) is a sensitive technique for the analysis of the properties and recognition of various molecular reactions, and through biosensors can directly detect various molecular events.For example, we have demonstrated the detection of hepatitis E virus with a manufactured biosensor electrode constituted by specific antibodies and nanomaterials based on an engineered impedimetric process.This article – adapted and summarized from the original [Takemura, K. et al. 2020. Electrochemical detection of white spot syndrome virus with a silicone rubber disposable electrode composed of graphene quantum dots and gold nanoparticle-embedded polyaniline nanowires. J Nanobiotechnol 18, 152 (2020)] – reports on a disposable electrode that can accurately detect WSSV and can have important applications in the aquaculture industry.Study setupFor detailed information on the highly technical process, equipment and materials used to manufacture the testing electrode – including the nanocomposite deposition on the sensor electrode as well as WSSV collection and pretreatment, and the detection of WSSV using the disposable electrode – refer to the original article.Also read: Innovation Award 2020 finalist: Simao Zacarias’ Shrimp Eyestalk Ablation ResearchResults and discussionThe disposable electrode we developed demonstrated during its testing a capability for detecting WSSV over a wide linear range, with high specificity and sensitivity. The sensor stability was also tested over more than one month to confirm its applicability for on-site virus detection.The electrical impedance (measure of the opposition that a circuit presents to a current when a voltage is applied) plot of the disposable electrode after incubation of different concentrations of the virus from 102 to 109 copies per mL are shown in Fig. 1a. The responses of the sensor electrodes increase with the concentration of WSSV due to the high resistance accumulation at the virus-loaded electrode. When WSSV binds to the sensing electrode, a large number of non-conducting virus particles cover the conducting surface, increasing the resistance.The calibration plot displays an excellent linear relationship between the resistance and the WSSV concentration (Fig. 1b). The limit of detection, LOD, was determined to be as low as 48.4 copies per mL – an extremely low and sensitive value with practical use. After the WSSV detection, the surface of the virus-loaded electrode exhibited a significantly increased roughness, indicating the presence of WSSV on the electrode.Fig. 1: WSSV detection using the disposable electrode. (a) Resistance plots for different concentrations of WSSV. Axis values in ohms, units used to measure electrical resistance. (b) Calibration curve of the corresponding impedance. The charge resistance value (Rct) is a measurement relevant to corrosion electrochemistry and electrochemical reactions. Each detection was performed three times and data are given as average ± SD (n = 3).We compared our sensing performance with various other WSSV detection methods. Many studies have successfully detected DNA, but it is not easy to implement on-site and rapid detection because of the need to extract DNA from the WSSV. Our detection system is practical because it shows high sensitivity, simplicity and adaptability for on-site detection.Regarding the selectivity and stability of the disposable electrode, and to confirm the specificity towards WSSV, various other viruses and some materials were also tested during our study with the sensor electrode. The sensor responses, except for WSSV, Fig. 2a), were similar to that of the bare electrode, indicating the sensor specificity for the target virus. The high selectivity of the sensors was achieved by its special coating with various materials and its effective cleaning. When many foreign substances were present and the non-specific adsorption occurred on the sensor surface, the substances other than the target WSSV were removed with a highly efficient washing solution, resulting in the high selectivity of our detection method.The stability of the disposable electrode was tested for eight weeks to observe its applicability for long-term usage. As depicted in Fig. 4b, the signal intensity after loading of 104 copies per mL of the virus remained at 86 percent until day 35. However, it dropped to 73.4 percent after 56 days of storage due to degradation of the antibody used.Fig. 2: (a) Selectivity test of the electrode coating used for WSSV detection compared with non-target viruses and various ions and other substances. (b) Stability test of the disposable electrode. The electrode was stored in the refrigerator for 56 days, and the detection performance was tested every week from the second week. Adapted from the original.After successful detection of WSSV in a buffer medium, virus samples were collected from 10 WSSV-infected shrimp and tested. Their DNA copy numbers were compared with the results obtained from this electrochemical detection technique. The overall trend of the PCR results for the samples showed outstanding similarity to the trend of the electrochemical sensor results, confirming the reproducibility of the sensor’s results. Overall, our data show that our sensing system has a higher sensitivity, by six to seven orders of magnitude, than other currently used testing techniques for WSSV like western blot, and can detect WSSV from infected animals in less than 20 minutes.Also read: Transcriptomic Analysis of Pacific White Shrimp in Response to AHPNDPerspectivesWe developed and validated a disposable electrode for the rapid and sensitive detection of the White Spot Syndrome Virus (WSSV) within 20 minutes. During testing, our sensor detected the virus over a wide linear range from 102 to 109 DNA copies per mL, with a limit of detection of 48.4 copies per mL. And the functionality of the disposable electrode was successfully demonstrated to have high selectivity and long-term stability for about five weeks.The sensing capability was also successfully tested for other viruses, suggesting its versatile applicability for future usage. The sensor was applied to detect the virus from WSSV-infected, aquacultured shrimp, and found to be comparable with currently used PCR analysis, which confirmed its applicability as an excellent monitoring system for real-time virus detection.This is the first demonstration of the detection of WSSV by a nanofabricated sensing electrode with high sensitivity, selectivity and stability, suggesting its potential as a diagnostic tool to monitor WSSV in the aquaculture industry. This detection system could play an important role in controlling the spread of WSSV for on-site detection systems at shrimp production facilities.Photo by Fernando Huerta.Source: Aquaculture Alliance ...
Sintasan dan Pertumbuhan Larva Ikan Patin yang Diberi Artemia Mengandung Vitamin C
PendahuluanSampai saat ini larva ikan patin (Pangasionodon sp.) produktivitasnya masih perlu ditingkatkan. Berdasarkan data KKP (2012) kebutuhan ikan patin konsumsi di Indonesia mencapai 155.000 ton/tahun, sedangkan produksi ikan patin konsumsi di Indonesia masih 145.000 ton/tahun. Peningkatan produksi ikan patin konsumsi ini perlu didukung oleh ketersediaan benih patin yang baik. Oleh karena itu, perlu dilakukan penelitian untuk meningkatkan kelangsungan hidup larva ikan patin agar didapatkan benih berkualitas dan kontinuitas sehingga produksi di tingkat pembenihan meningkat. Pakan yang biasa digunakan pada saat stadia larva hingga larva menjadi benih yang berukuran 19,05 mm adalah Artemia (Artemia salina) dan tubifex (Tubifex sp.). Menurut Gammanpila et al. (2007) vitamin C diperlukan ikan untuk perkembangan larva, proses kematangan gonad, serta kualitas gamet. Walaupun artemia telah mengandung vitamin C , diduga masih perlu ditambahkan, sehingga perlu penelitian untuk mengetahui dosis yang tepat sehingga dapat memenuhi kebutuhan vitamin C pada larva ikan patin.Peningkatan kelangsungan hidup pada stadia larva dapat dilakukan dengan menambahkan nutrien pada pakan alami dengan pengayaan (Stottrup et al. 2003). Salah satu yang dapat dilakukan yaitu penambahan vitamin C dalam pakan alami. Penelitian ini bertujuan mengetahui pengaruh pemberian vitamin C dengan dosis berbeda, yaitu 50, 100, dan 150 mgL pada media pengayaan artemia yang digunakan sebagai pakan alami terhadap kelangsungan hidup dan pertumbuhan larva ikan patin.Baca juga: Cara Mudah Supaya Larva Ikan Mas Cepat TumbuhBahan dan Metode Penelitian ini diawali dengan pembuatan emulsi vitamin C dosis 50, 100, dan 150 mg/L, kemudian emulsi tersebut dimasukkan ke dalam media pemeliharaan artemia yang baru ditetaskan selama 24 jam sesuai dengan dosis perlakuan. Artemia yang telah diperkaya kemudian diberikan pada larva ikan patin selama tujuh hari pemeliharaan.Pembuatan emulsi vitamin CSebelum dilakukan pembuatan emulsi, vitamin C murni digerus dengan mortar, kemudian ditimbang sesuai dengan perlakuan yaitu dosis 50, 100, dan 150 mg/L. Bahan-bahan yang ditambahkan untuk pembuatan emulsi vitamin C disajikan pada Tabel 1.Langkah pertama yang dilakakuan adalah kuning telur dicampur dengan minyak ikan, kemudian dihomogenkan dengan vorteks selama satu menit. Setelah homogen, vitamin C dimasukkan ke dalam campuran kuning telur dan minyak ikan sebagai bahan pengemulsi, kemudian dihomogenkan kembali selama satu menit hingga terbentuk emulsi berwarna putih.Terakhir emulsi ditambahkan dengan akuades 10 mL dan dihomogenkan selama 0,5 menit sehingga terbentuk larutan sebagai bahan untuk dicampurkan pada media pengayaan artemia. Hasil pembuatan emulsi dapat segera digunakn dan sisanya dapat disimpan di dalam lemari pendingin. Emulsi yang telah dibuat dapat digunakan untuk empat kali perlakuan pengayaan. Penggunaan minyak ikan juga digunakan sebagai sumber nutrien lain.Baca juga: Teknologi Artemia INVE Terbaru dan Optimalisasi Penetasan ArtemiaProses penetasan artemiaArtemia ditetaskan dalam wadah plastic dengan volume 1,5 L yang telah dilubangi bagian bawahnya dan pada bagian tutup disambung dengan selang aerasi dan pengatur air dan udara. Wadah diletakkan secara terbalik dan dilapisi dengan plastik hitam yang dapat dilihat pada Gambar 1.Wadah penetasan diisi dengan 1 L air tawar kemudian ditambahkan garam sebanyak 30 gram. Penambahan garam dilakukan agar salinitas air meningkat menjadi 30 ppt. Setelah itu, 1 g siste artemia dimasukkan ke dalam wadah penetas dan diberi aerasi keras selama 24 jam sehingga siste artemia dapat teraduk dengan baikSetelah 24 jam, dilakukan pemanenan artemia dengan cara aerasi dimatikan (sebelumnya aliran udara pada selang ditutup dengan pengatur aliran udara) dan selang diarahkan pada saringan artemia dengan membuka secara perlahan pengatur aliran air pada selangPemanenan dilakukan setelah cangkang siste terpisah dan mengapung sampai air berada hingga tutup botol wadah penetasan. Hal ini dilakukan agar cangkang siste tidak ikut tersaring dan terbawa pada hasil panen. Artemia yang telah dipanen kemudian dibilas dengan air tawar dan dimasukkan ke dalam wadah pengayaan. Pada saat penelitian proses kultur dan panen artemia dilakukan sebanyak empat kali sehari.Proses pengayaan artemiaWadah pengayaan artemia yang digunakan adalah wadah plastik 300 mL yang telah dilubangi bagian bawahnya dan pada tutupnya disambung dengan selang aerasi dan pengatur aliran air dan udara. Kemudian wadah diletakkan terbalik yang dapat dilihat pada Gambar 2.Wadah pengayaan diisi dengan 200 mL air tawar dan ditambah dengan 6 g garam. Kemudian pada media pengayaan ditambah dengan 0,5 m emulsi vitamin C sesuai perlakuan. Nauplii artemia yang telah dipanen dengan kepadatan 1 naupli/mL dimasukkan ke dalam media pengayaan dan dipanen setelah 10, 12, dan 14 jam untuk tiga kali pemberian pakan larva. Pada penelitian di digunakan tiga wadah pengayaan dan satu wadah untuk artemia tanpa pengayaan pada setiap perlakuan sehingga pada pemanenan dilakukan panen secara total. Artemia yang telah dipanen kemudian dibilas dengan air tawar dan langsung diberikan pada larva ikan patin. Proses pengayaan artemia dilakukan empat kali sehari, sedangkan pemanenan artemia dilakukan 12 kali sehari sesaat sebelum pemberian pakan pada larva ikan patin. Baca juga: Manajemen Pakan Pada Pemeliharaan Larva Udang VanamePemeliharaan larva ikanLarva ikan patin dipelihara pada akuarium berukuran 15x15x20 cm3 yang diletakkan pada akuarium besar yang berukuran 40x50x60 cm3 . Pada masing-masing akuarium besar diisi dengan lima akuarium kecil, thermostat, dan thermometer yang dapat dilihat pada Gambar 3. Thermostat dipasang pada akuarium besar untuk menjaga agar suhu air tetap stabil antara 29-30 ⁰C. Pemasangan instalasi aerasi dilakukan dengan cara menghubungkan selang aerasi ke titik aerasi yang terdapat pada pipa yang telah dihubungkan dengan blower. Pada setiap akuarium dipasang satu titik aerasi dengan selang yang diberi pengatur aliran udara untuk mengatur besar kecilnya gelembung udara aerasi.Setelah itu dilakukan, pengisian air pada akuarium kecil sebanyak 3 L dan akuarium besar sebanyak 120 L dengan kualitas air suhu 28-32 ⁰C, pH 7-8, kandungan oksigen terlarut 6,2-6,7 mg/L, alkalinitas 32-36 mg/L, kesadahan 31,39 – 35,88 mg/L, dan total amonia nitrogen dalam air 0,16-0,17 mg/L.Larva ikan patin yang digunakan adalah larva yang baru menetas dengan ukuran bobot awal 0,7±0,1 mg/ekor dan panjang 39,04±2,62 mm, yang masih mengandung kuning telur (cadangan makanan pada larva). Sebelum ditebar larva dalam wadah plastik diapungkan di akuarium besar selama 15 menit agar suhu air yang berada di wadah plastik sama dengan suhu air yang berada di dalam akurium. Larva ikan patin ditebar pada masing-masing akuarium kecil dengan padat tebar 40 ekor/L. Larva kemudian diberi pakan artemia yang telah diperkaya dengan vitamin C dosis 0, 50, 100, dan 150 mg/L dengan kepadatan artemia 1 indvidu/mL, dan frekuensi pemberian artemia 12 kali sehari setiap dua jam hingga tujuh hari masa pemeliharaan. Pemberian pakan larva dilakukan dengan cara artemia yang berada pada wadah pengayaan dipanen secara total, kemudian artemia dibilas dengan air tawar dan dimasukkan ke dalam mangkuk yang sebelumnya telah diisi dengan air tawar sebanyak 250 mL. Setelah itu, 250 mL air tawar yang telah berisi artemia dengan kepadatan 1 individu/mL dibagi lima untuk pakan larva pada lima akuarium kecil sebagai ulangan pada setiap perlakuan. Jadwal kegiatan pemeliharaan dapat dilihat pada Tabel 2. Parameter ujiParameter uji yang diamati adalah kadar vitamin C pada artemia yang sudah diperkaya selama 10-14 jam, kelangsungan hidup dan pertumbuhan larva ikan patin selama tujuh hari. Kelangsungan hidup adalah jumlah larva yang hidup selama penelitian dibandingakan dengan jumlah larva pada awal pemeliharaan dan dinyatakan dalam persen. Parameter pertumbuhan yang diamati adalah panjang total dan bobot individu larva di akhir penelitian.Analisis statistikAnalisis statistik dilakukan menggunakan rancangan acak lengkap (RAL) dengan lima ulangan. Parameter dianilisis menggunakan analisis sidik ragam (ANOVA) dengan uji lanjutan Duncan.Analisis kimiaAnalisis kimia yang dilakukan pada penelitian adalah analisis kadar vitamin C dalam tubuh artemia dengan teknik titrasi metode Rasanu et al. (2005). Pengukuran kadar protein dengan metodel Kjeldahl dan lemak dalam tubuh artemia dengan metode folch, serta dilakukan analisis kualitas airAnalisis biologiDi akhir penelitian 30 ekor ikan pada setiap akuarium diukur biomassa akhir menggunakan timbangan digital ketelitian 0,00001 mg, kemudian dihitung bobot rata-rata individu ikan. Panjang larva di akhir penelitian diukur menggunakan kertas milimeter blok ketelitian 1 mm.Hasil dan PembahasanPengkayaan artemiaPengaruh pengayaan artemia dengan vitamin C dosis berbeda terhadap kadar vitamin C, kadar lemak, dan kadar protein artemia pada setiap perlakuan disajikan pada Tabel 3. Penambahan vitamin C hanya berpengaruh pada kadar vitamin C dalam tubuh artemia, sedangkan untuk kadar lemak dan protein dalam tubuh artemia tidak terpengaruhi.Semakin tinggi dosis vitamin C yang diberikan maka semakin tinggi kandungan vitamin C yang terdapat pada tubuh artemia. Menurut Ahn et al. (2009) faktor penting yang harus diperhatikan pada saat pemilihan pakan artemia adalah ukuran partikel pakan yang kurang dari 50 µm, daya cerna makanan, nilai nutrisi, dan kelarutan dalam media kultur yang dianjurkan, yaitu yang kelarutannya minimal. Kadar lemak artemia berkisar antara 21,14-24,43% dan kadar protein berkisar antara 43,55-48,52%. Akbary et al. (2011) menyatakan bahwa nauplii artemia yang baru menetas mengandung 11,44% kadar lemak dan 61,7% kadar protein.Baca juga: Maggot, Pakan Alternatif Berprotein Tinggi untuk IkanKinerja pertumbuhan larvaPada akhir penelitian dilakukan penghitungan jumlah dan pengukuran bobot serta panjang larva untuk mengetahui pengaruh pemberian artemia yang diperkaya vitamin C terhadap kelangsung hidup dan pertumbuhan larva ikan patin yang dapat dilihat pada Tabel 4. Pemberian vitamin C dengan dosis 100 mg/L memiliki tingkat kelangsungan hidup dan penambahan bobot tertitinggi, namun tidak berpengaruh pada panjang total larva. Sedangkan pada dosis vitamin C 150 mg/L menghasilkan tingkat kelangsungan hidup terendah dan menurunkan panjang total larva.Vitamin C adalah mikronutrien yang hanya sedikit dibutuhkan oleh tubuh dan akan berdampak buruk bila dikonsumsi secara berlebihan. Vitamin C diabsorbsi secara akitf di dalam tubuh dan secara difusi pada bagian atas usus halus, lalu masuk ke peredaran darah melalui vena porta yang didistribusi ke seluruh tubuh.Vitamin C berperan dalam proses pemeliharaan terhadap membran mukaosa yang dapat berpengaruh terhadap fungsi kekebalan dan peningkatan daya tahan terhadap infeksi. Selan itu juga vitamin C membantu dalam pertumbuhan serta penyembuhan luka dan perdarahan di bawah kulit. Vitamin C berfungsi untuk pertumbuhan, kebutuhan metabolisme basal tubuh, dan reproduksi ikan (NRC, 2011; Bae et al. 2012). Beberapa hasil penelitian menunjukkan bahwa pemberian vitamin C pada pakan dapat meningkatkan kelangsungan hidup dan pertumbuhan ikan dan udang. Penggunaan vitamin C dengan dosis 50 mg/L media pengayaan rotifer dapat meningkatkan kelangsungan hidup larva udang vaname (Darvishpour et al., 2012). Penambahan vitamin C dengan dosis 40,3 mg/kg pakan menghasilkan kelangsungna hidup ikan golden shiner tertinggi (Chen et al., 2003; Chen et al., 2004)Nilai minimal kebutuhan vitamin C bagi pertumbuhan normal ikan secara umum antara 30-1500 mg/kg pakan (Halver & Hardy, 2003). Defisiensi vitamin C dapat menyebabkan pertumbuhan menurun, perubahan warna kulit, erosi sirip dan kulit, dan kerusakan filament insang yang dapat menyebabkan tingkat kematian tinggi (Wang et al, 2003).Menurut Halver & Hardy (200) hipervitaminosis vitamin C dapat menyebabkan overload Fe yang berpengaruh pada kerusakan hati, jantung, dan pancreas yang dapat menyebabkan kematian. Keracunan vitamin C juga disebabkan karena larva ikan gagal menskresikan kelebihan vitamin C dalam tubuhnya.Penambahan vitamin C pada artemia dapat memberikan asupan vitamin C sehingga larva ikan patin tidak mengalami defisiensi, tetapi kadar vitamin C-nya masih kurang sehingga penambahan vitamin C dapat diberikan sampai dengan dosis 100 mg/L.KesimpulanPemberian artemia diperkaya vitamin C dosis 100 mg/L sebagai pakan alami selama tujuh hari memberikan kelangsungan hidup dan pertumbuhan larva ikan patin terbaik. Sebaliknya, pemberian Artemia yang diperkaya vitamin C 150 mg/L memberikan kinerja pertumbuhan yang rendah.Sumber Jurnal:Setiawati M, Putri D, Jusadi D. 2013. Sintasan dan pertumbuhan larva ikan patin yang diberi artemia mengandung vitamin C. Jurnal Akuakultur Indonesia. 12(2): 136-143Tentang MinapoliMinapoli merupakan marketplace++ akuakultur no. 1 di Indonesia dan juga sebagai platform jaringan informasi dan bisnis akuakultur terintegrasi. Dengan memanfaatkan teknologi, pembudidaya dapat menemukan produk akuakultur dengan mudah dan menghemat waktu di Minapoli. Platform ini menyediakan produk-produk akuakultur dengan penawaran harga terbaik dari supplier yang terpercaya. Selain itu, bentuk dukungan Minapoli untuk industri akuakultur adalah dengan menghadirkan tiga fitur utama yang dapat digunakan oleh seluruh pembudidaya yaitu Pasarmina, Infomina, dan Eventmina. ...
Many fishes migrate long distances to spawn. In order to better understand these movements, scientists have classified these migrations into several categories.Anadromous fish are born in freshwater, then migrate to the ocean as juveniles where they grow into adults before migrating back into freshwater to spawn.Examples: salmon, smelt, American shad, hickory shad, striped bass, lamprey, gulf sturgeonCatadromous fish are born in saltwater, then migrate into freshwater as juveniles where they grow into adults before migrating back into the ocean to spawn.Examples: American eel, European eel, inanga, shortfin eel, longfin eelAmphidromous fish are born in freshwater/estuaries, then drift into the ocean as larvae before migrating back into freshwater to grow into adults and spawn.Examples: bigmouth sleeper, mountain mullet, sirajo goby, river goby, torrentfish, Dolly VardenPotamodromous fish are born in upstream freshwater habitats, then migrate downstream (still in freshwater) as juveniles to grow into adults before migrating back upstream to spawn.Examples: sicklefin redhorse, lake sturgeon, robust redhorse, flathead catfish Oceanodromous fish are born near spawning grounds, then drift on ocean currents as larvae before settling as juveniles to grow into adults before migrating back to spawning grounds.Examples: black grouper, mutton snapper, goliath grouper Although these different types of migration classifications may be difficult to pronounce, they are important to understand in order to help maintain connectivity between critical habitats.Source: thefisheriesblog.com ...