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The aims of this review are to describe the role of 'blue‐food production' (animals, plants and algae harvested from freshwater and marine environments) within a circular bioeconomy, discuss how such a framework can help the sustainability and resilience of aquaculture and to summarise key examples of novel nutrient sources that are emerging in the field of fed‐aquaculture species. Aquaculture now provides >50% of the global seafood supply, a share that is expected to increase to at least 60% within the next decade. Aquaculture is an important tool for reducing resource consumption in global protein production and increasing resilience to climate change and other global disruptions (i.e. pandemics, geo‐political instability). Importantly, blue foods also provide essential nutrition for a growing human population. Blue foods are helping to help the global goal of 'zero hunger' (United Nation's Sustainable Development Goal 2) while reducing the dependency on finite natural resources but further refinement and new solutions are needed to make the industry more 'circular' and sustainable, particularly with respect to sourcing raw materials for aquafeeds. This review describes the feed resources that are available or may be created within a circular bioeconomy framework, their role within the framework and in aquaculture and ultimately, how these resources contribute to de‐risking and establishing a resilient aquaculture production chain. [ABSTRACT FROM AUTHOR]

While there is a growing need to increase farm fish production to meet food security needs of a growing population, humane slaughter treatments are not well understood. Use of sedative agents prior to slaughter can facilitate a more rapid and humane slaughter process. The present study was undertaken to evaluate the effects of implementing preslaughter electrosedation on the quality and consumer acceptance of farmed rainbow trout. A consumer sensory panel (n = 65) was conducted comparing rainbow trout slaughtered according to two methods: (1) immersion in an ice-water slurry (Control) or (2) immersion in an ice-water slurry immediately preceded by electrosedation (Electrosedation). Results from a sensory triangle test determined that there was no significant difference between the two fish harvested by different methods. These results suggest that electrosedation does not impact the sensory quality of farmed rainbow trout. This demonstrates that preslaughter electrosedation effectively aligns interests regarding animal welfare, efficiency, and product quality in the production of farm rainbow trout. This is an important finding as the results could provide insights for treating fish humanely without sacrificing the quality while meeting the demands of a highly regulated industry. [ABSTRACT FROM AUTHOR]

Problem statement: In the past, aquafeeds were comprised largely of fish meal and fish oil derived from marine reduction fisheries. In addition to being highly palatable and readily digested by cultured fishes, these feedstuffs were historically inexpensive sources of protein, energy and essential nutrients. However, increasing cost and concerns over safety and sustainability have greatly incentivized the transition from fish meal and oil to alternative sources of protein and lipid for aquafeed formulation. Fish oil replacement is proving more difficult than originally anticipated, particularly for marine carnivorous species. Approach: If complete fish oil replacement is not a viable goal for fish nutritionists and aquafeed manufacturers, at a minimum, we must strive for judicious use of limited marine-derived resources. In the present review, we explore the opportunities of using rendered fats as alternatives to marine-derived fish oils in aquaculture feeds, beginning with a discussion of the products themselves before reviewing the most recent literature and concluding with a discussion of the future of these products in aquafeed formulations. Results: Rendered fats have not been as intensively evaluated in aquaculture nutrition as grain and oilseed-derived lipids, although a number of recent publications on the subject suggest increasing interest in the use of rendered products in aquafeeds. Conclusion: Poultry fat, beef tallow, pork lard and to a lesser extent, yellow/restaurant grease and catfish oil, have been investigated individually or in combination with other lipids in feeds for a broad range of cultured taxa with generally acceptable results. Key words: Aquaculture, fish oil, alternative lipid, rendering, fatty acid, fish nutrition, INTRODUCTION In the past, aquafeeds were comprised largely of products derived from marine reduction fisheries, i.e., fish meal and fish oil. In addition to being highly palatable and readily digested [...]

The omega-3 sparing effect of saturated fatty acids: A reason to reconsider common knowledge of fish oil replacement It was discovered that some species - largely omnivores - were able to sufficiently synthesise LC-PUFA from C SB 18 sb polyunsaturated fatty acids (C SB 18 sb PUFA), such as 18:2n-6 and 18:3n-3 found in terrestrial lipids. Keywords: aquafeed; DHA; EPA; fatty acids; fish nutrition EN aquafeed DHA EPA fatty acids fish nutrition 213 217 5 12/03/21 20220101 NES 220101 OPINION Fish oil (FO) is four times more expensive than it was 30 years ago,1 yet it remains the most economical source of eicosapentaenoic acid (20:5n-3, EPA), docosahexaenoic acid (22:6n-3, DHA) and other long-chain polyunsaturated fatty acids (LC-PUFA) for aquafeeds. A more accurate term would be "LC-PUFA sparing effect", as SFA and MUFA are known to spare n-6 and n-3 LC-PUFA like 20:4n-6, 20:5n-3 and 22:6n-3, but not n-6 and n-3 C SB 18 sb PUFA like 18:2n-6 and 18:3n-3. [Extracted from the article]

The National Research Council (NRC) reports that the essential fatty acid requirements of Rainbow Trout Oncorhynchus mykiss can be satisfied by 0.7–1.0% 18:3(n‐3) or 0.4–0.5% n‐3 long‐chain (LC) polyunsaturated fatty acids (PUFAs; defined by NRC as 20:5[n‐3] + 22:6[n‐3]) in the diet. These requirements were defined roughly 50 years ago and do not consider the importance of n‐6 PUFAs in the diet. Therefore, we assessed survival, growth performance, and tissue fatty acid composition of juvenile Rainbow Trout (mean initial weight ± SE = 24.6 ± 0.1 g; 10 fish/tank, 4 tanks/diet) that were fed experimental diets (53% protein; 13% lipid) containing fish oil, fully hydrogenated soybean oil, or fully hydrogenated soybean oil with five different combinations of fatty acid ethyl esters (18:2[n‐6], 18:3[n‐3], 20:4[n‐6], 20:5[n‐3], and 22:6[n‐3]) to illuminate the relative essentiality of n‐3 and n‐6 PUFAs. Final individual weight (78.2–132 g), weight gain (216–433%), feed conversion ratio (0.93–1.42), specific growth rate (2.05–2.98% body weight/d), and hepatosomatic index (1.4–2.1) were significantly affected by dietary treatment whereby Rainbow Trout that received the fish oil‐based diet outperformed all other treatments. Growth of fish that were given different combinations of fatty acid ethyl esters was not statistically different. Fatty acid tissue composition generally reflected dietary treatment, with the greatest profile changes observed in intraperitoneal fat, fillet, and liver and the smallest changes occurring in brain and eye tissues. Results largely validate previous reports indicating that Rainbow Trout are physiologically able to synthesize LC‐PUFAs from C18PUFAs and therefore do not necessarily require LC‐PUFA‐rich feeds. However, numeric increases in the growth of Rainbow Trout suggest that this species achieves an energetic advantage if offered n‐3 and n‐6 LC‐PUFAs in the diet. [ABSTRACT FROM AUTHOR]

Understanding fatty acid requirements in multiple taxa is necessary to determine the degree to which dietary fish oil can be reduced or replaced with less costly, more abundant lipid sources. The polyunsaturated fatty acid (PUFA) requirements of hybrid Striped Bass (White Bass Morone chrysops × Striped Bass M. saxatilis) are currently reported as 0.5–1.0% eicosapentaenoic acid (20:5n‐3) and/or docosahexaenoic acid (22:6n‐3). This requirement does not account for n‐3 PUFA essentiality on an individual fatty acid basis and does not address possible requirements for n‐6 PUFAs (i.e., linoleic acid [18:2n‐6] or arachidonic acid [20:4n‐6]). Accordingly, hybrid Striped Bass were fed diets containing selected individual n‐3 and n‐6 C18PUFAs, n‐3 and n‐6 long‐chain (LC) PUFAs, or combinations thereof to determine the essentiality or expendability of these nutrients. These experimental feeds were compared to feeds containing only saturated fatty acids (negative control) or menhaden fish oil (positive control). Growth performance and ratios of 22:5n‐6 : 22:6n‐3 observed in tissue fatty acid profiles suggested that dietary provision of 22:6n‐3 was adequate to satisfy physiological demand for LC‐PUFAs. However, reductions in feed conversion ratio and numeric improvements in growth suggest that dietary provision of 20:4n‐6 is also important. Results of this study indicate that provision of C18PUFAs alone is insufficient to avoid essential fatty acid deficiency and to support optimal growth of this fish. To ensure that essential fatty acid requirements are met and performance is optimized, diets for hybrid Striped Bass should be formulated to contain 22:6n‐3 and 20:4n‐6, if not a full complement of n‐3 and n‐6 LC‐PUFAs. [ABSTRACT FROM AUTHOR]

Nile Tilapia Oreochromis niloticus have a reported dietary requirement for the n‐6 C18 polyunsaturated fatty acid (PUFA) 18:2n‐6 (linoleic acid), but direct provision of the n‐6 long‐chain (LC) PUFA 20:4n‐6 (arachidonic acid) may be a more efficient approach. No quantitative requirement for n‐3 fatty acids has been formally recognized for tilapias, but beneficial effects of having both n‐3 and n‐6 PUFAs in the diet have been reported. To better understand PUFA essentiality in tilapias, we formulated diets to assess the growth performance and tissue fatty acid composition of juvenile Nile Tilapia (mean ± SD = 25.7 ± 0.2 g/fish) that were fed different combinations of n‐3 and n‐6 PUFAs: a positive control containing menhaden fish oil, a negative control containing hydrogenated soybean oil, and experimental diets containing hydrogenated soybean oil amended with ethyl esters of 18:3n‐3; 18:3n‐3 and 18:2n‐6; 22:6n‐3; 22:6n‐3 and 20:4n‐6; or 20:5n‐3, 22:6n‐3, and 20:4n‐6. After 7 weeks, weight gain, feed conversion ratio, and specific growth rate were significantly greater among fish that received the positive control feed than among fish that were fed the negative control feed. The addition of n‐3 and n‐6 PUFA supplements generally improved performance in most cases. No fish showed any gross indications of fatty acid deficiency, although significant differences in fatty acid deficiency indicator ratios (i.e., 20:3n‐9 : 20:4n‐6 and 22:5n‐6 : 22:6n‐3) were present in all tissues analyzed. Nile Tilapia that were fed an n‐3 PUFA‐free diet exhibited significantly elevated 22:5n‐6 : 22:6n‐3 ratios, indicating a developing n‐3 PUFA deficiency. Feeding n‐3 PUFAs—as 18:3n‐3, 22:6n‐3, or a combination of n‐3 LC‐PUFAs—had a corrective effect on these ratios, affirming the importance of a proper balance of n‐3 and n‐6 PUFAs to satisfy the essential fatty acid requirements of Nile Tilapia and further illustrating the ability of this species to satisfy physiological demand for LC‐PUFAs through de novo biotransformation of C18PUFAs. [ABSTRACT FROM AUTHOR]

Antibiotic use in animal production, including aquaculture, has become a controversial subject in recent years. It is unclear whether antibiotic use by fish hatcheries or farms is functionally related to the development of resistance in important human pathogens. Nevertheless, antimicrobial resistance is relevant to aquaculture because it may reduce the effectiveness of the limited treatment options available for fish health management. We used linear regression models to explore possible temporal trends in antibiotic susceptibility of several bacterial fish pathogens over a 20‐year period at 12 Idaho Department of Fish and Game (IDFG)‐operated hatcheries. Observed antibiotic susceptibility was variable among hatcheries and among pathogens. Predicted susceptibility was generally unchanged or increased on average over the study period, suggesting no significant loss in susceptibility to the antibiotics tested. Collectively, our results indicate that fish health management, including occasional antibiotic treatment, has not substantively influenced antibiotic susceptibility of pathogens at IDFG‐operated hatcheries. [ABSTRACT FROM AUTHOR]