Global fishmeal and fish-oil supply: inputs, outputs and markets

Exploring the Potential of Atlantic Mesopelagic Species Processed on Board Commercial Fishing Vessels as a Source of Dietary Lipids

This study investigates the use of untapped mesopelagic species as a source of long-chain polyunsaturated omega-3 fatty acids (LC n-3 PUFAs) to meet the growing demand. The challenges faced by commercial fishing vessels, such as varying catch rates and species distribution affecting lipid levels, are addressed. Marine oils were produced post-catch using thermal separation and enzymatic hydrolysis during four commercial cruises, screening approximately 20,000 kg of mixed mesopelagic species. Maurolicus muelleri and Benthosema glaciale were the dominant species in the catch, while krill was the primary bycatch. The lipid composition varied, with B. glaciale having a higher prevalence of wax esters, while triacylglycerols and phospholipids were more predominant in the other species. LC n-3 PUFAs ranged from 19% to 44% of lipids, with an average EPA + DHA content of 202 mg/g of oil. Both processing methods achieved oil recoveries of over 90%. Estimates indicate that the mesopelagic biomass in the Northeast Atlantic could supply annual recommended levels of EPA + DHA to 1.5 million people, promoting healthy heart and brain functions. These findings offer valuable insights for considering mesopelagic species as a potential source of dietary marine lipids, laying the groundwork for further research and innovation in processing and obtaining valuable compounds from such species.

The application of protease in aquaculture: Prospects for enhancing the aquafeed industry

Low-fishmeal and protein-saving diets are two prominent nutritional strategies utilized to address challenges related to the scarcity and sustainability of protein sources in aquaculture. However, these diets have been associated with adverse effects on the growth performance, feed utilization, and disease resistance of aquatic animals. To mitigate these challenges, exogenous protease has been applied to enhance the quality of diets with lower protein contents or fishmeal alternatives, thereby improving the bioavailability of nutritional ingredients. Additionally, protease preparations were also used to enzymatically hydrolyze fishmeal alternatives, thus enhancing their nutritional utilization. The present review aims to consolidate recent research progress on the use of protease in aquaculture and conclude the benefits and limitations of its application, thereby providing a comprehensive understanding of the subject and identifying opportunities for future research.

Microalgae as fishmeal alternatives in aquaculture: current status, existing problems, and possible solutions

Fishmeal is an indispensable ingredient for most aquatic animals. However, the finite supply and escalating price of fishmeal seriously limit its use in aquaculture. Thus the development of new, sustainable protein ingredients has been a research focus. Microalgae are potential fishmeal alternatives owing to their high protein content and balanced amino acid profile. Studies suggest that suitable replacement of fishmeal with microalgae is beneficial for fish growth performance, but excessive replacement would induce poor growth and feed utilization. Therefore, this paper aims to review research on the maximum substitutional level of fishmeal by microalgae and propose the main issues and possible solutions for fishmeal replacement by microalgae. The maximum replacement level is affected by microalgal species, fish feeding habits, quality of fishmeal and microalgal meals, and supplemental levels of fishmeal in the control group. Microalgae could generally replace 100%, 95%, 95%, 64.1%, 25.6%, and 18.6% fishmeal protein in diets of carp, shrimp, catfish, tilapia, marine fish, and salmon and trout, respectively. The main issues with fishmeal replacement using microalgae include low production and high production cost, poor digestibility, and anti-nutritional factors. Possible solutions to these problems are recommended in this paper. Overall, microalgae are promising fishmeal alternatives in aquaculture.

Antioxidant, Antibacterial Properties of Novel Peptide CP by Enzymatic Hydrolysis of Chromis notata By-Products and Its Efficacy on Atopic Dermatitis

This study investigated the antioxidant, antimicrobial, and anti-atopic dermatitis (AD) effects of a novel peptide (CP) derived from a Chromis notata by-product hydrolysate. Alcalase, Flavourzyme, Neutrase, and Protamex enzymes were used to hydrolyze the C. notata by-product protein, and the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical-scavenging activity was measured. Alcalase hydrolysate exhibited the highest ABTS radical-scavenging activity, leading to the selection of Alcalase for further purification. The CHAO-1-I fraction, with the highest ABTS activity, was isolated and further purified, resulting in the identification of the peptide CP with the amino acid sequence Ala-Gln-Val-Met-Lys-Leu-Pro-His-Arg-Met-Gln-His-Ser-Gln-Ser. CP demonstrated antimicrobial activity against Staphylococcus aureus, inhibiting its growth. In a 2,4-dinitrochlorobenzene (DNCB)-induced AD-like skin model in mice, CP significantly alleviated skin lesions, reduced epidermal and dermal thickness, and inhibited mast cell infiltration. Moreover, CP suppressed the elevated levels of interleukin-6 (IL-6) in the plasma of DNCB-induced mice. These findings highlight the potential of CP as a therapeutic agent for AD and suggest a novel application of this C. notata by-product in the fish processing industry.

Environmental and biodiversity performance of a novel single cell protein for rainbow trout feed

Seafood has an important role to play to achieve a sustainable food system that provides healthy food to a growing world population. Future seafood production will be increasingly reliant on aquaculture where feed innovation is essential to reduce environmental impacts and minimize feed and food competition. This study aimed to investigate whether a novel single cell protein feed ingredient based on Paecilomyces variotii grown on a side stream from the forest industry could improve environmental sustainability of farmed rainbow trout (Oncorhynchus mykiss) by replacing the soy protein concentrate used today. A Life Cycle Assessment including commonly addressed impacts but also the rarely assessed biodiversity impacts was performed. Furthermore, feeding trials were included for potential effects on fish growth, i.e., an assessment of the environmental impacts for the functional unit 'kg feed required to produce 1 kg live-weight rainbow trout'. Results showed that the best experimental diet containing P. variotii performed 16-73 % better than the control diet containing soy protein concentrate in all impact categories except for energy demand (21 % higher impact). The largest environmental benefits from replacing soy protein with P. variotii in rainbow trout diets was a 73 % reduction of impact on biodiversity and halved greenhouse gas emissions. The findings have high relevance for the aquaculture industry as the production scale and feed composition was comparable to commercial operations and because the effect on fish growth from inclusion of the novel ingredient in a complete diet was evaluated. The results on biodiversity loss from land use change and exploitation through fishing suggest that fishery can dominate impacts and exclusion thereof can greatly underestimate biodiversity impact. Finally, a novel feed ingredient grown on side streams from the forest industry has potential to add to food security through decreasing the dependence on increasingly scarce agricultural land resources.

Modeling the effects of ration on individual growth of Oncorhynchus tshawytscha under controlled conditions

Fed aquaculture is one of the fastest-growing and most valuable food production industries in the world. The efficiency with which farmed fish convert feed into biomass influences both environmental impact and economic revenue. Salmonid species, such as king salmon (Oncorhynchus tshawytscha), exhibit high levels of plasticity in vital rates such as feed intake and growth rates. Accurate estimations of individual variability in vital rates are important for production management. The use of mean trait values to evaluate feeding and growth performance can mask individual-level differences that potentially contribute to inefficiencies. Here, the authors apply a cohort integral projection model (IPM) framework to investigate individual variation in growth performance of 1625 individually tagged king salmon fed one of three distinct rations of 60%, 80%, and 100% satiation and tracked over a duration of 276 days. To capture the observed sigmoidal growth of individuals, they compared a nonlinear mixed-effects (logistic) model to a linear model used within the IPM framework. Ration significantly influenced several aspects of growth, both at the individual and at the cohort level. Mean final body mass and mean growth rate increased with ration; however, variance in body mass and feed intake also increased significantly over time. Trends in mean body mass and individual body mass variation were captured by both logistic and linear models, suggesting the linear model to be suitable for use in the IPM. The authors also observed that higher rations resulted in a decreasing proportion of individuals reaching the cohort's mean body mass or larger by the end of the experiment. This suggests that, in the present experiment, feeding to satiation did not produce the desired effects of efficient, fast, and uniform growth in juvenile king salmon. Although monitoring individuals through time is challenging in commercial aquaculture settings, recent technological advances combined with an IPM approach could provide new scope for tracking growth performance in experimental and farmed populations. Using the IPM framework might allow the exploration of other size-dependent processes affecting vital rate functions, such as competition and mortality.

Egg production, egg quality, and fatty acids profiles in eggs and tissues in Lohmann LSL lite hens fed algal oils rich in docosahexaenoic acid (DHA)

Enriching eggs with omega-3 fatty acids (n-3 FA), such as docosahexaenoic acid (DHA), is a well-accepted practice that benefits the egg industry and consumers. However, issues around cost, sustainability, and product acceptance have necessitated the search for alternatives to feeding hens fish oil for DHA enrichment. The effects of feeding 2 algal oils on egg production and DHA enrichment in eggs and selected tissues were investigated. The algal oils were: 1) OmegaPro (OPAO) standardized algal oil for DHA content and 2) Crude algal oil (CAO). A total of 400, 46-wk-old Lohmann LSL lite hens were housed in enriched cages (10 birds/cage) and allocated 5 diets (n = 8) for a 12-wk trial. The iso-caloric and -nitrogenous diets were a standard corn and soybean meal diet, standard plus 0.25 or 0.76% OPAO and standard plus 0.23 or 0.69% CAO; algal oils diets supplied similar DHA at each level. Egg production indices (hen day egg production, feed intake, FCR, egg weight, egg mass, and eggshell quality) were monitored for 10 wk. Diet samples were analyzed for fatty acids (FA) on wk 1, 6, and 12 and eggs on wk 4, 5, 6, 9, and 12. At the end of the trial, one hen/cage was weighed and dissected for liver, breast and thigh for FA and long bones for ash content analyses. Concentration of omega-6 to omega-3 FA ratio was 12.9, 6.64, 3.48, 6.96, and 3.59 for standard, 0.23 and 0.76% OPAO, 0.25 and 0.69% CAO, respectively. Algal oils increased (P ≤ 0.046) eggshell thickness linearly. The concentration of DHA in the eggs from the birds fed the standard, 0.23 and 0.76% OPAO, 0.25 and 0.69% CAO was 84, 195, 286, 183, and 297 mg/100g egg, respectively, and algal oils enriched eggs with DHA linearly and quadratically (P ≤ 0.01). In conclusion, algal oils increased the concentration of DHA in eggs and had no adverse effects on egg production and eggshell quality.

Foodborne Diseases in the Edible Insect Industry in Europe-New Challenges and Old Problems

Insects play a key role in European agroecosystems. Insects provide important ecosystem services and make a significant contribution to the food chain, sustainable agriculture, the farm-to-fork (F2F) strategy, and the European Green Deal. Edible insects are regarded as a sustainable alternative to livestock, but their microbiological safety for consumers has not yet been fully clarified. The aim of this article is to describe the role of edible insects in the F2F approach, to discuss the latest veterinary guidelines concerning consumption of insect-based foods, and to analyze the biological, chemical, and physical hazards associated with edible insect farming and processing. Five groups of biological risk factors, ten groups of chemical risk factors, and thirteen groups of physical risks factors have been identified and divided into sub-groups. The presented risk maps can facilitate identification of potential threats, such as foodborne pathogens in various insect species and insect-based foods. Ensuring safety of insect-based foods, including effective control of foodborne diseases, will be a significant milestone on the path to maintaining a sustainable food chain in line with the F2F strategy and EU policies. Edible insects constitute a new category of farmed animals and a novel link in the food chain, but their production poses the same problems and challenges that are encountered in conventional livestock rearing and meat production.

Microorganisms in Fish Feeds, Technological Innovations, and Key Strategies for Sustainable Aquaculture

Aquaculture, the world's fastest growing food sector, produces over half of all fish for human consumption. Aquaculture feeds include fishmeal and fish oil, extracted from wild-caught fish such as sardines, and poses ecological, food security, and economic drawbacks. Microalgae, yeasts, fungi, bacteria, and other alternative ingredients show promise as potential ingredients in aquafeeds that provide protein/amino acids, lipids, or omega-3 sources and sources of bioactive molecules. This review article discusses the issues that the literature often lacks data on, such as the recent development of using microorganisms, technological innovation, challenges, and opportunities to develop a low environmental footprint of aquaculture diet. The ingredients often require novel processing technology to improve digestibility and fish growth and reduce antinutritional factors. This is an important gap to fill because microalgae are the most frequently used organism in fish feed, particularly as a dietary supplement or mixed with other ingredients. The production, processing, and formulating steps can affect the nutritional qualities. Stepwise strategies are required to evaluate these ingredients for feed application, and in this article, I articulated the stepwise key approaches of evaluating nutritional and environmental response metrics to develop highly sustainable aquaculture feed using these microorganisms, which would guide a more judicious inclusion of these novel ingredients.

Assessing fisheries nutrient yields: The Northwest Atlantic, 1950-2014

Fisheries are important sources of nutrients for people, but fisheries science and management do not consider nutrient information. The result is that fisheries are conducted without knowledge of how exploited species portfolios produce nutrients, how these yields have changed over time, and how they may change in the future. Here, we develop approaches for nutrient-informed analysis, and illustrate their use by applying them to catches from northwest Atlantic fisheries from 1950 to 2014. Relative to catch weights, nutrient yields showed more change over time and greater degrees of concentration in fewer taxa. Species that were minor from a weight perspective were identified as key sources of specific nutrients. Atlantic herring (Clupea harengus) emerge as a cornerstone of regional nutrient yields, with recent yields of some nutrients so disproportionately reliant upon herring as to indicate a potential lack of resilience. Insights such as these emphasize the need for nutrient informed approaches to fisheries assessment.

Impact of face mask microplastics pollution on the aquatic environment and aquaculture organisms

Microplastic pollution in our environment, especially water bodies is an emerging threat to food security and human health. Inevitably, the outbreak of Covid-19 has necessitated the constant use of face masks made from polymers such as polypropylene, polyurethane, polyacrylonitrile, polystyrene, polycarbonate, polyethylene, or polyester which eventually will disintegrate into microplastic particles. They can be broken down into microplastics by the weathering action of UV radiation from the sun, heat, or ocean wave-current and precipitate in natural environments. The global adoption of face masks as a preventive measure to curb the spread of Covid-19 has made the safe management of wastes from it cumbersome. Microplastics gain access into aquaculture facilities through water sources and food including planktons. The negative impacts of microplastics on aquaculture cannot be overemphasized. The impacts includes low growth rates of animals, hindered reproductive functions, neurotoxicity, low feeding habit, oxidative stress, reduced metabolic rate, and increased mortality rate among aquatic organisms. With these, there is every tendency of microplastic pollution to negatively impact fish production through aquaculture if the menace is not curbed. It is therefore recommended that biodegradable materials rather than plastics to be considered in the production of face mask while recycle of already produced ones should be encouraged to reduce waste.

A simple method to isolate fatty acids and fatty alcohols from wax esters in a wax-ester rich marine oil

Calanus finmarchicus is one of the most important zooplankton species in the North Atlantic. The zooplankton is currently being harvested and industrially processed to a marine oil product for human consumption as a marine nutraceutical containing long-chain omega-3 polyunsaturated fatty acids. This oil is very rich in wax esters, a lipid class where fatty acids are esterified to long chain fatty alcohols. In this paper we describe a simple method to 1) isolate the wax esters from the other lipid classes present in the oil, 2) hydrolyze the wax esters, and 3) separate the fatty acids from the fatty alcohol, all by means of solid phase extraction. Starting with an average of 322 mg Calanus oil, we obtained 75 mg fatty alcohols and 63 mg fatty acids. Contrary to previously described techniques, our method neither oxidize the fatty alcohols to fatty acids, nor are the fatty acids methylated, allowing the native, unesterified fatty acids and fatty alcohols to be used for further studies, such as in cell culture experiments to study the metabolic effects of these specific lipid fractions rather than the intact oil or wax esters.

Optimal Levels of Fish Meal and Methionine in Diets for Juvenile Litopenaeus vannamei to Support Maximum Growth Performance with Economic Efficiency

This work investigated the optimal levels of fish meal (FML) and dietary methionine (Met) required for maximum growth performance of juvenile Litopenaeus vannamei with economic efficiency. Four sets of diets were prepared to contain 0.00, 6.00, 12.00 and 18.00% FML. Each set was supplemented with DL-methionyl-DL-methionine (DL-Met-Met) to result in a total dietary Met (Met + Cys) content of 0.58 (1.05), 0.69 (1.16), and 0.82% (1.29%), on a fed basis. Shrimp of 1.00 ± 0.08 g were stocked in 60 outdoor tanks of 1 m³ with 100 shrimp/m², allowing five replications per dietary group. Shrimp in all the groups were fed 10 times daily for 70 days. In a subsequent trial, dietary protein and amino acid digestibility of four FML groups, but only at high dietary Met levels (~0.82%), were evaluated in 40 60 L indoor tanks (11 replicates per diet) for 93 days with 70 shrimp/m². Final shrimp survival (92.85 ± 4.82%, mean ± standard deviation), weekly weight gain (1.17 ± 0.08 g), apparent feed intake (13.3 ± 0.5 g of feed per stocked shrimp), and feed conversion ratio (1.18 ± 0.06) were unaffected by dietary FML level and Met content. Gained yield was adversely affected when FML was reduced from 18 and 12% (1156 and 1167 g/m², respectively) to 0 (1090 g/m²), but no change was observed at 6% (1121 g/m²). A significant interaction was detected between FML level and dietary Met. Under 0 and 6% FML conditions, higher levels of total dietary Met, 0.69 and 0.82%, respectively, were required to maximize shrimp BW. In comparison, at 12 and 18% FML, a dietary Met content of only 0.58% was sufficient. Overall, results indicated the use of FML can be minimized or completely eliminated without major detrimental effects on feed digestibility or shrimp growth performance, as long as proper supplementation of Met is carried out. Diets with 0 FML or with only 6% delivered the highest profit and return on investment compared to diets with higher levels.

Effects of Replacing Fishmeal with Defatted Black Soldier Fly (Hermetia illucens Linnaeus) Larvae Meal in Japanese Eel (Anguilla japonica) Diet on Growth Performance, Fillet Texture, Serum Biochemical Parameters, and Intestinal Histomorphology

An 8-week feeding trial was conducted to investigate the effects of replacing fishmeal with defatted black soldier fly larvae meal (DBSFLM) in the diets of Japanese eel on their growth performance, fillet texture, serum biochemical parameters, and intestinal histomorphology. Six isoproteic (520 g kg^-1), isolipidic (80 g kg^-1), and isoenergetic (15 MJ kg^-1) diets were formulated with fishmeal replacement levels of 0% (R0), 15% (R15), 30% (R30), 45% (R45), 60% (R60), and 75% (R75). The growth performance, feed utilization efficiency, survival rate, serum liver function enzymes, antioxidant ability, and lysozyme activity of fish were not affected (P > 0.05) by DBSFLM. However, the crude protein and cohesiveness of the fillet in groups R60 and R75 significantly decreased, and the fillet hardness significantly increased (P < 0.05). Additionally, the intestinal villus length significantly decreased in the R75 group, and the goblet cell densities were significantly lower in the R45, R60, and R75 groups (P < 0.05). Overall, high levels of DBSFLM did not affect growth performance and serum biochemical parameters but significantly altered fillet proximate composition and texture and intestinal histomorphology (P < 0.05). The optimal fishmeal replacement level is 30% with 184 g kg^-1 DBSFLM.

Substituting fish meal with castor meal in diets of hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂): Effects on growth performance, immune response, antioxidant and digestive enzyme activities, gut morphology, and inflammatory-related gene expression

The present study was conducted to investigate the effects of replacing fishmeal (FM) with castormeal (CM) on the growth performance, immune response, antioxidant and digestive enzyme activities, intestinal morphology, and expression of inflammatory-related genes in juvenile hybrid grouper (Epinephelus fuscoguttatus♀ ×E. lanceolatus♂). Six iso-nitrogenous (50% crude protein) and iso-lipidic (10% crude lipid) diets were formulated; namely, a reference diet (FM) containing 50% FM and five experimental diets (4% (CM4), 8% (CM8), 12% (CM12), 16% (CM16), and 20% (CM20)) in which FM protein was substituted with CM at varying levels to feed fish (initial weight: 9.12 ± 0.01 g) for 8 weeks. The results showed that the final weight, weight gain rate, and specific growth rate were highest in the FM, CM4, and CM8 groups, whereas the feed conversion ratio, hepatosomatic and viscerosomatic indexes were significantly enhanced in the CM4 group in comparison to the others. The CM4 and CM12 groups were observed to show the highest intestinal length index values compared to the other groups, with the CM20 revealing the worst growth performance. The serum total protein content first increased (P < 0.05) in the CM4 group and decreased (P < 0.05) afterward. Nonetheless, a decreasing significant (P < 0.05) cholesterol and triglyceride contents were witnessed with the increasing replacement of FM with CM. Compared to the control group, a significant increase (P < 0.05) in the activities of serum and liver immunoglobulin-M, superoxide dismutase, glutathione peroxidase, total antioxidant capacity, and complement-3 (except serum activity for CM12 group); liver lysozyme; intestinal amylase, and lipase, was witnessed in the CM groups. However, the serum lysozyme activity was highest (P < 0.05) in the CM4 group and lowest in the CM20 group. While the least serum malondialdehyde contents were observed in the CM4 group, that of the liver malondialdehyde was least witnessed in the FM, CM4, CM8, CM12, and CM16 groups as compared to the CM20. The intestinal histological examination revealed a significantly decreasing trend for villi height and villi width with increasing replacement levels. However, the muscle thickness, crypt depth, and type II mucus cells first increased upto 4% replacement level and later decreased. The increasing of dietary replacement levels significantly up-regulated pro-inflammatory (il-1β, tnf-α, myd88, ifn-γ, tlr-22, and il-12p40) and down-regulated anti-inflammatory (il-10, tgf-β, mhc-iiβ) and anti-bacterial peptide (epinecidin and hepcidin) mRNA levels in the intestine. The mRNA levels of il-6 was up-regulated firstly upto 4 and 8% replacement levels, and later down-regulated with increasing replacement. These results suggested that, although higher dietary CM replacement enhances the immune, antioxidant and digestive enzymes, it aggravates intestinal inflammation. Replacing 4 and 8% of FM with CM could enhance the growth performance of fish.

Food system by-products upcycled in livestock and aquaculture feeds can increase global food supply

Many livestock and aquaculture feeds compete for resources with food production. Increasing the use of food system by-products and residues as feed could reduce this competition. We gathered data on global food system material flows for crop, livestock and aquaculture production, focusing on feed use and the availability of by-products and residues. We then analysed the potential of replacing food-competing feedstuff-here cereals, whole fish, vegetable oils and pulses that account for 15% of total feed use-with food system by-products and residues. Considering the nutritional requirements of food-producing animals, including farmed aquatic species, this replacement could increase the current global food supply by up to 13% (10-16%) in terms of kcal and 15% (12-19%) in terms of protein content. Increasing the use of food system by-products as feed has considerable potential, particularly when combined with other measures, in the much-needed transition towards circular food systems.

Effects of Decreasing Fishmeal as Main Source of Protein on Growth, Digestive Physiology, and Gut Microbiota of Olive Flounder (Paralichthys olivaceus)

Simple Summary

The demand for fishmeal is increasing due to aquaculture development, but the supply is unstable. This indicates the need to reduce the fishmeal content in the feed and develop an optimal fish-feed formulation through substitutes. However, most studies on reducing fishmeal content in feed were conducted at the laboratory level. In this study, the application of a low-fishmeal diet as feed to olive flounder was evaluated in terms of growth-related factors, digestive physiology, and microbiota raised for five months in a fish farm using four feed formulations- FM70 [control (CON), 70% fishmeal], FM45 (45% fishmeal), FM35A (35% fishmeal), and FM35B (35% fishmeal + insect meal). There was no difference in growth-related factors, digestive physiology, and gut microbiota diversity compared with the CON-fed fish. Therefore, reducing the fishmeal content of the feed by up to 35% does not adversely affect growth and physiological characteristics under farm conditions.

Abstract

In olive flounder (Paralichthys olivaceus), growth performance, expression of growth-related factors, digestive physiology, and gut microbiota were assessed under farm conditions in the fish fed diets with low levels of fishmeal. Four experimental diets were prepared, FM70 [control (CON), 70% fishmeal], FM45 (45% fishmeal), FM35A (35% fishmeal), and FM35B (35% fishmeal + insect meal), and fed to the fish for five months. The CON-fed fish had the highest plasma GH, but IGF-1 and hepatic IGF-1 mRNA expression of the olive flounder fed diets with low-fishmeal levels did not significantly differ among diets. The intestinal villus length, muscular thickness, and the number of goblet cells were statistically similar, and ocular examination of hepatopancreas showed no discernable difference in all experimental diets. The chymotrypsin content of FM35B-fed fish is significantly lower, but trypsin and lipase contents are similar. The diversity of gut microbiota did not differ among groups, although the FM35B group had a higher composition of Firmicutes. Thus, a diet with reduced fishmeal content and several alternative protein sources can be used as feed ingredients in feed formulation for olive flounder reared under typical aquaculture farm conditions.

The judicious use of finite marine resources can sustain Atlantic salmon (salmo salar) aquaculture to 2100 and beyond

The production of farmed Atlantic salmon (Salmo salar) is currently linked to finite marine resources, particularly fish oil (FO) and fish meal (FM). Understanding this relationship in a quantitative manner is imperative if this critical balance is to be maintained within sustainable limits as the industry grows. Here we project the potential production and associated growth of the Atlantic salmon aquaculture industry on the basis of a variety of FO and FM utilization scenarios in aquafeed. Reducing FO and FM dietary inclusion to 3% each could permit production growth of 2% per year until the turn of the century (2097 and beyond 2100, respectively), independent of a host of alternatives now being utilized-with three portions of salmon per week providing almost all the recommended weekly long-chain omega-3 fatty acids for human intake. The Atlantic salmon industry's positive annual growth can continue in an era of finite marine resource availability-without the need for additional finite marine resource inputs.

Egg quality and laying performance of Julia laying hens fed with black soldier fly (Hermetia illucens) larvae meal as a long-term substitute for fish meal

The use of insects in animal feed appears to be an efficient approach that contributes to solving the environmental issues related to leftover disposal; however, it has not been approved in some countries due to concerns about pathogenic infections. This study aimed to evaluate the feasibility of long-term substitution of fish meal in poultry feed with organic defatted black soldier fly larvae (BSFL) meal prepared from BSFL raised on leftovers. The 87 Julia laying hens (178-day-old) were allotted in a completely randomized design with three treatments (29 layers in each treatment). The laying hens were fed maize grain and soybean meal-based diet containing either 3% fish meal, 1.5% fish meal and 1.5% BSFL meal, or 3% BSFL meal supplements for 52 wk (541-day-old). Results showed that substituting fish meal with BSFL meal had no effect on the laying rate, feed intake, and feed conversion ratio of laying hens, and only the complete replacement (3% BSFL meal) significantly increased the body weight of laying hens. In terms of egg quality, there was no significant effect on eggshell parameters (weight, thickness, and strength), albumen weight, yolk height, yolk color, and Haugh unit. However, both half (1.5% fish meal and 1.5% BSFL meal) and complete substitution of fish meal increased yolk weight (P < 0.01) and egg weight (P < 0.05). In conclusion, even if BSFL were fed leftovers and the meal was defatted with organic solvents, it can be used as a poultry feed ingredient without any adverse effect. Moreover, the complete substitution of fish meal with BSFL meal may be a feasible way to effectively contribute to the laying hens' performances and poultry farming costs. In addition to fish meal, the replacement of soybean meal with BSFL meal may also needs to be further studied for the extensive BSFL meal application in poultry feed.

Microalgae-Based PUFAs for Food and Feed: Current Applications, Future Possibilities, and Constraints

Microalgae are currently considered an attractive source of highly valuable compounds for human and animal consumption, including polyunsaturated fatty acids (PUFAs). Several microalgae-derived compounds, such as ω-3 fatty acids, pigments, and whole dried biomasses are available on the market and are mainly produced by culturing microalgae in open ponds, which can be achieved with low setup and maintenance costs with respect to enclosed systems. However, open tanks are more susceptible to bacterial and other environmental contamination, do not guarantee a high reproducibility of algal biochemical profiles and productivities, and constrain massive cultivation to a limited number of species. Genetic engineering techniques have substantially improved over the last decade, and several model microalgae have been successfully modified to promote the accumulation of specific value-added compounds. However, transgenic strains should be cultured in closed photobioreactors (PBRs) to minimize risks of contamination of aquatic environments with allochthonous species; in addition, faster growth rates and higher yields of compounds of interest can be achieved in PBRs compared to open ponds. In this review, we present information collected about the major microalgae-derived commodities (with a special focus on PUFAs) produced at industrial scale, as well genetically-engineered microalgae to increase PUFA production. We also critically analyzed the main bottlenecks that make large-scale production of algal commodities difficult, as well as possible solutions to overcome the main problems and render the processes economically and environmentally safe.

Ultra-Performance Liquid Chromatography-Mass Spectrometry-Based Untargeted Metabolomics Reveals the Key Potential Biomarkers for Castor Meal-Induced Enteritis in Juvenile Hybrid Grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂)

The intensification of aquaculture to help kerb global food security issues has led to the quest for more economical new protein-rich ingredients for the feed-based aquaculture since fishmeal (FM, the ingredient with the finest protein and lipid profile) is losing its acceptability due to high cost and demand. Although very high in protein, castor meal (CM), a by-product after oil-extraction, is disposed-off due to the high presence of toxins. Concurrently, the agro-industrial wastes’ consistent production and disposal are of utmost concern; however, having better nutritional profiles of these wastes can lead to their adoption. This study was conducted to identify potential biomarkers of CM-induced enteritis in juvenile hybrid-grouper (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂) using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) alongside their growth and distal intestinal (DI) health evaluation. A total of 360 fish (initial weight = 9.13 ± 0.01g) were randomly assigned into three groups, namely, fish-meal (FM) (control), 4% CM (CM4), and 20% CM (CM20). After the 56-days feeding-trial, the DI tissues of FM, CM4, and CM20 groups were collected for metabolomics analysis. Principal components analysis and partial least-squares discriminant-analysis (PLS-DA, used to differentiate the CM20 and CM4, from the FM group with satisfactory explanation and predictive ability) were used to analyze the UPLC-MS data. The results revealed a significant improvement in the growth, DI immune responses and digestive enzyme activities, and DI histological examinations in the CM4 group than the others. Nonetheless, CM20 replacement caused DI physiological damage and enteritis in grouper as shown by AB-PAS staining and scanning electron microscopy examinations, respectively. The most influential metabolites in DI contents identified as the potential biomarkers in the positive and negative modes using the metabolomics UPLC-MS profiles were 28 which included five organoheterocyclic compounds, seven lipids, and lipid-like molecules, seven organic oxygen compounds, two benzenoids, five organic acids and derivatives, one phenylpropanoids and polyketides, and one from nucleosides, nucleotides, and analogues superclass. The present study identified a broad array of DI tissue metabolites that differed between FM and CM diets, which provides a valuable reference for further managing fish intestinal health issues. A replacement level of 4% is recommended based on the growth and immunity of fish.

Next Generation Sequencing-based DNA metabarcoding for animal species profiling in fish feed

The expansion of worldwide aquaculture has been accompanied by extensive growth in the fish feed industry. However, improper labelling of many commercially available fish feeds has raised security and safety concerns over the species' origin of the ingredients. The inclusion of ruminants-derived ingredients in fish feed is prohibited according to EU legislation while porcine inclusion in fish feed has been a great concern among Muslim farmers. In contrast to the limited species that could be simultaneously determined using multiplex PCR, this study utilised Next Generation Sequencing-based DNA metabarcoding assay to determine the compositional profiles of animal species in fish feed samples in a more holistic manner. In relation to the religious issue associated with porcine-derived ingredients in fish feed, this study firstly aimed to determine the sensitivity of the methods in profiling fish feed adulterated with porcine blood and muscle tissues. Next, 10 commercially available fish feed samples were analysed. As a result, a detection limit of as low as 3% (w/w) porcine muscle and blood in the laboratory-prepared fish feed was obtained. The analysis of 10 commercial fish feeds shows surprising findings: 50% of the feeds contain Sus scrofa and 80% contain Bos taurus, a ruminant. Only one commercial fish feed was found to be solely composed of marine species. This study shows that commercial fish feeds sold in Malaysia contain undesirable animal species, and emphasises the need for accurate and legally enforced labelling of mammalian species in fish feed products.

Valorization of Side Stream Products from Sea Cage Fattened Bluefin Tuna (Thunnus thynnus): Production and In Vitro Bioactivity Evaluation of Enriched ω-3 Polyunsaturated Fatty Acids

The valorization of side streams from fishery and aquaculture value-chains is a valuable solution to address one of the challenges of the circular economy: turning wastes into profit. Side streams produced after filleting of sea cage fattened bluefin tuna (Thunnus thynnus) were analyzed for proximate composition and fatty acid profile to evaluate the possibility of producing tuna oil (TO) as a valuable source of ω-3 polyunsaturated fatty acids (PUFA) and testing its bioactivity in vitro. Ethyl esters of total fatty acids (TFA), obtained from TO, were pre-enriched by urea complexation (PUFA-Ue) and then enriched by short path distillation (SPD) up to almost 85% of the PUFA fraction (PUFA-SPe). The bioactivity of TFA, PUFA-SPe, and ethyl esters of depleted PUFA (PUFA-SPd) were tested in vitro, through analysis of lipid metabolism genes, in gilthead sea bream (Sparus aurata) fibroblast cell line (SAF-1) exposed to oils. TFA and PUFA-SPd upregulated transcription factors (pparβ and pparγ) and lipid metabolism-related genes (D6D, fas, fabp, fatp1, and cd36), indicating the promotion of adipogenesis. PUFA-SPe treated cells were similar to control. PUFA-SPe extracted from farmed bluefin tuna side streams could be utilized in fish feed formulations to prevent excessive fat deposition, contributing to improving both the sustainability of aquaculture and the quality of its products.

Sustainable Utilization of Fishery Waste in Bangladesh—A Qualitative Study for a Circular Bioeconomy Initiative

Living marine resources are limited; therefore, utilizing them sustainably is essential. Not all resources obtained from the sea are used adequately, causing discards, on-board waste, and by-products and waste on land. Recognition of the limited marine resources and increasing environmental pollution has emphasized the need for better utilization of by-products. Waste may include particles of flesh, skin, bones, entrails, shells or liquid stick water. Unfortunately, no fishery waste and by-product management initiatives or projects exist in Bangladesh; by-products are generally thrown into dustbins, ponds, rivers, and the sea. Bangladesh’s fish-processing waste and fishery by-products could be exported, providing a source of foreign currency earnings. Primary and secondary data were collected through documentary analysis, a literature review, and in-depth interviews (n = 129) with fishers and other relevant stakeholders regarding the challenges of Bangladesh’s sustainable fishery by-products and fish-processing waste. The data were analyzed thematically, guided by the most meaningful stories, and show that fish waste, or fishery by-products, should not be considered less valuable than the fish itself but is a precious and profitable resource capable of bringing health, social, economic, and environmental benefits. Our results reveal that fishery waste can expand local communities’, especially fishers’ and other workers’, potential for jobs or alternative income-generating tasks during fishing ban seasons. Finally, suggestions for managing fishery waste and fishery by-products are made to ensure improved and sustainable utilization via a circular bioeconomy.

Assessing the effectiveness of microplastic extraction methods on fishmeal with different properties

Microplastic presence in fishmeal is an emerging research area because of its potential to enter food chains, and the importance of fishmeal within global food security. However, fishmeal is a complex medium dependant on fish composition. This study measured properties (organics, carbonates, protein and density) of five fishmeal types (trimmings, sardine and anchovy, krill, tuna and salmon), sourced from locations worldwide (Norway, South America, Antarctica, Spain and Scotland). Microplastic recovery rates were compared for existing methodologies using sodium chloride overflows and potassium hydroxide digestions and then compared to newly developed methods. These methods included dispersants and calcium chloride density separations which were developed and designed to be environmentally conscious and affordable, which we argue should become an international standard approach for researchers. A calcium chloride overflow with dispersant and potassium hydroxide digestion provided the highest recovery rate in sardine and anchovy fishmeal (66.3%). Positive correlations with recovery rate were found with protein content, and negative correlations with organic content. Low recovery rates found here suggest microplastics in fishmeal reported in the literature are underestimated. With complex media such as fishmeal, attention must be paid to variation between types and composition when choosing methods and interpreting results.

Projecting global mariculture production and adaptation pathways under climate change

The sustainability of global seafood supply to meet increasing demand is facing several challenges, including increasing consumption levels due to a growing human population, fisheries resources over-exploitation and climate change. Whilst growth in seafood production from capture fisheries is limited, global mariculture production is expanding. However, climate change poses risks to the potential seafood production from mariculture. Here, we apply a global mariculture production model that accounts for changing ocean conditions, suitable marine area for farming, fishmeal and fish oil production, farmed species dietary demand, farmed fish price and global seafood demand to project mariculture production under two climate and socio-economic scenarios. We include 85 farmed marine fish and mollusc species, representing about 70% of all mariculture production in 2015. Results show positive global mariculture production changes by the mid and end of the 21^st century relative to the 2000s under the SSP1-2.6 scenario with an increase of 17%±5 and 33%±6, respectively. However, under the SSP5-8.5 scenario, an increase of 8%±5 is projected, with production peaking by mid-century and declining by 16%±5 towards the end of the 21^st century. More than 25% of mariculture-producing nations are projected to lose 40%-90% of their current mariculture production potential under SSP5-8.5 by mid-century. Projected impacts are mainly due to the direct ocean warming effects on farmed species and suitable marine areas, and the indirect impacts of changing availability of forage fishes supplies to produce aquafeed. Fishmeal replacement with alternative protein can lower climate impacts on a subset of finfish production. However, such adaptation measures do not apply to regions dominated by non-feed-based farming (i.e. molluscs) and regions losing substantial marine areas suitable for mariculture. Our study highlights the importance of strong mitigation efforts and the need for different climate adaptation options tailored to the diversity of mariculture systems, to support climate-resilient mariculture development.

Fatty Acid Composition and Contents of Fish of Genus Salvelinus from Natural Ecosystems and Aquaculture

Fatty acids (FA) of muscle tissue of Salvelinus species and its forms, S. alpinus, S. boganidae, S. drjagini, and S. fontinalis, from six Russian lakes and two aquacultures, were analyzed. Considerable variations in FA compositions and contents were found, including contents of eicosapentaenoic and docosahexaenoic acids (EPA and DHA), which are important indicators of fish nutritive value for humans. As found, contents of EPA+DHA (mg·g⁻¹ wet weight) in muscle tissue of Salvelinus species and forms varied more than tenfold. These differences were supposed to be primarily determined by phylogenetic factors, rather than ecological factors, including food. Two species, S. boganidae and S. drjagini, had the highest EPA+DHA contents in their biomass and thereby could be recommended as promising species for aquaculture to obtain production with especially high nutritive value. Basing on revealed differences in FA composition of wild and farmed fish, levels of 15-17-BFA (branched fatty acids), 18:2NMI (non-methylene interrupted), 20:2NMI, 20:4n-3, and 22:4n-3 fatty acids were recommended for verifying trade label information of fish products on shelves, as the biomarkers to differentiate wild and farmed charr.

Production of rainbow trout (Oncorhynchus mykiss) using black soldier fly (Hermetia illucens) prepupae-based formulations with differentiated fatty acid profiles

The aquaculture sector is expanding rapidly and needs an increasing supply of fishery products. To ensure an ecological transition of this sector, alternative feed ingredients are required for fish nutrition. Potential alternatives include insects, particularly the black soldier fly (BSF, Hermetia illucens L. 1758), which is being increasingly targeted for their nutritional qualities and their sustainable production practices. BSF have a well-balanced amino acid profile; however, their fatty acid profile is not sufficiently balanced for most aquafeed formulations but can be modulated through their feed. In this study, two different batches of BSF prepupae (BSFP) were firstly produced: BSFP with a standard ω3 content (C18:3n-3 ≈ 1.36%) and ω3-enriched BSFP (C18:3n-3 ≈ 9.67%). Then, three isoproteic, -lipidic and -energetic trout feeds were formulated and produced: one control and two feeds containing 75% BSF meal as a substitute for fish meal (standard vs ω3-enriched-BSF). Finally, a trout feeding trial (n = 3 for each feed batch) in a recirculating aquaculture system was carried out for 75 days. BSFP meal inclusion in trout diets did not impact most nutritional and growth parameters of trout compared to the control; however, the coefficient of fatness increased, weight gain decreased and fatty acid profiles of fillets were altered. In conclusion, this study presents a more sustainable model of trout production by including insects from bioconversion of local byproducts in aquafeed.

A New Biorefinery Approach for the Full Valorisation of Anchovy Residues: Use of the Sludge Generated during the Extraction of Fish Oil as a Nitrogen Supplement in Anaerobic Digestion

Several anchovies species are captured all over the world; they are consumed fresh but also preserved by the industry, either by brine-fermentation or canning in oil. The industrial process generates large amounts of residue (about 50% of the original fish biomass) that is generally used to produce fish flour. In this paper, the advancement of a recently proposed process for the full valorisation of anchovies aimed at the extraction of fish oil (to be used as an omega-3 source) and at the production of biomethane through anaerobic digestion is presented. Particularly, in the experiments presented, a co-digestion of anchovy sludge—used as a nitrogen supplement—and market waste (5% and 95% on a Total Solids basis) was performed. Since the proposed extraction process uses, as a green-solvent, d-limonene, the well-known problems of toxicity for the anaerobic biomass must be overcome during the digestion process. As discussed below, the granular activated carbon (GAC) is used to reclaim and improve anaerobic digestion processes in a reactor displaying clear signs of inhibition. In fact, GAC demonstrates multiple benefits for anaerobic digestion, such as adsorption of toxic substances, biomass selection, and triggering of direct interspecies electron transfer (DIET).

Fishmeal replacement by periphyton reduces the fish in fish out ratio and alimentation cost in gilthead sea bream Sparus aurata

Aquaculture threatens natural resources by fishing down the sea to supply fishmeal. Alternative protein sources in aquafeeds can provide a solution, particularly those that are waste from other operations and thereby reduce feed production costs. Toward this goal, we examined the waste biomass of marine periphyton from biofilters of an integrated multi-trophic aquaculture (IMTA) system as a replacement for fishmeal in diets of gilthead seabream (Sparus aurata). Four isoproteic (41%) and isolipidic (16.7%) aquafeeds were formulated with increased content of periphyton and a corresponding decrease in fishmeal from 20 to 15, 10, or 0%. The growth and biochemical content of seabream fingerlings (initial body weight 10 g) were examined over 132 days. Replacing 50% of fishmeal by waste periphyton improved feed conversion ratio (1.2 vs. 1.35 in the control diet) without harming fish growth. The complete replacement of fishmeal with periphyton resulted in 15% slower growth but significantly higher protein content in the fish flesh (59 vs. 52% in the control diet). Halving fishmeal content reduced feed cost by US$ 0.13 kg⁻¹ feed and saved 30% in the cost of conversion of feed to fish biomass (US$ 0.58 kg⁻¹ produced fish vs. $0.83 in the control diet). Finally, the total replacement of fishmeal by waste periphyton in the diet reduced the fish in—fish out ratio to below 1 (0.5–0.9) as compared to 1.36 in the control diet. Replacing fishmeal with on-farm produced periphyton minimizes aquaculture footprint through the removal of excess nutrients in effluents and the use of waste biomass to reduce the ‘fish in’ content in aquafeeds and fish production costs. The present study demonstrates the great practical potential of this dual use of marine periphyton in enhancing the circular economy concept in sustainable fish production.

Does dietary incorporation level of pea protein isolate influence the digestive system morphology in rainbow trout (Oncorhynchus mykiss)?

In the present study, fish meal (FM) was replaced by pea (Pisum sativum) protein (PP) in diet for Rainbow trout (Oncorhynchus mykiss) at levels of 0% (PP0), 25% (PP25), 50% (PP50), 75% (PP75) and 100% (PP100), and the effect of dietary PP level on the digestive system tracts and liver was investigated by micromorphological and histopathological evaluations. Morphometric measurements (mm 100g fish^-1 ) of the liver width and stomach length in rainbow trout were found to be significantly larger (p <0.05) in fish with high-level pea protein as the main protein source (PP75, PP100) compared to the low-level PP replacement group (PP25). No significant differences were found in morphometric measurements for pyloric caecum and intestines among treatment groups, whereas the number of the caecum of fish fed the PP25 diets significantly increased over the control (PP0) (p<0.05). In the histological examination of the liver, mild hydropic and vacuolar degeneration was observed in all experimental groups except PP0 and PP25. The measurements of pyloric caecum fold height, enterocyte length and width of tunica muscularis of the high-level pea protein groups of PP75 and PP100 were significantly higher (p <0.05) compared to the control group. In conclusion, 25% substitution of PP can be suggested for FM in trout diets, because the findings of the present study provided evidence that the digestive system improved by increasing the number of pyloric caecum at this replacement level.

Insect-Based Feed Ingredients for Aquaculture: A Case Study for Their Acceptance in Greece

Simple Summary

Since 2017, insects can be used as ingredients in aquafeeds in the EU. However, insect-based aquafeeds are still not broadly accepted by European aquaculture companies. Understanding the beliefs of people associated with the aquaculture sector on the use of insect-based fish diets could assist their adoption. In the present study, we ran a survey among the participants of an aquaculture conference held in Greece, in order to ask them what they think regarding the inclusion of insect meal in aquafeeds. Furthermore, we inquired nine Greek aquaculture and aquafeed companies about this issue. Greece is among the largest farmed fish producers in the EU; however, there are currently no data available on the acceptance of insect-based aquafeeds in Greece. Based on our results, the majority of the respondents were aware and in favor of the inclusion of insects in aquafeeds, mainly due to their potential to lower fishing pressure on wild fish stocks used for fishmeal production and enhance the ecological footprint and sustainability of aquaculture. Moreover, six out of nine companies were favorably disposed towards the use of insects in fish diets and four of them were willing to produce or use such diets. Further studies are warranted towards this direction.

Abstract

Although the inclusion of insects in fish diets is officially allowed in the EU since 2017, insect-based aquafeeds have not been widely adopted by the European aquaculture sector. In order to investigate the perceptions related with adoption trends, it is critical to explore the beliefs of people associated with the aquaculture sector on the use of insects in farmed fish diets. A survey was conducted among 228 participants of an aquaculture conference to explore their perceptions on the inclusion of insect meal in fish diets. Additionally, we investigated the attitudes of nine companies operating in the aquaculture and aquafeed sector in Greece that attended the conference towards this direction. The findings of the conference survey provide evidence that there is a wide-range awareness and acceptance regarding the use of insect-based feeds in farmed fish diets among the respondents. This is mainly driven by the expectations for the decline in fishing pressure on wild fish stocks, the reduction of the ecological footprint and the enhancement of the sustainability of the aquaculture sector. The results of the stakeholder survey show that six out of the nine companies that participated in the survey are favorably disposed towards the use of insect-based feeds. Specifically, four of them stated that they would produce or use aquafeeds based on insects. However, the results highlight the need for further research on the implementation of the wider adoption of insect-based feeds in aquaculture. The present study provides some first insights into the use of insect-based aquafeeds in Greece, for which there are no data available.

A Cursory Look at the Fishmeal/Oil Industry From an Ecosystem Perspective

By supporting the fishmeal industry, are we competing with marine predators? Should we be taking away food from marine predators to subsidize agriculture? If not for human consumption, should forage fish be left in the sea for predators? Are there more sustainable alternatives to fishmeal; can the fishing industry be part of developing these? These are all pressing questions being posed by marine scientists, particularly in the light of the increasing aquaculture industry and associated increasing demand in recent decades for fishmeal and oil to sustain cultured fish. We concisely summarize the global context of marine sourced fishmeal and then use the South African marine ecosystem as a working example. This article draws on research into the trophic role of forage fish in marine ecosystems and ponders whether a reduced demand for fishmeal, given increasing global pressures such as climate change, could benefit marine ecosystems, fisheries on predatory species, and vulnerable marine predators.

Farmed Gilthead Sea Bream (Sparus aurata) by-Products Valorization: Viscera Oil ω-3 Enrichment by Short-Path Distillation and In Vitro Bioactivity Evaluation

This study shows a pilot scale protocol aimed to obtain an omega 3-enriched oil after the processing of farmed gilthead sea bream viscera (SBV); this was oil was tested in vitro for bioactivity, attesting to the possibility to turn waste into profit The quality of the oil, in terms of requirements for animal and human consumption, was assessed by determining some chemical parameters, such as peroxide value (PV), thiobarbituric acid reactive substances (TBARS), ρ-anisidine (ρ-AV) content, total oxidation value (TOTOX), and phospholipids and free fatty acid (%), both in crude viscera oil (CVO) and refined viscera oil (RVO). Among the extraction conditions, the higher CVO yields were obtained at 60 °C for 10 min (57.89%) and at 80 °C for 10 min (67.5%), and the resulting oxidation levels were low when utilizing both extraction conditions. RVO, obtained from CVO extracted at 60 °C, showed the highest quality on the basis of the assessed parameters. The ethyl esters of the total fatty acid (TFA) contents extracted from RVO were enriched in the ω-3 polyunsaturated fatty acid fraction (PUFAE) up to almost 56% via short path distillation (SPD). Antioxidant activities and adipogenic properties were tested in vitro. PUFAE protected 3T3 L1 cells from oxidative stress and exerted an anti-adipogenic effect in Dicentrarchus labrax pre-adipocytes, attesting to the beneficial properties for both farmed fish and human health. These results could stimulate the adoption of solutions aimed to recover and utilize aquaculture by-products at a higher scale, turning "waste into profit" and indicating a strategy to reach more sustainable business models in aquaculture resource utilization according to the principles of the circular economy.

Microplastics in fish and fishmeal: an emerging environmental challenge?

Microplastics are contaminants of emerging concern; they are ingested by marine biota. About a quarter of global marine fish landings is used to produce fishmeal for animal and aquaculture feed. To provide a knowledge foundation for this matrix we reviewed the existing literature for studies of microplastics in fishmeal-relevant species. 55% of studies were deemed unsuitable due to focus on large microplastics (> 1 mm), lack of, or limited contamination control and polymer testing techniques. Overall, fishmeal-relevant species exhibit 0.72 microplastics/individual, with studies generally only assessing digestive organs. We validated a density separation method for effectiveness of microplastic extraction from this medium and assessed two commercial products for microplastics. Recovery rates of a range of dosed microplastics from whitefish fishmeal samples were 71.3 ± 1.2%. Commercial samples contained 123.9 ± 16.5 microplastics per kg of fishmeal—mainly polyethylene—including 52.0 ± 14.0 microfibres—mainly rayon. Concentrations in processed fishmeal seem higher than in captured fish, suggesting potential augmentation during the production process. Based on conservative estimates, over 300 million microplastic particles (mostly < 1 mm) could be released annually to the oceans through marine aquaculture alone. Fishmeal is both a source of microplastics to the environment, and directly exposes organisms for human consumption to these particles.

Extraction and Characterization of Collagen from Elasmobranch Byproducts for Potential Biomaterial Use

With the worldwide increase of fisheries, fish wastes have had a similar increase, alternatively they can be seen as a source of novel substances for the improvement of society's wellbeing. Elasmobranchs are a subclass fished in high amounts, with some species being mainly bycatch. They possess an endoskeleton composed mainly by cartilage, from which chondroitin sulfate is currently obtained. Their use as a viable source for extraction of type II collagen has been hypothesized with the envisaging of a biomedical application, namely in biomaterials production. In the present work, raw cartilage from shark (Prionace glauca) and ray (Zeachara chilensis and Bathyraja brachyurops) was obtained from a fish processing company and submitted to acidic and enzymatic extractions, to produce acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC). From all the extractions, P. glauca PSC had the highest yield (3.5%), followed by ray ASC (0.92%), ray PSC (0.50%), and P. glauca ASC (0.15%). All the extracts showed similar properties, with the SDS-PAGE profiles being compatible with the presence of both type I and type II collagens. Moreover, the collagen extracts exhibited the competence to maintain their conformation at human basal temperature, presenting a denaturation temperature higher than 37 °C. Hydrogels were produced using P. glauca PSC combined with shark chondroitin sulfate, with the objective of mimicking the human cartilage extracellular matrix. These hydrogels were cohesive and structurally-stable at 37 °C, with rheological measurements exhibiting a conformation of an elastic solid when submitted to shear strain with a frequency up to 4 Hz. This work revealed a sustainable strategy for the valorization of fisheries' by-products, within the concept of a circular economy, consisting of the use of P. glauca, Z. chilensis, and B. brachyurops cartilage for the extraction of collagen, which would be further employed in the development of hydrogels as a proof of concept of its biotechnological potential, ultimately envisaging its use in marine biomaterials to regenerate damaged cartilaginous tissues.

Minimizing marine ingredients in diets of farmed Atlantic salmon (Salmo salar): effects on liver and head kidney lipid class and fatty acid composition

Limited fish meal and fish oil supplies have necessitated research on alternatives for aquafeeds. Seven dietary treatments with different protein and lipid sources were formulated for farmed Atlantic salmon, and their effects on liver and head kidney lipid class, fatty acid, and elemental composition were studied. Fish meal, fish oil, and EPA + DHA content ranged from 5-35%, 0-12%, and 0.1-3%, respectively. Elemental analysis showed that the C to N ratio was higher in the head kidney than in the liver, which is consistent with higher content of total lipids in the head kidney compared with the liver. There was a greater susceptibility to dietary lipid alterations in the liver compared with the head kidney despite liver having a greater proportion of phospholipid and a much lower proportion of triacylglycerol. So long as fish oil levels were 5% or more of the diet, arachidonic acid (ARA) and docosahexaenoic acid (DHA) proportions were the same for each tissue as with feeding the marine diet with 12% fish oil; however, livers and head kidneys from fish fed the lowest amount of fish meal and fish oil had the lowest levels of eicosapentaenoic (EPA) and DHA and the highest ARA levels. Removal of fish oil and reduction of fish meal to 5% in diets of farmed Atlantic salmon affected elemental and lipid compositions of the liver and head kidney tissues potentially increasing susceptibility to inflammation. However, with 10% of the diet comprising fish meal and fish oil, lipid contents were comparable with fish fed marine-based diets.

Water and Land as Shared Resources for Agriculture and Aquaculture: Insights from Asia

Although agriculture and aquaculture depend on access to increasingly scarce, shared water resources to produce food for human consumption, they are most often considered in isolation. We argue that they should be treated as integrated components of a single complex system that is prone to direct or indirect tradeoffs that should be avoided while also being amenable to synergies that should be sought. Direct tradeoffs such as competition for space or the pollution of shared water resources usually occur when the footprints of agriculture and aquaculture overlap or when the two practices coexist in close proximity to one another. Interactions can be modulated by factors such as hydropower infrastructure and short-term economic incentives, both of which are known to disrupt the balance between aquaculture and agriculture. Indirect tradeoffs, on the other hand, play out across distances, i.e., when agricultural food sources are diverted to feed animals in aquaculture. Synergies are associated with the culture of aquatic organisms in rice paddies and irrigation waters, seasonal rotations of crop cultivation with aquaculture, and various forms of integrated agriculture–aquaculture (IAA), including jitang, a highly developed variant of pond-dike IAA. Policy decisions, socioeconomic considerations, and technology warrant increased scrutiny as determinants of tradeoffs and synergies. Priority issues for the future include guiding the expansion of aquaculture from its traditional base in Asia, taking advantage of the heterogeneity that exists within both agricultural and aquaculture systems, the development of additional metrics of tradeoffs and synergies, and adapting to the effects of climate change.

Recovery of Fatty Acid Composition in Mediterranean Yellowtail (Seriola dumerili, Risso 1810) fed a Fish-Oil Finishing Diet

The present study evaluated the effects of wash-out on the fatty acid (FA) composition in the muscles of Mediterranean yellowtail. After 109 days during which fish were fed either a fish oil (FO)-based diet (FO 100) or a diet (FO 0) in which FO was completely substituted by vegetable oils, all fish were subjected to a wash-out with FO 100 diet for 90 days. The FA profile of muscles in fish fed FO 0 diet at the beginning of the experiment reflected that of dietary vegetable oils, rich in linoleic acid (LA), and α-linolenic acid (ALA), and was deficient in AA (arachidonic acid), EPA (eicosapentaenoic acid), and DHA (docosahexaenoic acid). No essential FA were fully restored in fish previously fed FO 0 diet on 45th or 90th day of wash-out. At the end of wash-out, the FA composition showed that AA, EPA, and DHA in the white muscles increased by +33%, +16%, and +43% (p < 0.001), respectively. Similarly, AA and DHA in the red muscles increased by +33% and +41% respectively, while EPA remained similar to fish fed FO 0 diet exclusively. Therefore, a 90-d wash-out can partially improve the FA profile in muscles of Mediterranean yellowtail previously fed vegetable oil-based diets.

The role of the gut microbiome in sustainable teleost aquaculture

As the most diverse vertebrate group and a major component of a growing global aquaculture industry, teleosts continue to attract significant scientific attention. The growth in global aquaculture, driven by declines in wild stocks, has provided additional empirical demand, and thus opportunities, to explore teleost diversity. Among key developments is the recent growth in microbiome exploration, facilitated by advances in high-throughput sequencing technologies. Here, we consider studies on teleost gut microbiomes in the context of sustainable aquaculture, which we have discussed in four themes: diet, immunity, artificial selection and closed-loop systems. We demonstrate the influence aquaculture has had on gut microbiome research, while also providing a road map for the main deterministic forces that influence the gut microbiome, with topical applications to aquaculture. Functional significance is considered within an aquaculture context with reference to impacts on nutrition and immunity. Finally, we identify key knowledge gaps, both methodological and conceptual, and propose promising applications of gut microbiome manipulation to aquaculture, and future priorities in microbiome research. These include insect-based feeds, vaccination, mechanism of pro- and prebiotics, artificial selection on the hologenome, in-water bacteriophages in recirculating aquaculture systems (RAS), physiochemical properties of water and dysbiosis as a biomarker.

V, Izquierdo M, Terova G. Assessment of dietary supplementation with galactomannan oligosaccharides and phytogenics on gut microbiota of European sea bass (Dicentrarchus Labrax) fed low fishmeal and fish oil based diet

There is an increasing interest from the aquafeed industry in functional feeds containing selected additives that improve fish growth performance and health status. Functional feed additives include probiotics, prebiotics, organic acids, and phytogenics (substances derived from plants and their extracts). This study evaluated the effects of dietary inclusion of a mucilage extract rich in galactomannan oligosaccharides (GMOS), a mixture of garlic and labiatae-plants oils (PHYTO), and a combination of them (GMOSPHYTO), on gut microbiota composition of European sea bass (Dicentrarchus labrax) fed with a low fishmeal (FM) and fish oil (FO) diet. Three experimental diets and a control diet (plant-based formulation with 10% FM and 6% FO) were tested in a 63-days feeding trial. To analyze the microbiota associated to feeds and the intestinal autochthonous (mucosa-adhered) and allochthonous (transient) microbial communities, the Illumina MiSeq platform for sequencing of 16S rRNA gene and QIIME2 pipeline were used. Metabarcoding analysis of feed-associated bacteria showed that the microbial communities of control (CTRL) feed deeply differed from those of experimental diets. The number of reads was significantly lower in CTRL feed than in other feeds. The OTU (operational taxonomic unit) number was instead similar between the feeds, ranging from 42 to 50 OTUs. The variation of resident gut microbiota induced by diet was lower than the variation of transient intestinal microbiota, because feedstuffs are a major source of allochthonous bacteria, which can temporarily integrate into the gut transient microbiome. However, the composition of transient bacterial communities was not simply a mirror of feed-borne bacteria. Indeed, the microbial profile of feeds was different from both faecal and mucosa profiles. Our findings suggest that the dietary inclusion of GMOS (0.5%) and PHYTO (0.02%) in a low FM and FO diet induces changes in gut microbiota composition of European sea bass. However, if on allochthonous microbiota the combined inclusion of GMOS and PHYTO showed an antagonistic effect on bactericidal activity against Vibrionales, at mucosa level, only GMOSPHYTO diet increased the relative abundance of Bacteroidales, Lactobacillales, and Clostridiales resident bacterial orders. The main beneficial effects of GMOS and PHYTO on gut microbiota are the reduction of coliforms and Vibrionales bacteria, which include several potentially pathogenic species for fish, and the enrichment of gut microbiota composition with butyrate producer taxa. Therefore, these functional ingredients have a great potential to be used as health-promoting agents in the farming of European sea bass and other marine fish.