Dietary Fish Research Articles

Effects of dietary selenium on growth performance, antioxidant status, and gut microbial diversity of zebrafish (Danio rerio)

Selenium (Se), is an essential trace element in the diet of fish and aquatic animals needed for growth, thyroid hormone metabolism, antioxidant activity, and immunity. Thus, this study has evaluated the dietary selenium yeast (Se-yeast) impact on the growth performance, antioxidant capacity, and gut bacterial community of zebrafish, Danio rerio. The fish with an average weight of 0.247 g ± 0.005 were distributed in 12 glass aquariums. 30 fish per aquarium in three replicates per group were exposed to different dietary Se-yeast concentrations: 0.3 mg/kg (control), 0 mg/kg, 3 mg/kg, and 30 mg/kg for three weeks. The result indicated a higher body weight gain and specific growth rate in the 3 mg/kg group in all groups. Se significantly accumulated in the liver, muscle, gill, and gut. The antioxidant genes superoxide dismutase 1 (SOD1), catalase (CAT), and glutathione peroxidase 1 (GPx1), and the gut marker genes: solute carrier family 15 member 1b (slc15a1b), fatty acid binding protein 2 (fabp2), cytochrome P450 family 8 subfamily B member 1 (cyp8b1), and cytochrome P450 family 3 subfamily A, polypeptide 65 (cyp3a65) were significantly expressed in the gut tissue. The 16 s rRNA sequencing showed a significant difference at phyla Proteobacteria, Fusobacteria, Firmicutes, and Actinobacteria and Cetobacterium, Aeromonas, mycobacterium, and Lactobacillus at the genus level. It was concluded that dietary Se 3 mg/kg can promote growth performance and antioxidant status, furthermore, dietary Se yeast has a significant impact on the gut microbiota of D. rerio.

The rise of dietary diversity in coral reef fishes.

Diet has been identified as a major driver of reef fish lineage diversification, producing one of the most speciose vertebrate assemblages today. Yet, there is minimal understanding of how, when and why diet itself has evolved. To address this, we used a comprehensive gut content dataset, alongside a recently developed phylogenetic comparative method to assess multivariate prey use across a diverse animal assemblage, coral reef fishes. Specifically, we investigated the diversification, transitions and phylogenetic conservatism of fish diets through evolutionary time. We found two major pulses of diet diversification: one at the end-Cretaceous and one during the Eocene, suggesting that the Cretaceous-Palaeogene mass extinction probably provided the initial ecological landscape for fish diets to diversify. The birth of modern families during the Eocene then provided the foundation for a second wave of dietary expansion. Together, our findings showcase the role of extinction rebound events in shaping the dietary diversity of fishes on present-day coral reefs.

Diet composition and plastic ingestion in Poecilia reticulata from urban streams.

Fish are excellent bioindicators and can reveal the presence of plastic in the environment. Diagnosing the composition and abundance of polymers in the fish diet makes it possible to evaluate their point sources and possible trophic transfers. We aimed to use the gastrointestinal contents of Poecilia reticulata in subtropical urban streams to detect the occurrence, shape, color, size, and chemical composition of polymers. For this, the diet of 240 individuals was analyzed using the volumetric method, and the microplastics (MPs; < 5mm) recorded were characterized using Raman spectroscopy. Individuals predominantly consumed organic detritus and aquatic macroinvertebrates, with higher proportions of Diptera. A total of 111 plastic particles (< 0.5 to 12mm) were recorded, and a subset of 14.4% was subjected to a micro-Raman spectrometer (830nm excitation). The occurrence of polyethylene terephthalate (PET) and polypropylene (PP) with phthalocyanine dye was recorded. Some fragments could not be identified by Raman, but they contained indigo blue dye. Poecilia reticulata had a predominantly detritivorous diet with a record of plastic consumption, reflecting environmental pollution. Our results demonstrate that individuals of P. reticulata have ingested MPs in urban streams. This reinforces the need for future studies on the relationship between the presence of MPs in fish and the level of pollution in streams, comparisons with species of different feeding habits, and the potentially harmful effects on the entire biota.

Influence of extruded soybean meal with different fat contents and varying oleic acid content on floating fish feed quality and composition

Soybean meal (SBM) is the most widely used source of high-quality plant protein within the feed industry. Raw soybeans are conventionally processed to reduce antinutritional factors, enhance protein bioavailability and improve the overall quality of the final feed product. New high-oleic (HO) cultivars with enhanced unsaturated fatty acids are being utilized in the production of HO SBM for use in the animal feed industry. However, no studies to date have examined the impact of HO SBM on feed formulation and processing of aquaculture feeds. Therefore, we aimed to determine the quality of feed for juvenile domesticated striped bass (Morone saxatilis) using SBM prepared from HO or normal-oleic (NO) soybeans and extrusion-expeller processing. The following four soybean meals were used in our experimental diets: solvent-extracted defatted normal oleic (SENO), full-fat normal oleic (FFNO), extruded-expelled defatted normal oleic (EENO), or full-fat high oleic (FFHO). These meals replaced half of the fishmeal (FM) normally included in a nutritionally complete marine finfish diet. Physico-chemical feed variables and chemical composition were determined during feed production. Data were analyzed using one-way ANOVA and means were separated using Tukey’s t-test. The specific mechanical energy of the diet was reduced with the addition of full-fat SBMs during the extrusion process. All finished fish diets were of similar high quality with high pellet durability index and protein content (P > 0.05). This suggested that using different types SBM, including high oleic, to replace 50 % of the fish meal in a floating feed for juvenile domesticated striped bass does not adversely affect the feed quality or nutritional content.

AMPK activation by dietary acadesine improves fillet texture in large yellow croaker (Larimichthys crocea) fed a linseed oil-based diet

The impacts of AMP-activated protein kinase (AMPK) activation by dietary acadesine (AICAR) on growth performance and muscle quality of large yellow croaker (Larimichthys crocea) fed a linseed oil-based diet (LO) were investigated by a 56-day feeding trial in this study. Fish (initial weight: 92.24 ± 0.30 g) were fed fish oil-based diet (FO), LO or LA (LO diet supplemented with 150 mg kg−1 AICAR) with three replicates of each treatment. Results indicated that weight gain rate and specific growth rate (SGR) were significantly decreased in the LO and LA groups than those of the fish fed FO, while the opposite was true for the feed conversion ratio. Moreover, the SGR of fish fed LA was significantly lower than that of the LO group. Dietary linseed oil and AICAR significantly lowered muscle eicosapentaenoic acid and docosahexaenoic acid contents. Furthermore, the LO group showed significantly lower fillet hardness, chewiness and pH, while higher lipid loss than those of the FO group. However, the FO and LA groups had similar fillet hardness, lipid loss and pH. Compared with the fish fed FO and LA, the LO group possessed significantly lower p-AMPK protein level and p-AMPK/AMPK ratio in muscle. The phosphorylation of TOR protein and the ratios of p-TOR/TOR and p-S6/S6 were significantly decreased in muscle of the LA group than those of the fish fed FO and LO. Meanwhile, totally replacing fish oil with linseed oil inhibited the AMPK/SIRT1/PGC-1α pathway, changed myofibre characteristics (e.g., density, diameter and type of myofibre) and raised the expression of genes or activity of enzyme related to anaerobic metabolism in fish muscle. Dietary AICAR activated AMPK/SIRT1/PGC-1α pathway, restored myofibre characteristics and promoted aerobic metabolism-related genes expression in muscle to some extent. In conclusion, total substitution of dietary fish oil with linseed oil reduced growth, feed utilization and nutritive value of large yellow croaker. And high level of dietary linseed oil induced softer texture and poorer liquid holding capacity (LHC) of muscle, which may be ascribed to the myofibre characteristics changed by linseed oil through depressing muscle AMPK/SIRT1/PGC-1α pathway. Inclusion of AICAR in a linseed oil-based diet improved fish muscle hardness and LHC, which may be relevant to the activated muscle AMPK/SIRT1/PGC-1α pathway and restored myofibre characteristics by AICAR. Notably, dietary AICAR could inhibit TOR pathway by activating AMPK in muscle, which may be responsible for the further decreased SGR of fish fed a linseed oil-based diet.

Efficiently Substituting Dietary Fish Meal with Terrestrial Compound Protein Enhances Growth, Health, and Protein Synthesis in Largemouth Bass.

Inappropriate substitution of dietary fishmeal (FM) can adversely affect the growth, health, and metabolism of carnivorous fish species. To effectively reduce the amount of dietary FM in carnivorous largemouth bass (Micropterus salmoides), a terrestrial compound protein (Cpro) with chicken meal, bone meal, and black soldier fly protein was used to formulate four isoproteic (52%) and isolipidic (12%) diets, namely T1 (36% FM), T2 (30% FM), T3 (24% FM), and T4 (18% FM), for feeding juveniles (initial weight: ~12 g) for 81 days. Results indicated that the growth performance, feed efficiency, and morphological indicators, as well as muscle texture and edible quality of fish, did not differ significantly among the four groups. However, the muscle protein contents and ATP/AMP ratio of fish in the T4 group were significantly increased in comparison with those of fish in the T1 group, while the opposite was true for muscle glycogen. Compared with the T1 group, high serum total amino acid and MDA contents, as well as low AST activities, were observed in the T3 and T4 groups, and relatively high intestinal trypsin and lipase activities were found in the T2-T4 groups. The transcripts of intestinal proinflammatory cytokines (il-1β, il-6, and tnf-α) were downregulated in the T2-T4 groups compared with T1 group, while the expression of anti-inflammatory cytokines (il-10) and tight junction (zo-1 and occludin) showed the reverse trend. The mRNA expression of positive regulators related to protein synthesis (sirt1, pgc1-α, pi3k, and akt) were significantly upregulated in the muscle of fish fed diets T3 and T4, while their negative regulators (4e-bp1) mRNA levels were downregulated. The results indicate that the dietary FM of largemouth bass could be effectively reduced to at least 18% by the Cpro, which is beneficial to health, digestion, and protein synthesis for maintaining accelerated growth.

Small pelagic fish in the shallow Wadden Sea show opportunistic feeding with a strong benthic link

Abstract Small pelagic fish (SPF) are crucial in marine food webs, transferring energy from plankton to higher trophic levels. This study focuses on herring (Clupea harengus) and sprat (Sprattus sprattus), addressing knowledge gaps in their feeding ecology in a nursery area, the Dutch Wadden Sea. We conducted a year-long, monthly survey, and used DNA metabarcoding to analyse zooplankton samples and stomach contents of two size classes of herring and sprat. Intra-, interspecific, and seasonal variations in fish condition, stomach fullness, and diet composition, along with selective feeding, were studied. Our study showed that condition and diet composition of herring and sprat, along with zooplankton density, exhibited a clear seasonal pattern. Juvenile herring and sprat displayed opportunistic feeding behaviour, rather than showing distinct prey selection. Besides copepods, we regularly observed (larvae of) benthic invertebrates in their diet. This emphasizes the crucial role of SPF as energy transfer agents, not solely between trophic levels, but also from benthic to pelagic habitats. Furthermore, fish post-larvae were part of the diet of larger herring (10–15 cm). Because of its unprecedented temporal and taxonomical detail, this study advances the understanding of seasonal dynamics of dominant components at the base of the Wadden Sea food web.

Eco-innovative aquafeeds biofortified with Asparagopsis taxiformis to improve the resilience of farmed white seabream (Diplodus sargus) to marine heatwave events

Extreme weather events, like marine heatwaves (MHWs), are becoming more frequent and severe due to climate change, posing several challenges to marine ecosystems and their services. As disease outbreaks are often prompted by these acute phenomena, it is essential to develop eco-innovative strategies that can efficiently improve farmed fish resilience, especially under sub-optimal rearing conditions, thereby ensuring a sustainable aquaculture production.This study aimed to unveil farmed juvenile white seabream (Diplodus sargus, 28.50 ± 1.10 g weight, n = 150) immune and antioxidant responses under a category II MHW in the Mediterranean Sea (+4 °C, 8 days of temperature increase plus 15 days of plateau at the peak temperature) and to investigate whether a 30 days period of prophylactic biofortification with Asparagopsis taxiformis (1.5 %, 3 % and 6 %) enhanced fish resilience to these extreme events. Several biomarkers from different organization levels (individual, cellular, biochemical and molecular) were assessed upon 30 days of biofortification (T30), exposure (after 8 days of temperature increase + 15 days at peak temperature, T53) and recovery (8 days of temperature decrease, T61) from the MHW.Results showed that MHW negatively affected the fish physiological status and overall well-being, decreasing specific growth rate (SGR) and haematocrit (Ht) and increasing erythrocyte nuclear abnormalities (ENAs) and lipid peroxidation (LPO). These adverse effects were alleviated through biofortification with A. taxiformis. Seaweed inclusion at 1.5 % was the most effective dose to minimize the severity of MHW effects, significantly improving immune responses of D. sargus (i.e. increased levels of immunoglobulin M, peroxidase activity and lysozyme expression) and modulating antioxidant responses (i.e. decreased LPO, catalase and glutathione S-transferase activity). These findings confirm that A. taxiformis is a functional ingredient of added value to the aquaculture industry, as its inclusion in marine fish diets can beneficially modulate fish immunity and resilience under optimal and adverse rearing conditions.

Fish Behavior, Mortality, Diet, and Movement Following a Monsoonal Spate in the San Juan River, Utah, USA

Fish Behavior, Mortality, Diet, and Movement Following a Monsoonal Spate in the San Juan River, Utah, USA

Improved digestibility of black gram leaf meal based diets for rohu (Labeo rohita) with supplementation of exogenous enzyme cocktail

Leaf meal is currently the most cost-effective source of protein and energy for use as a supplement in fish feed. The drawback associated with integrating it into the fish diet pertains to the presence of anti-nutritional elements that must be eliminated through a viable approach such as the addition of exogenous enzymes for achieving optimal fish production. Consequently, a 60-day feeding trial was conducted to evaluate the black gram leaf meal (BGLM) as a potential ingredient to replace de-oiled rice bran (DORB) in the diet of Labeo rohita juveniles and reported for the first time. Three hundred acclimatized juveniles (average weight 11 ± 0.09 g) were allocated randomly into ten treatment groups in triplicate. Ten iso-nitrogenous (32 %) and iso-lipidic (6 %) diets were made with varying degrees of BGLM inclusion by gradually replacing DORB without or with exogenous enzyme mixture (E) of protease, xylanase, and phytase at a ratio of 1:1:1 viz. Control (40 % DORB, 0 % BGLM), BG10 (30 % DORB, 10 % BGLM), BG20 (20 % DORB, 20 % BGLM), BG30 (10 % DORB, 30 % BGLM), BG40 (0 % DORB, 40 % BGLM) & CE (C + 0.1 % E), BG10E (BG10 + 0.1 % E), BG20E (BG20 + 0.1 % E), BG30E (BG30 + 0.1 % E), BG40E (BG40 + 0.1 % E) were prepared. Fish fed with BG20E diet exhibited maximum growth rates, nutrient utilization and digestibility co-efficient of the diet (P<0.05) however these were similar in C+E treatment (P>0.05). Inclusion of 20 % or more BGLM without enzyme cocktail significantly (P<0.05) decreased the nutrient utilization and growth performance of L. rohita. The dry matter and nutrient digestibility of the experimental diet were significantly decreased (P<0.05) with the inclusion of 20 % or more BGLM in place of DORB, however supplementation of exogenous enzyme cocktail significantly increase (P<0.05) the digestibility and highest was recorded in BG20E. The present study concluded that supplementation of exogenous enzyme cocktail (protease, xylanase, and phytase) increase the digestibility of BGLM and increases its inclusion level up to 30 % in the diet of L. rohita, however, 20 % BGLM supplemented with enzyme cocktail registered the best growth, nutrient utilization and digestibility coefficient of the diet.

Influence of dietary bitter orange peel powder on growth, body composition, blood parameters, gut morphometry, and thermal tolerance of Nile tilapia (Oreochromis niloticus).

The potential of bitter orange peel powder (BOPP) as a nutritional strategy for fish was investigated in Nile tilapia. A total of 120 juveniles with an average initial weight of 9.8 ± 0.7g were divided into four groups, replicated three times, resulting in 12 experimental units (60 L each) at a stocking density of 1.63g of fish per liter. Productive parameters, whole-body composition, blood biochemistry, erythroid morphometry, intestinal histology, and heat tolerance were assessed in the juveniles subjected to one of the following treatments: non-supplemented basal diet (control group); basal diet with BOPP at 10g/kg (BOPP10 group); basal diet with BOPP at 20g/kg (BOPP20 group); and basal diet with BOPP at 40g/kg (BOPP40 group). The BOPP additive had a positive influence on Nile tilapia growth, as final weight and weight gain were greater in all BOPP-treated fish, despite the reduction in crude protein in BOPP10 and BOPP20 groups. Fish receiving BOPP40 had an increase in total lipids and showed the highest levels of triglycerides and total cholesterol. Villi development was greater in the tilapia given BOPP10. It may be concluded that BOPP presented the most promising results for Nile tilapia juveniles when used at 10g/kg diet. Regarding the erythroid morphometry, there was a general increase in nuclear and cytoplasmic areas in BOPP-fed tilapia; this seems to be the first report on the direct impact of the inclusion of functional additives in fish diet upon such parameters. As concerns the thermal tolerance evaluated at the end of the feeding trial, no differences were registered among the experimental groups. Thus, BOPP represents a feasible alternative ingredient to be explored in fish nutrition, since orange peel is a natural low-cost source of essential nutrients and valuable bioactive compounds.

Diet characteristics of tidal creek-associated fishes of the northeastern Arabian Sea with special reference to microplastic ingestion

The present study assessed the diet characteristics, trophic guild structure, and microplastics (MPs) ingestion by a group of fish sourced from the tidal creeks of the Mumbai coast along the Eastern Arabian Sea. The diet patterns were characterized using gastro-somatic index (GaSI), relative length of gut (RGL), diet overlap (α), diet breadth (Bi), and relative abundance of food items (%IOP), with a special emphasis on MPs contamination. The findings revealed that teleost and shrimps are the most preferred food items for these species. Whereas MPs contribute 5.50% of the total diet composition of the selected fishes. Additionally, we tried to find out the influence of fish size and dietary attributes on MP ingestion, identifying trophic level as a significant factor influencing contamination levels. Using the Polymer Hazard Index (PHI), the potential risks posed by MPs in fish samples were assessed, revealing notable discrepancies among polymers. For instance, polyvinyl chloride showed the highest PHI score of 198.75 and a hazard score reaching the highest risk category (IV), indicating substantial environmental risk. In summary, our findings highlight the impact of fish diet characteristics on MPs contamination and the varying levels of MP risks along the Mumbai coast, categorized according to polymer type from low to high risk.

From traditional to industrial use of insects as feed: a review

Abstract Insects are part of the natural diet of fish and poultry species and to a lesser extent of pigs, dogs and cats. In traditional farming, poultry gather their food in a free roaming manner, and insects are part of the diet. Similarly, a large fraction of the diet of freshwater fish consists of aquatic insects. These features are exploited by farmers all over the world, as feed costs are high. For example, farmers lure termites to baskets filled with organic matter, and the insects are then fed to chickens. They also employ light sources above fishponds to attract insects for their fish. More sophisticated methods are, for example, attracting naturally occurring houseflies to containers filled with organic waste, e.g. manure. The captured maggots or pupae are then fed to poultry. We discuss the following insect groups as feeds for poultry, pigs, fish, dogs and cats: bees, caterpillars, cockroaches, flies, grasshoppers and termites. Feed for poultry can also consist of insect pests, which are then controlled at the same time, for example ducks to control rice pests. Moreover, leftovers from the silk industry can be used to feed chickens, pigs and fish. Insects are also commonly used as bait for fishing. The interest in a more industrial production of insects such as the black soldier fly and housefly as animal feed started in the 1970s. In the last 15 years, large-scale rearing of insects for animal feed has taken off, with the industry receiving more than 1.5 billion dollars in investment. The market is expanding, the legislation is becoming more conducive, while academic interest is increasing exponentially. The environmental, nutritional and functional benefits of insects as feed are becoming more and more recognized. Insects are poised to play an increasingly prominent role in shaping the future of animal feed production.

Nutritional Evaluation of Short-horned Grasshopper (Oxya hyla hyla Serville) as a Substitute for Soybean Meal in Compound Diets of Rohu (Labeo rohita Hamilton)

The growth effects of partial substitution of soybean meal for grasshopper meal (Oxya hyla hyla) in compound diets of Rohu fish (Labeo rohita) were evaluated for 75 days at the aquaculture research center in IAAS, Paklihawa Campus with 16 meshed cages of 1 m3 size, stocked with 12 fingerlings. Completely Randomized Design was used with 4 treatments and 4 replications. Treatments included the incremental substitution of Soybean meal (SM) for Grasshopper meal (GM) as 0% GM, 10% GM, 20% GM and 30% GM. Feeding rates were adjusted every month based on observed body weight. Fish parameters were observed at 16, 27, 45, 60 and 75 days after stocking, whereas, the physical water parameters were observed daily. During the study period, the recorded mean water temperature, pH, dissolved oxygen and survivorship were 19°C, 8.2, 6.4 mg/L and 64.6% respectively. Average growth rate, relative growth rate, specific growth rate, daily weight gain and protein efficiency ratio showed no significant difference (p&gt;0.05) among the treatments. The Feed Conversion Ratio of 20% GM and 30% GM were statistically similar and superior to 0% GM and 10% GM as well. To sum up, we did not have enough evidence to prove the superiority of grasshopper meal incorporated diet on rohu, perhaps because of a lower feed efficiency.

Considerations for protein and amino acids in standardized reference diet for parthenogenetic marbled crayfish Procambarus virginalis model organism

The concept of a standardized reference diet (SRD) is used in laboratory model organisms to ensure nutritional control between studies and laboratories. Although models using the genetically identical, all female parthenogenetic marbled crayfish (Procambarus virginalis) are growing in popularity, research into nutrition in this species still has many knowledge gaps. To fast track the development of a SRD in terms of protein and amino acids (SRDprotein) for this species, we first analyzed the composition of its body amino acids to determine the ideal protein concept (IPC) of indispensable amino acids in wild-caught P. virginalis (which had an unusually high preponderance of leucine and arginine). Then, we strategically evaluated three common clusters of types of fish feed: (1) ornamental fish feed (SER) fortified with a naturally occurring alga (Spirulina). This type of feed was protein-high in arginine and leucine (SER + SPI) that fulfils the species’ IPC for iso-protein (~ 40%), iso-phosphorus (~ 0.8%) and near iso-energetic (~ 475 kcal 100 g−1); (2) freeze-dried live feed consisting of chironomid larvae (CHI) fortified with Spirulina (CHI + SPI) that fulfils the IPC for iso-protein (~ 46%), iso-phosphorus (~ 0.7%) and near iso-energetic (~ 405 kcal 100 g−1); and (3) a commercially standardized ‘starter diet’ for carnivorous fish larvae (FISH) and post-larval shrimps (SHRIMP) with iso-protein (~ 56%) and iso-phosphorus (~ 1.6%). A total of six diets, embracing a diverse range of proteinaceous feeds, were used in a 100-day ad libitum feeding and growth trial. The FISH group outperformed all the other groups (p < 0.05) and our exploratory multivariate analysis revealed an ideal demand of > 44% protein (tailored to deliver high arginine 3% and leucine 4%, followed by the usual lysine > 3.5% and methionine 1.2%) but also the lowest carbohydrate level (21%). For SRDprotein, our findings show that the FISH diet is ideal and suggest the possibilities of using a CHI + SPI diet for further optimization (more economic use of protein and phosphorus).

Replacement of fish oil by palm oil in diet for juvenile greenfin horse-faced filefish (Thamnaconus septentrionalis): Effects on growth performance, fatty acid composition, antioxidant capacity and inflammatory responses

This study investigated the effects of replacing dietary fish oil (FO) with palm oil (PO) on the growth performance, proximate composition, antioxidant capacity, and inflammatory responses of juvenile greenfin horse-faced filefish, Thamnaconus septentrionalis. Five isonitrogenous and isocaloric diets with varying levels of PO inclusion (0%, 25%, 50%, 75%, and 100%) were prepared, and each diet was administered in triplicate to juvenile fish for 10 weeks. Results indicated that moderately partial replacement of FO did not result in detrimental effects whereas complete or high-level replacement of FO compromised survival, growth, and feed utilization. Moderate PO inclusion slightly increased the antioxidant capacity. However, this effect was significantly impaired by high levels of dietary PO. The moisture and ash content of whole fish showed an increasing trend, while crude lipid and crude protein content tended to decline, showing significant linear response. Dietary PO appeared to affect triglyceride synthesis, albeit with minimal impact on the lipid content of the liver. Fatty acid compositions in both liver and muscle tissues were linearly correlated with dietary FA profiles, with fish liver being more reflective of dietary fatty acid composition than muscle tissue. ARA, EPA and DHA were selectively retained in the muscle tissue, whereas EPA retention was significantly reduced in the liver tissue with the gradual replacement of FO. High levels of PO inclusion in the diet resulted in elevated gene expression related to hepatic inflammation, including TLRs, MyD88 and TNFa. In conclusion, palm oil could potentially serve as an alternative to fish oil in the diet for juvenile T. septentrionalis, with up to 50% substitution without deteriorating growth performance, n-3 LC-PUFA deposition in muscle, and health status of juvenile greenfin horse-faced filefish.

Ontogenetic variation in the marine foraging of Atlantic salmon functionally links genomic diversity with a major life history polymorphism.

The ecological role of heritable phenotypic variation in free-living populations remains largely unknown. Knowledge of the genetic basis of functional ecological processes can link genomic and phenotypic diversity, providing insight into polymorphism evolution and how populations respond to environmental changes. By quantifying the marine diet of Atlantic salmon, we assessed how foraging behaviour changes along the ontogeny, and in relation to genetic variation in two loci with major effects on age at maturity (six6 and vgll3). We used a two-component, zero-inflated negative binomial model to simultaneously quantify foraging frequency and foraging outcome, separately for fish and crustaceans diets. We found that older salmon forage for both prey types more actively (as evidenced by increased foraging frequency), but with a decreased efficiency (as evidenced by fewer prey in the diet), suggesting an age-dependent shift in foraging dynamics. The vgll3 locus was linked to age-dependent changes in foraging behaviour: Younger salmon with vgll3LL (the genotype associated with late maturation) tended to forage crustaceans more often than those with vgll3EE (the genotype associated with early maturation), whereas the pattern was reversed in older salmon. Vgll3 LL genotype was also linked to a marginal increase in fish acquisition, especially in younger salmon, while six6 was not a factor explaining the diet variation. Our results suggest a functional role for marine feeding behaviour linking genomic diversity at vgll3 with age at maturity among salmon, with potential age-dependent trade-offs maintaining the genetic variation. A shared genetic basis between dietary ecology and age at maturity likely subjects Atlantic salmon populations to evolution induced by bottom-up changes in marine productivity.

Carp growth, body composition, lipidomics, and flesh quality in response to replacing dietary fish meal with a complex protein source

Alternatives to fish meal (FM) in fish feed are urgently required in aquaculture. We therefore examined the effect of replacing FM with a complex protein source (CPS) comprising soybean meal, peanut meal, corn protein meal, feather meal, and yeast protein, on carp (Cyprinus carpio) growth, body composition, lipidomics, and flesh quality. Lipidomics analysis was conducted to reveal the impact of dietary changes on fish lipid composition and metabolism, which is closely related to flesh quality and nutritional value. Over an eight-week growth trial, fish meal was replaced with CPS at 0 % (FM only), 20 %, 40 %, 60 %, 80 %, or 100 %. Weight gain and other growth parameters did not differ significantly among the treatments. Lipid deposition (LD) was positively correlated, and protein deposition negatively correlated, with CPS levels. LD and fillet ether extract were significantly elevated at 100 % CPS, whereas superoxidase dismutase expression, claudin-1 expression, and lipase activity were significantly reduced. The n-3 PUFA level and n-3/n-6 PUFA ratio were significantly lower following CPS feeding, reducing flesh quality. These findings indicate that CPS successfully replaced 60–80 % of dietary FM in carp diets, while the 100 % replacement group provided insights into the comprehensive effects of total substitution. Future studies will further optimize formulations based on these results to resemble practical production more closely. CPS with nutrient supplementation may therefore present a viable and safe partial replacement for dietary FM.

Considerations for fatty acids in standardized reference diet for parthenogenetic marbled crayfish Procambarus virginalis model organism

Fatty acid accumulation was studied in the parthenogenetic all-female marbled crayfish Procambarus virginalis using six arbitrarily designed experimental feeds and related to individuals with glair glands (sexual maturity) after 100 days of ad libitum feeding at 21 °C, including gravid females from the wild as a reference. Fatty acids 16:0 and 18:1n-9 comprised 40% of the total amount of fatty acids and tended to up-concentrate in bodies. Shorter chain 14:0 depleted from feed to body. Across diets, there was a concomitant decrease in precursor fatty acid and increase in product fatty acid, such as reinforcements in monounsaturated fatty acid (18:1n-9), eicosanoid precursors 20:4n-6 (arachidonic acid, ARA) and 20:5n-3 (eicosapentaenoic acid, EPA) in-vivo, but not 22:6n-3 (docosahexaenoic acid, DHA) except when deficient in CHI or CHI + SPI diets. Saturation kinetics modeling (R2 0.7–0.9, p < 0.05) showed that when the ARA share is ~ 1%, the EPA share is ~ 8%, and the DHA share is ~ 2% in the food lipids, the accumulation of fatty acids in body lipids levels off. The lowest DHA in the CHI (0% glair glands) or CHI + SPI (0–3.9% glair glands) diets, and the lowest ARA in SER (0% glair glands) or SER + SPI (0–3% glair glands) diets, were synchronous with negligible sexual maturity despite a wide range of observed specific growth rates (2.77–3.60% per day), body size (0.44–0.84 g), ≤ 5% crude lipid and 40–46% crude protein feed. The FISH and SHRIMP diets (56% protein, 11–14% lipid) with the highest ARA, EPA, and DHA together seem to be the most conducive diets for sexual maturity (up to 20% of individuals with glair glands). We propose a fatty acid profile mimicking the FISH or SHRIMP diets as a starting point for designing the lipid content required in the marbled crayfish standardized reference diet.

Effects of dietary polyunsaturated fatty acid enriched diets on breeding, embryonic development and organogenesis of Rohu carp, Labeo rohita (Hamilton 1822)

There is a considerable interest in supplementing fish diets with bio-functional substances such as polyunsaturated fatty acids (PUFAs), and research is being conducted to evaluate their effects on fish physiology, particularly on breeding performances. The objective of this study was to find out how squid-derived lipids (PUFAs) influence the Rohu carp, Labeo rohita, in terms of reproduction, and embryonic and larval growth. The experimental fish were provided with formulated diet for a duration of 90 days, containing 1 % squid-extracted lipids as a primary source of polyunsaturated fatty acids (PUFAs). To determine the accuracy of the formulation, a proximate analysis of the feed ingredients and the formulated feeds were conducted. The results demonstrated remarkable reproductive outcomes during the spawning trial. Observations in fish treated with PUFAs revealed a significant improvement (p < 0.001) in sperm quality and viability, despite spawning occurring late in the breeding season. In addition, the fertilization rate (92.27 ± 1.74), hatching rate (89.33 ± 1.76), and survival rate (85.83 ± 1.74) of the offspring exhibited a statistically significant increase (p < 0.05) when subjected to PUFAs treatment in L. rohita. Consequently, the treated fish exhibited enhanced early embryonic and larval development in comparison to the control group. Hence, the current study demonstrates that the inclusion of PUFAs in the diet of Rohu carp leads to improved maturation, breeding, and developmental outcomes, specifically in terms of embryonic development and organogenesis.