Search

Nutritional programming is a promising concept for promoting metabolic adaptation of fish to challenging conditions, such as the increase in water temperature. The present work evaluates in ovo arginine or glutamine supplementation as enhancers of zebrafish metabolic or absorptive capacity, respectively, at optimum (28 ºC) and challenging temperatures (32 ºC) in the long-term. Growth performance, free amino acids profile, methylation index and the activity levels of digestive and intermediary metabolism enzymes were analysed to assess the metabolic plasticity induced by an early nutritional intervention. Temperature affected fish larvae growth performance. At the end of the experimental period 28 ºC-fish showed higher dry weight than 32 ºC-fish. The effects of the early supplementation were reflected in the larval free amino acids profile at the end of the experiment. Higher methylation potential was observed in the ARG-fish. In ovo amino acid supplementation modulated the metabolic response in zebrafish larvae, however, the magnitude of this effect differed according to the amino acid and the temperature. Overall, arginine supplementation enhanced carbohydrates metabolism at 32 ºC. In conclusion, the present work suggests that in ovo arginine supplementation may promote a better adaptive response to higher temperatures., (© 2024. The Author(s).)

This study delves into the early development of Vieja fenestrata (Cichlidae), with a specific focus on the description of external morphological and morphometric changes, and growth patterns from hatching to the loss of larval characters under controlled laboratory conditions at a temperature of 28°C. Asynchronous hatching was observed between 58 and 60 h postfertilization, with the posterior body emerging first. Over 14 days, significant morphological, physiological, and behavioral changes were observed, revealing a complex developmental trajectory. The initial developmental phases were characterized by rapid vascularization, fin differentiation, and heightened activity, and the subsequent days witnessed the flexion of the notochord, emergence of swim bladder functionality, and transition to exogenous feeding. Maturation progressed with the absorption of the yolk sac, regression of cement glands, and fin ray development, culminating in metamorphosis by 14 days post-hatching. Throughout this period, evolving pigmentation patterns and structural adaptations highlight the species' adaptive strategies. During the larval period of V. fenestrata, substantial changes in morphological proportions were observed. Before the inflection, tail length, trunk length, and body depth had negative allometric growth, and head length, eye diameter, and snout length had positive allometric growth. After the inflection, body depth and snout length showed positive allometric growth; head length and trunk length exhibited isometric growth, whereas tail length and eye diameter demonstrated negative allometric growth. These findings contribute insights into the intricate developmental dynamics of V. fenestrata. Moreover, further research may explore these developmental dynamics' ecological and evolutionary implications., (© 2024 The Author(s). Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of Fisheries Society of the British Isles.)

Leptins and other related genes have been proven to play vital roles in food intake, weight control, and other life activities. While the function of leptins in yellowtail kingfish (Seriola lalandi) has not yet been explored, in the present study, we investigated the structure and preliminary function of four leptin-related genes in S. lalandi. In detail, the sequence of two leptin genes (lepa and lepb), one leptin receptor gene (lepr), and one leptin receptor overlapping transcript (leprot) gene were obtained by homology cloning and RACE methods, in which lepa and lepb have similar structure. Moreover, homologous sequence alignment and evolutionary analysis of all four genes were clustered with Seriola dumerili. The tissue distribution of these four genes in thirteen tissues of yellowtail kingfish was detected by RT-qPCR. Both lepa and leprot were highly expressed in the brain and ovary, while lepb was highly expressed in the pituitary, gill, muscle, and ovary; lepr was highly expressed in the gill, kidney, and ovary. Additionally, these four genes also played roles in embryo development and early growth and development of larvae and juveniles of yellowtail kingfish. Finally, the function of leptin and leptin-related genes was investigated during fasting and re-feeding adaption of yellowtail kingfish. The results showed that these four genes have different regulation functions in five tissues; for example, the mRNA levels of lepa, lepr, and leprot in the brain decreased during fasting and immediately increased after re-feeding, while the mRNA level of lepb did not show significant fluctuation during starvation but significantly lowered after re-feeding. However, lepa and lepb mRNA levels were significantly elevated during fasting and returned to control levels after re-feeding, and there were no significant changes in the expression of lepr and leprot in the liver during fasting and after re-feeding. Moreover, the body mass of fish in the experimental group was measured, and compensatory growth was found after the resumption of feeding. These results suggested that leptin and receptor genes play different functions in different tissues to regulate the physiological state of fish in food deficiency and gain processes., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Formulation and preparation of larval feed according to the requirement of Indian major carp is a prerequisite for improving the survival (%) and growth during early developmental stages. A feeding trial of 50 days in a replicate of five was conducted to determine the optimal inclusion levels of fish oil (lipid) in the larval diet of Labeo rohita. Four isonitrogenous (50% CP) nanoparticulate diets with four lipid inclusion levels, L5 (5%), L7 (7%), L9 (9%), and L11 (11%) were prepared and fed to four groups of rohu (Labeo rohita) larvae. At the end of feeding trial, survival (%), growth performance, digestive enzyme activity, gut morphology, and expression of growth and feed intake genes were evaluated. All pairwise comparisons among groups indicated higher growth performance (weight gain, specific growth rate, and daily weight gain), survival (%), and IGF-1 gene expression of the L9 group followed by the L7 while the L11 showed poor performance even less than L5. All studied intestinal enzymes except amylase showed a similar trend. Amylase showed comparable results among L7, L9, and L5, while L11 showed the lowest value. The intestinal villi length also showed higher values in L9 followed by L7, and lowest in the L11 group. Feed intake regulating genes, leptin showed lipid inclusion level upregulation, while ghrelin showed the highest expression in the L9 group. Based on growth performance, gut morphology, intestinal enzyme activity, and gene expression analysis, 9% dietary lipid could be recommended to ensure the optimum growth and survival of L. rohita larvae., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Live food in the initial life stages of neotropical fish is essential for their development and health; however, it can significantly increase production costs. This study uses complete diets with varying moisture contents (47%, 35%, 24%, and 8%) as a cost-effective alternative in the co-feeding phase of surubim larvae, assessing their influence on development, digestive enzymes, and liver metabolism. In a completely randomized design, 3200 three-day-old Pseudoplatystoma sp. larvae (0.001 g) were distributed evenly among 16 aquariums (20 L), with 200 individuals per aquarium. For the first five days, all larvae were fed Artemia exclusively, after which they were fed experimental diets with varying levels of humidity (47%, 35%, 24%, and 8%) six times a day across four treatments and four replicates. The 21-day feeding trial demonstrated that larvae fed with 24% and 8% moisture diets exhibited increased (p < 0.05) weight gain, final length, and protein efficiency rate. The remaining growth parameters (i.e., specific growth rate and condition factor) did not show significant differences (p > 0.05) among the dietary treatments. Enzymatic analysis revealed that the 47% moisture diet enhanced the amylase and alkaline phosphatase activities, whereas the 24% and 35% moisture diets elevated the lipase and protease activities. The 47% moisture diet also resulted in increased alanine aminotransferase, aspartate aminotransferase, and albumin levels, along with visible hepatic histopathologies in samples, such as visible lipid vacuoles, displacement of the nucleus of the hepatocyte, and increased sinusoid spaces. No significant liver changes were observed in fish fed with other diets. Principal component analysis showed that diets with 8-24% moisture content were the most beneficial during the co-feeding phase of surubim larviculture., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Simple Summary: Natural feed attractants are regularly used in aquafeeds to improve their palatability but show a number of disadvantages related to their natural origin, such as inconsistent quality of the raw materials, variable availability, and their dependency from natural sources. Contrariwise, synthetic flavors obtained through standardized processes are emerging as novel, more sustainable and effective substitutes to natural ones. The aim of the present study was to evaluate the use of synthetic flavors as novel feed attractants in zebrafish (Danio rerio) diet. A multidisciplinary approach was used to evaluate the dietary effects of the tested flavors—two attractive and one repulsive—on fish feed intake and growth, as well as on appetite regulation, brain reward system, and reproductive performances. Both diets containing the attractive flavors enhanced zebrafish feed intake and growth, promoting the fish reproductive performances without affecting fish welfare. Having ingested more feed, fish were able to invest to a greater extent in high-metabolic-demanding processes such as growth and reproduction. Improving the feeding practices of aquaculture, especially obtaining a quick feeding response by the fish, is a critical aspect for aquafeed production to minimize both the economic and environmental impacts. The present study aimed to test over a six-month period different synthetic flavors in zebrafish (Danio rerio) as an experimental model. Specifically, two attractive and one repulsive synthetic flavors were added (1% w/w) to a specific zebrafish diet, which was administered to the fish during the whole life cycle (from larvae to adults), to evaluate their physiological responses, emphasizing fish welfare, feed intake, growth, reward mechanisms, and reproductive performances. Fish welfare was not affected by all tested flavors, while both attractive flavors promoted fish feed ingestion and growth. The results were supported by both molecular and immunohistochemical analyses on appetite-regulating neurohormonal signals, along with the influence of the feed hedonic properties induced by the brain reward sensation, as demonstrated by the dopamine receptor gene expression. Finally, the present study demonstrated that a higher feed intake also had positive implications on fish reproductive performances, suggesting a promising role of synthetic flavors for the aquaculture industry. In conclusion, the results highlighted the potential of synthetic flavors to improve fish feeding strategies by providing a consistent and effective alternative to traditional stimulants, thereby reducing dependence on natural sources. [ABSTRACT FROM AUTHOR]

Simple Summary: Due to the underdeveloped digestive tracts of larval fish, predigested fish protein has been included in feeds to help increase dietary protein utilization. The predigested protein has been produced from various protein sources and broken down using different methods. This has ultimately led to variable results when included in larval diets, and there is still a lack of an optimal dry diet for larval fish. This study tested the use of adult Walleye muscle as a protein source to provide the optimal dietary amino acid composition for same-species larvae. The muscle was also broken down with enzymes from the adult Walleye gut to predigest protein in a way that mimics the digestion of live Walleye. This protein source was tested against protein produced from muscle and/or enzymes from Nile Tilapia, as a non-species-specific source. The dietary inclusion of predigested protein produced from same-species muscle and digestive enzymes led to increased growth and amino acid absorption in larval Walleye. However, reduced survival in fish fed with the predigested protein suggests that further research is required to improve the pellet stability of the larval diets and reduce the loss of nutrients to the water. Fish protein hydrolysates used in larval diets have been prepared from a variety of fish species, with different enzymes used to hydrolyze the protein. This study's objectives were to determine the effect of the dietary inclusion of fish muscle hydrolysates obtained from species-specific muscle/enzymes—versus hydrolysates produced from muscle/enzymes of a different species—on the growth performance, survival, skeletal development, intestinal peptide uptake, and muscle-free amino acid (FAA) composition of larval Walleye (Sander vitreus). Eight protein products were obtained for this study, comprising an unhydrolyzed and hydrolyzed product from each combination of muscle/enzymes from Walleye and Nile tilapia (Oreochromis niloticus). Four diets were produced, and the dietary protein was provided in a 50/50 ratio of unhydrolyzed and hydrolyzed protein from the respective muscle/enzyme combination. Four groups were fed one of the corresponding formulated diets, and two groups of larvae, fed a commercial starter diet and Artemia, respectively, served as reference groups. Larval Walleye fed the diet containing protein produced with the species-specific muscle and enzymes had a significantly higher weight after the study—30% higher than any other group. A significant interaction effect between muscle and enzyme sources on the growth of Walleye larvae was observed. The species-specific combination also led to a significant increase in postprandial FAA and indispensable amino acid concentrations in muscle. No significant differences were observed between the hydrolysate-fed groups in survival, deformity occurrence, or peptide uptake. Each hydrolysate-based diet significantly reduced skeletal deformities and survival compared to the commercial diet. The results of this study suggest that species-specific muscles and enzymes produce a more optimal dietary protein source for larval fish than non-species-specific products. Further research should focus on improving the physical properties of the formulated diets to reduce possible leaching of hydrolyzed protein and improve the survival of fish larvae. [ABSTRACT FROM AUTHOR]

Monitoring and understanding marine heatwaves (MHWs) are essential for assessing the impacts of climate change on oceans and implementing strategies to mitigate their consequences. This study examined the spatial distribution, long-term trends, and temporal variability of MHW characteristics (frequency, duration, intensity, and total number of MHW days) using four satellite-based sea surface temperature (SST) datasets from 1982 to 2021. Despite slight variations, the spatial patterns, trends, and temporal variabilities in the MHW characteristics were consistent across the observational SST datasets. Discrepancies in high-frequency variability among SST datasets may lead to differences in MHW characteristics. This study introduces new proxy indices for annual MHW characteristics, derived from the annual counts of months exceeding specified SST percentiles and the sum of positive SST anomalies beyond these thresholds. The evaluation, conducted in terms of temporal correlation and spatial root-mean-square errors, suggests superior performance in capturing the interannual variability of MHW characteristics over previously proposed proxy indices. The robustness of the new proxy indices is further assessed using an extended analysis period. These findings underscore the potential of these indices for the multi-decadal to centennial scale estimation of MHW characteristics. [ABSTRACT FROM AUTHOR]

Early stages of fish are easily sensitive to any alteration of environments, thus understanding their dispersions in a dynamic system like estuaries are important in protection and conservation of fish diversity and fishery resources. Especially, it is more significant for a mangrove-associated mudskipper, Periophthalmus modestus, which are distributed in mudflats along the Northwest Pacific, and now are listed as near threatened due to climate change and human activities. In the present study, a hybrid model, Extreme gradient boosting (XGBoost)-Artificial neural networks (ANN), was applied to forecast the distribution of P. modestus larvae and juveniles collected from a large estuary in northern Vietnam, which are driven by temperature and mangrove changes. Present results demonstrate the usefulness and applicability of ANN-XGBoost model in ecological studies, with an excellent estimation accuracy. Furthermore, employing Generative adversarial networks (GANs) model, this study exhibits a decrease in mangrove areas due to human activities between 2010 and 2023. This change with a rise in temperatre during this period would have impacted on P. modestus larvae and juveniles, which tend to be distributed in mangroves and avoid human-affected areas. Thus, it is concluded that changes in P. modestus' environment like mangroves have a significant influence on their distribution and survival. Applying a novel model in ecological research, this work further indicates the importance of mangrove forests for aquatic organisms, especially mudskippers. This research will allow scientists and biological managers to make more precise forecasts regarding the spread of P. modestus, while also helping to the protection of this mudskipper and other species. Protecting and developing mangrove forests are the first and crucial action to supply a suitable habitat for any fish species. The models employed in this work will be helpful for other relevant studies when obtaining a highly accurate performance. [ABSTRACT FROM AUTHOR]

High larval and frymortality has been amajor challenge to the commercial culture of the African bony-tongue (Heterotis niloticus). Research indicates inadequate feeding to be a possible cause of the high mortality rates of larvae/fry grown in captivity. An experiment was conducted to first describe the developmental stages of H. niloticus eggs and larvae until schooling, 6 days after hatching (DAH), at 26°C. The morphological development, survival, growth (weight gain and length), and swimming behavior of the larvae were monitored. A follow-up feeding trial was conducted with H. niloticus fry from 6 to 27 DAH involving four treatments: feeding with Artemia nauplii; a combined feed of 50% Artemia nauplii and 50% rotifers (w/w); feeding with rotifers; and no feeding. The activities of three digestive enzymes (trypsin, lipase, and amylase)were assessed in fry exposed to the live feed treatments. At hatching, the larvae had a large, vascularized yolk sac filled with yolk platelets, which occupied approximately one-third of the total body length of the abdominal cavity. Yolk platelet reabsorption started at 1 DAH and was complete at 6 DAH. Metamorphosis was completed at 6 DAH, and schooling behavior was observed. For the feeding trial, the fry that received Artemia nauplii underwent the fastest development until 27 DAH. Similarly, the survival rate was considerably higher in fry fed with Artemia nauplii than in those that received a combination of Artemia nauplii and rotifers or only rotifers. Overall, the survival rates for fry fed with Artemia nauplii and larvae co-fed were 72.7% ± 0.9% and 41.2% ± 3.3%, respectively. Fry did not survive until 27 DAH in the rotifer-fed and unfed treatment groups. Digestive enzyme activity differed significantly (p< 0.05) between treatments and sampling dates. All digestive enzymes were detectable at the onset of mouth opening (5 DAH) and fluctuated through the 7 and 9 DAH. Lower enzyme activity was observed when the fry were subjected to starvation or the rotifer treatment. Results indicate that Artemia nauplii is the best live feed organism for H. niloticus larviculture. [ABSTRACT FROM AUTHOR]

Atlantic salmon (Salmo salar) were fed diets containing black soldier fly larvae (BSFL) meal at two inclusion levels for 13 months in open sea-cages. BSFL meal replaced plant-based ingredients and dietary insect meal inclusion levels were at 5% and 10%. A commercial salmon diet was fed as a control diet. Fish were reared from ~173 g to ~ 4 kg andwere randomly distributed into nine open sea-cages with ~6000 salmon/cage (12×12m²; 1900m³). Fish from the sea-cages were sampled at two time points (mid and final samplings) to study the dietary effects of BSFL meal on the general health and welfare. Monthly assessments of sea-lice and gill score were conducted to evaluate the overall well-being of the salmon. The findings from the current study revealed that dietary inclusion of BSFL meal up to 10% did not have any significant effects in general growth, welfare or survival. However, significant positive response was observed in the general skin mucosal, hematological, and gene expression profiles of salmon. Notably, the group of salmon fed with 5% BSFL meal showed a significant decrease in plasma aspartate transaminase and alanine transaminase. Also, a significantly higher expression of interleukin1β in both skin and gill along with upregulation of matrix metallopeptidase9 and mucin18 in gill were observed in salmonfedBSFL at 5%, which aidedinincreased immune responses. A part fromthat, this group had significantly higher mucus secretions, decreased cortisol response and increased number of erythrocytes. Furthermore, the delousing stress had a significant effect on the plasma cortisol, and these responses were independent of the dietary effect. Moreover, these immune responses behaved differently at different fish size and time points, acknowledging the influence of various factors in immune modulation. Overall, the findings from this study showed the effects of dietary BSFL meal to modulate the immune status of salmon. This study aims to fill the existing knowledge gaps regarding the impact of incorporating BSFL meal as a functional feed ingredient into the salmon diet on health and immune status replicating real farm conditions. [ABSTRACT FROM AUTHOR]

The proportion of fats or oils in natural or artificial feed is generally 6%-30%, since this is essential to cover fish's energetic and structural requirements. Therefore, studies of the ontogeny or response of lipase activity to food treatments are widespread. A systematic review of articles published over 5 years (2016-2020) on lipase activity in fish in aquaculture was carried out; however, this was taken only as a representative example. Any 5-year period between 201-2022 would have shown similar results in terms of the actual lipase method used. As a result of this review, it was found that the methods used by the authors are very varied and have significant differences in terms of the type of substrate, substrate concentration, bile salt type and concentration, pH, temperature, incubation time, measurement of hydrolysis products, and definition of lipase units. The above does not mean that comparison of these studies is of no value, but that it is significantly limited. The most used methods (with p-nitrophenyl derivates, β-naphthyl derivates, and emulsified natural oils as substrate) can be reviewed to determine the most appropriate standard curves or the corresponding molar extinction coefficient for defining the lipase units. Standardizing current lipase analytical procedures should improve the reliability of comparative studies of aquaculture fish species. [ABSTRACT FROM AUTHOR]

A 12-week growth trial was conducted to evaluate the complete coreplacement of fish meal (FM) and fish oil (FO) in juvenile Florida pompano (Trachinotus carolinus) diets. Five open-formula experimental diets were formulated as iso-nitrogenous (approximately 46% crude protein) and isolipidic (approximately 15% crude lipid). It is assumed that Florida pompano lack the mechanisms for synthesizing sufficient LC-PUFA. In the FM/FO-free diets, to meet the necessary dietary intake of LC-PUFA, a commercially available Schizochytrium algal oil was used. Four diets were prepared from a basal mix, with spirulina and poultry by-product meal as the principal protein sources. They differed only in their oil source, containing fish oil (FO), algal oil (AO), soy oil (SO), or a 50/50 blend of algal oil and soy oil (A/S). The fifth experimental diet (control) was a standard open-formula FM diet. In addition to the experimental diets, two commercial closed-formula diets served as references. The seven diets, each with four replicates, were stocked with 20 Florida pompano (approximately 4 g) in each. The experimental open-formula diets were tested against the control using Dunnett's t-test, and different oil sources were tested against each other using orthogonal contrasts. The four experimental diets were each tested against the two reference diets with equivalency tests. Feed intake and survival were not different between the experimental diets and control. However, all production metrics were lower in the SO diet than the control. No other differences were observed between the FO, AO, and A/S diets and the control, or between the three diets. The feed conversion ratio (FCR) was higher in fish fed the SO diet than in fish fed the control diet, and no other differences were found. The protein efficiency ratio (PER) was higher in fish fed the control diet than in fish fed the experimental diets. Protein productive values (PPV) were similar to PER, except that the PPV in fish fed the AO diet was not different from the control. The contrasts revealed that the FO, AO, and A/S diets resulted in a lower FCR than the SO diet. The PER was higher in fish fed the AO diet, and lower in fish fed the SO diet. The PPV was higher in fish fed the AO diet than in fish fed the A/S and SO diets, but similar to that of fish fed the FO diet. There were striking differences in performance between the two commercial reference feeds, underscoring the importance of using well-defined open-formula diets as a reference or control. To our knowledge this is the first study to demonstrate that co-replacement of FM and FO can be achieved in Florida pompano by supplying an FM- and FO-free diet. The development of successful open-formula diets without FO will help spur innovation and sustainability in aquaculture production. [ABSTRACT FROM AUTHOR]

Optimizing fish performance depends on several factors, with dietary protein levels and rearing temperature playing important roles. In this study, Nile tilapia fingerlings (Oreochromis niloticus) weighing an average of 20.00 ± 1.26 g were divided into nine groups (in three replicates). Each group was subjected to different water temperatures (26 °C, 28 °C, and 30 °C) and received one of three dietary protein levels (20%, 25%, and 30%) for two months. Our findings indicate that higher temperatures, particularly at 30 °C, increased water electrical conductivity and total dissolved salts, especially noticeable in fish fed 25% or 30% crude protein (CP). Lower total ammonia nitrogen levels were observed at 28 °C with 25% CP, 30 °C with 30% CP, and 26 °C with 30% CP. Hepatic growth hormone receptor 1 and insulin-like growth factor 1 expression gradually rose with higher dietary CP percentages in fish at 26 °C but declined in those at 30 °C, albeit remaining higher than in the 28 °C groups with 25% CP. Fish at 28 °C showed the best final body weights and growth performance when fed 20% or 25% CP, with no significant difference between these groups. Hepatic leptin expression did not differ significantly among groups, but hepatic fatty acid binding protein expression notably increased in fish fed 30% CP at both 26 °C and 30 °C compared to those at 28 °C with 25% CP. Within the same temperature group, fish fed 30% CP exhibited higher globulin levels, particularly thriving at 28 °C or 30 °C. Hepatic mucin-like protein expression significantly increased across all groups, especially in fish at 30 °C with 30% CP compared to those at 28 °C with 25% CP. Hepatic lysozyme expression also increased notably in fish at 30 °C with 30% CP. Notable changes in superoxide dismutase, catalase, and glutathione peroxidase expression were observed, with the highest serum superoxide dismutase and catalase activities recorded in fish at 30 °C with 25% CP. Overall, dietary protein levels of 25% and 30%, combined with temperatures of 28 °C and 30 °C, yielded favorable outcomes, particularly favoring 28 °C with 25% protein. [ABSTRACT FROM AUTHOR]

The increasing frequency and duration of marine heatwaves (MHWs) due to climate change pose severe threats to aquaculture, causing drastic physiological and growth impairments in farmed fish, undermining their resilience against additional environmental pressures. To ensure sustainable production that meets the global seafood demand and animal welfare standards, cost-effective and eco-friendly strategies are urgently needed. This study explored the efficacy of the red macroalga Asparagopsis taxiformis on juvenile white seabream Diplodus sargus reared under optimal conditions and upon exposure to a MHW. Fish were fed with four experimental diets (0%, 1.5%, 3% or 6% of dried powdered A. taxiformis) for a prophylactic period of 30 days (T30) and subsequently exposed to a Mediterranean category II MHW for 15 days (T53). Biometric data and samples were collected at T30, T53 and T61 (8 days post-MHW recovery), to assess performance indicators, biomarker responses and histopathological alterations. Results showed that A. taxiformis supplementation improved catalase and glutathione S-transferase activities and reduced lipid peroxidation promoted by the MHW, particularly in fish biofortified with 1.5% inclusion level. No histopathological alterations were observed after 30 days. Additionally, fish biofortified with 1.5% A. taxiformis exhibited increased citrate synthase activity and fish supplemented with 1.5% and 3% showed improved digestive enzyme activities (e.g., pepsin and trypsin activities). Overall, the present findings pointed to 1.5% inclusion as the optimal dosage for aquafeeds biofortification with A. taxiformis, and confirmed that this seaweed species is a promising cost-effective ingredient with functional properties and great potential for usage in a climate-smart context. [ABSTRACT FROM AUTHOR]

The threat posed by microplastics has become one of the world's most serious problems. Recent reports indicate that the presence of microplastics has been documented not only in coastal areas and beaches, but also in water reservoirs, from which they enter the bodies of aquatic animals and humans. Microplastics can also bioaccumulate contaminants that lead to serious damage to aquatic ecosystems. The lack of comprehensive data makes it challenging to ascertain the potential consequences of acute and chronic exposure, particularly for future generations. It is crucial to acknowledge that there is still a substantial need for rapid and effective techniques to identify microplastic particles for precise evaluation. Additionally, implementing legal regulations, limiting plastic production, and developing biodegradation methods are promising solutions, the implementation of which could limit the spread of toxic microplastics. [ABSTRACT FROM AUTHOR]

(1) Background: We examined the effect of the acute administration of olive oil (EVOO), linseed oil (GLO), soybean oil (SO), and palm oil (PO) on gastric motility and appetite in rats. (2) Methods: We assessed food intake, gastric retention (GR), and gene expression in all groups. (3) Results: Both EVOO and GLO were found to enhance the rate of stomach retention, leading to a decrease in hunger. On the other hand, the reduction in food intake caused by SO was accompanied by delayed effects on stomach retention. PO caused an alteration in the mRNA expression of NPY, POMC, and CART. Although PO increased stomach retention after 180 min, it did not affect food intake. It was subsequently verified that the absence of an autonomic reaction did not nullify the influence of EVOO in reducing food consumption. Moreover, in the absence of parasympathetic responses, animals that received PO exhibited a significant decrease in food consumption, probably mediated by lower NPY expression. (4) Conclusions: This study discovered that different oils induce various effects on parameters related to food consumption. Specifically, EVOO reduces food consumption primarily through its impact on the gastrointestinal tract, making it a recommended adjunct for weight loss. Conversely, the intake of PO limits food consumption in the absence of an autonomic reaction, but it is not advised due to its contribution to the development of cardiometabolic disorders. [ABSTRACT FROM AUTHOR]

This review synthesizes the multifaceted role of vitamin A in fish well-being, encompassing immune function, antioxidant capacity and growth regulation, providing a comprehensive understanding of its significance in fish diets and implications for aquaculture. Key objectives include exploring the role of vitamin A in fish immunology, growth impact, oxidative stress status, and future directions. Vitamin A is critical for immune cell development, enhancing both innate and adaptive immune responses. It maintains mucosal integrity and modulates phagocytic activity, crucial for pathogen defense. Growth regulation is influenced by vitamin A through cellular differentiation and morphogenesis, essential for tissue and skeletal development. Studies indicate that vitamin A supplementation improves growth metrics and body composition across various fish species. Vitamin A also combats oxidative stress by scavenging free radicals, enhancing antioxidant enzyme activity, and inducing autophagy, thus protecting cellular components from oxidative damage. Interactions with other vitamins like E, D, and C highlight the importance of balanced nutrition in aquaculture. Integrative management practices, including nutritionally balanced diets, optimal water quality, stress reduction, and environmental enrichment, are recommended to maximize fish health and productivity through adequate vitamin A utilization. [ABSTRACT FROM AUTHOR]

Simple Summary: Cholecystokinin (cck) is an important factor in regulating feed intake. According to a previous study, replacing fish meal (FM) in the diet of largemouth bass could downregulate the expression of the cck gene; however, the underlying regulatory mechanism remains unclear. Therefore, we investigated the effect of cck on feed intake and its potential mechanism of action via injecting exogenous CCK peptide and its receptor antagonist. This study's results indicate that cck could regulate the feed intake of largemouth bass through regulating feeding-related genes in the brain and intestine. Furthermore, cck required binding with the receptor to inhibit feed intake more effectively in largemouth bass, and the binding effect of cholecystokinin receptor 1 (CCK1R) was better than that of cholecystokinin receptor 2 (CCK2R), which could lay a theoretical foundation for the study of fish feeding regulation. This study investigated the role of cholecystokinin (cck) in the feeding regulation of largemouth bass (Micropterus salmoides) via peptide activation and antagonist inhibition. The results show that the cck gene was expressed in various tissues, with the highest expression level occurring in the brain. Feeding, continuous feeding, and refeeding after fasting could significantly improve the mRNA levels of cck in the brain. Moreover, the activation of cck via injecting an exogenous CCK peptide could inhibit feed intake by regulating the mRNA levels of anorexigenic and feed-promoting factors in the brain and intestine. Furthermore, the CCK peptide reduced feed intake; however, the presence of an antagonist (Ly225910-CCK1R and devazepide-CCK2R) could reverse this effect through regulating the mRNA levels of anorexigenic and feed-promoting factors in the brain and intestine. Treatment with devazepide + CCK (CCK2R) reversed feed intake more effectively than Ly225910 + CCK (CCK1R) treatment. In summary, cck could regulate the feed intake of largemouth bass through regulating feeding-related genes in the brain and intestine. In addition, cck required binding with the receptor to inhibit feed intake more effectively in largemouth bass, and the binding effect of CCK1R was better than that of CCK2R. [ABSTRACT FROM AUTHOR]

Central administration of valine has been shown to cause hyperphagia in fish. Although mechanistic target of rapamycin (mTOR) is involved in this response, the contributions to feed intake of central and peripheral metabolite changes due to excess valine are unknown. Here, we investigated whether intracerebroventricular injection of valine modulates central and peripheral metabolite profiles and may provide insights into feeding response in fish. Juvenile rainbow trout (Oncorhynchus mykiss) were administered an intracerebroventricular injection of valine (10 µg·µL−1 at 1 μL·100·g−1 body wt), and the metabolite profile in plasma, hypothalamus, and rest of the brain (composing of telencephalon, optic tectum, cerebellum, and medulla oblongata) was carried out by liquid chromatography-mass spectrometry (LC/MS)-based metabolomics. Valine administration led to a spatially distinct metabolite profile at 1 h postinjection in the brain: enrichment of amino acid metabolism and energy production pathways in the rest of the brain but not in hypothalamus. This suggests a role for extrahypothalamic input in the regulation of feed intake. Also, there was enrichment of several amino acids, including tyrosine, proline, valine, phenylalanine, and methionine, in plasma in response to valine. Changes in liver transcript abundance and protein expression reflect an increased metabolic capacity, including energy production from glucose and fatty acids, and a lower protein kinase B (Akt) phosphorylation in the valine group. Altogether, valine intracerebroventricular administration affects central and peripheral metabolism in rainbow trout, and we propose a role for the altered metabolite profile in modulating the feeding response to this branched-chain amino acid. NEW & NOTEWORTHY: Valine causes hyperphagia in fish when it is centrally administered; however, the exact mechanisms are far from clear. We tested how intracerebroventricular injection of valine in rainbow trout affected the brain and plasma metabolome. The metabolite changes in response to valine were more evident in the rest of the brain compared with the hypothalamus. Furthermore, we demonstrated for the first time that central valine administration affects peripheral metabolism in rainbow trout. [ABSTRACT FROM AUTHOR]

Many organisms exhibit social behaviors and are part of some scheme of social structure. Zebrafish are highly social, shoaling fish and therefore, social isolation may have notable impacts on their physiology and behavior. The objective of this study was to evaluate the effects of social isolation on feed intake, monoaminergic system related gene expression, and intestinal health of juvenile zebrafish fed a high-inclusion soybean meal based diet. At 20 days post-fertilization zebrafish were randomly assigned to chronic isolation (1 fish per 1.5 L tank) or social housing (6 fish per 9 L tank) with 18 tanks per treatment group (n = 18). Dividers were placed between all tanks to prevent visual cues between fish. Zebrafish were fed a commercial fishmeal based diet until 35 days post-fertilization and then fed the experimental high-inclusion soybean meal based diet until 50 days post-fertilization. At the end of the experiment (51 days post-fertilization), the mean total length, weight, and weight gain were not significantly different between treatment groups. Feed intake and feed conversion ratio were significantly higher in chronic isolation fish than in social housing fish. Expression of monoaminergic and appetite-related genes were not significantly different between groups. The chronic isolation group showed higher expression of the inflammatory gene il-1b, however, average intestinal villi width was significantly smaller and average length-to-width ratio was significantly higher in chronic isolation fish, suggesting morphological signs of inflammation were not present at the time of sampling. These results indicate that chronic isolation positively affects feed intake of juvenile zebrafish and suggest that isolation may be useful in promoting feed intake of less-palatable diets such as those based on soybean meal. [ABSTRACT FROM AUTHOR]

Simple Summary: Taurine has a wide range of biological functions in vertebrates but does not participate in protein synthesis. Recent studies showed taurine exhibits an important role in the regulation of fat metabolism in fish and has the effect of reducing liver fat accumulation in high-fed fish. However, it is still unclear how taurine exerts the effect and the underlying metabolic mechanism of taurine intervention. In this study, we conducted an experiment to investigate the fat-lowering effect of taurine on orange-spotted groupers at the proteomic level. Furthermore, we performed an integrated analysis of transcriptomics and proteomics and excavated the key genes and key proteins involved in the regulation of liver fat metabolism, in an attempt to better understand the intrinsic connection between the transcriptional and translational levels and interpret the trajectories in terms of the biological phenomena in a more comprehensive way after taurine intervention on high-fat fed orange-spotted groupers. In order to understand the intervention effect of taurine on liver fat deposition induced by high fat intake in the orange-spotted grouper (Epinephelus coioides), we performed proteomic analysis and association analysis with previously obtained transcriptomic data. Three isoproteic (47% crude protein) diets were designed to contain two levels of fat and were named as the 10% fat diet (10F), 15% fat diet (15F), and 15% fat with 1% taurine (15FT). The 10F diet was used as the control diet. After 8 weeks of feeding, the 15F diet exhibited comparable weight gain, feed conversion ratio, and hepatosomatic index as the 10F diet, but the former increased liver fat content vs. the latter. Feeding with the 15FT diet resulted in an improvement in weight gain and a reduction in feed conversion ratio, hepatosomatic index, and liver fat content compared with feeding the 15F diet. When comparing liver proteomic data between the 15F and 15FT groups, a total of 133 differentially expressed proteins (DEPs) were identified, of which 51 were upregulated DEPs and 82 were downregulated DEPs. Among these DEPs, cholesterol 27-hydroxylase, phosphatidate phosphatase LPIN, phosphatidylinositol phospholipase C, and 6-phosphofructo-2-kinase were further screened out and were involved in primary bile acid biosynthesis, glycerolipid metabolism, the phosphatidylinositol signaling system, and the AMPK signaling pathway as key DEPs in terms of alleviating liver fat deposition of taurine in high-fat fed fish. With the association analysis of transcriptomic and proteomic data through KEGG, three differentially expressed genes (atp1a, arf1_2, and plcd) and four DEPs (CYP27α1, LPIN, PLCD, and PTK2B) were co-enriched into five pathways related to fat metabolism including primary bile acid synthesis, bile secretion, glycerolipid metabolism, phospholipid D signaling, or/and phosphatidylinositol signaling. The results showed that dietary taurine intervention could trigger activation of bile acid biosynthesis and inhibition of triglyceride biosynthesis, thereby mediating the liver fat-lowering effects in high-fat fed orange-spotted grouper. The present study contributes some novel insight into the liver fat-lowering effects of dietary taurine in high-fat fed groupers. [ABSTRACT FROM AUTHOR]

All organisms require the ability to engage in either sexual or asexual reproduction in order to ensure their own survival. In aquaculture, when one sex outgrows the other faster, farmers use hormones to stimulate growth. Furthermore, the production of fish based on sexual dimorphism is predominantly executed through the utilization of estrogens and androgens. Environmentally, these compounds may pollute the ecosystem and cause endocrine system alterations that cause harmful effects; thus, they must be handled carefully to assure environmental, biological, and food safety. Phytoestrogens as natural non-steroidal phenolic plant chemicals that resemble 17-β-estradiol, could be employed as a safe alternative source of natural estrogens. The phytoestrogens have many biological effects due to their ability to compete with estrogen receptors, but they may negatively affect fish production, reproduction, and behaviors under controlled conditions. Thus, the current literature emphasizes on the beneficial effects of phytoestrogens on aquatic animal performance, behaviors, and some reproductive features. [ABSTRACT FROM AUTHOR]

Research has focused on alternative plant materials or additives that can be used instead of fish meal due to limited stocks and increased feed prices, although it is important for carnivorous fish species. Taurine is a functional amino acid supplemented to low fish meal diets to improve the growth performance of fish. In this study, eight experimental diets with 0%, 0.5%, 1% and 2% ratios of taurine supplemented (T0, T0.5, T1 and T2) high (HFM) and low fish meal (LFM) diets were prepared (defined as HFMT0, HFMT0.5, HFMT1, HFMT2, LFMT0, LFMT0.5, LFMT1 and LFMT2). The experiment was carried out in twenty-four 400 L rectangular fiberglass tanks conducted in a marine water system, and fish (initial mean weight of 23.5 g) were stocked in each tank. The nutrition trial was carried out for 90 days with three replicates. Meagre fed with the HFMT1 diet had a higher final mean weight (FMW) and specific growth rate (SGR) than fish fed with HFMT0 and all LFM diets. Including taurine in all LFM diets also enhanced growth performance. The FMW and SGR of fish fed the LFMT0.5 diet were similar when compared to HFMT0 (P>0.05) and increased compared to that of other LFM diets with taurine (P<0.05). Meagre fed the LFM0.5 diet had a lower feed conversion rate (FCR) than those provided for all HFM diets, although there was no significant difference between treatments. Dietary taurine has decreased the hepatosomatic index (HSI), viscerosomatic index (VSI) and total ammonia-nitrogen excretion (TAN), irrespective of taurine and fish meal levels. Including dietary taurine at both fish meal levels enhances the number of red blood cells (RBC) and whole-body amino acids of meagre. The most remarkable conclusion of this study is the inclusion of taurine in low fish meal diets improved growth performance and profitability in meagre, and the level of 0.5% has been recommended. [ABSTRACT FROM AUTHOR]

The impact of ocean warming on fish and fisheries is vigorously debated. Leading theories project limited adaptive capacity of tropical fishes and 14-39% size reductions by 2050 due to mass-scaling limitations of oxygen supply in larger individuals. Using the world's hottest coral reefs in the Persian/Arabian Gulf as a natural laboratory for ocean warming - where species have survived >35.0 °C summer temperatures for over 6000 years and are 14-40% smaller at maximum size compared to cooler locations - we identified two adaptive pathways that enhance survival at elevated temperatures across 10 metabolic and swimming performance metrics. Comparing Lutjanus ehrenbergii and Scolopsis ghanam from reefs both inside and outside the Persian/Arabian Gulf across temperatures of 27.0 °C, 31.5 °C and 35.5 °C, we reveal that these species show a lower-than-expected rise in basal metabolic demands and a right-shifted thermal window, which aids in maintaining oxygen supply and aerobic performance to 35.5 °C. Importantly, our findings challenge traditional oxygen-limitation theories, suggesting a mismatch in energy acquisition and demand as the primary driver of size reductions. Our data support a modified resource-acquisition theory to explain how ocean warming leads to species-specific size reductions and why smaller individuals are evolutionarily favored under elevated temperatures. The impact of ocean warming on fish size structure is debated. Here, the authors test mass scaling of metabolism and swimming performance of fish across different water temperatures and regions, suggesting that resource-acquisition explains size reduction due to ocean warming. [ABSTRACT FROM AUTHOR]

Aquaculture production has been growing consistently over the last few decades to meet the increasing animal protein demand of the human population. However, increased production and rearing intensities raise the challenges of guaranteeing fish health and welfare, which is essential to avoid losses and ensure product quality. Biomarkers can provide insights into the fish's nutritional, physiological, and health status, and aid in the evaluation of early nutritional and physiological imbalances, distress conditions, and pathological diagnosis. The discovery and validation of biomarkers rely mostly on the use of information provided by different parameters, including biochemical, metabolic, or immunologic, as well as several omics, from genomics and transcriptomics to proteomics and metabolomics. In this review, a summary of the main biomarkers used in aquaculture is provided along with an overview of the main omics technologies available for further biomarker research. This review also highlights the need to develop non-lethal biomarkers that can easily and quickly be measured to provide a prompt response to producers. [ABSTRACT FROM AUTHOR]

A 56-day feeding trial was conducted to evaluate the quantitative methionine requirements in the diets of Florida pompano (Trachinotus carolinus). Eight practical diets using soybean meal, poultry meal, and red lentil meal as the primary protein sources were formulated using graded levels of methionine supplement (0 to 0.70 g/100 g diet). Groups of 15 juvenile Florida pompano (4.04 ± 0.05 g) were size-sorted and placed into one of 40 glass aquaria (132 L) with five replicates per diet. Significant differences (p ≤ 0.05) were observed in overall biomass, mean weight, weight gain, thermal growth coefficient (TGC), and feed conversion ratio (FCR). To estimate the dietary methionine requirement, a series of statistical models, including the one-slope broken line model (BLM1), two-slope broken line model (BLM2), broken quadratic model (BQM), and four-parameter saturation kinetic model (SKM-4) were used to assess mean weight, weight gain, TGC, apparent net protein retention (ANPR), and methionine retention (MR). The model selection showed that BLM1 fit the data best for MW and TGC, SKM-4 for PWG and ANPR, and BQM for MR. Based on these results, a minimum dietary methionine requirement of 0.68% of the diet or 1.70 g/100 g protein is recommended. [ABSTRACT FROM AUTHOR]

The alien Red Sea goatfish, Parupeneus forsskali (Fourmanoir & Guézé, 1976), is a Lessepsian migrant, entering the Mediterranean through the Suez Canal. This study explores its seasonal diet and biological traits in Cyprus, its non-native habitat. From August 2019 to July 2021, a total of 249 specimens were collected, ranging in total length (TL) from 5.8 to 27.7 cm, with a mean TL of 15.1 ± 4.54 cm (SD). These specimens were examined with respect to sex and season. Through various methods (F%, N%, W%, and IRI), the feeding habits of the species were analysed, revealing a diet dominated by Crustacea (mainly Decapoda) and Polychaeta, with the secondary consumption of Mollusca, Echinodermata, and others. Significant differences were found between males and juveniles and females and juveniles, with adults preferring Decapoda and juveniles Copepoda, while seasonal variations were mainly influenced by prey availability. The Red Sea goatfish exhibited ontogenetic niche shifts in its depth and habitat distribution, influenced by size and age. The trophic level (TROPH) of P. forsskali ranged from 3.22 to 3.46, corresponding to an omnivorous diet with a preference for animals. These findings suggest that P. forsskali is an opportunistic predator with a diverse diet, thriving in its new habitat and potentially impacting the local marine food webs by competing with economically important native species for resources. [ABSTRACT FROM AUTHOR]

Simple Summary: This study evaluated the effect of dietary supplementation with organic silicon on the growth performance, blood biochemistry, digestive enzymes, morphohistology, intestinal microbiota and stress resistance in juvenile hybrid Tilapia (Oreochromis mossambicus × Oreochromis niloticus). It is concluded that organic silicon had no negative effects on the physiology and metabolism of the fish. The results showed that up to 50 mg·kg−1 of organic silicon can be applied to the diet of red Tilapia, improving digestive, metabolic and growth performance. The interactions between zootechnical performance, physiological digestive and metabolic capacity in hybrid red Tilapia still deserve further exploration. In recent decades, interest has been aroused worldwide in the use of silicon in nutrition; however, information on its effect on nutrition and metabolism of fish is limited. The objective of the research was to evaluate the effect of dietary supplementation with organic silicon on the growth performance, blood biochemistry, digestive enzymes, morphohistology and intestinal microbiota and stress resistance in hybrid Tilapia (Oreochromis mossambicus × Oreochromis niloticus). Methodologically, six levels of organic silicon (DOS) [control (0), 10, 20, 30, 40 and 50 mg·kg−1] were used to feed juvenile fish (initial weight 7.51 ± 0.25 g) grown for eight weeks in 18 aquariums (15 fish/aquarium). The results indicated that growth performance showed differences (p < 0.05) for specific growth rate, feed conversion and survival. Triglycerides, cholesterol and glucose, transaminases and digestive enzymes were significantly influenced by DOS levels. The histological study confirmed that the administered diets did not cause damage and induced significant morphological changes in the proximal intestine. The 16S rRNA gene sequencing analysis of the gut microbiota showed a high diversity and richness of OTU/Chao-1, with Fusobacteria, Proteobacteria, Bacteroidetes and Acidobacteria predominating in the DOS treatments compared to the control (p < 0.05). Induction of hypoxia stress after the feeding period showed a significant relative survival rate of 83.33% in fish fed 50 mg·kg−1. It is concluded that the DOS treatments performed better than the control treatment in most of the variables analysed. DOS had no negative effects on the fish. The results showed that up to 50 mg·kg−1 DOS improved digestive, metabolic and growth performance in hybrid Tilapia. [ABSTRACT FROM AUTHOR]

This study aimed to explore the impact of adding methionine on growth performance, feed utilization, biochemical parameters, and economic assessment of Oreochromis niloticus. A total of 180 fries were acclimated and then randomly allocated into the experimental aquariums. Fish were distributed across 12 aquaria with 15 fry each, having an initial average weight of 83.50± 0.485g per aquarium. Methionine was incorporated at levels of 0, 5, 10, and 15g/ kg in experimental diets labeled D1, D2, D3, and D4, respectively for 56 days. Growth performance metrics such as total body weight gain (TBWG), daily gain (ADG) and specific growth rate (SGR) increased in the methionine-supplemented groups compared to the control. The mortality rate was 6.67% in the control group, while it was zero in the methionine-supplemented groups. The feed conversion ratio and protein efficiency ratio also improved. Total protein and albumin were higher in all methionine treatments compared to the control group. Levels of AST, ALT, and cholesterol were not significantly affected by methionine supplementation. The highest uric acid level was found in the group receiving 15g/ kg methionine. Fish body composition, including moisture, crude protein, and ash content, showed significant increases. Energy retention (ER%) improved by 6.90 and 21.29% in the groups receiving 10 and 15g/ kg methionine, respectively, compared to the control (D1). Protein productive value (PPV%) improved by 129.06, 142.41, and 151.32% for the 5, 10, and 15g/ kg methionine groups, respectively, compared to the control. The net improvement in feeding efficiency, reflected by a decrease in feeding costs, was 13.85, 25.44, and 31.54% compared to control. Our observations indicate that, including methionine in fish diets enhances performance metrics, increases total protein and globulin levels, improves energy retention and protein productive values, and boosts the net economic benefits of feeding. [ABSTRACT FROM AUTHOR]

This document is a compilation of research articles that focus on the gut microbiota of fish. The articles cover a range of topics, including the impact of sampling season and catching site on gut microbiota composition, the effects of diet on the microbiota and health of fish, the role of gut microbiota in fish disease and immunity, and the interactions between the gut microbiome and the aquatic environment in fisheries and aquaculture. These articles provide valuable insights into the diversity and functions of fish gut microbiota and its implications for fish health and aquaculture practices. [Extracted from the article]

The copepods are nutritionally superior and important live-feed organisms in aquaculture. However, attaining the high density and continuous production of copepods to fulfil the requirements of fish larval production is still a challenge, as compared to other live feeds such as artemia and rotifer. The lack of effective technology in the live feed industry failed to produce a mass density of copepods. Pseudodiaptomus annandalei is a common tropical calanoid copepod species. Hence, the present study attempted the high-density and continuous production of P. annandalei through various optimization technologies, namely, selective and induced breeding by environmental induction, hormone induction, and microbial induction. The copepod P. annandalei was tested with various selective breeding methods, i.e. (a) 18°C cold selective breeding (18°C CSB), (b) 26°C normal selective breeding (26°C NSB), and (c) non-selective breeding (control). This study reveals, compared to 18°C CSB and control copepods, the 26°C NSB copepod P. annandalei produced a significant population of 17181.6 ± 371.2 ind/l using RASC. Across the five generations, the mean nauplii production genetic gain (∆G) for G5 was 29.6% with calculated heritability (h2) of 0.30. For the continuous production of copepod, P. annandalei was optimized with suitable environmental parameters. In hormone induction, 20 μg/L bisphenol A and 40 μg/L 17β-estradiol produced high NPR, but the survival rate (SR) decreased while using these hormones. In the meantime, probiotic induction gave a positive result in terms of NPR. The maximum NPR in P. annandalei was induced by Bacillus subtilis at a concentration of 106 CFU/mL, and probiotic induction also improved the copepod SR. Our findings provide the first concrete proof that P. annandalei would be a candidate species with favourable outcomes for selective breeding—improving its reproductive capacity. [ABSTRACT FROM AUTHOR]

Docosahexaenoic acid (DHA) enrichment of live food is a common practice to improve growth and survival of larvae. The current research aimed to test the effect of rotifer enrichment with DHA on growth, survival, fatty acid profile, digestive enzymes, antioxidant parameters, and histology in yellowtail clownfish (Amphiprion clarkii) larvae. Four levels of enrichments emulsions with DHA were considered, including DHA6 (6% DHA), DHA12 (12% DHA), DHA24 (24% DHA), and DHA36 (36% DHA). No substantial differences in growth data were recorded, suggesting that even 6% DHA emulsion enrichment which resulted in 4.22% DHA in rotifers is enough to fulfil the DHA requirements of yellowtail clownfish larvae to maximise the growth rate. Excessive levels of DHA (36%) decreased the survival rate of larvae. This fatty acid accumulated in the larvae body at high levels (24.72%). The DHA12 group had the lowest growth, possibly due to lower digestive enzymes and antioxidant activities in this treatment. There was a positive correlation between final weight and lipase (59%), protease (73%), and lactate dehydrogenase (69%). Furthermore, amylase, lipase, protease, and alkaline phosphatase had significant positive correlations with catalase (72%, 84%, 74%, and 66%, respectively) and lactate dehydrogenase (64%, 85%, 79%, and 77%, respectively). Superoxidase dismutase and catalase also had positive correlations with arachidonic acid levels in the body. Increased DHA levels, based on histology data, caused lipid vacuoles in enterocytes and hepatocytes. In conclusion, yellowtail clownfish larvae can grow well with high survival even with feeding rotifers enriched with 4.22% DHA or less. [ABSTRACT FROM AUTHOR]

Aquaculture supplies the world food market with a significant amount of valuable protein. Highly productive aquaculture fishes can be derived by utilizing genome-editing methods, and the main problem is to choose a target gene to obtain the desirable phenotype. This paper presents a review of the studies of genome editing for genes controlling body development, growth, pigmentation and sex determination in five key aquaculture Salmonidae and Cyprinidae species, such as rainbow trout (Onchorhynchus mykiss), Atlantic salmon (Salmo salar), common carp (Cyprinus carpio), goldfish (Carassius auratus), Gibel carp (Carassius gibelio) and the model fish zebrafish (Danio rerio). Among the genes studied, the most applicable for aquaculture are mstnba, pomc, and acvr2, the knockout of which leads to enhanced muscle growth; runx2b, mutants of which do not form bones in myoseptae; lepr, whose lack of function makes fish fast-growing; fads2, Δ6abc/5Mt, and Δ6bcMt, affecting the composition of fatty acids in fish meat; dnd mettl3, and wnt4a, mutants of which are sterile; and disease-susceptibility genes prmt7, gab3, gcJAM-A, and cxcr3.2. Schemes for obtaining common carp populations consisting of only large females are promising for use in aquaculture. The immobilized and uncolored zebrafish line is of interest for laboratory use. [ABSTRACT FROM AUTHOR]

Feed conversion ratio (FCR) is widely used as a measure of feed use efficiency in commercial aquaculture production and research. Surprisingly, little work has focused on the factors that affect FCR in plankton‐based, commercial ponds despite the widespread use of FCR as a production metric. Proposals to use FCR as a numeric standard for environmental regulation (mandatory or voluntary) raise questions as to whether FCR meets the reliability and consistency requirements of a good metric, and whether it would lead to desired behavioral changes. This article summarizes FCR data from university research verification programs conducted on US catfish farms and databases developed from commercial farm records. The relevant research literature is synthesized with respect to factors that affect FCR. US catfish is used as a case study because pond‐level data from verification trials (Extension/research‐led on‐farm trials of best available science) and commercial farm records are available. While specific to US catfish production, the analysis provides insights into factors affecting FCR that likely apply to other pond‐based aquaculture species. Commercial verification of pond data showed (1) significant variation in FCR (coefficients of variation from 1% to 47%) among ponds with similar stocking, feeding, and aeration rates; (2) significant effects of survival on FCR; and (3) no significant effects on FCR of yield, feed type, management, or production system. Improvements in FCR would occur with improved survival that requires improved management of federally protected fish‐eating bird populations and development of additional, effective vaccines for diseases. FCRs were found to not exhibit the degree of reliability and consistency required for use as an effective metric or numeric standard for regulatory purposes. Use of FCR for mandatory or voluntary regulation is unlikely to lead to behavioral changes by farmers. [ABSTRACT FROM AUTHOR]

Nowadays, including vegetable ingredients in fish diets without growth effects is common; however, their intestinal oxidative status under these conditions is less known. Five isonitrogenous and isolipidic diets with 75% vegetable oil (VO) inclusion were formulated for juvenile gilthead sea bream (Sparus aurata). As VO, one diet contained palm oil (diet P), another rapeseed oil (diet R), and the other three included linseed oil (L) combined with the above-mentioned VOs (named PL, RL and RPL diets). After 18 weeks, pyloric caeca (PC) and proximal intestine (PI) were analyzed for oxidative stress biomarkers, lipid peroxidation (LPO), and gene expression. Dietary linseed oil diminished the superoxide dismutase activity in both intestinal regions, catalase in PC and glutathione reductase in PI; rapeseed oil reduced the glutathione peroxidase (GPx) and glutathione-S-transferase activities in PC, and palm oil upregulated GPx activity in PI. The PL diet triggered LPO levels in the PI, and RPL-fed fish showed the highest levels of LPO in the PC due to lower antioxidant activities, while RL-fed fish presented the best oxidative status. The results suggest that the dietary amount of n-6 and the unsaturated/saturated fatty acids ratio are factors to be considered in aquafeed formulation, including VOs, to improve the intestinal oxidative status in fish. [ABSTRACT FROM AUTHOR]

Fishmeal replacement in aquafeed is a prime challenge for researchers in the modern era of fish nutrition. Six isonitrogenous diets (27% protein) were prepared with graded fishmeal replacement i.e., 0% (Control), 20% (D1), 30% (D2), 40% (D3), 50% (D4) and 100% (D5) by brewer's spent yeast (BSY). The efficiency of these diets was evaluated on Labeo rohita (2.0 ± 0.02 g) fingerlings in 90-day feeding trial under controlled environmental conditions of 250 L FRP tanks. All treatments were having three replicates and fed with 4% body weight. The result revealed that 30% replacement of fishmeal showed significantly higher values in terms of growth attributes like weight gain, average daily growth, specific growth rate and survival (%) than that of control and other BSY incorporated diet. The feed utilization in terms of feed conversion ratio, feed conversion efficiency, protein efficiency ratio and apparent net protein utilization was significantly better in D2, followed by D3. The highest value of RBC, haemoglobin and packed-cell volume was found in D2, whereas that of WBC was found in D5. The amylase activity was highest in D1 whereas lipase and protease were highest in D2. The level of cortisol, glucose, alkaline phosphatase and lactate dehydrogenase was lowest in D2. Both liver enzymes such as alanine aminotransferase and aspartate aminotransferase were also significantly lower in D2 and gradually increased with the inclusion of brewer's yeast. A similar trend was observed in serum protein, albumin and globulin level. Hence the study infers that a 30% replacement of fishmeal with brewer's spent yeast can significantly induce growth performances and immunity in L. rohita. [ABSTRACT FROM AUTHOR]

The fish brain is crucial for adjusting to environmental changes. Metabolic changes play a vital role in the adaptation to salinity change in aquatic animals. However, few studies have evaluated the responses of the fish brain to salinity changes. To evaluate the response to various salinities, spotted scat (Scatophagus argus) was cultured in water with salinity levels of 5 (low salinity: LS), 25 (control group: Ctrl), and 35 (high salinity group: HS) for 22 days. The brain transcriptome was analyzed. In total, 1698 differentially expressed genes (DEGs) were identified between the HS and Ctrl groups, and 841 DEGs were identified between the LS and Ctrl groups. KEGG analysis showed that the DEGs in the HS vs. Ctrl comparison were involved in steroid biosynthesis, terpenoid backbone biosynthesis, fatty acid biosynthesis, ascorbate and aldarate metabolism, other types of O-glycan biosynthesis, and fatty acid metabolism. Glyoxylate and dicarboxylate metabolism, one carbon pool by folate, steroid biosynthesis, and cysteine and methionine metabolism were significantly enriched in the LS vs. Ctrl comparison. Additionally, the genes related to metabolism (acc, fas, hmgcr, hmgcs1, mvd, soat1, nsdhl, sqle, cel, fdft1, dnmt3a and mtr) were significantly up-regulated in the HS vs. Ctrl comparison. The genes related to metabolism (lipa, sqle, acc, fas, bhmt, mpst, dnmt3a, mtr, hao2, LOC111225351 and hmgcs1) were significantly up-regulated, while hmgcr and soat1 were significantly down-regulated in the LS vs. Ctrl compparison. These results suggest that salinity stress affects signaling pathways and genes' expressions involved in metabolic processes in the brain, and the differences in metabolism play an important role in adaptation to hyperhaline or hypohaline environments in spotted scat. This research provides a comprehensive overview of transcriptional changes in the brain under hyperhaline or hypohaline conditions, which is helpful to understand the mechanisms underlying salinity adaptation in euryhaline fishes. [ABSTRACT FROM AUTHOR]

There has been a surge of research in the aquaculture industry investigating probiotic, prebiotic, and synbiotic interventions on the physiological mechanisms of fish, specifically digestive enzymes, oxidative stress, and antioxidant defense. In fish, probiotics have been shown to improve nutrient utilization and growth performance by stimulating digestive enzymes. Meanwhile, probiotics, prebiotics and synbiotics have also been studied for their ability to modulate oxidative stress and antioxidant defense mechanisms in fish, highlighting their multifaceted health benefits. This review identified current trends, research gaps, and future considerations in this evolving field. Although promising findings have been made, a significant research gap exists in understanding the specific role of probiotics prebiotics, and synbiotics in modulating digestive enzymes, oxidative stress, and antioxidant defense systems in a variety of fish species. As this study investigate into the existing body of literature, it becomes evident that while certain aspects of these interactions have been elucidated, a nuanced and comprehensive understanding still needs to be discovered. The variations in experimental design, species-specific responses, and the lack of standardized methodologies contribute to the complexity of the field. Digestive physiology and antioxidant defense mechanisms vary among different fish species, so future research should focus on species-specific responses to probiotic, prebiotic, and synbiotic formulations. It will also be possible to establish robust correlations between dietary interventions and observed effects through a systematic experimental design and methodology approach. Accordingly, further research is needed to understand the interactions between probiotics, prebiotics, and synbiotics in fish and digestive enzymes, oxidative stress, and antioxidant defense. Identifying research gaps and adopting standardized methodologies can help develop tailored strategies to optimize aquaculture fish health and growth performance. [ABSTRACT FROM AUTHOR]

Methods: Therefore, in this study, we assessed the changes in growth, morphology, digestive enzymes, and hormone levels in T. modestus from 0--60 days post-hatching (dph) and revealed growth turning points by morphological measurement and determination of digestive enzyme activities and hormone levels. We found that ontogenesis could be divided into the larval (0--20 dph) and juvenile (20--60 dph) stages. Acid and alkaline protease activity significantly increased and decreased, respectively, from 12-- 25 dph, likely due to the development of stomach and gastric glands. Acid phosphatase levels significantly increased at 0 and 4 dph, whichmay be related to the regulation of metabolism and immune protection. A sharp increase in alkaline phosphatase levels at 20 and 25 dph was observed and was likely due to the development of the brush border membrane of enterocytes. The amylase level was significantly higher at 25, 30, and 35 dph, possibly due to better digestion and absorption during the transition from consuming Artemia to compound feed. In newly hatched larvae, the level of thyroid hormones triiodothyronine (T3) and thyroxine (T4) gradually increased and peaked at 35 dph, highlighting the importance of these hormones during the development of T. modestus. Growth hormone (GH) levels first increased from 0--8 dph, with a plateau at 8--20 dph, and then increased at 25--30--35 dph. For insulinlike growth factor 1 (IGF-1), a significant increase with a subsequent plateau was observed between 8 and 20 dph, followed by a substantial decrease between 30 and 35 dph. These results suggest that the regulating functions of GH and IGF-1 are synchronised. Digestive enzyme activity and hormone levels of abnormal fry at 30 dph were lower than those of normal fish, highlighting the importance of specific hormones, especially T4 and IGF-1, in the development of T. modestus. [ABSTRACT FROM AUTHOR]

This study aimed to examine the effect of various live foods on the fatty acids (FAs) and amino acids (AAs) profiles in Persian sturgeon (Acipenser persicus) larvae. One thousand and two hundred larvae were cultured in circular concrete tanks, and four treatments were administered as: (1) Artemia + Daphnia, (2) Artemia, (3) Artemia + Chironomid, and (4) Chironomid. Each treatment was considered as three replicates over an 11-day period. At the end of the experiment, treatment 1 (Artemia + Daphnia) showed the highest average weight of larvae, and the lowest weight was observed in treatment 4 (Chironomid). Survival rate ranged from 83.84% to 88.86% and no significant difference was observed among the groups (P > 0.05). Among Artemia-fed larvae, the predominant FAs were docosahexaenoic acid (DHA), oleic acid (ω9), and monounsaturated fatty acids (MUFA), while saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA) (ω3 + ω6) were present in a lesser proportion (P < 0.05). In larvae fed with Artemia and Daphnia, the predominant proportions were observed in SFAs, eicosapentaenoic acid (EPA), ω3, DHA + EPA, and the n3/n6 ratio, all registering the highest percentages. Conversely, MUFA, ω6, and the DHA/EPA ratio displayed the lowest percentages (P < 0.05). Moreover, larvae fed with Artemia exhibited higher levels of ω6, PUFA (ω3 + ω6), and DHA/EPA ratio. In contrast, larvae fed with Chironomid showed lower levels of EPA, DHA + EPA, and n3/n6 ratio (P < 0.05). Among larvae fed with Chironomid, solely the DHA/EPA ratio exhibited a higher value compared to larvae fed with Artemia and Daphnia (P < 0.05). The amount of leucine in fish fed Artemia + Daphnia was more than the other treatments (P < 0.05). This study revealed a significant difference in amino acids composition among various live foods (P < 0.05), but no significant difference in AAs was observed in the body of Persian sturgeon larvae (P > 0.05). The results of this study suggest that the Persian sturgeon larvae possess the ability to maintain a balanced state of AAs. It is also evident that the FA profile of different live foods can affect the overall FA levels in the body of Persian sturgeon larvae, ultimately contributing to the enhancement of fish survival rate and growth. [ABSTRACT FROM AUTHOR]

To investigate the impact of the effect of high temperature stimulation on Monopterus albus larvae after a certain period of time, five experimental groups were established at different temperatures. Then, the M. albus under high temperature stress was fed at 30°C for 70 days. After that, the growth index of the M. albus was counted and analyzed. In terms of growth index, high temperature stress had significant effects on FCR, FBW, WGR, and SGR of M. albus (p < 0.05). The SR increased after being stimulated by temperature (p < 0.1). The study revealed that liver cells of M. albus were harmed by elevated temperatures of 36°C and 38°C. In the experimental group, the activities of digestive enzymes changed in the same trend, reaching the highest point in the 32°C group and then decreasing, and the AMS activity in the 38°C group was significantly different from that in the 30°C group (p < 0.05). The activities of antioxidase in liver reached the highest at 34°C, which was significantly different from those at 30°C (p < 0.05). In addition, the expression levels of TLR1, C3, TNF-α, and other genes increased in the experimental group, reaching the highest point at 34°C, and the expression level of the IL-1β gene reached the highest point at 32°C, which was significantly different from that at 30°C (p < 0.05). However, the expression level of the IRAK3 gene decreased in the experimental group and reached its lowest point at 34°C (p < 0.05). The expression level of the HSP90α gene increased with the highest temperature stimulus and reached its highest point at 38°C (p < 0.05). In the α diversity index of intestinal microorganisms in the experimental group, the observed species, Shannon, and Chao1 indexes in the 34°C group were the highest (p < 0.05), and β diversity analysis revealed that the intestinal microbial community in the experimental group was separated after high temperature stimulation. At the phylum level, the three dominant flora are Proteus, Firmicutes, and Bacteroides. Bacteroides and Macrococcus abundance increased at the genus level, but Vibrio and Aeromonas abundance decreased. To sum up, appropriate high-temperature stress can enhance the immunity and adaptability of M. albus. These results show that the high temperature stimulation of 32°C–34°C is beneficial to the industrial culture of M. albus. [ABSTRACT FROM AUTHOR]

The spotted seatrout (Cynoscion nebulosus)—an important commercial species—has a high potential for aquaculture in the Gulf of Mexico. To optimize its feeding during larval rearing, this study aims to evaluate the primary gastric (pepsin), intestinal (leucine aminopeptidase and alkaline phosphatase), and pancreatic (alkaline protease, trypsin, chymotrypsin, amylase, and lipase) enzyme activities from hatching to day 30. A multivariate analysis identified three digestive enzyme development stages during the spotted seatrout larval transformation. The first stage occurred between 1 (mean ± standard error (SE) = 1.73 ± 0.14 millimeter (mm) standard length (SL)) and 3 (2.14 ± 0.07 mm SL) days after hatching (DAH); a period of digestive stability showed the highest activity in amylase and bile salt-dependent lipase. The second stage (from 4 (2.53 ± 0.09 mm SL) to 20 (10.92 ± 0.51 mm SL) DAH) was a period of digestive transition, during which leucine aminopeptidase, chymotrypsin, and alkaline proteases were identified as the predominant enzymes from 4 to 5 DAH. In the third stage—a period of digestive stability—pepsin was the major enzyme that occurred between 25 (16.51 ± 0.81 mm SL) and 30 (25.91 ± 0.82 mm SL) DAH. These results indicate that the spotted seatrout larvae have a digestive system adapted to lipids and carbohydrates at the onset of feeding, with an immediate transition to protein digestion when exogenous feeding begins. Additionally, the digestive system of the spotted seatrout may be considered mature at 25 DAH. Further research is needed to elucidate the mechanisms of digestive tract development in the spotted seatrout larvae. [ABSTRACT FROM AUTHOR]

Endocrine-disrupting chemicals (EDCs) may mimic the endogenous neuroendocrine and endocrine messengers and interfere with developmental, reproductive, immune, metabolic and other physiological functions. Modulation of basal metabolic rate, energy metabolism, food intake and engorgement by endocrine disruptors may lead to loss of metabolic equilibrium. EDC-induced loss of metabolic homeostasis and obesity gave rise to the concept of metabolic-disrupting chemicals (MDC) and environmental obesogens. Elevated oxidative stress, alterations in the circadian clock, and energy-sensing homeostasis are some of the major pathophysiological conditions implicated in promoting metabolic disruption. Reportedly, fish are the most vulnerable candidate due to their direct exposure to metabolic disruptors in aquatic habitats. Though limited, studies conducted using piscine models have helped to identify MDCs in the aquatic environment. Notably, the molecular mechanisms through which MDCs can negatively influence the metabolism of hormones, epigenetic alteration, gut dysbiosis, and changes in endocrine and metabolic receptor expression and functions have recently gained considerable attention. In this review, we provide an update on the impact of MDCs on the initiators, cellular mediators, and hormone receptors related to the maintenance of metabolic homeostasis, with particular emphasis on fish models. [ABSTRACT FROM AUTHOR]

Although early embryonic protein production relies exclusively on maternal molecules such as messenger RNAs (mRNAs) incorporated into ovarian follicles, knowledge about any thermally induced, intergenerational effects is scarce in ectotherms. Here, we investigated how elevated temperatures (9°–12°C vs. 6°C) during oogenesis influenced the next generation by targeting maternal mRNAs in Atlantic cod (Gadus morhua) embryos, in view of up- and down-regulated genes in ovarian follicles of pre-spawning adults. Overall, the spawning female liver showed significantly higher levels of free amino acids and N-metabolites at 9°C than at 6°C. Higher-than-optimal temperatures induced adjustments in embryo transcriptome proportional to the temperature increase relative to the control group. The adjustments included alterations in maternal-effect genes, which are developmentally conserved among vertebrates. The transcriptomic differences for a selection of genes in embryos were reflected in ovarian follicles (containing multiple cell types) several months ahead of the spawning season, implying that environmental conditions of the adults are key for adjusting the genetic instructions for offspring development. This programming of fundamental traits from mother to offspring appears part of a sophisticated process to adapt the offspring to a changing ocean, though within life stage-specific, physiological thermal tolerance windows. [ABSTRACT FROM AUTHOR]

Feeding is a critical process in aquaculture, as it has a direct impact on the quantity and quality of fish. With advances in convolutional neural network (CNN) and vision transformer (ViT), intelligent feeding has been widely adopted in aquaculture, as the real-time monitoring of fish behavior can lead to better feeding decisions. However, existing models still have the problem of insufficient accuracy in the fish behavior-recognition task. In this study, the largemouth bass (Micropterus salmoides) was selected as the research subject, and three categories (weakly, moderately, and strongly hungry) were defined. We applied the deformable attention to the vision transformer (DeformAtt-ViT) to identify the fish hunger degree. The deformable attention module was extremely powerful in feature extraction because it improved the fixed geometric structure of the receptive fields with data-dependent sparse attention, thereby guiding the model to focus on more important regions. In the experiment, the proposed DeformAtt-ViT was compared with the state-of-the-art transformers. Among them, DeformAtt-ViT achieved optimal performance in terms of accuracy, F1-score, recall, and precision at 95.50%, 94.13%, 95.87%, and 92.45%, respectively. Moreover, a comparative evaluation between DeformAtt-ViT and CNNs was conducted, and DeformAtt-ViT still dominated the others. We further visualized the important pixels that contributed the most to the classification result, enabling the interpretability of the model. As a prerequisite for determining the feed time, the proposed DeformAtt-ViT could identify the aggregation level of the fish and then trigger the feeding machine to be turned on. Also, the feeding machine will stop working when the aggregation disappears. Conclusively, this study was of great significance, as it explored the field of intelligent feeding in aquaculture, enabling precise feeding at a proper time. [ABSTRACT FROM AUTHOR]

Simple Summary: The silkworm has fascinated people all around the world for centuries due to numerous applications of by-products resulting from its metamorphosis. A decline has been noticed due to industrialization and some disease concerns; however, several reasons strengthen compelling arguments for keeping up this species. The most prevalent nutrients identified along silkworm rearing, from mulberry leaves up to larvae, pupae, and silk, are proteins. The biological value of protein is based on amino acids. The presence of other nutrients, especially fatty acids (n-3 family), vitamins, minerals, and polyphenols, along with the profile in amino acids, which are taken from mulberry leaves and metabolized by larvae and then transferred to pupae, strengthen the conviction according to which silkworm by-products have a great nutritional potential that is either comparable with fish meal or better than other aquaculture-specific feedstuffs. This paper aims to present deep knowledge about amino acids (classification, metabolism, occurrence, mechanisms, and potential functions) for silkworms and fish to further understand these species. The silkworm Bombyx mori, the second most varied group of insects, is a fascinating insect that belongs to the Lepidoptera species. We aimed to deepen our knowledge about the composition and significance of amino acids (AA) from the sericulture chain to fish. AAs are the most prevalent molecules throughout the growth process of silkworms. We described AAs classification, occurrence, metabolism, and functions. Online datasets revealed that the essential AAs (EAA) level in fish meal and silkworm pupae (SWP) is comparable. SWP have a high content of methionine and lysine, which are the principal limiting AAs in fish diets, indicating that SWP have nutritional potential to be added to fish diets. Additionally, an overview of the data analyzed displays that SWP have a higher protein efficiency ratio than fish meal, the classical protein-rich source (>1.19 times), and compared to soybean meal, the second-most preferred source of protein in aquaculture (>2.08 times), indicating that SWP can be considered effective for animal feeding. In this study, we provide an overview of the current knowledge concerning AAs, paying special emphasis to EAAs and explaining, to some extent, certain mechanisms and functions of these compounds, from mulberry leaves to larvae–pupae and fish diets. [ABSTRACT FROM AUTHOR]