Aquaculture Research

Siniperca chuatsi is an economically important carnivorous fish. The efficient commercial culture of this fish is hindered by suboptimal nutrient utilization and the emergence of diseases, specifically viral diseases. Compound Chinese herbal medicine (CCHM) and probiotics can be used to enhance disease resistance and improve digestion. We have previously isolated Bacillus velezensis, a probiotic with a desirable effect on S. chuatsi. In this study, we aimed to evaluate the antiviral effect of a CCHM compound at the cellular level by conducting animal tests to investigate the synergistic effect of CCHM and B. velezensis GY65 in a simulated S. chuatsi culture. The animal experiments were divided into four groups: control group (G0); CCHM group (G1); B. velezensis GY65 group (G2); and Chinese herbal medicine compound probiotic group (CHCP) (G3). CCHM showed significant blocking and killing effects on the largemouth bass virus (LMBV) (p<0.05), while the inhibiting effect was not significant. In animal tests, CCHM significantly improved S. chuatsi growth, while CHCP reduced S. chuatsi mortality. Regarding biochemical and nonspecific immune parameters, CHCP reduced serum lipid and hepatic malondialdehyde levels and increased serum lysozyme and hepatic catalase activities (p<0.05). CCHM and B. velezensis GY65 increased the serum glutathione transaminase levels (p<0.05). Digestive enzymes in the intestine of S. chuatsi improved in all groups, and the best result was observed in the CHCP group. Additionally, the intestinal development improved in all groups, but the best intestinal development was observed in the CCHM group. However, in the kidney, only TNF-α was significantly upregulated in the CHCP group (p<0.05). In conclusion, CCHM exerted significant blocking and killing effects on LMBV. CHCP effectively protected the growth and immunity of S. chuatsi. Our findings provide preliminary data and lay the foundation for the practical application of herbal medicines and probiotics in aquaculture.

Previously, dietary humic substances (HSs) or protease complexes (PCs) in fingerling channel catfish Ictalurus punctatus (Rafinesque) have demonstrated potential for health enhancement. Two trials were conducted to elucidate an optimal HS or PC administration plan for growth and health promotion. The first feeding trial was conducted within a recirculating aquaculture system. Catfish fingerlings were fed a commercial control (28% protein) or supplemented diet (control + PC or HS). Diets were administered through four feeding regimens of either HS, or PC-supplemented diet. After 60 days, continuous feeding of diets with HS or PC contributed to improved feed efficiency and weight gain of the fish. Similarly, catfish growth was enhanced following the application of HS or PC for the final 4 weeks. Serum lysozyme activity was relatively improved in catfish when a PC or HS diets were offered for 60 days. Feeding either of the supplements for the final 4 weeks improved skin lysozyme activity compared to the control group. In the second trial, catfish were fed either the commercial control diet, PC-supplemented diet, or HS-supplemented diet in an outdoor production environment for 60 days. Both HS and PC catfish groups had higher survival rates than the control group. Furthermore, growth performance was superior in additive-fed groups. After HS or PC application, gut microbiota analysis from catfish fecal at two time points revealed significant variation in alpha diversity, community abundance, and beta diversity. However, the association of dietary HS or PC on improved survival, immunity, and gut microbiota modulations presents their importance as functional immunostimulants in catfish aquaculture.

Aquaponics, a sustainable agricultural approach, integrates aquaculture and hydroponics to optimize water consumption and enhance resource efficiency. The coastal region of Bangladesh, prone to frequent natural disasters, necessitates the development of resilient food production systems. In the present study, an adaptive aquaponic system was developed to evaluate the effectiveness of fish and vegetable production and assess the adoption process of this technology by the local communities to address climatic effects. The study design involved three treatment groups from the local communities, namely: local farmers (T1), school teachers (T2), and boat sailors (T3). The aquaponics system was stocked with monosex tilapia (Oreochromis niloticus) fry and various fast-growing vegetable crops. The tilapia fry had an initial mean length of 7.1 ± 0.845 cm and weight of 10.02 ± 0.02 g and were introduced at a stocking density of 95 fry per 0.8 m³ in a 1000-L capacity water tank. Seedlings of tomato, basil, turnip, cauliflower, and eggplant were planted in separate tubs and tank heads within the aquaponic systems. Results indicated that both fish and plant production in the treatment managed by local farmers surpassed that of other community groups. Treatment T1 demonstrated the highest fish production at 1542.69 ± 1.0 kg/ha/120 days, followed by T2 (1317.44 ± 0.37 kg/ha/120 days) and T3 (1278.204 ± 0.37 kg/ha/120 days). Similarly, turnip production mirrored this trend, with values of 8960 ± 672, 7440 ± 432, and 5120 ± 640 (kg/ha/120 days) for T1, T2, and T3, respectively. Tomato production ranked second highest production, with values of 5132.31 ± 361.85, 4520 ± 272, and 4349.6 ± 300.48 kg/ha/120 days in T1, T2, and T3, respectively. The measured water quality parameters were recorded as follows: temperature at 20.17 ± 0.23°C, dissolved oxygen (DO) at 5.80 ± 0.55 mg/L, pH at 8.04 ± 0.11, NH3─N at 0.26 ± 0.01 mg/L, NO2─N at 0.35 ± 0.01 mg/L, NO3─N at 0.03 ± 0.01 mg/L, and PO4─P at 0.43 ± 0.01 mg/L. A survey on the implementation of the technology revealed that participants had positive perceptions regarding the effectiveness of the aquaponic system, with 76.67% strongly agreeing to adopt the technology for future fish and vegetable production. Significantly, there were no opposing views, demonstrating a high level of acceptance. The study highlights the need to assess the technology’s effectiveness and community acceptance in other climatically vulnerable regions.

Although the benefits of incorporating algal oil (AO) in plant-based aquafeeds have been established for most commercial fish species, knowledge on the effects of such incorporation in shrimp feeds is scarce. The present study assessed how AO inclusion at different levels in a plant-based shrimp feed could promote growth and fatty acid (FA) deposition in the muscle. Pacific white shrimp, Litopenaeus vannamei, were fed a reference diet with marine animal ingredients (F0) or a marine-free plant-based diet with vegetable oil (VO) alone (P0), or in combination with 1% (P1) or 2% (P2) AO. After 51 days of culture, zootechnical and nutritional performance of shrimp fed with AO supplemented diets was significantly improved. The sensory attributes of shrimp fed P1 and P2 were slightly improved relative to P0 while the eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) content was three to four times higher, thereby increasing the nutritional value of shrimp. Therefore, plant-based feeds can sustain an efficient production of L. vannamei with controlled FA profiles, provided they are supplemented with AO. In addition, the use of AO eliminates the reliance of shrimp feeds on the limited supplies of marine ingredients while maintaining the forage fish dependency ratio for fish oil (FO) of zero and allows for the use of more flexible formulae based on different meals of nonmarine origin.

Aquaculture in sub-Saharan African accounts for less than 2% of world aquaculture production. The use of unimproved species limits the growth of aquaculture. In order to increase production, there is a need to develop aquaculture species that show vigor and adapt to different culture conditions. A genetic improvement program for Oreochromis shiranus was initiated at the National Aquaculture Center (NAC), in Zomba, Malawi. The program used pedigree records during mate allocation to avoid mating of siblings. After six consecutive generations of selection, a sample of 32 fish was taken for genetic analysis using a panel of 16 microsatellite markers. Genetic diversity and population differentiation indices of the sixth filial generation (F6) were compared with wild fish populations sampled from the corresponding locations from which the initial brood stock was collected. The study results show that the genetic diversity of the F6 generation and wild populations was not significantly different after the Kruskal–Wallis tests. However, the number of private alleles was lower in generation F6 (0.80) than in the overall average for wild populations (1.28). Discriminant analysis of principal components (DAPCs) supported analysis of molecular variance (AMOVA) by showing that there were no significant overlaps of inertia ellipses among F6 generation and wild populations. The experimental population differentiated into a separate group because of the random brood stock contribution from only a few fish from the wild population. The results suggest that the initial genetic diversity of the brood stock was sufficient as shown by the high number of alleles and polymorphic information content (PIC) values which contributed to the success of the selection program. The selection program successfully produced large fish at harvest and ensured genetic diversity of the F6 generation.

Freshwater aquaculture plays a crucial role in addressing the growing demand for seafood, providing a sustainable solution, and contributing to global food security. It offers notable advantages for saltwater aquaculture in terms of cost-effectiveness, environmental management, and reduced ecological impact. As a system for farming aquatic organisms, aquaculture significantly contributes to human food production and addresses issues like protein shortages and diet-related diseases. However, it also faces challenges such as fish epidemics and ecosystem impacts. This Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-based systematic review focuses on the needs of both the modulation of chemical–physical environmental factors and natural ingredients used in feed formula to improve the wellness of farmed fish in freshwater aquaculture. We analyzed published articles between 1 January 2013 and 30 June 2024 using PubMed, Scopus, and Web of Science databases. The results highlighted the good effects of ultraviolet light (UV-C) treatment about bacterial infections and the use of oxolinic acid (OA) and alpha-lipoic acid (ALA) on fish welfare through diet. These factors highlighted the importance of dose-dependent applications of both environmental physico-chemical factors and natural feed ingredients. Tailoring diets with specific nutritional components is crucial to improve productive outcomes in freshwater aquaculture systems, ultimately supporting the health and welfare of farmed fish.

To address the issues of accurately identifying and tracking individual fish abnormal behaviors and poor adaptability in the aquaculture field, this paper proposes a Mask2former model combined with a bidirectional routing attention mechanism (BiFormer) and a multiscale dilated attention (MSDA) module for fish abnormal behavior recognition and segmentation. To compensate for the lack of publicly available datasets on fish abnormal behavior, we created the “FISH_segmentation_2023” abnormal behavior dataset, which includes four types of fish behaviors. First, by introducing the BiFormer attention mechanism, the model can better capture critical temporal and spatial information in image sequences, significantly enhancing feature representation. Second, after processing the feature maps with the pixel decoder, the MSDA module is introduced to perform multiscale fusion on these features. The fused features are then passed to the transformer decoder, further enhancing the model’s ability to recognize fish abnormal behaviors. Finally, to further improve model performance and address class imbalance issues in the dataset, we designed a composite loss function combining focal loss and dice loss (FD loss). This loss function can balance the influence of easy and difficult-to-classify samples while optimizing segmentation performance, thereby improving the model’s recognition accuracy and mean intersection over union (mIoU) metrics. Experimental results show that the BiFormer multiscale dilated attention FD loss (BMF)-Mask2former model exhibits high performance, achieving average intersection over union (IoU), accuracy, and recall values of 92.33%, 95.63%, and 94.82%, respectively, on the self-built FISH_segmentation_2023 dataset, representing improvements of 6.10%, 4.50%, and 5.09%, respectively, compared to the Mask2former model. The study demonstrates that the proposed model can accurately capture both local and contextual features of fish abnormal behaviors through multiscale fusion methods, resulting in high-quality segmentation outcomes.

The quest to reduce dependency on fish- or vegetable-based oil resources has prompted aquaculture experts to intensify their search for a suitable and sustainable alternative for aquafeed production. Based on this reality, the current study was designed to evaluate the dietary influence of African palm weevil oil (PWO) on the growth performance, serum biochemistry, lipid peroxidation products, antioxidant enzyme response, and organ integrity of African catfish (Clarias gariepinus) juveniles. Four diets were formulated, wherein the control diet was prepared using soybean oil (SO) as the main dietary oil source and was replaced with PWO in the treatment diets at 50% (PWO-50), 75% (PWO-75), or 100% (PWO-100). A total of 180 African catfish (average weight: 18.76 ± 0.043) were randomly stocked at 15 fish per 50-L tank in triplicate and hand-fed to apparent satiation twice daily for 45 days. The results showed that the highest weight gain (WG), specific growth rate (SGR), and thermal growth coefficient (TGC) were found in control (SO)-fed fish, which is similar to the PWO 50% but differs significantly from others (p<0.05). The feed conversion ratio (FCR) and protein productive value (PPV) showed linear and quadratic trends, with a significantly lowest and highest value recorded in fish-fed control and PWO 50%, respectively, compared to other dietary groups (p<0.05). The protein efficiency ratio (PER) value decreases linearly (p<0.001) as the level of PWO increases. The highest total immunoglobulin (TIG) and superoxide dismutase (SOD) activity were recorded in fish fed PWO-50%, while PWO-75% registered the highest lysozyme activity (LA). There was no statistically significant difference (p>0.05) in the physiological parameters such as total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), alanine aminotransferase (ALT), C-reactive protein (CRP), and lipid peroxidation index (malondialdehyde [MDA]) among the groups. The fish fed PWO-100% had the lowest recorded values of villus height, area of absorption, and cryptal depth (p<0.05). In summary, the current finding shows that oil extracted from African palm weevils appears promising at a 50% dietary level without impairing the growth performance, liver, or intestinal health of African catfish.

Sea urchins, ecologically important marine species, host a complex gut microbiota that plays a significant role in their digestion, nutrient acquisition, and overall health. The gut microbes, along with endogenous enzymes, facilitate the breakdown of macroalgae and other food sources. Environmental factors, including temperature, salinity, and habitat type, can greatly influence the microbial communities within sea urchins. Dietary variations can also lead to shifts in the abundance and composition of intestinal bacteria, highlighting the strong connection between diet and gut microbiota. The sea urchin’s unique anatomy and digestive system adaptations contribute to their ability to process and absorb nutrients efficiently, supporting their varied diets. Gut microbes not only participate in the decomposition of complex carbohydrates, but also in detoxifying compounds and mitigating the impacts of inhospitable environments. Further research is needed to fully understand the intricate relationships between sea urchin species, their habitats, diets, and gut microbiota composition. A deeper understanding of these interactions may inform sustainable management and aquaculture strategies, ensure the long-term viability of economically valuable sea urchin species, and provide insights into their ecological roles and adaptability to changing environments.

This study investigated the effects of commercial probiotics on the growth, feed utilization, hematology, innate immunity, and disease resistance of climbing perch (Anabas testudineus). One gram of each locally available branded commercial probiotic, Pro-1, Pro-2, Pro-3, and Pro-4, was incorporated into commercial fish feed to prepare treatment diets T1 to T4, respectively, and feed without any probiotics was used as control (C). After 8 weeks of feeding, all groups demonstrated significantly improved percent weight gain (WG) and specific growth ratio (SGR; except T3) and lower feed conversion ratio (FCR) relative to C. Moreover, these growth and feed utilization parameters were positively modulated in T2 compared to C and the other three treatments. Serum biochemical parameters, such as liver stress enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST), were lower (p<0.05) in the probiotic-supplemented group, but variations in triglyceride (TG, mg dl⁻¹) levels were detected. Important hematological parameters, including white blood cells (WBC), lymphocytes (Lymphs), mean corpuscular hemoglobin concentration (MCHC), red blood cell (RBC) distribution width (RDW)-standard deviation (SD), and platelets (PLT), also improved after probiotic administration. Innate immune parameters, such as respiratory burst (RB) in T3 and alkaline phosphatase (ALP) in T2 to T4, also increased. The pathogenetic bacterial challenge with Aeromonas hydrophila (1 × 10⁸ colony-forming units (CFUs)/mL) revealed the enhanced survival rates in T2 and T3 compared to other groups. Therefore, locally available commercial probiotic administration through fish diet inoculation enhanced the growth, boosted immunity and hematology, and increased infectious disease protection against A. hydrophila infection in A. testudineus to and ensured the sustainable aquaculture rearing of this species.

Infectious pancreatic necrosis (IPN) has highly contagious disease and an important viral disease-causing economic loss for fish farming, which has developed in recent years. The virus is the first fish virus isolated in vitro. Horizontal and vertical transmission plays an important role in the spread of the virus. In addition, the resistance of the virus to environmental conditions makes it difficult to control the virus. Therefore, it is important to develop vaccines and analyze the effectivity of antivirals for the prevention and control of infectious pancreatic necrosis virus (IPNV) infection. This study investigated the antiviral effect of two different mutagens, ribavirin (RBV) and 5-fluorouracil (5-FU), on IPNV, and their mutation-inducing potential on the susceptible cell line Epithelioma papulosum cyprini (EPC), in vitro. For this purpose, cytotoxic doses of RBV and 5-FU were first investigated and were found to be 50 and 100 µM/mL, respectively. Serial passages of IPNV were then performed, both with and without drug suppression. At the end of each passage, confirmation was performed by real-time transcriptase polymerase chain reaction (RT-PCR). Serial passages were checked for viral load using quantitative RT-PCR (qRT-PCR). The viral copy number of the RBV-suppressed virus decreased from 1.18 × 10⁵ copies/µL for the 1st passage to 1.49 × 10² copies/µL at the end of the 5th passage. The viral copy number of the 5-FU-suppressed virus decreased gradually with each passage, from 3.84 × 10³ copies/µL for the 1st passage to 1.78 × 10² copies/µL at the end of the 5th passage, with the exception of the 2nd passage, where the viral load increased. Passages 1st and 5th of both the RBV- and 5-FU-suppressed virus, and the non-drug-suppressed virus, were checked by partial sequence, but mutations in VP2 were not observed. In conclusion, in this study, we obtained data on the antiviral activity of two mutagens on IPNV.

Over the past three decades, global aquaculture production has significantly increased, emphasizing the need for sustainable and cost-effective alternatives to traditional fish meal in aquafeed. This study’s objective was to elucidate the impact of utilizing a combination of fish and crustacean byproducts—namely, smoked salmon (Salmo salar) skins (SSs), smoked salmon trimmings (STs), and shrimp (Litopenaeus setiferus) heads (SHs)—as primary ingredients in pelleted aquafeed. Importantly, this work focuses on nonextruded pellets, where the physical properties are more influenced by ingredient composition compared to extruded pellets. The tested formulations were not nutritionally comprehensive for any specific commercial aquaculture species, as the goal of this study was to highlight the effect of the byproducts on pellet physical integrity. SH and de-oiled solid fractions of SS and ST were dehydrated for 24 h at 60°C, ground into dried powders, and formulated into six samples at a 1:1 (w/w) ratio and one sample at a 1:1:1 ratio. Potato starch (80 g/kg) was added to each sample, along with varying deionized (DI) water amounts before steam conditioning, pelletizing, and drying. Analyses included pellet nutrient composition, floatability, durability, water stability, bulk density, water absorption index (WAI), and water solubility index (WSI). Results revealed that SS pellets exhibited 97% floatability at 1 min, decreasing to 70% at 60 min. SS and ST combinations showed slow sinking behavior, while all other formulations sank quickly. Pellets containing SH had lower water stability (65.65% ± 4.44% to 0.05% ± 0.07%), in contrast to over 92% for SS and ST pellets. Durability ranged from 98.48% ± 0.37% for SS to 75.29% ± 5.82% for SH and ST combinations, further underlining the significant impact of byproduct choice on pellet performance. Overall, the inclusion of SS or ST and their combination as primary ingredients for pelleted aquafeed produced pellets that scored well on important quality parameters, while pellets containing SH performed poorly. This information may be used in the development of nutritionally comprehensive nonextruded aquafeeds containing SS and/or ST to conduct feeding trials with commercially relevant species.

In order to produce gynogenetic diploid of Manila clam, Ruditapes philippinarum, we studied the optimal conditions of gynogenetic diploid induced by ultraviolet (UV). The irradiance of UV-induced sperm was 230 μW (cm²·s), and the irradiation time was 0, 3, 6, 9, 12, 15, 18, 21, 24, and 27 s. After the egg fertilized with genetically inactivated sperm, the fertilized eggs were treated with cytochalasin B (CB) at different concentrations of 0, 0.25, 0.50, 0.75, and 1.0 mg/L for 20 min. The ploidy of larvae under different induction concentrations were analyzed by flow cytometry, and the chromosome division process during sperm entry and cleavage was observed by fluorescence microscope. In addition, the ultrastructure of sperm, embryonic development, and chromosome were observed. The results showed that the fertilization rate and cleavage rate decreased gradually with the prolongation of UV irradiation time. We found UV irradiation for 9 s was the optimal time for haploid formation, with an induction rate of 100%. The CB treatment at 0.75 mg/L was the optimal concentration for the formation of D-larvae, and the induction rate was 9.60% ± 5.10%. The results showed that the optimal conditions for inducing gynogenetic diploid of R. philippinarum were irradiation with UV intensity of 230 μW (cm²·s) for 9 s and inhibited second polar body release by CB at concentration of 0.75 mg/L. In this study, the conditions for inducing Manila clam gynogenetic diploid were obtained, which lays the basis for further genetic research on the gynogenesis of R. philippinarum.

In order to create new value in biomass production using sterile Ulva with high production efficiency, we selected sterile Ulva with high culture stability from the coast of Imari City in Japan and investigated the conditions for generating high concentrations of dissolved oxygen through photosynthesis using the sterile Ulva. In the cultivation of sterile Ulva, we investigated the conditions for generating high concentrations of dissolved oxygen (DO) by controlling conditions such as aeration, NO3-N concentration, and population density. As a result, we found that under the cultivation control conditions we found, DO reached about 3.8 times the saturation concentration after 3 h. It was found that this high level of DO can be maintained if the supersaturated DO seawater obtained here is properly sealed. Seawater containing high levels of DO is essential for the cultivation of oysters and shellfish, which also prefer a growth temperature of 20°C−25°C. Therefore, from the perspective of creating new value in biomass production, we developed a new system for simultaneously cultivating sterile Ulva and cultivating oysters.

Aquaponic production relies on microbial activity to convert fish wastes into nutrients for plants. An aquaponic system contains multiple compartments that each have varying environmental pressures that can impact the types of microbes living in the compartment. Furthermore, differences in fish and plant species, system startup and management, and water source can impact microbial communities that colonize an aquaponic system. In this study, we sampled two aquaponic facilities that each operated six replicate aquaponic systems. Metataxonomic analyses were performed on the samples to compare the microbial communities of aquaponic facilities in Minnesota (MN) and Wisconsin (WI), assess the consistency of the microbial communities across multiple systems within a single facility, and evaluate the abundance and types of microbes present within each compartment of a system. Proteobacteria, Bacteroidetes, and Actinobacteria were common in both facilities, but nitrifying organisms were in greater abundance at the WI facility. Microbial communities were largely consistent among systems within a facility, but microbial communities among different compartments of the systems varied. Nitrifying organisms were primarily associated with the biofilter compartment of the MN systems but were found throughout the WI systems, which do not have a dedicated biofiltration compartment. While nitrifying organisms have an important role in an aquaponic system, they comprise less than 10% of the total microbial community of the aquaponic systems we sampled. Other taxa are likely to have equally important roles in the productivity of an aquaponic system, but those taxa and their functions have not been well characterized, and it is unclear how system startup, management, and other factors impact colonization and maintenance of these taxa.

The shortage of lipid sources has been a limiting factor of the aqua-feed industry. Lysophospholipid (LPL) is a highly efficient lipid emulsifier, which may help improve lipid utilization efficiency and thus spare the dietary lipid. This study aimed to evaluate the effects of LPL on growth performance, fatty acid composition, and lipid metabolism of juvenile Litopenaeus vannamei (averagely, 2.4 g). Five diets were prepared: a control diet with 6.5% lipid, the control diet supplemented with 0.05% or 0.1% LPL (0.05% LPL and 0.1% LPL), a moderately low-lipid (MLL) diet supplemented with 0.05% LPL (0.05% LPL-MLL), and an extremely low-lipid (ELL) diet supplemented with 0.1% LPL (0.1% LPL-ELL). Each dietary group had triplicate tanks (30 shrimp in each tank). The feeding experiment lasted 8 weeks. Compared with the control group, the addition of 0.05% LPL promoted the growth by 9.95%; diet 0.05% LPL-MLL resulted in a comparable growth to the control, but diet 0.1% LPL-ELL tended to adversely affect the growth. Dietary LPL had little effect on the whole-body proximate composition. The content of 18:2n−6 and 18:3n−3 was significantly higher in the 0.05% LPL group compared to the control. The 20:5n−3 content was the highest in the 0.05%LPL-MLL group. In addition, the 0.05% LPL and 0.1% LPL group increased the plasma high-density lipoprotein-cholesterol content. Meanwhile, all LPL groups reduced the low-density lipoprotein-cholesterol content. The addition of LPL significantly regulated the messenger RNA (mRNA) expression of genes related to cholesterol homeostasis, such as ldlr, srb1, abca1, and abcg8. In conclusion, dietary supplementation with 0.05% LPL tended to promote shrimp growth and can spare 15% dietary lipid. However, when the dietary lipid content decreased from 6.5% to an extremely low level of 4.8%, dietary LPL was ineffective to spare lipids. This was the first study to validate the lipid-sparing effect of dietary LPL in shrimp.

Among salmonids, brook charr, Salvelinus fontinalis has been gaining popularity in aquaculture. However, major limitations associated with opportunistic diseases that result from unstable egg and fry-rearing conditions are experienced under intensive rearing conditions. Great losses in brook charr culture result from viral (e.g., infectious pancreatic necrosis, viral hemorrhagic septicemia virus), fungal (e.g., saprolegniosis), and bacterial (e.g., furunculosis, cold water disease, columnaris) diseases. Unfortunately, there is no effective treatment for viral diseases for brook charr, and the chemical disinfectants and antibiotics commonly used against bacterial and fungal infections are reaching their limits (pathogen resistance, microbial community disruption), making alternative and more sustainable rearing approaches essential to bolster aquaculture. In this regard, recent studies show that many microbial species (bacteria, archaea, viruses, eukaryotes-like protozoa, and unicellular fungi) are essential from the earliest life stages for the proper development and growth of fish. Based on ecological theory and work on marine fish, it has been hypothesized that current aquaculture practices favor r-strategic, opportunistic microbes that are detrimental to fish health and development. Consequently, to ensure the success and sustainability of brook charr farming, a new aquaculture paradigm involving recirculating aquaculture systems (RAS) that select a K-enriched, specialized microbial community as a preventive measure against those microbial diseases is a very promising avenue. In this review, after introducing brook charr biology, the role of microbes in brook charr rearing and the general problems of disease and low fry survival due to an imbalance in the microbial community will be discussed. Various curative and prophylactic treatment methods currently used to control these diseases and their impact on microbial ecology will be covered, and we will conclude with the rationale of microbial ecology management and its effectiveness in promoting fry survival through disease prevention. To our knowledge, this is the first literature review addressing the promises of managing microbial ecology in a sustainable way in the brook char industry.

The use of fish meal/oil in carnivorous fish feeds remains a concern for the environmental sustainability of aquaculture. In this study, we investigated the impact of an innovative diet designed to be cost-effective and environmentally sustainable (i.e., 60% replacement of fish meal by a blend of plant, yeast [Saccharomyces cerevisiae], and krill meal feed ingredients) on the growth, health, and welfare of gilthead seabream (Sparus aurata). Over a 135-day experiment, fish were fed either the innovative or a commercial diet (control), and various parameters were evaluated, namely growth performance, levels of physiological blood parameters related to stress, immunity, health, and welfare, as well as swimming activity, serving as a proxy for energy expenditure. Results revealed that the innovative diet enhanced growth compared to fish fed the control diet. Hematological and biochemical indicators did not highlight any impaired welfare condition in fish fed innovative diet while higher levels of Immunoglobulin M were measured in plasma of fish fed innovative diet, potentially suggesting enhancement of humoral immunity. However, accelerometer tags data revealed that fish fed the innovative diet exhibited higher overall swimming activity, suggesting higher energy expenditure, which was consistent with greater prealbumin levels measured in the plasma. In conclusion, the higher energy metabolism in fish fed the innovative diet might be compensated by the diet’s content, which may boost humoral immunity and hence help the fish develop a better adaptation to rearing environment, including its viral and bacterial load, ensuring overall better growth. Longer term investigations, including measurements of additional parameters, are required to validate these promising preliminary outcomes.

Biocontainment methods for aquaculture are in development and implementation to prevent farmed fish from breeding and thus invading the surrounding environment following an escape from open netpens. Current methods have not demonstrated 100% efficacy in achieving the desired sterility, highlighting the need for the development of novel biocontainment strategies to implement in aquaculture. Using zebrafish as a model organism, we determined the efficacy of the Cre-LoxP system to conditionally express the active form of caspase-3, an apoptosis-inducing cell-death protein, in the developing ovary. This was achieved through the use of two transgenic lines, Tg(zpc:cre; cmlc2-mCherry) and Tg(ef1a:loxP:caspase3:loxP; cmlc2-EGFP), that induce the expression of active caspases in the developing ovary of progeny containing both constructs. Fish positive for only one of the two constructs displayed wildtype (WT) gonadal tissue and bred successfully. However, 78.3% of progeny that carried both constructs did not breed successfully and possessed either little or no gonadal tissue compared to WT controls upon dissection. When combined with induced triploidy, fish that were transgenic for both constructs were 100%. Our results suggest that conditional expression of a cell-death-inducing protein could be used as part of a strategy for the confinement of fish species and demonstrates the utility of “stacking” containment approaches to enhance reproductive containment.

This study aimed to evaluate the effect of two protein sources (black soldier fly [Hermetia illucens] meal [BSFM] vs. fish meal [FM]) on intake target “diet preference” in juvenile Nile tilapia (Oreochromis niloticus) by a self-feeding method (trial 1). Growth, body composition, blood parameters, and immunity genes expression were also evaluated to be correlated with behavioral data (trial 2). Four experimental diets were prepared containing 0%, 33%, 66%, and 100% BSFM as a substitute for FM protein, which were considered treatments T0 (control), T33, T66, and T100, respectively. In trial 1 (32 days), 60 juveniles (77.97 ± 8.5 g, standard error of the mean [SEM]) were randomly distributed in 60 aquariums (40 L). Fish were challenged to select among A, T0 vs. T33; B, T0 vs. T66; C, T0 vs. T100; D, T33 vs. T66; E, T33 vs. T100; and F, T66 vs. T100 using two floating food halls per aquarium to provide different diets. In trial 2, 240 juveniles (2.80 ± 0.25 g) were distributed in 16 tanks (40 L). The experimental design was completely randomized with four treatments (T0, T33, T66, and T100) and four replies. Fish were fed (5% body weight [BW]) experimental diets for 2 months. For the trial 1 results, no difference was observed in A, T0 vs. T33 (p>0.05). Fish were allowed to select conditions B, C, D, E, and F and preferred the diets containing no or low BSFM content: B = T0, C = T0, D = T33, E = T33, and F = T66 (p<0.05). In trial 2, final weight and daily weight gain had lower values when animals were fed 100% FM replacement with BSFM (p<0.05). The fish fed T0 showed lower viscerosomatic indices (p<0.05). Moisture and total protein were higher in the fish fed T0, but protein content did not differ from T33 (p>0.05). Ethereal extract increased with rising BSFM (p<0.05). There were no significant differences in glucose, creatinine, total protein, high-density lipoprotein (HDL), low-density lipoprotein (LDL), aspartate transaminase (AST), and alanine transaminase (ALT) (p>0.05). Total cholesterol, triglycerides, and albumin lowered in fish when increase dietary BSFM (p<0.05). gpx, il-8, il-10, tnf-α, sod, cat, tlr-1, myd, and nf-κb did not differ among treatments (p>0.05). However, il-1β expression increased in T0 and T100 (p<0.05). Diets with up to 66% BSFM did not affect performance of juvenile tilapia. However, fish showed a preference for diet containing 33% BSFM.

In this study, we developed an injectable DNA vaccine targeting the aopB gene of Aeromonas hydrophila, encapsulated within poly(lactic-co-glycolic acid) (PLGA) nanoparticles, for use in common carp. Juvenile common carp were divided into six groups with three replicates each. Groups A and B received intramuscular injections of the plasmid containing the target gene (pCDNA3.1-aopB) with or without encapsulation, respectively. Groups C and D received the plasmid lacking the target gene via the same route. Group E received PLGA, while Group F (control) received phosphate-buffered saline. Sampling occurred on days 0, 30, and 60, and hematological and immunological indices were compared among the groups. On day 60, all groups were challenged with Aeromonas hydrophila, and cumulative mortality rates were assessed. Our results indicated successful detection of the target gene in various tissues of vaccinated fish. Notably, vaccinated groups exhibited a significant decrease in cumulative mortality (p<0.05). Immunological indices, such as serum antibody titer and nonspecific immune responses, significantly improved in vaccinated groups, particularly those receiving the DNA vaccine with PLGA encapsulation (p <0.05). Overall, the DNA vaccine, especially when nanoencapsulated with PLGA, demonstrated efficacy and immunogenicity against A. Hydrophila in common carp, suggesting its potential as a vaccination strategy against this infection. Further research could optimize its effectiveness and applicability.

MyD88 and IκBα are inflammation-related genes involved in various immune responses in vertebrate, but their function in Acanthopagrus schlegelii was not clear. In this article, the open reading frame (ORF) of A. schlegelii MyD88 (AsMyD88) is 867 bp, encoding 288 amino acids, and containing a death domain and a TIR domain. The ORF of A. schlegelii κBα (AsIκBα) is 951 bp, encoding 324 amino acids and containing multiple ANK domains. The results of qRT-PCR showed that AsMyD88 was most distributed in the liver, followed by the gill, while AsIκBα was highly distributed in the kidney and muscle. After infection with Vibrio parahaemolyticus, the transcription of AsMyD88 in the liver and kidney was significantly increased, and the transcription of AsIκBα in the liver and kidney was inhibited. After the successful overexpression in RAW264.7 cells, it was found that the overexpressed AsMyD88 was distributed in both the nucleus and cytoplasm, while the IκBα was mainly located in the cytoplasm. The expression of p65 was increased, while the expression of IκBα was decreased after AsMyD88 overexpression. Meanwhile, the transcription of inflammatory factors was significantly increased after overexpression of AsMyD88, while the transcription of inflammatory factors was inhibited after overexpression of AsIκBα. The result showed that NF-κB pathway was activated by AsMyD88. Meanwhile, the phosphorylation of JNK, ERK, and p38 was significantly changed after overexpression of AsMyD88 and AsIκBα, respectively. In conclusion, AsMyD88 and AsIκBα could regulate cellular inflammatory response to participate in the immune response of fish.

Rationing aquaculture farming feed is challenging for producers due to high feed costs, representing 30%–60% of the total operating costs. Therefore, optimal timing of feeding could lead to improved economic returns from an aquatic system. An optimal dynamic feeding model has been determined considering the von Bertalanffy growth model. A bioeconomic model of tilapia production in Mexico for specific markets was used for numerical illustration. The von Bertalanffy growth model was parameterized with experimental data from tilapia (Oreochromis niloticus) fed four ration sizes (50%, 80%, 100%, and satiety), in order to determine different optimal rationing for different fish sizes (200, 300, and 400 g), market prices (Monterrey, Cancún, Mexico City, and On site), and optimal harvesting times (OHT), considering the time value of money. The results of the modeled optimal feeding trajectories show a continuous decrease from stocking to reach a minimum value and then slightly approaching the harvest size. This result contrasts with the recommendations of the feed suppliers and with those found when a potential growth model was used. The results in the case study showed that the Monterrey market presented the highest present value of the benefits in the OHT and the different market sizes. The implications of the Bertalanffy model for optimal rationing trajectories are presented in the discussion.

Barramundi (Lates calcarifer) is an important aquaculture species extensively farmed throughout its natural distribution of Australia and Southeast Asia, as well as being increasingly farmed in the Middle East, USA, and Europe. Barramundi has a firm, pink-white flesh; however, fillets from farmed barramundi often exhibit grey colouration. This grey colouration detracts from its market appeal, leading to challenges in consumer acceptance and competitiveness of the product against other white fillet fish. Selective breeding, environmental manipulation, and dietary adjustments are being investigated to reduce grey flesh colouration. Yet, the absence of a rapid, noninvasive approach to predict greyness in flesh means that large numbers of samples cannot be quickly evaluated, and issues cannot be mitigated preharvest and noninvasively to preserve the fish. To address this issue, rapid analysis of flesh greyness was developed using noninvasive near-infrared (NIR) spectroscopy through the fish skin. Thirty fish were purchased from a barramundi farm, filleted, and divided into 3 cm sections, yielding a total of 335 samples from both dorsal and ventral fillet regions. NIR spectral data were obtained from the skin side of all samples, and colouration data were collected from the flesh side of the same samples. Data were randomised into a training set (256 spectra) and a validation set (79 spectra). Predictive models were developed using flesh colour as the training input for skin NIR spectra. The refined partial least squares regression model explained 78% of the variation in the medial flesh colour (R²pe of 0.776, an RMSEP of 2.820, and an RPDpe of 2.122) demonstrating the ability to adequately predict the flesh quality through skin spectra. This highlights the potential of NIR spectroscopy as a dependable, noninvasive tool, enabling the rapid evaluation of large samples and offering the potential to address flesh colouration issues in barramundi preharvest.

Climate-smart agriculture (CSA) has been promoted in Kenya as a panacea for climate change impacts on agricultural productivity. Consequently, various climate-smart aquaculture technologies, innovations, and management practices (CSA-TIMPs) have been developed, validated, and adopted through the Kenya Climate-Smart Agriculture Project (KCSAP). Nevertheless, there has been no evaluation of the climate-smartness of the CSA-TIMPs for priority setting. In this study, we evaluated and ranked the CSA-TIMPs using a modified Climate-smart Agriculture Prioritization Framework (CSA-PF). The prioritization process included multistakeholder validation workshops involving researchers, fisheries officers, farmers, traders, and policy makers. The climate-smartness scores of the CSA-TIMPs were given based on the CSA pillars (i.e., adaptation, mitigation, and productivity) under various climate-smartness indicators, with a score ranging from −10 (for a negative impact) to +10 (for a positive impact). This resulted in the identification and documentation of forty (40) CSA-TIMPs. Climate-smartness scores varied from 3.8 to 6.1, with higher values indicating strong synergies between the CSA pillars, with productivity having the highest average score of 6.4. The top 5 list of CSA-TIMPs with the best synergies among the CSA pillars was then developed for prioritization. Adoption of these CSA-TIMPs would be instrumental in achieving the CSA triple wins, especially in improving aquaculture productivity. Therefore, sustained efforts in stakeholder engagement, capacity building, and policy support are essential to ensure the successful adoption of CSA-TIMPs in Kenya. A dynamic approach that includes continuous validation, comprehensive monitoring and evaluation, and an enabling environment for adoption will be key to achieving sustainable and scalable impacts.