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Morphometric aspects, sexual ratio and reproductive activity of striped red snapper (L. synagris) in the Atlantic coastal zone were analyzed, based on the relationship between length and weight of the fish and weight of the gonad and reproductive indices. The coefficient of determination of the total length and total weight in females (R2=0.98) and in males (R2=0.91), gonad weight and total length in females (R2=0.73). indicating relationship between total length and total weight. Meanwhile, for males there was no relationship between gonad weight and total length (R2=0.49). [ABSTRACT FROM AUTHOR]

Vertebral deformities are a big challenge in Rainbow Trout seawater aquaculture. However, supportive scientific literature is missing. The present study used radiology to follow the development of vertebral deformities in a population of farmed Rainbow Trout as they grew from 36 g to 5.5 kg. In addition, separately collected deformity screening data from three other farmed populations were included for comparison. The fish developed deformities in different vertebral regions over time, eventuating to affect almost the entire vertebral column. At this point, the fish were ∼ 5.5 kg and 93 % of the fish had one or more deformed vertebrae. A negative relationship between severity of deformity (number of deformed vertebrae per individual), and fish length and weight strongly suggest a negative impact on fish welfare. The most frequently affected area was the ural region of the vertebral column. This region is a part of the caudal fin complex which also suffered from degradation of the fin rays. Ural region deformities were also frequent in the separately investigated populations. The current results indicate that Rainbow Trout are not able to maintain normal bone development under current farming conditions, consequently, jeopardizing the welfare of the fish. [Display omitted] • There was a continuous development of vertebral deformities up to 5.5 kg harvest weight. • A larger portion of the vertebral column got affected over time. • Deformities reduce harvest weight. • Tail fin malfunction causes ural region vertebral deformities. [ABSTRACT FROM AUTHOR]

This study aimed to determine the effects of the addition of Spirulina and Chlorella of the diets of rainbow trout (Oncorhynchus mykiss) on their growth, nutrient composition, the parameters of their antioxidant defense systems, liver histology, and the cadmium removal process of their tissues. Fish with an average weight of 84.25 ± 3.55 g containing Cd in their tissues were distributed in 15 tanks with 18 fish per tank. The fish were fed diets consisting of 0% (Control-1), 0% (Control-2), 4% Chlorella, 4% Spirulina and Chlorella +2% Spirulina twice a day until they were satiated for a period of 80 days. At the conclusion of the experiment, it was determined that diets containing microalgae demonstrated increased growth rates, and that the growth values obtained from the 4% Spirulina and the Control-1 were similar (p > 0.05). Regarding the fatty acid content, with the addition of microalgae to the diet, a significant (p < 0.05) decrease in SFA values and a significant (p < 0.05) increase in PUFA values were observed compared to the groups Control-1 and Control-2. On days 40 and 80, Cd levels in the muscle and liver tissue of the fish were found to be significantly (p < 0.05) lower in the groups that were fed diets containing microalgae in comparison with the Control-2 group. On days 40 and 80, the SOD, CAT, GSH, GST, and GPx values of liver tissues were higher (p < 0.05) than those of the Control-2 group. As a result of the semiquantitative histopathological evaluation of the liver tissues, improvements were observed in all groups containing microalgae; however, the most remarkable improvement was achieved in the Spirulina group. The results obtained in the study revealed that the addition of microalgae to rainbow trout feed removed Cd from liver and muscle tissues, reinforced the antioxidant defense system parameters, and increased growth. However, when the groups containing microalgae were compared among themselves, the diets containing 4 % Spirulina and 2 % Chlorella +2 % Spirulina were found to be more effective on these parameters. • The addition of spirulina, chlorella and spirulina + chlorella to the diet increased Cd excretion in liver and muscle tissue of trout. • The type of microalgae added to the diet influenced the amount of Cd detoxified. • Spirulina and a mixture of spirulina and chlorella added to the diet repaired Cd-induced liver damage. • Spirulina and chlorella supplementation improved the liver's antioxidant defense system. • Dietary supplementation with spirulina and chlorella improved growth parameters in trout. [ABSTRACT FROM AUTHOR]

Plastic inventions have had an impact on various industries, and people easily approach to plastic products, degrading into microplastic (MP). In this study, distribution of MP was evaluated in freshwater fishes collected in a tributary stream of the Han River, Gyeongan-cheon. Totally 38 fishes, mostly Zacco platypus , were used to analyze, and they were collected in two different seasons as the normal and rainy seasons. Fishes contained 34–284 particles/individual. The prevalent size of MP in fishes ranged from 45 to 100 μm, followed by 100–300 and 20–45 μm. Shapes of MP in fishes were mostly fragments, and types of MP were polypropylene (PP) > polyethylene (PE) > polytetrafluoroethylene (PTFE). By 4-day ingestion of Nylon at 100 μg/L (equivalent to 55,000 particles/L, about 20–40 μm) in Zacco koreanus, the treated fish showed MP concentration with an average number of 53 Nylons. Mean retention time value was considered as 13.4 days by the uptake-depuration test using Z. platypus at 500 μg/L Nylon. Taken together, MP concentration found in smaller freshwater fish was dependent on living habitat and MP size. These findings underscore the importance of ongoing monitoring of MPs in freshwater ecosystems and the need to understand MP ingestion and excretion patterns in small freshwater fish species. [Display omitted] • Microplastic (MP) contamination of fish in tributaries of the Han River was found. • Zacco platypus were mostly found, and they had 34-284 MP particles/individual. • Mostly detected MPs ranged from 45 to 100 μm, and they were fragments and PP. • MP numbers in fish were not related to the fish weight and fish body length. • MRT in Z. platypus was 13.4 days for 500 μg/L of 20–40 μm Nylon particles. [ABSTRACT FROM AUTHOR]

The aqueous environment has been reported to be seriously threatened by the pollution of microplastics (MPs), which has been confirmed in numerous studies affecting various aquatic habitats. Despite this, few investigations exist on MP contamination in fish of specific regions. Thus, the current study aims to determine MP concentrations in the fish species of the Chhota Nagpur zone of eastern India. From August to September 2023, fish samples were collected from 10 km distance between two locations of Subarnarekha and Kharkai river banks through fishermen. Microplastics were found in the gastrointestinal tract of 45 fish of 8 species out of 48 samples. Of these species, six species were secondary consumers, while the remaining two were primary consumers. The average amount of microplastics consumed by each fish (n = 48) was 3.0 ± 1.8. A total of 144 microplastics were found in collected samples of fish species. Among the analysed sample of MPs, 69.4% were fibers, films were (22.3%), and (8.3%) were fragments. The least contaminated species was T. ilisha (0.8 ± 0.7 particles/ind.), while L. rohita had the highest microplastic contamination (4.5 ± 1.7 particles/ind.). The present study found a negative correlation of - 0.83 between MP consumption and the mean body weight of fish. Similarly, a negative correlation of - 0.5 was found between the length of fish and MP intake. Polyamide (nylon), polypropylene, polyvinyl chloride, polycarbonate, polyethylene terephthalate, and polyethylene polymers were found. The size of MPs ranged from 45 to 355 μm and mainly were fibers. They were also predominantly blue and black. Polyamide and polyvinyl chloride were the common MP types in every specimen. The possible sources of MPs were fishing nets, ropes, and packaging material. This investigation points to MP contamination in aquatic ecosystems and particular species. It provides advanced knowledge of MP pollution, sources, and effects on regional ecosystems and public health. [Display omitted] • 144 particles of microplastic were found in 45 fishes of eight different species found in East India. • Fibers-type MPs were detected in the highest concentration with 69.4%. • Most MPs were observed in size <355 μm with 90.9% composition. • PE, PP, and PET show risk in hazard categories I and II, while PA, PVC, and PC stand for high-value PHI and are classified as very high-risk hazards. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are a growing environmental concern in marine ecosystems, posing serious risks to marine life and human health, though their specific health impacts remain unclear. This study evaluated MP contamination in three popular seafood fish, analyzing organ speficic distribution and raltionship with body weight and feeding habits. It further calculated human health exposure and risks using established models. Samples of gill, gastrointestinal tract (GIT), and muscle tissues from Thunnus obesus, Pampus chinensis, and Acanthopagrus datnia collected from the northern Bay of Bengal were analyzed using wet peroxide oxidation, stereomicroscopy, and Fourier transform infrared (FTIR) spectroscopy. Analyses revealed that MPs were ranged from 1.57 ± 0.58 to 8.73 ± 2.55 MP items/g in gill samples, 1.37 ± 0.62 to 5.39 ± 1.55 MP items/g in the GIT, and 0.2 ± 0.15 to 0.475 ± 0.21 MP items/g in muscle tissue. The presence of MPs in fish muscle indicated that these particles have passed through the digestive system and been absorbed into body tissues, resulting in direct exposure for consumers. Interestingly, a negative correlation was found between MP levels and weight of the fish species suggesting that larger fish might process and excrete microplastics more efficiently than smaller fish. Interestingly, a negative correlation was observed between the levels of MPs and both the length and weight of the fish species. Carnivorous species generally exhibited higher MPs load than omnivorous species. Overall, fiber-type MPs predominated, followed by sheet and fragment, with the majority appearing filamentous and measuring <0.5 mm in size. Notably, violet and red were the most prevalent colors observed among the MPs. Interestingly, a negative correlation was found between MP levels and weight of the fish species suggesting that larger fish might process and excrete microplastics more efficiently than smaller fish. Carnivorous species typically showed a higher load of microplastics than omnivorous species. FT-IR analyses identified four types of polymers—EVA, nylon, PE, and PP—suggesting that the potential sources of MPs may be fishing gear or packaging materials. With the estimated average human intake projected to be 1,244,460 MPs/person/year for the local population, the health risk posed by MPs is substantial. The PLI and CF values (>1) indicated significant overall contamination of fish by MPs. Polymeric Hazard Index (PHI) assessments identified risk levels across various categories (Grade I to Grade III) for different polymer types, ranging from minimal to significant risk. • MPs were present in all samples ranging from 0.2 ± 0.15 to 8.73 ± 2.55 MP items/g. • Predominant MPs were fibers and filamentous, mostly <0.5 mm, violet. • Four polymer types identified, ranked by percentage as EVA > nylon > PE > PP. • More MPs were found in the gills compared to the muscle and gastrointestinal tract. • PHI indicated risk of polymers from grade I (<1) to III (10–100). [ABSTRACT FROM AUTHOR]

Food adulteration is an important and common problem that can affect public health, safety, and the global economy. Fish is often adulterated by fraudulent activities such as mislabelling the species, substituting lower-quality or cheaper fish for higher-value species, or by adding artificial components to enhance the appearance or weight of the fish product. Here, we demonstrate an untargeted proteomics analysis method using liquid chromatography–high-resolution mass spectrometry for authenticating fish products. Our research focused on identifying peptide markers for differentiating hake and pollock, two widely consumed high-value fish that are among the most often intentionally substituted and swapped fish species. Twenty-two heat-resistant pollock-specific differentiating peptides and 17 hake-specific differentiating peptides were identified. The applicability of the method was tested using fish fillets and a popular fish product, battered fish fingers. The utility of the method for fish authenticity testing was confirmed. The proposed method can be used in food quality control laboratories. Moreover, targeted multiple reaction monitoring methods for the identified marker peptides using triple quadrupole mass spectrometry may be developed, which will facilitate and expedite the adoption of this approach by the food industry. • Hake and pollock could be differentiated using panels of peptide markers. • Peptide markers are detectable in raw and cooked hake and pollock samples. • Panels of peptide markers may be applied for the fish products authentication. [ABSTRACT FROM AUTHOR]

Demand for organic aquaculture is rising, but its viability will depend on the availability of economically viable raw materials to formulate organic diets. In the current work, organic diets were formulated based on different alternative protein sources distinguished by their ecological origin, insect meal (IN), seabass by-products (SB) and Iberian pig by-products (IB) in rainbow trout (Oncorhynchus mykiss) and their effects on growth, efficiency, productivity, and intestinal health. Fish with an initial weight of 67.2 g were fed two times a day until apparent satiation for 150 days. The control diet containing fish meal (FM) originated the highest final weight (298 g). Results obtained in the final body weight and the specific growth rate feed conversion ratio average daily gain indicate that the SB-FM, SB-IB, and SB-IN-IB diets presented a lower performance (272 g, 257 g, and 258 g final weight respectively) and FM-IN and IN-IB diets had the lowest final weight (215 g and 183 g respectively). An improvement in growth performance and nutrient utilization was observed in the SB-FM, SB-IB, and SB-IN-IB diets concerning the FM-IN and IN-IB diets. The lowest retention efficiencies of protein, fat, and essential amino acids were found in the IN-IB diet. The highest apparent digestibility coefficients (ADCs) of protein, energy, calcium, and phosphorus are found in Control and FM-IN diets. Results of enzymes showed that both trypsin and chymotrypsin are relatively low in IN-IB and SB-IN-IB. Fish-fed FM-IN and IN-IB diets showed histological changes in the liver and intestine. Considering the intestinal microbiota composition, the three dominant phyla were Firmicutes (59–89%), Spirochaetota (5–35%), and Proteobacteria (3–16%), but no differences between diets were obtained. No significant differences were observed on the Alpha diversity Shannon index. Therefore, although differences in growth were observed, the high substitution of fishmeal did not imply an alteration of the intestinal microbiota, possibly due to the high dominance of Firmicutes. Nevertheless, from an economic point of view, SB-IB diets gave the lowest economic conversion index and the highest economic profit index. In conclusion, the substitution of fishmeal affected the growth of the animal, registering the best results in the control followed by diets containing fishmeal of marine origin, but the lowest price of animal by-products originated the best economic results. • Organic diets for rainbow trout utilizing eco-friendly sources. • Findings from a 150-day study highlighting performance variations. • Critical insights into nutrient retention guiding the optimization of organic diets. • Despite growth differences, stability was observed in microbiota. • Cost-effective approach for organic aquaculture. [ABSTRACT FROM AUTHOR]

A breeding trial was conducted to investigate the impact of a chitosan nanoconjugated formulation of Salmon gonadotropin-releasing hormone analogue (ChN-sGnRH-a) on the induced breeding performance of female Clarias magur (magur). A total of 72 magur breeders were divided into six treatment groups: Cn, the Negative Control (injected with bare chitosan nanoparticles); Cp, the Positive Control (injected with Gonopro-FH®, a commercially available inducing hormone, at a dose of 1 mL/kg body weight of fish); T1, injected with ChN-sGnRH-a at a dose of 1 mL/kg; T2, T1 + 10 mg/kg domperidone; T3, injected with ChN-sGnRH-a at a dose of 0.5 mL/kg; T4, T3 + 10 mg/kg domperidone. Blood was collected at 0 (before injection), 6, 12 and 18 h post-injection to determine the serum steroid profile. In the Cp treatment group, the serum steroid levels of testosterone, estradiol, and 17α, 20β-dihydroxy progesterone in the fish, displayed a sharp increase, peaking at the 6-h post-injection, followed by a significant decrease. However, the fish in the T2 and T4 treatment groups exhibited serum steroid peaks at the 12-h post-injection and maintained those levels up to the 18-h post-injection. The reproductive performance, as measured by spawning fecundity, fertilization rate, and hatching rate, was significantly higher in the T2 treatment group (p < 0.05). No significant differences (p > 0.05) were observed between the Cp and T4 treatment groups. Compared to the Cn treatment group, the mRNA expression levels of pituitary follicle stimulating hormone subunit beta and luteinizing hormone subunit beta , as well as ovarian 17β-hydroxysteroid dehydrogenase type 3 , were significantly higher in the T2 treatment group, followed by Cp and T4 treatment groups. Fish in the T2 treatment group displayed fewer mature oocytes and numerous post-ovulatory follicles in their ovaries. Additionally, the ovarian histology of fish in the T4 treatment group closely resembled that of the Cp treatment group. The results indicate that the chitosan nanoconjugated formulation of Salmon GnRH analogue might contribute to maintaining elevated levels of gonadotropic and steroid concentrations, resulting in improved reproductive output in female magur breeders. It is also revealed that the induced breeding of magur cannot be achieved without using dopamine inhibitors in GnRH analogue injection. Using chitosan nanoparticles as a nano-delivery system could reduce the Salmon GnRH analogue dose without compromising the reproductive performance of female magur breeders. • Nanoconjugated GnRH analogue was tested for induced breeding in female magur. • The nanoconjugated GnRH analogue sustained steroid surge in female magur. • Nanoconjugated formulation improved reproductive performance in female magur. • GnRH dose for induced breeding was reduced by using nanoconjugated GnRH analogue. • Nanoconjugated GnRH analogue is an effective induced breeding agent in female magur. [ABSTRACT FROM AUTHOR]

• A weight estimation system based on the perimeter of bass was established. • A stereo matching dataset has been created for 3D reconstruction of fish contours. • The NeRF-supervised stereo matching network was used for fish depth estimation. • The weight estimation system has the potential to be applied in aquaculture. Non-invasive methods of accurate estimation of fish weight are essential for biomass assessment, precision feeding, and effective management in aquaculture. However, the lack of large-scale stereo matching datasets and costly depth sensing equipment in underwater scenarios present significant challenges to accurately measure the size of free-swimming fish. This study introduces a novel NeRF-supervised stereo matching network for precise depth estimation and 3D reconstruction of the fish body. The state-of-the-art neural rendering methods are employed to generate stereo training data from image sequences. In this study, the residual network with deformable convolutions was proposed to extract contextual texture features, significantly enhancing disparity estimation accuracy at the edge of the fish body. Additionally, multiscale spatial features are fused using a feature pyramid network (FPN). To enhance the adaptability of disparity search, we introduce a lightweight Triplet Attention module to capture cross-dimensional dependencies prior to constructing the correlation volume. Experimental results demonstrate the effectiveness of the proposed depth estimation method, achieving an impressive result of 92.35% in the similarity metric, compared to the ground truth. Moreover, we developed a weight estimation model based on bass perimeter using instance segmentation and 3D reconstruction techniques. Notably, a robust correlation (correlation coefficient of 0.98) between fish perimeter and weight is observed, highlighting the potential application of our methods to enhance the accuracy of weight estimation for free-swimming fish. [ABSTRACT FROM AUTHOR]

Fish condition is often defined as a deviation in the relationship between fish weight and length, indicating if the fish is leaner or fatter than the average. The proportion of a stock in critically poor condition may indicate a component of the total natural mortality rate M , which has been called the starvation mortality rate (i.e., M K ≤ M). The weight-length relationship may vary spatially and temporally (both between and within years). Hence, M K may also vary the same way. We developed a spatiotemporal condition model to derive a spatiotemporal and length-specific index of M K. We aggregated M K across space and months to produce an annual and length-specific M K index for the entire stock, as a potential input to assessment models. We applied the model to survey data for cod on the Southern Grand Bank of Newfoundland. Our results indicated that M K was: 1) higher in the spring than the fall, 2) higher for cod between 55 and 80 cm and cod ≥ 120 cm, and 3) higher during 1991–1993 when the stock declined substantially, but was also high in 2016. We discuss potential drivers of starvation mortality as well as how this information can be included in a stock assessment model to improve fisheries management advice. [ABSTRACT FROM AUTHOR]

• Diet data reveal persistent trophic clusters for size groups of 35 fish species. • The trophic groups are generally distinct with one predominant prey type. • Groups of benthivores tend to have more mixed diet than planktivores. • Piscivores are larger species which grow from being planktivores when small. • Taxonomy (species) is more important than size for explaining variance in diet composition. A large data set on stomach content (over 27,000 individual fish) – collected in the Barents Sea in 2015 – was used to examine ontogenetic and interspecific changes in diet with size for 35 fish species. The analysis combined the use of hierarchical clustering and random forest. Two different diet metrics were used (% weight of prey types per weight of stomach content or per weight of fish, the latter reflecting also feeding intensity), and data were analysed based on average diet of predator groups (species and size groups) across the entire sample series (from the whole Barents Sea in different seasons), or for data broken down by geographical areas and seasons. Similar trophic groups (clusters) were identified for the various data sets suggesting that the results on trophic structure were robust. The trophic groups including size information were broadly similar to groups found earlier with data averaged at species level. Hierarchical clustering produces a hierarchy of trophic groups (or trophic guilds) at various levels of diet dissimilarity. With 12 clusters identified, one cluster had fish as dominant prey, and 5–6 others had either plankton or benthos as dominant prey. The clusters tended to be distinct and homogenous with one dominant prey category in average diet (often > 60 %). This was especially the case for the plankton clusters, with copepods, euphausiids, hyperiid amphipods, or gelatinous zooplankton as dominant prey in each of 4 trophic groups. The benthos clusters tended to be less dissimilar with more overlap in diet composition, with predominance of either hard-shelled forms (echinoderms and molluscs) or softer prey (polychaetes and crustaceans) for groups of clusters. There were clear patterns of ontogenetic shifts in fish diet. Fish that clustered as piscivores at larger size tended to grow from being planktivores when smaller. Smaller species of planktivores or benthivores shifted position among trophic groups but remained within the categories of planktivores or benthivores, respectively. Taxonomy (species) tended to be more important than size for explaining the diet composition of the different clusters of fish predators. [ABSTRACT FROM AUTHOR]

Cooling experiments using flake ice and chilled brine/seawater were carried out on ungutted and gutted cod. Core temperatures of the fish loins and tails were measured during the cooling process. The study aims were to investigate different approaches to chilling gutted and ungutted whole fish and compare controlled brine chilling with traditional flake ice chilling. Experiments were conducted in controlled environment using fish in three weight categories, around 2.5, 4 and 9 kg. The experimental results were used as design parameters for newly developed onboard industrial chilling processes using different approaches to superchill whole gutted cod (slurry ice and refrigerated seawater/brine). Industrial chilling processes were evaluated by mapping temperature profiles onboard three wet-fish trawlers using different chilling systems and methods. Temperature measurements were then used to generate a model to estimate chilling time and the convective heat transfer coefficient between 2, 4 and 6 kg fish and cooling medium. The chilling time of equal weight fish from +8°C to 0°C proved to be 30-50% shorter with refrigerated brine chilling compared to flake ice chilling. The difference between chilling gutted and ungutted cod was apparent, as expected, due to a greater surface area between gutted fish and the cooling medium. The chilling time difference between gutted and ungutted fish was less with flake ice chilling than with refrigerated brine chilling. Comparison of the model results with onboard measurements indicate that the thermal conductivity of the fish is limiting to the energy transfer and efficiency of the onboard chilling systems rather than the heat transfer coefficient. • Temperature measurements for ungutted and gutted cod in flake ice and chilled brine. • Temperature profiles in different onboard chilling systems were measured. • Chilling time difference between gutted and ungutted fish was smaller with flake ice chilling than with RSW. • Chilling time was 30-50% shorter with RSW compared to flake ice chilling. • Results from onboard systems are comparable to controlled experiments. [ABSTRACT FROM AUTHOR]

In precision aquaculture, the primary goal is to maximize biomass production while minimizing production costs. This objective can be achieved by optimizing factors that have a strong influence on fish growth, such as feeding rate, temperature, and dissolved oxygen. This paper provides a comparative study of four model predictive control (MPC) strategies for fish growth reference tracking under a representative bioenergetic growth model in precision aquaculture. We propose to evaluate four candidate MPC formulations for fish growth reference tracking based on the receding horizon. The first MPC formulation tracks a desired fish growth trajectory while penalizing the feed ration, temperature, and dissolved oxygen. The second MPC optimization strategy directly optimizes the feed conversion ratio (FCR), which is the ratio between food quantity and fish weight gain at each sampling time. This FCR-like optimization strategy minimizes the feed while maximizing the predicted growth state's deviation from the given reference growth trajectory. The third MPC formulation includes a tradeoff between the growth rate trajectory tracking, the dynamic energy, and food cost. The last MPC formulation aims to maximize the fish growth rate while minimizing the costs. Numerical simulations that integrate a realistic bioenergetic fish growth model of Nile tilapia (Oreochromis niloticus) are illustrated to examine the comparative performance of the four proposed optimal control strategies. A sensitivity analysis is conducted to study the robustness of these MPC strategies with respect to the effect of the prediction horizon, the regularization term, and the additive input disturbances to the process. The obtained results show great potential and flexibility to meet the fish farmers' needs depending on the type of fish, selling price, culture duration, and feed cost. [Display omitted] [ABSTRACT FROM AUTHOR]

Recirculating aquaculture systems offer sustainable fish production but face challenges related to ammonia levels. Ammonia, particularly the un-ionized fraction, NH3, can negatively impact fish growth and health. Traditional ammonia estimation methods, including offline analyses and affordable, yet inaccurate, in-situ measurements, lack the ability to provide reliable real-time insights. Data assimilation combines simulation models and in-situ measurements to provide more accurate estimations. In this study, we demonstrate a novel approach using data assimilation to enhance real-time ammonia estimation in RAS. First, ammonia dynamics are described by forming equations that constitute a simulation model, based on the feeding amounts and the biofilter removal rate parameters. Then, an extended Kalman filter is presented and customized to integrate the simulation model and total ammonia nitrogen measurements for estimating NH3, NH4+, and biofilter parameters. We validated our method through synthetic and laboratory case studies and demonstrated its superior estimation capability as compared to in situ measurements or simulation models. Furthermore, improved ammonia estimation led to improved current and future fish weight estimations, which can be essential for reliable RAS management. The proposed approach facilitates wider adoption of DA in challenging estimations in aquaculture. • Data Assimilation (DA) was applied in an aquaculture setup. • A method for ammonia estimation in RAS using DA was introduced. • DA outperformed ammonia estimations by either simulations or measurements. • Improving ammonia estimation enhanced fish weight estimations. • DA has the potential to reliably provide complex aquaculture estimates. [ABSTRACT FROM AUTHOR]

The accurate estimation of fish weight relies on the crucial parameter of individual fish contour features. While instance segmentation proves effective in extracting fish contours, challenges arise from diverse fish postures and reduced image sharpness underwater. Current instance segmentation methods often struggle to effectively balance global and local detailed features, which can result in inaccurate positioning of contour keypoints and consequently limit the accuracy of fish weight estimation. To overcome this, our study introduces a novel instance segmentation network tailored for precise fish contour extraction. The proposed approach incorporates multi-scale feature fusion and an attention mechanism based on the Segmenting Objects by Locations (SOLO) network, referred to as SOLO-MFFA. This paper designs a multi-scale context aggregation module to integrate features with a wider range of receptive fields, augmenting the model's capability to comprehend both local features and global information. At the same time, the introduction of a mixed-domain attention mechanism emphasizes more critical channel features and simultaneously improves the localization accuracy of contour points. Compared with SOLO and its improved model CAM-SOLO on the fish instance segmentation dataset, SOLO-MFFA demonstrated an effective improvement, with a 4.3% and 1.6% increase in mAP (mean Average Precision), respectively. The Decoupled-SOLO-MFFA achieved higher mAP. The visualization results also demonstrate that the contour features extracted in this paper are smoother and more accurately positioned. Additionally, in comparison to other well-known instance segmentation networks, our method has demonstrated significant improvements in both qualitative and quantitative evaluations. Furthermore, the integration of contour features derived from Decoupled-SOLO-MFFA, along with binocular vision, was utilized for the precise estimation of fish perimeter and weight. The findings reveal a strong correlation between the perimeter calculated by Decoupled-SOLO-MFFA and the actual weight, with a notably reduced error in weight estimation. Compared to previous methods, RMSE, MAE, and MAPE of the linear model constructed in this paper decreased by 3.92, 3.19, and 1.4%. [ABSTRACT FROM AUTHOR]

To follow up field observations in the Chornobyl Exclusion Zone (ChEZ), a series of controlled model aquarium experiments were conducted to determine the uptake and depuration rates of 137Cs and 90Sr in silver Prussian carp (Carassius gibelio) in fresh water, varying in temperature from 5 to 27 °C, with daily feeding rates of 0–1.5 % fish weight day−1. In the present study, the 137Cs uptake rates in muscle tissues directly from water, 0.05–0.09 day−1 at temperatures of 5–27 °C, were significantly lower than previously reported for fish fed under natural conditions in contaminated lakes within the ChEZ. The rate of 90Sr uptake in bone tissues of silver Prussian carp varied from 0.055 day−1 at a water temperature of 5 °C and feeding rates ≤0.15 % fish weight day−1 to 1.5 ± 0.2 day−1 at a temperature of 27 ± 1 °С and at the highest tested feeding rate of 1.5 % day−1. The rate of decrease of 137Cs concentration in muscle tissues was k b = 0.0028 ± 0.0004 day−1 (T 1/2 = 248 ± 35 days) at the lowest water temperature tested (5 °С). At water temperatures between 13 and 26 °С and a feeding rate of 0.15 % day−1, the rate increased to k b = 0.0071–0.0092 day−1 (T 1/2 = 75–99 days). The rates of decrease of 90Sr activity concentration in bone tissues at water temperatures between 22 and 25 °С and a feeding rate of 0.5 % day−1 were k b = 0.004–0.0014 day−1, and the associated biological half-life T 1/2 ranged 50–160 days, respectively. The present work supported conclusions related to the main pathways of 137Cs and 90Sr uptake by silver Prussian carp, and demonstrated the usefulness of combining field and laboratory uptake and depuration experiments. • The 137Cs uptake rate by fish from water is 5–100 times lower than from contaminated food. • The 137Cs uptake rate by fish from water increased at high water temperatures. • The 90Sr uptake rate by fish from water is much higher than from contaminated food. • The 90Sr uptake rate from water increased with increasing water temperature and feeding rate. • The rates of decrease in 137Cs and 90Sr concentrations increase due to biodilution. [ABSTRACT FROM AUTHOR]

The goal of this study was to evaluate the energy and environmental performance over the life cycle of Nile tilapia production for harvesting in different weight. The reference flow was 1 t (megagram – Mg) of fished Nile tilapia with the following weight: 0.6 kg, 0.9 kg, 1.2 kg, 1.5 kg, 1.8 kg and 2.0 kg. The inventory was defined for the stages of feed production and fish production with the processes for fingerlings, followed by rearing of juvenile and fattening of adult in cage. In addition, the inventory covered the supply of the remaining material and energy inputs, transport, infrastructure and waste management. The assessed categories were area occupation, water consumption, energy demand, global warming, acidification and eutrophication. Even though the smaller-sized fish demanded more fingerlings to produce 1 t of Nile tilapia than the larger ones, the feed conversion of the smaller-sized fish was more favorable compared to that of the larger-sized fish. The energy and environmental burden of Nile tilapia showed a tendency to increase with larger-sized fish. The largest contribution of area occupation, water consumption, energy demand and global warming was from feed production, while that of acidification and eutrophication was from the rearing and fattening processes of fish production. The choice of feed ingredient suppliers from more efficient and clean sources at feed production and the control of feed loss at fish production are key strategies to improve the energy and environmental performance of the fished Nile tilapia. Therefore, the sustainability of pisciculture must consider feed production from more eco-efficient ingredients, higher efficiency in feed conversion, control of feed loss, and the use of production effluent. • Energy and environmental performance of varied Nile tilapia weight were assessed. • Feed conversion efficiency was the main parameter in the evaluated scenarios. • Smaller-sized fish favored the assessed categories compared to larger-sized fish. • Feed production, feed loss and fish excreta were the main contributions. • Feed ingredient supplier and feed loss control favored the assessed categories. [ABSTRACT FROM AUTHOR]

This study investigated the potential immune-enhancing effects of Origanum oil on Nile tilapia (Oreochromis niloticus) under normal conditions and after a challenge with Pseudomonas aeruginosa. The fish were categorized as follows: not challenged and received no supplements; not challenged and received Origanum oil; challenged and not received any supplements; challenged and received florfenicol; challenged and received Origanum oil; challenged and received both Origanum oil and florfenicol. Origanum oil was administered at a dose of 10 mL/kg of diet for 28 days, and florfenicol at a dose of 10 mg/kg of fish weight after the challenge for a duration of 7 days. Origanum oil significantly aided florfenicol in reducing mortality and morbidity resulting from the challenge with P. aeruginosa. Fish that received Origanum oil alone demonstrated slight increases in proximate composition, including moisture, crude lipid, crude fiber, and crude ash, compared to those that did not undergo any administration or bacterial challenge. The total blood protein levels exhibited significant increases in the group that was not challenged and received Origanum oil and the group that was challenged and received both Origanum oil and florfenicol, following both linear and quadratic patterns. The latter group also showed significant increases in the levels of globulin. There was a notable variation in the total leukocytic count among the groups, with a discernible increase from group 1 to group 6 (in the same order as the groups mentioned above). It appeared that florfenicol maintained neutrophil and lymphocyte percentages in the challenged fish at levels similar to those not challenged and receiving no supplements. Meanwhile, Origanum oil seemed to increase neutrophil percentage and decrease lymphocyte percentage, either alone or when combined with florfenicol, whether in challenged or non-challenged fish. The fish that were challenged and received both Origanum oil and florfenicol showed the lowest serum levels of ALT, urea, and creatinine among the challenged groups. Necrosis was observed in the gills, hepatopancreas, spleen, intestine, and stomach in the group challenged with P. aeruginosa. However, these pathological changes were markedly not detected in the challenged fish that received Origanum oil, with only focal lesions in the hepatopancreas and intestine. Interestingly, the challenged fish that received both Origanum oil and florfenicol exhibited a normal histological architecture of examined organs. In conclusion, the results suggest that Origanum oil shows properties indicative of a moderate immune enhancer. Furthermore, when combined with florfenicol, it exhibits a synergistic effect in combating P. aeruginosa. • Origanum oil boosted florfenicol, cutting mortality from Pseudomonas aeruginosa challenge. • Fish that received Origanum oil alone demonstrated slight increases in proximate composition. • Fish that received both Origanum oil and florfenicol showed good liver and kidney functions among the challenged groups. • Origanum oil exhibited properties indicative of a moderate immune enhancer. • Origanum oil helped restore the normal histological architecture and function of the examined organs. [ABSTRACT FROM AUTHOR]

Biosynthesis and storage of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is under dietary and genetic control in Atlantic salmon (Salmo salar). Enhanced EPA and DHA biosynthesis and storage may improve utilization, and thus reduce marine forage fish oil use in aquafeeds. To determine phenotypic variability in EPA and DHA tissue content and growth performance, 50 families (n = 30 salmon/family, 48 g/fish initial weight) of Atlantic salmon (Saint John River strain) were reared in freshwater and fed either a fish oil (FO) control diet or FO-free diet. After 16 weeks, body size was recorded. Salmon fed the FO-free diet overall showed significantly lower growth performance compared to salmon fed the FO control diet, regardless of family. To determine the relationship between growth and FA content, the five families with the highest and the five families with the lowest weight gain were sampled for tissue and liver FA analysis. There was a significant interaction between growth and diet. The family x diet interaction was significant for final weight, final length, weight gain, growth rate and feed conversion ratio. Among the five fastest growing families, there was a significant family effect for EPA and DHA storage in the liver but not for muscle. Among the five slowest growing families, by comparison salmon had similar liver DHA and EPA content, independent of diet treatment. Family and diet were interacting factors that determine EPA and DHA storage in liver. Certain fast-growing families also had significantly higher DHA content in liver and muscle. This study demonstrates the potential for selecting families that can better utilize a diet without marine forage fish oil. • Growth among 50 families of salmon was dependent on family x diet interaction. • EPA+ DHA storage was more influenced by family in liver than muscle. • Family and diet were interacting factors that determined EPA+ DHA storage in liver. • Specific fast-growing families were identified that had higher DHA storage. • There is potential for selecting families that better utilize a fish oil-free diet. [ABSTRACT FROM AUTHOR]

Dissolved oxygen is an environmental factor that affects fish survival. Aquatic environments suffer from an increasing oxygen deficiency resulting from global warming and environmental pollution. In this study, we combined high-throughput transcriptome analysis with non-targeted liquid chromatography-mass spectrometry-based metabolome sequencing to assess the metabolic response to hypoxia in the liver of Pelteobagrus fulvidraco. Healthy fish with body weight of 12.39 ± 1.37 g were subjected to hypoxic conditions at a concentration of 1.02 ± 0.09 mg/L for durations of 6, 24 and 48 h. Hypoxia exposure increased the content of MDA, lactate, glucose and the level of T-AOC, enhanced the activity of T-SOD, CAT, GPx and LDH, and decreased SDH activity. Histological examination revealed that liver tissue was damaged after exposure, and the degree of damage increased with the prolongation of hypoxia time. In the liver transcriptome, 1527 DEGs were identified, of which 240 were co-identified in the three comparison groups. These DEGs showed significant enrichment in pathways associated with oxidation-reduction and metabolic processes. RT- qPCR confirmed transcriptional induction of metabolism-related genes in response to hypoxia. Metabolomic results showed that the SDMs were related to amino acid, carbohydrate, and lipid metabolism. Moreover, a conjoint analysis demonstrated an increase in the activity of several key enzymes, such as phosphoenolpyruvate carboxykinase, phospholipid phosphatase 1a, and betaine-homocysteine methyltransferase. An integrated regulatory network was observed to be involved in glycine, serine, and threonine metabolism; glycolysis/gluconeogenesis; tricarboxylic acid cycle; protein digestion and absorption; and lipid metabolism in response to hypoxia exposure. Overall, the findings indicated that hypoxia can cause oxidative stress in yellow catfish and that their bodies can resist stress by activating the antioxidant defense system and mobilizing multiple metabolic pathways to meet the energy demand. These results will aid in the development of strategies aimed at mitigating the adverse effects of hypoxic exposure on fish. • The metabolic response of yellow catfish to acute hypoxia was studied. • Hypoxia induces oxidative stress and activates antioxidant system in P. fulvidraco. • Glycolysis is the main source of energy under hypoxic stress. • Endogenous metabolic small molecules maintain homeostasis. • A metabolic regulatory network was constructed under hypoxia for 48 h. [ABSTRACT FROM AUTHOR]

The extensive use of bio-based plastics has led to their widespread distribution in the environment. However, their long-term ecological impact on aquatic animals is not well understood. In this study, adult zebrafish (Danio rerio) were exposed to 1000 items·L−1 of either polylactic acid (PLA) or polyethylene terephthalate (PET) microplastics (MPs), for 90 days. PLA is a typical bio-based plastic, while PET is a typical petroleum-derived plastic. The abundances of PLA and PET MPs in fish intestines were 981 ± 66 and 671 ± 151 items per fish, respectively, indicating a greater amount of PLA MP residues than PET MPs. However, the inhibitory effect of PET on fish weight was 1.8 times higher than that of PLA, suggesting energy compensation in PLA-treated zebrafish. Proliferation of Lactobacillus was observed in the fish intestines of the PLA group , indicating increased utilization capacity of intestinal flora for lactic acid production during PLA degradation. Metabolomics showed that the tricarboxylic acid pathway was up-regulated in the PLA group compared with that in the PET group, providing evidence of energy compensation. However, more ingested PLA MPs caused more significant histological damage to fish intestines than PET MPs. Therefore, the ecological risks of bio-based plastics still require attention. [Display omitted] • Zebrafish ingested more PLA MPs than PET MPs after long-term exposure. • Nano-sized PLA granules were detected due to the biodegradability of PLA. • PLA MPs caused lower growth inhibition in zebrafish than PET MPs. • Lactic acid produced in PLA degradation provides energy for zebrafish growth. [ABSTRACT FROM AUTHOR]

The approach for estimating biomass in non-contact, free-swimming fish has encountered difficulties such as fish body occlusion, bending, non-orthogonal angles, and low efficiency. To address these issues, this study had combined fish posture recognition (using deep learning technology) with biomass estimation (utilizing stereo vision technology) for the first time, and developed a fast, precise, and fully automatic fish biomass estimation system. The improved single-stage target detection algorithm significantly improved the direct detection and extraction of high-quality images of moving fish in real-time, eliminating the need for manual processing of images that may have imperfect posture. Fish body length and height were measured in the real world using binocular stereo vision technology. Finally, the fish body weight can be estimated by considering the relationship among their body length, height, and weight. The experiment confirmed that the system had successfully avoided influencing factors that could affect fully automatic estimation. The results demonstrated a strong linear relationship between the estimated and measured fish body weights, with a mean relative error (MRE) of 2.87%. There were no significant differences between the estimated and measured weights (p = 0.94). The MRE of the multi-factor model was much lower than that of the single-factor model (length-weight of 8.86% and height-weight of 7.41%). The results indicate that the system developed is a highly effective approach to fully automated biomass estimation. This can be used to guide actual production and further study of the mechanism of fish growth. • A fast, precise and fully automatic system was proposed for free-swimming fish biomass estimation based on binocular stereo vision technology. • An improved target detection algorithm has been developed for real-time detecting and extraction of high-quality images of moving fish. • The multiple factor model was utilized to estimate the weight of fish and exhibited greater accuracy than the single factor model. [ABSTRACT FROM AUTHOR]

Underwater vehicles and other mobile platforms are seeing increased use as tools within fish farming, particularly due to current trends towards Precision Farming practices, and more exposed farming sites. Although many of the applications of such tools (e.g., net cleaning and inspection) have become well established industrial practices, it is largely unknown how much such operations disturb the fish and the consequence of this disturbance. In this study, we explored this by exposing Atlantic salmon in commercial net cages to intrusive objects and monitoring the distribution of fish around these using on-board 360-degree sonars. Six different object designs were tested covering variations in size, shape, and colour, which are important static characteristics of underwater vehicles/platforms. The sonar data was first aggregated into images containing the Cumulative Fish Presence over 1-, 5- and 10-min periods to provide a more robust foundation for further analyses. By training a deep learning based method using UNet++ architecture to automatically segment the fish distribution patterns, the mean distance between the inner perimeter of the fish distribution and the object was assessed. Results from the study implied that fish keep greater distances to larger objects. There was, however, no clear impact of the shape. Regarding the effect of colour, fish kept greater distances to yellow than to white objects. When comparing results from tests on fish of different size, data indicate a positive linear relationship between fish weight (age) and distance to an object, that can be expressed as an avoidance distance of an average 3.8 body-lengths. Our findings provide new fundamental knowledge on the dynamics between the fish and objects such as vehicles or other mobile platforms in fish farms, and thus provides valuable insights that can be useful when designing such tools specifically for aquaculture. • Exploring fish avoidance of objects with different physical properties. • Deep learning method for automatic processing of sonar data to obtain avoidance distance to the objects. • Fish displayed greater avoidance distance to large than small objects, and to yellow than white objects. • Fish weight was proportional with the avoidance distance to objects. • Object shape did not have an apparent impact on avoidance distance. [ABSTRACT FROM AUTHOR]

Although concerns about the impacts of antibiotics in aquatic organisms are reported worldwide, the potential adverse effects on fish gut microbial communities and fish health are still not well known. In this study, we investigated the effects of florfenicol (FFC) on the gut microbiome and gastrointestinal (GIT) gene expression in juvenile Atlantic salmon (Salmo salar). Three doses of FFC were used to coat experimental feed at 10, 20 and 30 mg/kg/ fish body weight (bw). The feed was administered for 18 days, followed by a 10-day recovery period. The metatranscriptome analysis revealed that 10 and 30 mg/kg bw of FFC led to the downregulation of genes involved in the transcription of NADH-ubiquinone oxidoreductase chain-1, suggesting that the antibiotic targets bacterial respiratory metabolism. The 30 mg/kg bw FFC treatment upregulated genes that encode glycolytic enzymes, such as phosphoglycerate kinase, indicating a disruption of energy metabolism in the microbiome. Analysis of the fish host transcriptome showed that the FFC treatment affected cellular processes in the GIT system of fish, including pathways related to apoptosis and DNA metabolism. The 30 mg/kg bw FFC treatment specifically activated pathways related to cellular regulation, including LXR/RXR activation, FXR/RXR activation, and protein ubiquitination. At the end of the recovery phase, the 30 mg/kg bw FFC treated group altered pathways related to EIF2 signaling and lysine degradation. This study identified molecular-level effects of FFC treatment on the gut microbiome and the GIT of juvenile Atlantic salmon, although phenotypic changes in growth or condition were not observed. Most of the observed changes were reversible and receded at the end of the recovery period, apart from the highest treatment group. These findings emphasize the importance of understanding the molecular mechanisms that underlie the potential effects of antibiotics in order to optimize antibiotic treatments in aquaculture. • Identification of molecular-level effects of florfenicol exposure in Atlantic salmon. • Metatranscriptome data suggests targeting of bacterial respiratory metabolism. • 30 mg/kg bw of florfenicol altered interactions between gut microbiome and host. • Fish transcriptome showed effects on cellular processes, apoptosis and DNA metabolism. • Phenotypic changes in growth or condition were not observed. [ABSTRACT FROM AUTHOR]

• At a temperature of 15 °C, resembling natural conditions, the minimum infection dose for the establishment of infection through horizontal transmission is determined to be 103.4 TCID 50 /ml or higher. • The number of infected fish increased with higher infection concentrations, and no significant difference in viral load in kidneys was observed among the infected fish. • Significant differences in weight and length were observed among the farms; however, no correlation was found between the number of infected fish and either weight or length. Viral hemorrhagic septicemia virus (VHSV) affects over 80 fish species, leading to viral hemorrhagic septicemia (VHS). Horizontal VHSV transmission is widely studied, with researchers utilizing various doses to establish infection models. Infected hosts shed the virus into the environment, elevating the risk of transmission to naïve fish within the same system. This study aimed to ascertain the minimum infective dose of VHSV in olive flounder (Paralichthys olivaceus). In olive flounder, the detection of VHSV within the kidney exhibited the highest infection rate on the third day among days 1, 3 and 5. Doses of 103.0 to 104.7 TCID 50 /ml were administered to juvenile olive flounder across three farms. Results showed resistance to infection below 103.4 TCID 50 /ml at 15 °C. While infection frequency varied by concentration, higher concentrations correlated with more infections. Nonetheless, viral copy numbers did not differ significantly among infected fish at varying concentrations. This study underscores the need for early VHSV management and contributes essential data for pathogenicity assessment and foundational knowledge. [ABSTRACT FROM AUTHOR]

Aquaculture of gilthead seabream, arguably the most important finfish aquaculture species in the Mediterranean, faces changing environmental conditions due to faster-than-average climate change in the region. We utilize physiological modelling to estimate effects of moderate and severe climate change on key indices of aquaculture production for all coastal regions of the Mediterranean. Two publicly available global climate change scenarios with daily sea temperature projections serve as forcing for the physiological model during two-year farming cycles representing: (i) reference period starting in 2021, (ii) mid-term effects starting in 2051, and (iii) long-term effects starting in 2091. We investigate effects of climate change by analyzing changes in time for fish to reach a market size, feed conversion ratio at the market size, and the weight of the fish and the associated feed conversion ratio after two years of farming. Additionally, we track the number of days with sea water temperatures equal to or greater than 28 °C during the two-year period, when gilthead seabream starts experiencing temperature stress. Time to market size generally decreases with climate change from the initial average of 450 days for the reference period by up to 36%. Feed conversion ratio at market size does not appreciably change with climate change, but it does change for the two-year culturing period for up to 10 %, primarily due to faster growth in warmer sea water, and the correspondingly greater weight achieved over the two-year growth cycle. While the outlook for aquaculture is positive in the mid-term, some indicators show a negative trend in the long-term. The long-term effects of climate change will be greatest in the currently most productive farming regions of the Mediterranean: Levantine, Aegean, and Adriatic seas, and coastal waters of Tunisia. Our analysis focuses on basin-level features, but we provide geospatially referenced simulation results that can be used to analyze effects of climate change in a particular region of interest. • Mediterranean basin-wide effects of climate change on githead seabream aquaculture. • Key aquaculture performance indicators defined and estimated. • Copernicus data used to drive Dynamic energy budget model on a spatial grid. • Time to market, feed conversion ratio (FCR), and days above 28 °C estimated. [ABSTRACT FROM AUTHOR]

The aquaculture sector has been steadily growing and thus there is an increasing need to develop mathematical models that allow the estimation of production-related parameters. Prediction of fish growth, feed requirements and waste outputs, are essential in order to ensure the profitability and sustainability of the production activities. Bioenergetic models have been widely used to estimate growth based on energy budgets, but they have some limitations by not explicitly considering the mass-balance of the main macronutrients (e.g., protein). In turn, nutrient-based models are more explanatory, as they consider both energy and nutrient inputs, and estimate fish growth by simulating nutrient accumulation in the fish body. Although some bioenergetic and nutrient-base models for predicting Nile tilapia growth exist in the literature, their suitability is not entirely clear, since their development is often based on uncertain or suboptimal criteria (e.g., relying solely on calibration goodness-of-fit measures). In this work, Nile tilapia growth datasets covering a wide range of rearing conditions and feed compositions were collected from the scientific literature. An exploratory analysis of the collected data was performed to clarify the relationships between energy/protein intake and gain. In this analysis, a direct relationship was observed between digestible energy intake and energy gain, as well as between digestible protein intake and protein gain. Protein gain showed better efficiency than energy gain, even at higher intake levels and without clear evidence of a saturation effect. While digestible energy intake negatively affects energy retention efficiency, digestible protein intake does not significantly impact protein retention efficiency. Furthermore, while energy retention efficiency varies with fish body weight, the same effect was not observed for protein retention efficiency. Finally, though DP/DE ratio has no apparent effect on energy retention efficiency, it seems to negatively affect protein retention efficiency. Considering these observations, plausible growth models with different levels of complexity were developed and calibrated under a diverse set of assumptions. Additionally, two growth models already published for Nile tilapia were calibrated using the same datasets, and their performance was compared with the models developed in the present study. The exploratory analysis of the data suggests a direct relationship between digestible energy intake and energy gain, and between digestible protein intake and protein gain. Furthermore, fish body weight seems to affect the energy retention efficiency. The results of model evaluation showed that energy-protein flux models (EP models) have lower errors in predicting fish growth than pure bioenergetic models (MAPE bw ∼ 9% against ∼13%, respectively), showing the importance of considering protein intake when estimating Nile tilapia growth. Furthermore, assuming the fixed standard metabolic body weight exponents of 0.80 and 0.70 (for energy and protein, respectively), rather than estimating them from the data, seemingly improved the predictive ability of the models. This approach demonstrates the benefits of coupling bioenergetics with nutrient-based models to predict growth and body composition of Nile tilapia along time. • Digestible energy intake has a negative effect on energy retention efficiency. • The DP/DE ratio has a negative effect on protein retention efficiency. • Energy retention efficiency increases/decreases with body weight. • Protein intake data is useful for estimation of tilapia growth and body composition. • Using standard body weight exponents results in the best models. [ABSTRACT FROM AUTHOR]

Abstract The effect of genotype x environment interaction for dietetic lysine on Nile tilapia of the GIFT line body weight, daily and total weight gains at 150 days of age was evaluated in this study. The experiment was composed of 700 fish from 26 full-sib families. Each fish was uniquely identified with a microchip tag and randomly distributed in 5 different levels of dietetic lysine (1.43, 1.53, 1.63, 1.73, 1.83%), each level had 7 replicates. Random regression models with homogeneity and heterogeneity (2, 3, and 4 classes) of residual variance were used for the estimation of the genetic parameters. Those models were evaluated via the BIC and model probability criterions. In order to access the sensitivity of the breeding values to the dietetic lysine levels, reaction norms, genetic and Spearman correlations were estimated. The results pointed out the need to consider heterogeneity of residual variance. Significant genotype x environment interaction between the levels of dietetic lysine was identified for daily weight gain. Thus, the results are suggestive that the predictions of the breeding values for the traits evaluated at 150 days of age for Nile tilapia of the GIFT line must consider the level of digestive lysine in the diet used in the production system. Highlights • Lysine is the first limiting amino acid in tilapia nutrition and differences in it level lead to changes in growth. • Identification of genetic sensitivity to lysine for GIFT tilapia is of importance for this fish production chain. • Changes in estimated genetic components and breeding values with reordering of the evaluated animals. [ABSTRACT FROM AUTHOR]

One of the main issues in the manufacturing of marinated herring is the variation in yield, which in turn, is affected by the processing conditions and the variance in fat content. In the present work, we study these effects on individual herring fillets, with focus on the intermediate brining process. Brining time, brine concentration, marinade composition and storage time were varied. For brine concentrations 8%, 16% and 26%, the diffusion coefficient was 2.31 × 10 −9  m 2  s −1 , which was used for model development of salt change prediction in herring during brining. Conducting experiments on single fillets revealed a correlation between the fat content and the weight change after 35 days of marinating. The greatest change occurred within the first few days and only minor changes were seen during the storage period of up to one year. These results contribute to a better understanding of the herring marinating process, which can aid the optimization process in the industry. [ABSTRACT FROM AUTHOR]

This study was carried out to evaluate morphometry and direct and indirect effects of measurements and morphometric relationships on the weight of pirarucu body components. A total of 96 fish were raised in captivity at the Federal University of Rondônia, Presidente Médici - RO, Brazil, with a mean body weight of 9.18 ± 0.1 kg and 104 ± 0.3 cm in length. After desensitizing, the fish were sacrificed, weighed and morphometric measurements of total (TL), standard (SL), head (HL), trunk (LA) and tail (CL) lengths and frontal perimeter (FP), larger perimeter (LP) and tail perimeter (CP) were determined. The fish were dissected and the following body components were measured: leather (with scales), head, viscera and carcass divided into meat layer and spines. The data were submitted to descriptive and multiple regression analyses and the correlation coefficients were separated into direct and indirect effects by a path analysis. Most of the measurements and morphometric ratios showed significant correlations with body weights and body components (carcass, head, meat layer, leather, viscera and spines). LP showed a greater direct and positive effect and was determinant for the variation of total weight and meat layer weight. [ABSTRACT FROM AUTHOR]

In literature, the variability in the estimated optimal digestible protein to digestible energy ratio (DP/DE) is high. The present study aimed to estimate the optimal DP/DE ratio in Nile tilapia ( Oreochromis niloticus ) using different criteria (performance, energy and nitrogen balances parameters). Duplicate aquaria were randomly assigned to one of 16 diets. These diets covered a wide range of dietary DP/DE ratio (from 16.7 to 27 g MJ −1 ). DP levels ranged between 36 and 50% and DE levels between 17.5 and 22 MJ kg −1 . Fish were fed restrictively based on a similar digestible protein amount at all 16 diets. Initial fish weight was 6.7 g. Broken line analysis showed that no optimal DP/DE ratio was present for Nile tilapia within the DP/DE ratio range studied. Regression analysis showed that growth declined as DP/DE ratio increased and seemed to level off at high DP/DE ratio (25 g MJ −1 ). FCR ranged between 0.8 and 1.1 and increased linearly with increasing DP/DE ratio. Decreasing the DP/DE ratio resulted in a linear increase in protein efficiency to a highest value of 53%. However, protein efficiency did not show a plateau or a maximum value. Moreover, decreasing the DP/DE ratio resulted in a very high fat content of the fish (over 16%). In conclusion, an optimal DP/DE ratio in Nile tilapia being fed restrictively seems to be absent or to be below 16 g MJ −1 . A maximum protein deposition level is not present in 5–40 g Nile tilapia. [ABSTRACT FROM AUTHOR]

Microplastics and fibres occur in high concentrations along urban coastlines, but the occurrence of microplastic ingestion by fishes in these areas requires further investigation. Herein, the ingestion of debris (i.e., synthetic and natural fibres and synthetic fragments of various polymer types) by three benthic-foraging fish species Acanthopagrus australis (yellowfin bream), Mugil cephalus (sea mullet) and Gerres subfasciatus (silverbiddy) in Sydney Harbour, Australia has been quantified and chemically speciated by vibrational spectroscopy to identify the polymer type. Ingested debris were quantified using gut content analysis, and identified using attenuated total reflectance Fourier transform infrared (ATR-FTIR) and Raman microspectroscopies in combination with principal component analysis (PCA). The occurrence of debris ingestion at the time of sampling ranged from 21 to 64% for the three species, and the debris number ranged from 0.2 to 4.6 items per fish for the different species, with ∼53% of debris being microplastic. There was a significant difference in the amount of debris ingested among species; however, there was no difference among species when debris counts were standardised to fish weight or gut content weight, indicating that these species ingest a similar concentration of debris relative to their ingestion rate of other material. ATR-FTIR microspectroscopy successfully identified 72% of debris. Raman spectroscopy contributed an additional 1% of successful identification. In addition, PCA was used to non-subjectively classify the ATR-FTIR spectra resulting in the identification of an additional 9% of the debris. The most common microplastics found were polyester (PET), acrylic-polyester blend, and rayon (semi-synthetic) fibres. The potential of using Raman microspectroscopy for debris identification was investigated and provided additional information about the nature of the debris as well as the presence of specific dyes (and hence potential toxicity). [ABSTRACT FROM AUTHOR]

Black soldier fly (BSF) individuals can consume animal excrement and transform it into high-protein food that can be used for animals. This study investigated the changes in the levels of heavy metals (HMs) in BSF individuals and their growth related to ingesting pig manure. According to the trial findings, BSFs fed pig manure had the highest protein concentration of 21.98% and were the least expensive, and its HMs within an acceptable range. Tilapia grew the best when its feed contained half of BSF. Its single-tailed fish weight gain rate was 73.12%, and its survival rate was 100%. The total target hazard quotient (TTHQ) values of tilapia fed with various concentrations of BSF were 0.098–0.181, which were all <1. This indicated that there were no potential hazards posed to humans or the environment. This study offers fundamental information regarding the safety of BSF assessment as well as scientific backing for the widespread utilization of BSF, especially in the pig manure–BSF–tilapia food chain. [Display omitted] • Black soldier fly (BSF) larvae fed by pig manure had high protein content of 21.98%. • When fed with 50% BSF and 50% fish food, tilapia had weight gain rate of 73.12%. • The reduction of heavy metals ranged from 68.2% to 100% in pig manure-BSF-tilapia. • Neither black soldier fly nor tilapia was harmful to humans and environment. [ABSTRACT FROM AUTHOR]

Anthropic exploitation of soil, forests, and water bodies contributes to the modification of river flow regimes and sediment transport dynamics, thus affecting fish habitats and water quality. In the last decades, the increasing awareness of the consequences of such modifications on natural contexts has stimulated researchers and practitioners to provide more innovative solutions aiming at enhancing river biodiversity. Recently developed eco-friendly approaches for river restoration evidenced the necessity of more careful planning and management of natural resources, including the maintenance and enhancement of fish species' habitats. The present study aims at assessing the interaction of different types of wood- and rock-made instream structures with river flow regimes and habitat requirements of many freshwater fish species, accounting for the influence of downstream scour potholes to facilitate fish species migration and spawning. Experimental tests showed that instream structures cause deep scour holes characterized by low flow velocity zones, thus decreasing the required fish swimming power and potentially providing suitable conditions for the migration of freshwater fish species. Using dimensional analysis, empirical relationships were derived to optimize the longitudinal distance between subsequent instream structures, accounting for the effects of various structure geometries and fish biological characteristics. Nevertheless, further investigation is needed to validate the proposed relationships at prototype scale. This study ultimately contributes at providing tools to design river instream structures favorable to fish migration. • The effects of different types of instream structures on fish swimming hydrodynamics have been investigated. • The analysis was conducted at model scale under identical fish Froude numbers F f. • Results showed that instream structures facilitate the migration of freshwater fish species. • Fish white muscles weight increases with the fish weight resulting in an increase of the available fish power. [ABSTRACT FROM AUTHOR]

Rising sea surface temperatures and heat waves are a challenge to salmon aquaculture, and the industry must endeavour to mitigate their impacts. To investigate genetic-based differences in upper thermal tolerance, 20 salmon families were exposed to an incremental temperature increase (+0.2 °C per day from 12 °C) to mimic the rise in temperatures experienced at sea-cages in Atlantic Canada during the summer, or held at 10 °C. Post-smolt Atlantic salmon exposed to the incremental temperature increase up to 20 °C gained more weight than fish reared at 10 °C over the same period, and there were family-specific differences (p < 0.05) in growth and body morphometrics. Significant differences were also detected between the families' incremental thermal maximum (IT Max), with average family IT Max values ranging from 23.3 to 25.0 °C. Fish weight and growth rate were not significantly related to IT Max , but a negative correlation (p < 0.01) was found between hepatosomatic index (HSI) and IT Max. In contrast, the critical thermal maximum (CT Max , measured using a temperature increase of 2 °C h−1 from 10 °C) of the bottom and top four temperature tolerant families (as determined by IT Max) did not differ (∼28.0 °C). A negative correlation (p < 0.01) between HSI and CT Max was also found. However, no relationship was evident between relative ventricular mass (RVM) and IT Max or CT Max. Our data show that IT Max is a more sensitive metric of a salmon's upper temperature tolerance than even an 'environmentally relevant/realistic' CT Max test, and suggest that it could be used in breeding programs that aim to enhance the salmon's tolerance to withstand rising ocean temperatures. • Twenty families of Atlantic salmon were given an incremental thermal maximum (IT Max) test (+ 0.2 °C day−1) or kept at 10 °C. • The IT Max of the families was significantly different and ranged from 23.3 to 25.0 °C. • The critical thermal maximum (CT Max) of the families with the 4 highest and lowest IT Max values did not differ (∼28 °C). • A significant negative correlation was found between hepatosomatic index (HSI) and both IT Max and CT Max. • IT Max is a more sensitive metric of an Atlantic salmon's upper thermal tolerance than CT Max. [ABSTRACT FROM AUTHOR]

Swordfish (Xiphias gladius) are large, economically and ecologically important predatory fish with a wide circumglobal distribution. While swordfish are coveted by anglers, development of recreational fisheries has been limited historically, due in part to the species' tendency to migrate into the mesopelagic zone during the day, effectively out of reach of typical game fishing methods. Recently, however, the adoption of 'deep-dropping', targeting swordfish during daytime with baits at > 300 m depth, has expanded access to the fish and led to the emergence of new regional fisheries. In 2014 a deep-dropping recreational swordfish fishery emerged in temperate southeast Australia and attracted international attention after yielding several swordfish line-class weight records. However, information is needed to guide best practices for emerging deep-dropping swordfish fisheries. Here, we present the first assessment of capture-related morbidity and post-release survival of swordfish caught by deep-dropping in southeast Australia. Among swordfish assessed to be in suitable condition for release, affixed pop-up satellite archival tags indicated 85.6% (57.8 – 95.7%; n = 13) survived after release. Including swordfish assessed as moribund after attempted resuscitation as mortalities, the survival rate for landed swordfish was 44% (95% CI 25.1 – 64.8%; n = 25). Severe abdominal distension (a notably protruding abdomen presumably due to swim bladder overinflation) and observed internal hooking injury (in the gut or gill area) were strong predictors of reduced survival (odds ratios 0.008 and 0.015 respectively), while angling duration and fish weight did not have a discernible effect on mortality. While the swordfish fishery is superficially like more common istiophorid billfish game fishing, the unique physiology and behaviour of swordfish and depths at which they are targeted present a unique challenge for stewardship as the typical catch-and-release billfish game fishing ethos may not be appropriate. The results of this preliminary study suggest swordfish caught deep-dropping are a poor candidate for purely catch-and-release angling. Predictors of post-release mortality are readily observable, so fishers should be prepared to humanely dispatch fish exhibiting symptoms of injury from gill or gut hooking, or abdominal distension severe enough to prevent the fish from righting itself beyond a brief resuscitation period. [ABSTRACT FROM AUTHOR]

Given the current degradation of Caribbean coral reefs, considerable regional emphasis has been put into monitoring the state of key exploited reef fish herbivores, namely surgeonfishes and parrotfishes, through underwater visual fish surveys (UVFS). However, like all survey methods, UVFS suffer from sampling errors that could mask real spatio-temporal trends in fish metrics. Here, we compare trends in simple reef fish herbivore metrics, i.e. average individual fish weight, fish abundance and fish biomass, between UVFS and fish trap surveys, an alternative survey method. Because both methods fundamentally differ in the underlying nature of their sampling errors, we argue that fish metrics exhibiting high consistency between methods will more likely reflect real environmentally-induced trends and should thus be emphasized in monitoring programs. We conducted repeated surveys using both methods concurrently at six sites along a fishing pressure gradient in a Caribbean island. We then examined between-method consistency in fish metric trends across sites and precision in fish metric estimates for each method using surgeonfish and parrotfish data at different levels of aggregation, i.e. species-, family- and functional-level (both herbivorous families combined). We found high and robust between-method consistency only for parrotfish data aggregated at the family level, which also exhibited the highest overall precision in metric estimates. All other fish groups exhibited poorer between-method consistency and poorer precision in their metrics, indicating comparatively higher sensitivity to method-specific sampling errors. Overall, our study supports that family-level parrotfish metrics are particularly robust to survey method, which considerably increases their value as indicators for Caribbean reef monitoring programs. [ABSTRACT FROM AUTHOR]

Studies with zebrafish use acclimatizing periods of at least one week immediately before the experiments. During this time, animals can be housed in sexually segregated conditions (only females or males in the tank) or in mixed-sex conditions (both sexes in the tank). The influence of sex and housing conditions regarding the presence of one or two sexes is largely unknown in zebrafish. Our aim was to evaluate the influence that sex and housing regarding the sex of animals had in the open tank task, in the inhibitory avoidance memory test, in cortisol levels and weight in zebrafish. Four groups of animals were used: 1) segregated housed females (only females were kept in the tank); 2) segregated housed males (only males were kept in the tank); 3) mixed-sex housed females (only females were analyzed from a tank containing 50% ratio of each sex); 4) mixed-sex housed males (only males were analyzed from a tank containing 50% ratio of each sex). Males showed higher total distance travelled and mean speed when compared to females. In the inhibitory avoidance memory, sexually segregated animals had higher latencies than their mixed-sex counterparts in the 1 day test and sexually segregated females presented a memory that persisted longer and was able to be reinstated. Whole-body cortisol levels were higher in mixed-sex animals while weight was lower in these fish. To the best of our knowledge, this is the first time that effects of sex and housing regarding sex were investigated in behavior and physiology of zebrafish. [ABSTRACT FROM AUTHOR]

The aims of this study were to determine the most suitable site and the histological responses to passive integrated transponder (PIT) tags inserted into three sites in far eastern catfish, Silurus asotus . During the experimental period, the tag retention rate and readability rate were greater for dorsal tags than for abdominal cavity or tail tags ( P < 0.05). The standard length, body weight, growth rate (GRW), condition factor (CF), and specific growth rate (SGR) were not significantly different among the experimental groups (all P > 0.05). GRW and SGR were lower in the winter than in the other season ( P < 0.05). In fish with abdominal tags, the tag was located in abdominal fat (in 60% of fish), around the kidney (15%), outside the air bladder (15%), or inside the air bladder (10%). Fibroblasts and a fibrous capsule were found in the tag site, but not in the epidermis. Melanopores and mucous cells were only found in the epidermis, and the area of mucous cells was larger than that of other cells in the epidermis. Based on the high rates of tag retention, readability, and survival, our results suggest that the dorsal muscle is the most favorable tag site for selective breeding systems of far eastern catfish. [ABSTRACT FROM AUTHOR]

Fifteen males of the Japanese eel (9 as the Japanese eel recombinant LH (rLH) group and 6 as the 0.9% NaCl group), which had received 7 weekly injections of rLH (500 μg/kg BW/wk), were used in the experiment. Two days after the 7th injection, milt was collected until the males were spent just before an injection of rLH (500 μg/kg BW) or 0.9% NaCl solution. After the injection, the amount of expressible milt weight and its quality (percentage motility, the velocity of the sperm movement, and sperm density of the milt) were examined every 6 h until 48 h after injection (h AI). In the 0.9% NaCl group, the amount of expressible milt remained small throughout the experimental period. In the rLH group, however, expressible milt increased after 12 h AI and peaked at 18–24 h AI before decreasing thereafter. The total weight of obtainable milt from each male up to 48 h AI was 13.7 times more in the rLH group compared to that of the 0.9% NaCl group. The percentage motility of sperm increased after 6 h AI of rLH and was maintained at high values (> 60%) until 42 h AI. Thus, a large quantity of high-quality milt was transported at 18–24 h AI from the testes to the sperm duct for storage when treated with rLH. Because female eels that have completed egg yolk formation release eggs within 13 to 14 h after the administration of a maturation-inducing steroid (MIS), the administration of rLH as the final shot for males should be given at 6 h before the MIS injection to females for the effective induction of spontaneous spawning. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of ambient temperatures (9, 16, 21 °C) and holding time (0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 h) on rate and quantity of temperature changes and drip losses for whitefish fillets. Different types of fillets were used for the experiment, fresh deepwater redfish ( Sebastes mentella ) fillets (105 g) and two sizes of saithe ( Pollachius virens ) fillets (289 g and 634 g). The fillet temperature increased with time, and more rapidly at higher ambient temperatures, particularly with smaller sized fillets. Similarly, the rate and quantity of drip formation were affected by all experimental factors. The effects decreased (p < 0.05) in the following order: holding time > type of fillets > ambient temperature. The rate of changes in both temperature and drip loss were greater during the first hour of holding but levelled off with longer holding time. Results indicated that time-temperature abuse, even during relatively short (<1 h) exposure of fillets, may lead to significant economic losses due to weight reduction of the products. [ABSTRACT FROM AUTHOR]

Fish anatomical vertical dimensions are extracted from a time-of-flight analysis of fish echo shape using narrow-bandwidth echosounding of swimming individuals. These vertical dimensions fit a Gumbel distribution model and are successfully correlated with fish weight. The proposed method can be used to estimate the mean weight of fish in aquaculture cages as an alternative to target strength measurements. Full-waveform acquisition and signal correlation techniques permitted to increase the signal-to-noise ratio and to improve the performance against traditional envelope-based echosounding. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the dietary tryptophan (Trp) requirements to optimize growth performance of juvenile Nile tilapia. A hundred and eighty fish (38.2 ± 0.09 g) were fed to extruded isonitrogenous (28% crude protein) and isoenergetic (14.5 MJ/kg digestible energy) diets, containing graded levels of dietary Trp (1.8, 2.3, 2.7, 3.2, and 3.7 g/kg). Fish were hand fed to triplicate groups of 12 fish, three times a day to apparent satiety for 45 days. The relationship between body weight gain, feed conversion ratio, protein efficiency ratio, and fish uniformity against dietary Trp levels could be expressed as a second-order polynomial regression analysis, where the best Trp levels were estimated to be 2.9, 3.1, 3.1, and 2.9 g/kg, respectively. No effects of dietary Trp on hepatosomatic index, visceral fat, survival, or body composition were observed. Whole body retentions of arginine, phenylalanine, and lysine were highest in fish fed 3.0, 3.1, and 3.1 g/kg Trp, respectively. The dietary Trp requirement of juvenile Nile tilapia was estimated to be 2.9 g/kg for maximum weight gain of fish. [ABSTRACT FROM AUTHOR]

Pop-up satellite archival tags (PSATs) were deployed on eight blackspotted rockfish ( Sebastes melanostictus ) (37–54 cm fork length) caught in southeast Alaska at depths from 148 to 198 m. Six of these fish were tagged and released immediately after capture in a commercially available inverted, weighted crab ring, descended quickly to what was assumed to be the seafloor, and remained at that depth until the PSATs released early (after 12–14 days). The remaining two fish were held in a laboratory after capture, one for 8 months and one for 46 months, and were then released at the surface nearby the capture site. One of these two tags released after 12 days while the tag deployed on a 37 cm fish was retained for 190 days. Both fish moved to deeper depths initially and then moved back to more shallow depths, indicating that rockfish may require time to acclimate to increased pressure if the swim bladder is not currently ruptured. For the tag that was retained for 190 days, we identified six phases of vertical movement behavior. During the longest phase (122 days) the fish made rapid descents, sometimes in less than 15 min, which were deeper during the day and during high-tide, but more frequent at night. During some of the shorter phases (lasting from 8 to 28 days) the fish was more sedentary or was deeper at night. Our results show that it is possible to tag a deepwater rockfish with a PSAT. [ABSTRACT FROM AUTHOR]

Histidine is necessary for the formation and repair of tissues to mitigate the effects of cataract on some fish species. Although the requirements for dietary amino acids of several Trachinotus species have been reported, the quantitative histidine requirement for a cost-effective diet for snubnose pompano or Trachinotus blochii , a high value finfish species in the Philippines, has been limited. A 90-day growth experiment determined the dietary histidine requirement of juvenile snubnose pompano (0.19 ± 0.03 g). Six isonitrogenous, isolipidic, and isoenergetic diets consisted of a control diet with 0% histidine inclusion level (basal histidine level of 0.65%) and five diets with histidine inclusion levels of 0.15 (0.80%), 0.3 (1.1%), 0.45 (1.55%), 0.6 (2.15%), and 0.75% (2.9%). To simulate the pompano whole-body amino acid composition, essential amino acids were added in the diet. Fifteen pompano juveniles per tank in three replicates were stocked randomly in 250-L fiberglass tanks and were fed to satiation for 90 d. When the dietary histidine level and percent weight gain were analyzed via quadratic regression, a dietary histidine level of 1.61 g per 100 g diet or 0.357 g per 100 g protein is required for juvenile snubnose pompano. Moreover, the occurrence of cataracts was not observed in fish fed all dietary treatments. • Fish weight improved when diets were supplemented with histidine. • Feed conversion ratio and proximate body compositions were not altered by the histidine levels in the diets. • Nutrient digestibilities were not significantly influenced by the histidine inclusion levels. • Dietary histidine level of 1.61 g per 100 g diet or 0.357 g per 100 g protein is required for juvenile snubnose pompano. [ABSTRACT FROM AUTHOR]

Disease outbreaks in intensive aquaculture, particularly from bacterial pathogens, represent major constraints to efficient fish production. Therefore, development of novel disease treatment and prevention strategies have been receiving considerable attention in recent years. This study analyzed the efficacy of the organic acid poly-β-hydroxybutyrate (PHB) as an immunomodulator in hybrid striped bass (Morone chrysops × M. saxatilis) (HSB) and red drum (Sciaenops ocellatus) based on both in vitro and in vivo approaches. In vitro immunological assays, namely intra- and extra-cellular superoxide anion production and bactericidal capacity of HSB head kidney-derived leukocytes were determined to be significantly (P < 0.05) reduced when graded doses of sodium 3-hydroxybutyrate (3HB; 0.0, 0.5, 1.0, 2.0, 4.0 and 8.0 mM), a precursor to PHB, was supplemented in the cell culture media. For the HSB in vivo feeding trial, PHB-synthesizing bacteria, Zobellella denitrificans (ZD1), were supplemented to basal diets to produce five isonitrogenous and isolipidic experimental diets (40% crude protein and 10% crude lipid) containing PHB in stepwise increments (0.0, 0.125, 0.25, 0.5, 1.0, and 2.0% of dry-diet weight). In addition, a control diet was supplemented with 0.5% of a commercial purified PHB product. In a separate feeding trial, a commercial PHB product was supplemented to a practical basal diet in stepwise increments (0.0,0.125, 0.25, 0.5, and 1.0%) to isonitrogenous and isolipidic experimental diets (40% crude protein and 10% crude lipid). Juvenile HSB, and red drum (∼5.5, and 4.4 g/fish initial weight, respectively) in separate feeding trials were stocked in 38-L aquaria operated as a recirculating aquaculture systemHSB experimental diets were randomly assigned to quadruplicate aquaria of fish while the red drum experimental tdiets were randomly assigned to quintuplicate aquaria and fed for an 8-week period. HSB and red drum exhibited limited responses to graded levels of PHB, including percentage weight gain, feed efficiency, protein conversion efficiency and hepatosomatic index. Only juvenile red drum showed significantly (P < 0.05) increased muscle yield values with increasing dietary PHB while whole-body proximate composition analyses revealed no significant (P > 0.05) differences, except for HSB whole-body crude lipid. Thus, PHB (ZD1-derived and commercial) had limited effects on growth parameters, body condition factors, and immunological responses of both HSB and red drum juveniles. • 3-hydroxybutyrate (3HB) decreased measured innate immune responses of hybrid striped bass head kidney-derived leukocytes in vitro. • PHB supplementation had limited responses on growth performance and whole-body composition of juvenile hybrid striped bass and red drum. • Red drum exposed to a Photobacterium infection had higher survival when supplemented with the PHB ingredient than fish fed the basal treatment. [ABSTRACT FROM AUTHOR]

Farmed Atlantic salmon (Salmo salar L.) are subject to a variety of stressors throughout production. Elevations of cortisol level in the blood are one of the major endocrine primary stress responses in vertebrates and are widely used as stress indicator. However, blood sampling is invasive and stressful procedures. Cortisol instantly released into the blood at sampling can easily interfere with the initial stress response of interest. Fecal corticoid metabolites (FCM) have been suggested for a less invasive assessment of stress in fish. In the present study, we evaluated stress responses by using plasma cortisol and FCM as stress indicators in Atlantic salmon. Atlantic salmon (with average weight 42 g) were exposed to 3 different stressors: 1) parr-smolt transformation; 2) infestation with salmon lice (Lepeophtheirus salmonis) for two-weeks; 3) infection with infectious salmon anaemia virus (ISAV) for four weeks. The results demonstrated that FCM levels correlated well with the plasma cortisol levels at single-point sampling during long-term stress (p < 0.05). Significant increases of both plasma cortisol and FCM were found two weeks after initiated 24 h light. Each tank was sampled twice, with around 40-min interval. The chasing during the first sampling was used as an acute stressor. The effects of sampling procedures on plasma cortisol and FCM levels are compared. Blood and feces were analyzed by an Enzyme-Linked Immunosorbent Assay (ELISA). Plasma cortisol and FCM levels increased within 40 min after fish perceived an acute stressor when the average weight of fish was below 100 g. Attenuated cortisol stress responses to acute stress were found after fish experiencing long-term stress. Collectively, FCM reflects changes in plasma cortisol and can be an alternative to analysis of plasma cortisol in Atlantic salmon, complementing evidence of using FCM as stress indicators for monitoring and improving fish welfare. The results highlight that standard sampling procedures and good experimental designs should be established to ensure robust and repeatable results in the study of stress based on the FCM measurement. Future study will investigate representative timepoints for FCM sampling, with particular attention to the types of stress and sizes of the fish. • FCM were significantly correlated with plasma cortisol levels in Atlantic salmon. • Elevated FCM levels were found in 40 min after fish (< 100 g) perceive stress. • FCM is an alternative to plasma cortisol for evaluating stress in Atlantic salmon. [ABSTRACT FROM AUTHOR]

Data about the presence of polycyclic aromatic hydrocarbons in biota from Tunisian coastal ecosystems is scarce. The present paper is the first work to report these chemicals in the biota of Ghar El Melh Lagoon. From Bizerte and Ghar El Melh Lagoons (Tunisia), levels of 15 priority polycyclic aromatic hydrocarbons in Chelon auratus (mullet) muscle were measured. Total PAH levels in the mullet were comparable to or lower than those found in other fish specimens from other countries. The nature of the detected chemicals was examined using several different compositional ratios, revealing petrogenic and pyrolytic anthropogenic contamination in both studied lagoons. [Display omitted] • PAHs were detected in fish from two coastal regions. • PAHs concentrations were similar or lower to other world locations. • Mixed sources of PAHs were identified in the investigated areas. • The risk of PAHs intake via Liza aurata consumption was negligible. • No correlation was revealed between PAHs levels and fish length or weight. [ABSTRACT FROM AUTHOR]

Rising global temperatures have raised the need for detailed knowledge of the effects of rising temperatures on the physiology of animals used in aquaculture. Here we used a multifactorial bioenergetic approach using groups of rainbow trout (Oncorhynchus mykiss) with an average single fish weight of 183.75 g ± 0.65 g to investigate the interactions of feeding and temperature with key metabolic variables. We used a recirculating aquaculture respirometry system (RARS) to test three ration sizes (0.65; 0.975; 1.3% of live body weight (BW)) over a range of three consecutive temperatures (14; 17; 20 °C). The fish were fed once per day for 6 days at each temperature and subsequently starved for 5 days to return to standard metabolic rate (SMR). This study aimed to answer the highly discussed topic of the temperature dependency of key metabolic specific dynamic action (SDA)-variables SDA coef and SDA dur. We were able to provide evidence, that in rainbow trout the SDA coef is highly dependent on the environmental temperature in the first ever approach to assess these variables in a group respirometer with this species. We compared the results of this study with a sophisticated bioenergetic model by Elliot and Hurley (2002) and thereby provide evidence for the practicability of group respirometry as a method to assess bioenergetic data under culture like conditions. [Display omitted] • Specific dynamic action coefficient is temperature dependent in rainbow trout. • Specific dynamic action duration mostly follows circardian cycle in group respirometry. • Group respirometry yields highly relevant results that well compare to other approaches. • Digestibility of nutrients and energy were unaffected by environmental temperatures. [ABSTRACT FROM AUTHOR]