Aquaculture, Fish and Fisheries最新文献

Expansion of pearl production using the silver-lip pearl oyster, Pinctada maxima, depends on increasing the availability of high-quality spat from hatcheries and optimization of existing hatchery protocols. Research to develop feeding regimes yielding higher quality spat is seen as a priority. This study evaluated the suitability of three microalgae (Rebecca salina, Chaetoceros simplex and Tisochrysis lutea), fed singly and in combination, for spat of P. maxima and assessed whether mixed diets yielded spat of higher quality. A model-fitting approach examined the response of spat fed microalgal diets for 35 days. Organic content of spat, as an indicator of quality, as well as metrics relating to spat size and weight were considered. On the basis of organic content, all microalgal diets tested were found suitable and there was no evidence that the mixed diets yielded higher quality spat compared to monospecific diets. Further, any gains in spat size attributed to the mixed microalgal diets were comparatively modest. Contrary to long-held assumptions, our results indicate that monospecific microalgal diets are not necessarily inferior to mixed microalgal diets for on-growing spat of P. maxima. They indicate potential to develop simpler and cheaper protocols for culture of P. maxima spat in land-based systems.

The cover image is based on the Article Toxic Effects of Tributyltin, Triphenyltin, and SnCl₂ on the Development of Zebrafish (Danio rerio) Embryos by Aref Barkhordari et al., https://doi.org/10.1002/aff2.70005.

Tasmanian Atlantic salmon broodstock may be conditioned in flow-through (FT) systems where water quality fluctuates and temperatures approach their upper limit of thermal tolerance, or in recirculating aquaculture systems (RAS) where conditions are comparatively cool and stable. The impact of broad conditioning approach on the molecular cargo of salmon eggs has never been explored in dynamic commercial settings. Therefore, this study aimed to characterise the reproductive features of broodstock conditioned using different commercial approaches and determine whether the fatty acid (FA) profiles of muscle, oocytes and eggs varied between groups during vitellogenesis and at stripping. The collective conditioning approach had a marked impact on the somatic and reproductive dynamics of female salmon broodstock, and the eggs produced by each group of fish were fundamentally different in terms of their FA composition. Of particular note is the increased maternal investment of saturated FAs (mg.g⁻¹) and monounsaturated FAs (percent and mg.g⁻¹) by FT-based eggs, and the higher n3 polyunsaturated FA (percent and mg.g⁻¹), docosahexaenoic acid (DHA, percent and mg.g⁻¹), arachidonic acid (ARA, percent), eicosapentaenoic acid (EPA, percent), n3:n6 ratio and ARA:EPA ratio of RAS-based eggs. These metrics combined with the apparently higher prevalence of neural development and survival of RAS embryos suggest that RAS eggs were of higher quality. On the other hand, there is evidence to suggest that FT broodstock attempt to prepare their offspring for a (presumably) challenging early life environment by producing larger eggs that are proportionally rich in short-chain FAs and contain a higher total quantity of FAs per egg.

Fish stocking continues to be an important and often-used tool in fisheries management. Mortality of fish may be high in the first few days after stocking due to predation and a lack of appropriate food and habitat. The objective of this study was to develop a conceptual model that may identify stocking locations that can help improve the survival of stocked fish. We identified three factors—predator risk, zooplankton (food) availability and measures of habitat that could be important to the survival of stocked Walleye (Sander vitreus) and White Bass (Morone chrysops) fingerlings in Lake McConaughy, Nebraska. The spatial distribution of these factors was used to create a predictive surface to identify those stocking locations hypothesised to lead to higher survival. Final stocking maps identified the best 12.8% and 13.9% of the predicted area of Lake McConaughy for stocking Walleye and White Bass, respectively. Both maps predicted that the best locations were along the south-central shoreline of Lake McConaughy. The maps for both species were interestingly similar. These results are likely due to the similarities in predators consuming the stocked species and the zooplankton consumed by fingerlings of both species. Habitat availability may be less important, or other aspects of habitat may need to be considered. Identifying the best locations for stocking based on predation risk and the availability of food and habitat could increase the survival of stocked fishes and help managers reach population objectives.

Seasonal feeding activity and ontogenetic dietary shifts of Cyprinus carpio (Linnaeus, 1758) were examined using 209 fish samples from Lake Arekit, Ethiopia. Among the 209 specimens, 174 (83.3%) displayed a range of dietary items in their stomachs. The species’ feeding patterns were determined through numerical indexes (frequency of occurrence and volumetric contribution) and composite indexes (index of preponderance [IOP] and Geometric Index of Importance [GIIi]). Detritus emerged as the primary food source for C. carpio, followed by macrophytes, insects and zooplankton. A lesser amount of phytoplankton, nematodes and ostracods were also consumed. On the basis of the findings, C. carpio can be classified as a detri-omnivore, as it consumes benthic species like nematodes, ostracods and insect larvae. Seasonal fluctuations in food item consumption were noted (p < 0.05), with higher intake during the rainy season and reduced consumption in the dry season. There was a distinct ontogenetic shift in the relative importance of food items and showed significant variations in food preferences among size groups (p < 0.05). The contributions of animal-origin food categories (ostracods, zooplankton and insects) were important in the diet of the smaller size class, whereas food of plant origin (macrophytes) and detritus were more important in the diet of adults. Understanding the seasonal feeding patterns and ontogenetic dietary shifts of C. carpio in Lake Arekit provides crucial insights into their ecological role within the lake's ecosystem and highlights their adaptability to eutrophic conditions.

Tin (Sn) is one of the heavy metals to which various functions in biological development are attributed in small quantities, for example, a role in cell structure, enzyme activities, and protein and carbohydrate metabolism in fish. Tributyltin (TBT) and triphenyltin (TPT) are endocrine disrupting chemicals that are widely distributed in the aquatic environment. The aim of this study was to investigate the effects of TBT, TPT, and SnCl₂ on the embryonic development of zebrafish. In this study, zebrafish embryos were used to observe the acute toxicity of TBT, TPT, and SnCl₂. Fish embryo toxicity analysis was performed for different TBT, TPT, and SnCl₂ concentrations (1, 5, 10, 15, and 20 ng/L). Fertilized eggs in 24-well plates (20 eggs in each concentration) were incubated at 26°C for 4 days, and embryo clotting, embryo heartbeat, and morphological abnormalities were recorded after 96 h. Coagulation increased significantly in a dose-dependent manner, and TBT was able to induce coagulation in zebrafish embryos. Heartbeat changes significantly decreased (p < 0.05) in a dose-dependent manner at different TBT doses (p < 0.05). The percentage of mortality was higher in embryos at trace levels of TBT, indicating that the embryos are more sensitive to the toxicity of TBT. TBT is therefore extremely toxic and can have fatal consequences for zebrafish embryos, ultimately leading to the extinction of species and a decline in biodiversity in the aquatic environment. After analyzing the images 96 h after fertilization and converting them to a teratogenic index score, it was found that the index for the two compounds TPT and TBT was 4.6 and 9.6 ng/L, respectively.

In recirculating aquaculture systems (RAS), off-flavours accumulated in fish muscle tissue can be problematic in terms of consumer acceptance and the reputation of farmed fish products. Off-flavours often give fish earthy, muddy, or other undesirable flavours. Typically, off-flavours are removed during a depuration period in which fish are fasted and held in clean water. Unfortunately, this causes additional costs and delayed sales, while fish lose weight and show a decrease in lipid content. First, we studied fish growth in a partial RAS (PRAS) where the conditions are very similar to those in depuration with a water exchange rate of 4000 L kg⁻¹ feed, compared to RAS with a 650-L water kg⁻¹ feed. Rainbow trout (Oncorhynchus mykiss) was reared in both systems. Our aim was to combine the benefits of a higher water exchange rate: the lack of need for biofilters and a lower accumulation of off-flavours while obtaining stable rearing conditions. Additionally, we studied the effects of moderate feeding and H₂O₂ addition during depuration. The fish grew faster in a PRAS than in a RAS when fed ad libitum. Thirteen off-flavour compounds were found in the fish flesh and 11 in the circulating water. The H₂O₂ addition led to decreased levels of off-flavours in the tank water and in fish muscle. The results showed no significant differences in off-flavours between the fed and not-fed systems, showing that moderate feeding did not prevent a good depuration result. However, the lipid content and the overall fish weight were higher in the fed systems, which suggests more effective depuration. Increased depuration efficiency can be an important tool when considering ways to improve the profitability of production.

Early mortality syndrome (EMS) or acute hepatopancreatic necrosis syndrome (AHPND) is an epizootic bacterial infection of shrimp that has had significant negative impact on the global shrimp aquaculture industry. This disease is largely attributed to pathogenic Vibrio parahaemolyticus EMS strains (VP-EMS). Application of probiotics was examined for control of pathogenic VP-EMS infections in Pacific white shrimp (Litopenaeus vannamei) under laboratory-scale conditions. Two probiotic products, a single strain (O14VRQ) of Bacillus subtilis and a blend (Plus10) of five strains of Bacillus from four different species (Bacillus amyloliquifaciens, Bacillus megaterium, Bacillus brevis, and two distinct strains of Bacillus subtilis), were evaluated at various concentrations as feed additives (applied as a top coat on commercial feed) or dosed directly into the culture water. Two trials were conducted in which shrimp were fed either a control feed (no probiotics) or probiotic-coated feed for 7 days prior to be being challenged with VP-EMS. Shrimp were observed for clinical signs of disease and mortalities during the disease challenge study. These experiments demonstrated that while both Bacillus probiotic products were shown to significantly (p < 0.05) improve shrimp survival, the O14VRQ strain provided the most consistent protection across the trials in top-coated feed. Overall, better efficacy was observed with probiotic-coated feeds. Findings were directly and positively correlated with concentration for top-coated and even more so for direct in-tank applications. Collectively, these findings contribute to our understanding about how probiotic strains could be applied to enhance shrimp health in aquaculture.

A major expense in the operation of bivalve nurseries is the culture of high-quality live microalgae feeds, and efforts to develop effective alternative feeds have had limited success. Juvenile bivalves are known to be able to absorb dissolved nutrients, but this ability has received minimal attention as a route for supplementary feeding. This study assessed the capacity of juvenile green-lipped mussels (GLMs) (Perna canaliculus) to uptake and assimilate dissolved glucose at five experimental concentrations (i.e. 10 µg mL⁻¹, 100 µg mL⁻¹, 1 mg mL⁻¹, 10 mg mL⁻¹ and 30 mg mL⁻¹) as a supplement to cultured microalgae. Growth and survival of the mussels were measured over 3 weeks. Although all glucose concentrations improved the performance of mussel spat compared to the control, the best performing was a concentration of 1 mg mL⁻¹ of dissolved glucose which enhanced daily spat growth 2.7 times that of the control live microalgal diet without glucose. Survival was high (i.e. >95%) for all treatments except for the highest experimental concentration of glucose, for which a concentration of 30 mg mL⁻¹ resulted in mean mortality of 24%. Mussel spat supplemented with dissolved glucose accumulated up to 30% greater lipid and improved the carbohydrate content per mg g⁻¹ of ash-free dry weight as much as 3.5 times compared to those in the control treatment, indicating that they were in greater nutritional condition. This demonstration that dissolved glucose can be used to fuel growth by GLM spat at concentrations as low as 10 µg mL⁻¹ suggests that other soluble nutrients may also act as a supplemental feed for cultured juvenile molluscs. Dissolved nutrients have the potential to improve the performance of spat in nursery systems while simultaneously reducing the reliance of cultured microalgae as a sole feed input.

To evaluate the success of a stocking program in Fox Lake, Minnesota, adult (≥76 cm total length) Muskellunge were captured with large nearshore trap nets and individually marked with passive integrated transponder tags during the 2011–2013 and 2015–2017 spawning seasons; then, capture–recapture data were analyzed at two different time scales. Despite substantial sampling effort, daily capture histories within a single season only supported closed-population abundance estimates for both sexes in half the years; estimates were imprecise, and there was evidence of trap shyness or violation of the short-term closure assumption in some years. Jolly–Seber models over all years supported relatively precise abundance estimates for both sexes every year, as well as estimates of annual survival, recruitment, and population growth rate. Link–Barker Jolly–Seber models provided estimates of population growth rate λ ≈ 1 indicating that per-capita annual recruitment rates of only about 0.15–0.20 were adequate to maintain the adult population given the high annual apparent survival rates of 0.80 for adult females and 0.89 for adult males. POPAN Jolly–Seber models revealed that about 80 adult females and 90–126 adult males were vulnerable to capture each year in the 385 ha lake, and about 16–18 fish of each sex recruited to the adult population annually. This study illustrates the importance of open-population models with multiple years of data to evaluate the abundance and population dynamics of a low-density, long-lived species.