Aquaculture, Fish and Fisheries最新文献

Wild fish utilise aquaculture habitats for shelter and/or food resources. It is often assumed that fish respond to feed input, the abundance of the farmed species or the associated assemblage of biofouling which naturally colonises the structural habitats. However, few studies have directly analysed the composition of the diet of fish within aquaculture habitats, and of these most have focused on fed finfish aquaculture. Snapper are commonly present as adults within coastal mussel farms and tend to become a resident species of these farms. Therefore, they are a suitable case study species for exploring differences in diet between natural and aquaculture habitats. This study investigated the gut contents of snapper in soft-sediment habitats within and outside of New Zealand green-lipped mussel farms. Visual gut analysis and DNA metabarcoding methods were used to provide complementary analyses on the composition of gut contents between the mussel farm and natural (i.e., control) sites. Snapper within mussel farms were consistently found to have consumed different prey groups compared to the control snapper. Prey groups identified from mussel farm snapper gut contents could be directly linked to species commonly present in the farms, that is cultured green-lipped mussels, blue mussels and barnacle biofouling. There was good alignment between the visual gut and genetic analyses for the key species identified. Overall, the results show that the highly abundant prey groups consumed by snapper in mussel farm habitats are likely to be beneficial to the snapper population, reducing foraging effort and potentially supplying more nutritious prey. These findings provide evidence towards the supporting services of mussel farm habitats through the provision of food resources.

The growth of aquaculture sector in Kenya has been anchored on farmed Nile tilapia Oreochromis niloticus. Different strains of the species exist in Kenya with unknown quality due to lack of stock improvement programmes coupled by variations in breeding and management practices in different hatcheries. The seeds supplied to farmers have not exhibited good performance and resilience to changing climate. There is need to validate the quality of strains supplied to fish farmers in Kenya. This study sought to compare the growth performance of three strains of farmed Nile tilapia; Sagana strain (SAG-F8) produced through selective breeding, super YY strain (KAM-YY) from Kamuthanga fish farm and the local strain (LOC-T) obtained from Siaya County. The fish were stocked in fertilised earthen ponds measuring 300 m² in triplicates at 3 fish/m². The fish were fed on 35% crude protein diet for 180 days at Bukani Aquapark located in Busia County, Kenya. There was no significant difference in mean weight gain (MWG) between SAG-F8 and LOC-T strain exhibiting 159.786 ± 6.76 g and 158.623 ± 4.67 g, respectively. However, under similar conditions, the KAM-YY strain had a significantly lower MWG (131.74 ± 4.75 g) compared to the two strains. Food conversion ratio (FCR), specific growth rate (SGR) did not demonstrate any significant difference among the different strains. The body protein content in the SAG-F8 fish strain was higher (65.40 ± 0.20%) followed by LOC-T strain (61.23 ± 2.34%) and lastly KAM-YY strain had the lowest (60.37 ± 0.89%). In this study, the impact of genetic improvement has been demonstrated to influence growth and feed efficiency as well as body composition. These improved strains will substantially increase fish production and productivity, hence, a positive impact on the fish farmers' livelihoods when supplied to the farmers and seed multipliers.

Larval eastern oysters (Crassostrea virginica) grown in shellfish hatcheries are susceptible to bacterial diseases, particularly vibriosis. Probiotics are microbes that confer health benefits to the host and have been identified as promising tools to manage diseases in aquaculture. The marine bacterium Phaeobacter inhibens S4 (S4) protects larval eastern oysters against challenge with the bacterial pathogen Vibrio coralliilyticus RE22 (RE22). A concentrated liquid formulation of probiont S4 that maintained high cell viability after long-term storage was developed for commercial use in shellfish hatcheries. The safety and efficacy of the formulation were tested in six different trials in two hatcheries. The S4 formulation was added to C. virginica larvae culture tanks daily at 10⁴ colony forming units (CFU)/mL from Day 1 post fertilisation until Day 6, 12 or 14, depending on the trial. Treatment of larvae in the hatchery with the S4 formulation did not significantly affect the survival and growth of the larvae. Formulated probiont S4 treatment in the hatchery led to a significant increase in relative percent survival (RPS) when larvae were subsequently challenged with the pathogen RE22 (10⁵ CFU/mL) for 24 h in a laboratory challenge as compared to probiotic-untreated RE22-challenged larvae (RPS increase of 46%–74%, p < 0.05). These results suggest that this novel S4 formulation is a safe, easy-to-use and effective tool in preventing larval losses due to vibriosis in hatcheries.

Ongoing global changes are expected to affect the worldwide production of many fisheries and aquaculture systems. Because invertebrates represent a relevant industry, it is crucial to anticipate challenges that are resulting from the current environmental alterations. In this review, we rely on the estimated physiological limits of six commercialised species of sea urchins (Loxechinus albus, Mesocentrotus franciscanus, Paracentrotus lividus, Strongylocentrotus droebachiensis, Strongylocentrotus intermedius and Strongylocentrotus purpuratus) to define the vulnerability (or resilience) of their populations facing ocean warming and acidification (OW&A). Considering that coastal systems do not change uniformly and that the populations’ response to stressors varies depending on their origin, we investigate the effects of OW&A by including studies that estimate future environmental mutations within their distribution areas. Cross-referencing 79 studies, we find that several sea urchin populations are potentially vulnerable to the predicted OW&A as environmental conditions in certain regions are expected to shift beyond their estimated physiological limit of tolerance. Specifically, while upper thermal thresholds seem to be respected for L. albus along the SW American coast, M. franciscanus and S. purpuratus southern populations appear to be vulnerable in NW America. Moreover, as a result of the strong warming expected in the Arctic and sub-Arctic regions, the local productivity of S. droebachiensis is also potentially largely affected. Finally, populations of S. intermedius and P. lividus found in northern Japan and eastern Mediterranean respectively, are supposed to decline due to large environmental changes brought about by OW&A. This review highlights the status and the potential of local adaptation of a number of sea urchin populations in response to changing environmental conditions, revealing possible future challenges for various local fishing industries.

Reynolds is correct in pointing out that electrofishing could theoretically cause electrolysis that would cause the disassociation of water molecules into their gaseous constituents that could possibly contribute to GBT. GBT is caused by the total gas pressure in the water that comprises mainly dissolved nitrogen and oxygen. While past studies have shown that at times oxygen partial pressure can contribute to GBT, evidence suggests that nitrogen is the primary factor that would not be influenced by the electrolysis described above (see the review by Weitcamp and Katz, 1980). Regardless, as Reynolds noted, in our study none of the control fish tested showed signs of GBT after receiving the electroshock treatment. Furthermore, none of the test fish that showed no signs of GBT prior to treatment ever showed signs of GBT following treatment. This further supports for our conclusion that electrofishing does not contribute to external signs of GBT. Reynolds suggests that the study should have focused on treating fish free from TDG (i.e., unsaturated water) to determine electroshock effects on GBT development. I question why a study like that would be done in the absence of any data that would suggest such an effect given the lack of a plausible physiological mechanism. Since the advent of electrofishing, I am unaware of any reports of GBT being observed in fishes collected from waters with unsaturated TDG.

As far as the lack of detailed methods, it was suggested that the original manuscript be shortened to the journal's “Short Communication” format. This necessitated reducing the manuscript length by over 50%, and much of the original detail in the Methods section was removed. The original full-length manuscript is included as an appendix in a report that can be found at https://www.cbfish.org/Document.mvc/Viewer/P197308.

Traditionally, population sizes, ecology, and threats to species and their habitats have been obtained by empirical scientific studies. However, the knowledge of local and indigenous communities worldwide has been acknowledged as an extremely rich and underused source of information on how the environment, biodiversity, and local conditions are changing over time. In this view, the objective of the study was to investigate local fishers’ knowledge of local names, habitats, uses, market price, change in population abundance, and threats faced by the snakehead fish (Parachanna obscura) in Ivorian freshwaters. The study was conducted using face-to-face interviews and a structured questionnaire with 381 fishers during the period from October 2020 to February 2021. The results show that this fish species is strongly appreciated for the good taste of its flesh, with market prices varying between 1.5 and 3€ on average. All respondents confirmed that the species is not yet produced in aquaculture and mentioned their willingness to support its introduction into aquaculture. Several local names of P. obscura fish were recorded, with ‘Sounôgô-djêguê’ (used in 36% of fishers’ ethnic groups), ‘Pino’ (21%), and ‘Édjoué-bile’ (21%) being the most popular names used in Ivorian fishers’ communities. All respondents agreed that P. obscura is a potamodromous fish species living preferably in wetlands, rivers, lakes, and streams. A significant decrease in the abundance of this fish was observed by 71% of fishers, perceived mainly due to overfishing, deforestation around watersheds, habitat destruction/modification, obnoxious fishing practices, pesticide use in farms close to watersheds, and climate change, especially lack of rainfall. The study clearly demonstrated the importance of local ecological knowledge of fishers in identifying threats to fish populations, habitat types used by the species, and other relevant information; therefore, this ecological knowledge has to be integrated into biomonitoring and conservation policy of aquatic biodiversity. The information obtained from this study is also helpful for future studies on the management and cultivation of this species.

This study was conducted to determine the growth performance, body composition, and haematological profile of Heteropneustes fossilis in response to the replacement of fish meal (FM) by sunflower meal (SFM). The experiment was conducted in a completely randomized design (CRD) with five treatments and three replications. The fish (initial average body weight of 2.42 ± 0.01 g) were reared in 15 glass aquaria (40 fish/aquarium) with a 150-L water capacity. Five isoproteic (35%) diets were prepared by replacing FM protein with SFM protein at a rate of 0% (T₀), 10% (T₁₀), 20% (T₂₀), 30% (T₃₀), and 40% (T₄₀). Fish were fed with experimental diet twice a day (9.00 and 16.00), 7 days a week for 8 weeks. Fish were sampled at the end of the experimental period of 8 weeks. At the end of the rearing period, the highest weight gain (6.25 ± 0.11g), % weight gain (163.32%), and specific growth rate (1.61 ± 0.03%/day) were observed in the control (T₀) treatment, but the difference was not significant (p > 0.05) with T₁₀ and T₂₀ treatments. However, all the growth factors were decreased with the further inclusion level of SFM in replacement of FM, and the lowest growth performance was observed in T₄₀ treatment. The protein efficiency ratio (PER) and feed conversion ratio (FCR) followed the same pattern as the growth parameters. It was found that the whole-body proximate composition of fish was also affected significantly (p < 0.05). Haematological parameters significantly (P < 0.05) altered at 30% and 40% levels of replacement of FM with SFM. Based on these results, it can be concluded that 20% FM protein can be substituted with SFM protein in the diet of H. fossilis without compromising growth performance, feed utilization, chemical composition, and haematological status. However, according to polynomial regression analysis, the optimum level of replacement of FM protein with SFM protein was determined to be 14.3% in the diet of H. fossilis.

Fish in the upper Madeira River basin (Bolivian Amazon) are an important source of livelihoods and protein for both rural and urban human populations. We characterised fisheries in the area of the port city of Riberalta, which possesses some of the most important fisheries landing sites bordering the Moxos lowlands, and evaluated the contribution of an invasive species (Arapaima gigas) to the landings. We compared the regional economic contribution of urban-based and rural indigenous fisheries. Both fisheries contribute significantly to local food security and livelihoods and take advantage in a different but complementary way of the abundance of the invasive species, avoiding conflicts by partitioning the fish catch and supplying different urban markets. Both fisher groups are involved in a debt peonage system making them dependent on middlemen. A. gigas represented 57.6% of the overall economic value of fish in the region. The socioeconomic impact of the invasive species might increase considerably if it would invade and colonise the available habitats in the nuclear area of the Moxos lowlands.

Predation and competition are among the most important factors affecting sandfish, Holothuria scabra, growth and survival in ocean-based production systems. In this study, the potential predators and competitors of sandfish juveniles reared at two sites in the Philippines using the floating hapa ocean nursery system were assessed. A total of 26 species of potential predators and competitors from 16 different families of fishes, molluscs and crustaceans were recorded. These taxa were dominated by the opisthobranch Stylocheilus striatus at Bolinao (north–west Luzon) and the isopod Cymodoce sp. at Maliwaliw (eastern Visayas). Highest number of potential predators and competitors that recruited and/or migrated to the inside of floating hapa nets was recorded on day 23 at Bolinao and day 30 at Maliwaliw, then decreased over the 69-day duration of the study. Mean length, absolute growth rates (AGRs) and survival of sandfish juveniles reared in floating hapas at the two sites varied during the study. AGRs were highest at 1.17 ± 0.06 mm day⁻¹ at Bolinao, and 1 ± 0.08 mm day⁻¹ at Maliwaliw, by days 23 and 60, respectively. Mean lengths of sandfish juveniles reared at Bolinao and Maliwaliw by the end of the study were 46.7 ± 0.15 and 58.8 ± 2.4 mm, respectively, and survival at both sites was high at 96% by the end of the study. Negative correlations were observed between the number of individual predators and competitors, and survival and growth rates of sandfish juveniles reared at Bolinao and Maliwaliw, respectively. Our results highlight the importance of predator and competitor management measures and appropriate site selection to optimize growth performance and survival of sandfish juveniles reared in ocean-based culture production systems.

The freshwater prawn Macrobrachium macrobrachion (Herklots, 1851) is widely exploited in the Oueme Delta and the low Mono in Benin. The structure and population parameters of M. macrobrachion were evaluated to provide accurate scientific information for the better exploitation and rational management of freshwater prawn species in these areas. In Oueme Delta (1928 specimens) and low Mono (1045 specimens), 2973 specimens were sampled by artisanal and experimental fishing and analysed. The prawns were caught between January and December 2016. Total length and total weight were taken from each specimen. Global and monthly size–frequency distributions showed that recruitment in both populations takes place from August to October with a peak in September. The population parameters obtained by analysing frequency data with FiSAT II software (FAO-ICLARM) showed an L∞ = 15.50 cm, K = 0.35 year⁻¹, t₀ = −0.56 year in Oueme Delta and L∞ = 15.30 cm, K = 0.45 year⁻¹, t₀ = −0.43 year in low Mono. The growth performance index (Φ′) was 1.93 and 2.02 for the Oueme Delta and low Mono populations, respectively. The exploitation rates (E_max and E_0.5) suggest that more than half of the M. macrobrachion population was exploited in the two areas. Natural and fishing mortality rates showed that both populations of M. macrobrachion were vulnerable to natural and fishing death. The estimated first capture size (L_c) revealed that the majority of the two populations of M. macrobrachion were captured before they reached the size at first sexual maturity (L₅₀), reflecting fishing pressure on small individuals and growth overfishing in both areas. These results showed that the used fishing gears and the fishing frequencies in both areas did not allow the majority of the prawn to grow and reproduce at least once before being caught.