Aquaculture, Fish and Fisheries最新文献

In recirculating aquaculture systems (RAS), understanding the relationship between feed load and its impact on water quality and overall shrimp health is important. This study utilised an indoor marine RAS for the intensive culture of Pacific white shrimp Litopenaeus vannamei. The shrimp were stocked into the grow-out system at an average body weight of 0.25 g and a stocking density of 347 shrimp/m³. Water quality parameters of temperature, salinity, total dissolved solids, pH, and dissolved oxygen (DO) were measured twice daily. Total ammonia nitrogen (TAN), nitrite and nitrate were measured once weekly or when needed. Sampling was conducted to calculate the daily feed ratio based on the total estimated biomass. Mortality was recorded as a means of evaluating the overall shrimp health. The data obtained were analysed using Pearson correlation (r) analysis and multi-linear regression with a significant difference accepted p < 0.05. Correlation (r) established relationships among the water quality parameters, feed load and mortality. The TAN level of 24.20 mg/L was recorded when the feed load increased by 81.2% resulting in the mortality of 40% of shrimp. A negative correlation between TAN and DO resulted in a synergistic effect causing a massive consumption of DO in the water, reducing its availability to the shrimp and leading to a drastic change in the shrimp's behaviour. Overfeeding can lead to an accumulation of uneaten feed and waste, causing ammonia spikes and oxygen depletion in the water. Monitoring and adjusting feed rates accordingly can help maintain optimal water conditions for shrimp growth and health. Therefore, it is essential to use appropriate feed rates in recirculating systems because feed load can influence water quality parameters that can be detrimental to shrimp culture.

Due to their high content of micronutrients, small indigenous species (SISs) of fish play a vital role in the diets of people. Dhela (Osteobrama cotio) is one of the most important micronutrient-rich SISs and was once abundant but is currently disappearing from inland waters. This study investigated the culture suitability of dhela with carp species in polycultures in a pond aquaculture system. The stocking density of the carp species was the same in all the treatments, with Labeo catla, Labeo rohita and Cirrhinus cirrhosus at 10,800/ha. Dhela were cultivated at a density of 10,000/ha in treatment 2 (Dhela-10K) and 15,000/ha in treatment 3 (Dhela-15K), and no dhela were cultivated in treatment 1 (Dhela-0). After 7 months of culture, there were no significant differences in total production among the treatments, with yields of 3393.27 ± 120.70, 3534.52 ± 57.03 and 3687.34 ± 244.41 kg/ha in Dhela-0, Dhela-10K and Dhela-15K, respectively. Notably, a significantly greater (p < 0.05) net profit and benefit‒cost ratio were found in Dhela-10K and Dhela-15K than in Dhela-0, but no significant difference was found between Dhela-10K and Dhela-15K. The inclusion of dhela in pond polycultures with carp species demonstrates the potential benefits of diversifying aquaculture systems. Farmers could consider incorporating SISs into their existing aquaculture practices to increase overall production and improve economic returns.

The existence of ultraviolet (UV) biofluorescence in nature has been documented in a wide range of flora and fauna. Biofluorescence is utilised throughout biological and ecological functionality, and although invisible to the human visual perception, this spectral range is known to be integral for communication across flocks, swarms, shoals and between individuals. Under UV illumination, European eel juveniles (glass eel) were found to fluoresce bright yellow. Follow-up experiments using the UV light source on preceding eel life stages such as pigmented glass eels (elvers), ‘bootlace eels’ (juvenile yellow eels), older yellow eels and migrating silver eels, all found that these stages had lost the capacity for biofluorescence. The information gathered from this study suggests that the use of UV light for presence/absence glass eel arrival surveying could be a useful and effective tool for researchers in the research field.

The frequency of skeletal deformations in fish is a common biomarker when investigating the environmental response to effluents of various origins. This study discovered a new biomarker: elevated mineralization levels of the vertebrae in the caudal region of perch Perca fluviatilis. The study was conducted in northern Sweden in lakes receiving discharges from an iron ore mine and adjacent reference lakes. The field observation was followed up with an egg-hatching experiment showing a similar lake-specific pattern in hatching and deformation frequencies in larvae.

The lake cisco (Coregonus artedi) is not often caught by recreational anglers in open-water in western Canada but becomes a common component of catch-and-release ice fisheries in the winter. Little is known about the composition of recreational cisco fisheries or factors that affect the success of winter catch and release. We examined the size and body condition of 555 cisco caught by anglers in four interconnected lakes in southern Saskatchewan, Canada. We also examined the influence of length on the probability of hooking injuries and determined the age of a subset of angled fish. Cisco caught by anglers ranged in total length from 24 to 48 cm and 110 to 1370 g mass; however, 60.2% of cisco caught ranged from 37 to 40 cm and 470 to 560 g. The scale ages of cisco caught by anglers ranged from 4 to 10 years, with the most common ages caught being 6–8 years; however, scales likely underestimated age beginning around 8 years. Overall, cisco from our four study lakes had lower body conditions compared to Lake Superior populations based on standard weight comparisons. The length, mass, age and body condition of cisco caught by anglers varied significantly among our four study lakes, following a west-to-east productivity gradient. Of the 555 cisco assessed, 54 (9.7%) experienced gill bleeding and 21 (3.8%) had other visible hooking injuries. Longer cisco had a significantly increased probability of gill bleeding, but length did not affect the probability of other injuries. Cisco are relatively slow growing in our study area and warrant more consideration from a catch-and-release angling perspective.

Aquaculture is the world's fastest-growing food-producing sector, making it a significant contributor to food and nutrition security for the globally growing human population. Nevertheless, its long-term growth is limited by the effects of climate change. Aquaculture in Sub-Saharan Africa (SSA), which is dominated by small-scale fish farming, is increasingly threatened by climate change, which has a substantial influence on its productivity and scalability. In this context, the present research looks at the socio-economic consequences of climate change on small-scale fish producers in SSA, as well as potential adaptation techniques to the effects of climate change. A clear understanding of these socio-economic repercussions of climate change is critical for developing effective strategies to reduce future impacts and safeguard aquaculture-based livelihoods. Furthermore, understanding the socio-economic consequences of climate change on communities dependent on aquaculture is important for advising policymakers and decision-makers on formulating and implementing policies that sustain aquaculture production amidst the climate change crisis. This article suggests various adaptation strategies to increase resilience to climate change, including diversification of livelihoods and species, use and incorporation of local and indigenous knowledge, shifting to aquaculture species less vulnerable to changing climatic conditions, capacity building through aquaculture insurance schemes, continued fish supply from capture fisheries, and consolidation of equity and human rights concerns. These adaptive methods, when combined, have the potential to enhance outcomes for populations who are more susceptible owing to their unstable socio-economic conditions.

This study analysed morphometric and meristic characteristics of Ompok pabda from two distinct culture systems, namely biofloc and traditional. Fish samples (90 days old) collected from both culture systems were reared in indoor tanks. Thirty-one morphometric and seven meristic characteristics were measured and analysed. The study showed that the morphometric measurements of various body parts depended on body length. A significant (p < 0.05) positive correlation was observed between total length (TL) and standard length, fork length (FL), highest body depth (HBD), lowest body depth, length of anal base (LAB), post dorsal length (PsDL) and length of caudal fin of fishes from both systems. However, most of the parameters in biofloc technology showed stronger relations than the traditional ones. Further, principal component analysis revealed significant variation across the samples for 60.43% contribution by TL, FL, head length, pre orbital length, LAB, post orbital length, PsDL and HBD in the first PC. Regarding meristic features, namely, anal fin ray, dorsal fin ray, ventral fin ray, pectoral fin ray and branchiostegal ray were found to be significantly varied between the fishes of the two culture systems. Altogether, the variation observed in morphometric and meristic data between the fishes of the two systems has revealed the role of bioflocs. The results of the present investigation might be key features for determining the morphology and growth status as well as for producing consumer-acceptable/preferred O. pabda in the biofloc system.

This study explored the potential of three local microalgal isolates as feed for oyster larvae in laboratory-rearing experiments, towards the optimisation of seed production of Crassostrea tulipa to support its large-scale farming along the West African coast. Three species of local microalgae—Rhodomonas sp., Nannochloropsis sp. and Pseudanabaena sp.—were isolated from waters off the coast of Ghana, West Africa, following a serial dilution technique. The growth performance of the isolates was assessed in the laboratory through daily estimation of cell density until the stationary phase was observed. Characterisation of the microalgal isolates was carried out by estimation of their biovolume, carbon content and energy content. Biovolumes of the microalgae were calculated from the estimated equivalent spherical diameters using proposed geometric shapes and formulae. Carbon weight and carbon energy content were subsequently calculated using derived conversions. The three microalgal isolates showed potential for large-scale cultivation in the laboratory with marked differences in daily increases in cell densities. Nannochloropsis sp. and Rhodomonas sp. recorded the highest and the lowest peak densities of 2.4 × 10⁵ and 1.5 × 10⁵ cell mL⁻¹, respectively, from an initial inoculating cell density of 1.05 × 10⁵ cell mL⁻¹. The estimated mean biovolumes of Rhodomonas sp., Nannochloropsis sp. and Pseudanabaena sp. were 238.9, 8.182 and 42.42 µm³, respectively, and the corresponding derived carbon energy contents were 1.7 × 10⁻⁶, 7.13 × 10⁻⁸ and 1.05 × 10⁻⁷ J, respectively. Results from a laboratory rearing experiment indicated that the individual microalgal isolates supported the growth and survival of oyster larvae at different scales, but a mixed diet of the three promoted superior growth and survival of C. tulipa larvae. The three local microalgal isolates- Rhodomonas sp., Nannochloropsis sp., and Pseudanabaena sp.- were well adapted to laboratory culture conditions, and the observed differences in growth and survival of the oyster larvae fed on these algal diets could be due to the differences in diet properties and biochemical compositions of the different species. A combination of the three algal diets, however, provided complementaery nutrients for the optimal growth and survival of C. tulipa larvae. The outcome of this study shows that local microalgal isolates have the potential to support hatchery rearing of C. tulipa, which is essential for the development of commercial mangrove oyster aquaculture in West Africa.

Fish is vital for reducing hunger and malnutrition. However, the combined impact of climate change and overfishing is increasing the hunger and malnutrition burden on the African continent and its population of over 200 million people who depend on marine capture fishing and related activities for survival. Fish farming was introduced to alleviate these problems, and our study assessed the extent to which current fish farming activities in the least developed countries (LDCs) like Sierra Leone provide sufficient micro- and macro-nutrients for local communities. The present study which is based on data from 300 survey questionnaires and 77 semi-structured interviews administered in three communities in Sierra Leone, and from two expert judgments which investigated the nutritional impact of fish farming activities in Sierra Leone, revealed that (1) there is a range of sub-standard fish farming activities from sampled farms; (2) that these activities could diminish the nutritional quality of farmed fish; and (3) that coastal communities were suspicious of eating or investing in fish farming. To alleviate Africa's increasing malnutrition, burden, our research highlights the need for investment in nutrition-sensitive fish farming – a refocus from an emphasis on increasing production and income. The nutritional quality of farmed fish is a more basic consideration than the quantity of production for securing a healthy and economically viable fish farming sector for LDCs like Sierra Leone.

The gill monogenean ectoparasite Gyrodactylus sprostonae is an emerging pathogen within recreational UK carp fisheries, and a major cause of mortality in adult carp. This gill infection has only been noted in adult carp and not in juveniles, and no reports of its fundamental infection dynamics exist. The current study compared the infective potential of G. sprostonae between adult and juvenile common carp (Cyprinus carpio) and quantified parasite numbers on the body surface and gills of infected juveniles at two temperatures (14 and 24°C). G. sprostonae was able to infect the body surface and the gills of juvenile carp, and temperature significantly impacted the duration of infection and number of parasites. Interestingly, however, all juveniles under both temperature treatments lost their infections after a maximum of 40 days, with no observed clinical signs of parasitaemia or mortalities. This study therefore indicates that G. sprostonae does not appear to be harmful to juvenile common carp, and we discuss why this infection only seems to impact prised adult carp in the UK.