Aquaculture, Fish and Fisheries最新文献

To investigate the food sources for juvenile and adult Penaeus monodon and reconstruct its diet, samples of potential food sources were collected from the nursery areas of Kondo, Mbegani and Kitame, as well as from the fishing grounds of Mwambakuni and Saadani, located in the Bagamoyo coastal waters of Tanzania in the Western Indian Ocean. The carbon and nitrogen isotopic ratios of both P. monodon muscle tissues and their respective potential food sources were determined from samples collected during the Northeast Monsoon (NEM, September–October) and Southeast Monsoon (SEM, April–May), representing the dry and wet seasons, respectively. P. monodon muscles exhibited a wide range of δ¹³C values from −20.87‰ to −12.22‰ (average of −16.23‰, n = 6) during NEM, alongside a narrower range of δ¹⁵N values from 5.32‰ to 8.86‰ (average of 6.63, n = 6). Similarly, during SEM, δ¹³C values ranged from −20.68‰ to −15.59‰ (average of −17.47‰, n = 6), while δ¹⁵N values ranged from 5.32‰ to 8.55‰ (average of 7.05‰, n = 6). Different size classes displayed distinct δ¹³C with a range of −8.27‰ but were closely related in δ¹⁵N, exhibiting an average range of only 2.66‰. The contributions of carbon and nitrogen from mangrove and terrestrial sources were found to be negligible as food sources for P. monodon across both seasons. However, both juvenile and adult P. monodon significantly relied on seagrass ecosystems for their food, with minimal connectivity (p ˂ 0.05) between the nursery and fishing grounds. Furthermore, it was observed that the primary carbon sources for P. monodon included shellfish (prawns), sergestid shrimps, plankton and algae during the SEM, with a slight shift towards algae and polychaetes during the NEM. Notably, P. monodon specialized in a specific food source during NEM, with juveniles showing significantly higher levels of cannibalism compared to adults.

Parasitic infections threaten the endangered Oreochromis jipe and other ichthyic populations in Lake Jipe, thereby hindering conservation efforts. Initiatives have been made to farm O. jipe as a conservation strategy. To develop effective conservation approaches and ensure the species' survival in its natural habitat and aquaculture systems, it is imperative to understand the diverse parasites in these habitats. Consequently, this cross-sectional study was conducted to determine parasitic loads in tilapias from selected farms and Lake Jipe. A total of 111 fishes were collected (76 farmed, 35 from the lake), comprising 66 O. jipe, 34 Oreochromis niloticus and 11 hybrids of O. jipe and O. niloticus. The fish were euthanized, necropsied and examined for parasitic infections via visual inspection and light microscopy. Out of 111 fishes examined, 58 (52.3%) were infected with 212 parasites, including 135 (63.7%) and 77 (36.3%) from farm and lake habitats, respectively. The prevalence of parasitic infections in fish from the lake and farm habitats was 68.6% and 44.7%, respectively. The most frequently occurring parasite genera identified were Diplostomum (30.63%), Acanthocephalus (20.7%), Dactylogyrus (9.9%) and Contracaecum (2.7%), with mean intensities of 2.9, 3.7, 1.9 and 1.7, respectively. Contracaecum and Camallanus were exclusively found in fish from Lake Jipe, while Euclinostomum and Gyrodactylus were only observed in farmed fish. O. jipe had the highest prevalence of parasitic infections (59.1%), followed by O. niloticus (44.1%) and hybrids (36.4%) (p > 0.05). In conclusion, the examined fishes were infected with diverse parasites, which have both public health concerns (Euclinostomum and Acanthocephalus) and economic significance (Dactylogyrus and Gyrodactylus). Consequently, it is imperative to enhance public awareness and enforce biosecurity measures to mitigate potential health risks and to improve the productivity of the pond culture system and lake ecosystem. These measures will help reduce parasite dissemination and promote sustainable fish production and populations.

This study aimed to conduct a stock assessment of Decapterus macarellus from Tanzanian coastal waters to determine its current stock status and provide appropriate management recommendations. We used a suite of length-based methods, including the Electronic Length Frequency Analysis (ELEFAN) programme to estimate growth parameters and catch curves to evaluate exploitation fishing and mortality parameters; Length-Based Spawning Potential Ratio (LBSPR) to calculate the spawning potential ratio (SPR), length-based indicators (LBI) to assess sustainable fishing levels and length-based reference point (LBRP) to determine the target reference point (RP) for stock spawning biomass (SB). The results indicated that this small pelagic species grows fast, with a growth rate (K) of 0.74 year⁻¹ and a growth performance index (Ф′) of 2.88. However, the stock is currently at risk of overfishing due to high fishing pressure (F/M > 1) and an elevated exploitation rate (E = 0.71), which resulted in a very low SPR (SPR = 0.11) and SB below the target RP. Yield-per-recruit analysis revealed that the current fishing effort (F_curr = 2.57) far exceeded the precautionary limit (F_0.1) and surpassed the fishing mortality rate that maximizes yield per recruit (F_max = 1.73). This excessive effort largely impacted mega-spawners, reducing their proportion in the catch to a critically low percentage (9%). On the basis of these findings, the study recommends reducing the current fishing effort to F_0.1 (0.84) by limiting the number of ring nets, implementing seasonal closures during peak spawning periods and operating in deeper waters (40–200 m) to protect juveniles and minimize mega-spawner capture.

The introduction of aquatic non-native species into novel systems may have negative impacts on native biodiversity. Introduced species can predate native species, compete for resources, transmit diseases, hybridise and degrade habitat. To minimise impacts on aquatic biota, management efforts are needed to reduce invasive species abundance. However, eradication or reduction efforts require information about the source of introductions and the biology and ecology of the organism. Therefore, the objective of this study was to quantify population dynamics, natal origins and dispersal characteristics of the introduced Weather Loach Misgurnus anguillicaudatus, which was recently discovered in Georgia, USA waters. Sagittal otoliths were extracted and aged to determine dynamic rate functions, and we performed microchemical analysis on a subset of otoliths to quantify dispersal and introduction events. Sampled Weather Loach consisted of a wide range of ages and lengths, indicating that natural reproduction and recruitment have been occurring for multiple years. The change in otolith microchemistry seen in some fish reveals that they have dispersed from their introduction or reproduction sites into different areas, while others have likely remained in the same system since hatching. Overall, our findings indicate that the Weather Loach populations in Georgia are disjunct, likely stemming from multiple introductions. These results will be used to develop management strategies as well as aid in the effort to continue and enhance outreach regarding the release of unwanted aquarium fish.

Hilsa shad (Tenualosa ilisha) is an anadromous fish, making the single largest wild fishery in Bangladesh, supporting the livelihoods of about 2% of the population and contributing 1% to the national GDP. Several studies reported positive outcomes associated with its catch status, biology, ecology, nutritional profile, conservation and management and socio-economic impacts. However, significant knowledge gaps exist in hilsa fisheries, particularly in the areas crucial for research and development. In this article, we conducted a systematic review of literature to identify and address the knowledge gaps, challenges and research priorities in hilsa fisheries to ensure their sustainable management and production. Recent data from the Department of Fisheries (DoF) indicate rising production of hilsa in Bangladesh, sparking debate about its accuracy. Reliable data are essential to avoid miscalculations that could lead to risk of overfishing or underfishing of this important fish. Hilsa matures at 6–12 months, lives 2–6 years, feeds primarily on phytoplankton and spawns mostly during full moon of September and October. The abundance of brood hilsa in the river systems before and after the peak breeding season suggests further research is needed to refine breeding period for sustainable production. Although recent molecular studies have mapped the complete genome of hilsa, there remains a lack of comprehensive knowledge on its biology, ecology, conservation and life cycle—the key areas for sustainable catches and domestication. Enhancing global demand for this species requires value addition, such as removing sharp pin bones in the flesh. DoF has implemented various policies and projects, including establishment of sanctuaries to protect and conserve hilsa fisheries for sustainable exploitation. However, these measures have sparked controversy due to their adverse impacts on income and livelihoods of fishermen. Addressing these challenges and knowledge gaps requires focused research and development initiatives to ensure sustainable hilsa fisheries in Bangladesh.

Post-harvest fish losses (PHFL) significantly impact the aquaculture sector in Kenya, undermining food security and economic growth. This study investigated socio-demographic factors and handling practices influencing PHFL in Kakamega County's cultured tilapia value chain. Data were collected from 94 value chain actors operating across multiple nodes, including farming, processing and retail stages from six sub-counties using surveys and observations. Results revealed that 64% of participants were female, and 40.3% had completed high school, with only 26.6% holding valid food handler certificates. Household sizes mostly ranged from 4 to 9 members, and experience in the value chain varied, with 33% having 5–10 years of experience and 17% had over 21 years of experience. PHFL were significant across nodes, with farm gate losses highest in Butere (32%) and lowest in Likuyani (8.42%). Wholesale and retail losses were also notable, with Mumias East showing the highest overall losses. Regression analysis identified key predictors of PHFL, including poor sanitary conditions, lack of training, inadequate water quality and cooling practices, explaining 87.2% of the variance in PHFL. Experience negatively correlated with PHFL (r = −0.354, p < 0.01), indicating that more experienced individuals incurred lower losses. Chi-square tests showed significant associations between PHFL and factors like household size, occupation, training and sanitation but not gender, education or age. The findings highlight the need for targeted interventions, including training programmes, infrastructure improvements and adherence to food safety standards, to minimise PHFL, improve fish quality and enhance food and nutrition security in Kakamega County.

Increasing consideration of welfare in aquaculture has prompted interest in non-invasive methods of monitoring that avoid unnecessary stress and handling. Machine vision (MV) provides a potential solution to these needs, as it can be used for non-invasive monitoring of animal health and welfare in real-time. We examined the practical applications of MV for welfare monitoring in aquaculture, the hardware and algorithms used for automated data collection, and the main challenges and solutions for data processing and analysis. The most common application of MV has been the estimation of size-related metrics (growth, biomass) in fish, but key aspects of welfare, such as monitoring of parasites and disease or detection of stress-related behaviours, are lagging behind. Numerous camera setups have been used, ranging from single to stereoscopic cameras and from emersed to submerged cameras, but these have often been used under optimal conditions that may not always reflect those prevalent in industry (high densities, low visibility), likely overestimating performance. Object detection algorithms, such as YOLO, have been the approach of choice for most MV applications in aquaculture, but our review has identified an increasing number of alternatives that can help circumvent some of the challenges posed by high densities and poor lighting typical of commercial farms. MV has the potential to transform welfare monitoring in aquaculture, but there are still important challenges that need to be overcome before it can become mainstream, namely the ability to detect ectoparasites and diseases, identify abnormal behaviours, and work across taxa, particularly in crustaceans.

The decline of central European salmonid populations is exacerbated by global warming impacts on disease and interspecific competition. In this context, sympatric naturally reproducing populations of rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta were sampled in three rivers in southern Germany where the myxozoan parasite T. bryosalmonae, the causative agent of the temperature-associated proliferative kidney disease (PKD), is widely distributed. As expected, parasite prevalence and kidney hyperplasia increased from summer to autumn while decreasing with fish total length. Parasite infection intensity was greater in brown trout than in rainbow trout. With ongoing climate change, this difference in species vulnerability may lead to higher prevalence of PKD in brown trout creating a competitive disadvantage.

Citation Borsetti S, Wiedenmann J, and Munroe D. 2022. “Evaluation of Natural Mortality of an Unfished Gastropod (Buccinum undatum) Population Using Statolith Age-Frequency Data in the Southern Mid-Atlantic Bight.” Aquaculture, Fish and Fisheries 2, no. 3 (May 23): 243–251. https://onlinelibrary.wiley.com/doi/10.1002/aff2.47 DOI: 10.1002/aff2.47

Description of error

Incorrect units were used when describing minimum landing sizes, specifically in the Methods and Results sections 2.3 and 3.3., as well as in Figure 4. The correct units for minimum landing size is millimeters (mm), not centimeters (cm). The correct units are reproduced below.

Methods 2.3. Fishing Mortality reference points “Therefore, three selectivity curves were calculated using three different minimum landing sizes (45, 55, and 65 mm) consistent with sizes used in other countries (see Borsetti et al., 2018 for a review).”

Results 3.3. Fishing Mortality reference points “The different minimum landing sizes (45, 55, and 65 mm) resulted in different age-based selectivity curves, with an age at 50% selection of approximately 3, 4, and 6 years old, respectively (Figure 4A). These selectivity curves, combined with the different values of M resulted in a range of SPR-curves and F_40% values (Figure 4B). For M = 0.45, the F_40% values were 0.29, 0.42, and 1.40 yr⁻¹ for the minimum size of 45, 55, and 65 mm, respectively. The corresponding estimates of Z (M + F) were 0.74, 0.87, and 1.85 yr⁻¹.Values of F_40% were higher using M = 0.6, with values of 0.38, 0.6, and 3.2 yr⁻¹ for the minimum size of 45, 55, and 65 mm, respectively. The corresponding estimates of Z with M = 0.6 were 1.03, 1.25, and 3.85 yr⁻¹.”

The authors apologize for these errors.

High feed costs constrain tilapia production, making exploring low-cost feeding strategies important. We assessed the growth of tilapia over a period of 6 months, fed 1%, 2%, or 4% of body mass day⁻¹ with and without fertilization in 18 liner ponds stocked with fingerlings (5.1 ± 0.71 g). Growth was significantly better in fertilized ponds than in unfertilized ponds. The best growth (320.7 ± 8.5 g) was in fertilized ponds where fish were fed 2%, achieving a 45% larger weight gain than in the group fed 4% in unfertilized ponds. These results show that with fertilization, the feeding can be reduced by half while still having better growth than in unfertilized ponds. In fertilized ponds fed 4%, the minimum nocturnal oxygen levels may have limited growth of the fish and, as a result, their final weight (180.1 ± 6.6 g) was lower than in groups fed 2% in fertilized ponds and 4% in unfertilized ponds. Fish up to 60–90 g rely mainly on zooplankton as a source of food, while fish of sizes ≥100 g rely mainly on supplementary feed. Analysis of the gut content of fish of different sizes suggested that tilapia up to 60–90 g do not consume the feed presented which instead ends up as an expensive form of fertilizer. The best economic return was in ponds that were fertilized and fed 2%. It is concluded that feed-use and production costs may be reduced even further by fertilizing the ponds and restricting or omitting feeding of fish < 100 g and only commence feeding when the fish have reached around 100 g. The results of the finding have a wider applicability in developing countries where pond culture of tilapia is common.