Journal of Fisheries

Exploring shellfish diversity, utilisation and conservation threats in the Chalan Beel, Bangladesh

2025-10-02T20:59:37+00:00

Shellfish are important components of aquatic ecosystems, including freshwater wetlands. In this study, we examined shellfish species diversity and their utilisation by humans in the largest wetland of Bangladesh, the Chalan Beel. Through systematic, standardised field surveys, we recorded 19 shellfish species, including 14 molluscs and five arthropods. The global conservation status of the recorded species was retrieved from the IUCN Red List database, and all were classified as Least Concern. Among the 19 recorded species, the majority—11 species—are used for human consumption, followed by use as animal feed (e.g. for fish, shrimp and poultry) (eight species), as fish bait (eight species), in traditional medicine (eight species), as ornamental species in aquariums (two species) and in freshwater pearl culture (one species). Six threats to shellfish populations have been identified: (i) harvesting for commercial trade, (ii) use of illegal fishing gear, (iii) construction of irrigation canals, (iv) destructive ‘katha’ fishing methods, (v) changes in land use and (vi) duck farming in the wetland. The findings of this study will serve as baseline data for future research. To ensure a sustainable supply of shellfish for human consumption and animal feed, we recommend focusing on shellfish aquaculture rather than harvesting from the wild. This approach may be particularly beneficial for mollusc populations. We also advocate for the formulation of conservation regulations for shellfishes in the country.

Optimizing paddy spacing for co-production: effects on rice-fish yields and soil-water quality in integrated farming systems

2025-10-02T06:31:05+00:00

Integrated rice-fish farming (IRFF) is a promising agronomic strategy that enhances crop and fish productivity while improving soil health and resource use efficiency. This study aimed to assess the effects of different rice planting spacing on the growth and yield of rice and fish and evaluate soil fertility and water quality within an IRFF system. A field experiment was conducted using four (T1–T4) planting spacing; T1: 10 cm × 10 cm, T2: 15 cm × 15 cm, T3: 20 cm × 20 cm, and T4: 25 cm × 25 cm. Each treatment with three replicates was randomly allocated in a randomized complete block design. Growth and yield parameters of rice and fish were measured along with soil and water quality indices. Data were analyzed using ANOVA and Tukey’s test. Spacing influenced both rice and fish performance significantly. The 15×15 cm spacing provided the best balance, supporting high yields for both rice and fish without adverse effects on soil fertility or water quality. Narrower spacing enhanced total rice yield through higher plant density but reduced individual plant performance. Wider spacing improved individual plant growth yet lowered total yield. Soil nutrient levels (N, P, and K) and organic matter (OM) significantly increased across treatments, with T2 showing the highest enrichment. Water quality parameters (pH, EC, temperature, DO, NO₃^–, NH₃) remained within non-toxic limits. This study suggests that 15×15 cm spacing optimizes rice-fish yields and enhances soil quality without compromising water quality in IRFF systems.

The effect of different dietary protein levels on the water quality and reproductive performance of Nile tilapia (Oreochromis niloticus) broodstock in biofloc system

2025-10-02T06:31:18+00:00

This study investigated the effect of protein levels on the water quality and reproductive performance of Nile tilapia (Oreochromis niloticus) in the biofloc system. Three isocaloric diets with different protein levels (32%, 38%, and 44%) were formulated. A total of nine one-tone tanks with a water holding capacity of 0.9 tons were prepared and equipped with the necessary materials to form biofloc. Seventy-two female and thirty-six male fish were tagged, numbered, and randomly released into the tanks at a female: male ratio of 2:1. The results showed that the lowest amount of TAN (0.21 mgL^–1), NO₂, and NO₃ were observed in the treatment of 32% protein. Mean final weight in the 32% and 38% treatments was 350 and 356 g, respectively, with no significant difference. The highest absolute fecundity (654) was observed in the 32% group, but no significant difference was found between the absolute fecundity of the 38% and 44% groups. The longest interval (17.8 days) was observed in the 44% protein group. The percentage of fertilization and hatching did not significantly differ between the groups. The highest percentage of fertilization (93%) and hatching (89%) were observed in the 32% protein group. The total number of eggs per female fish did not differ between the 32% (12840) and 38% (12670) groups, while the 44% group had the lowest number of eggs (12040). The present study showed that a dietary protein level of 32% is optimal for water quality and reproductive performance of Nile tilapia in the biofloc system.

Partial replacement effect of dietary fish meal with blood meal on growth performance, body composition, and haematology of butter catfish Ompok bimaculatus

2025-10-01T06:31:16+00:00

Escalating costs and the constrained supply of fish meal have underscored the imperative to identify alternative, economically viable protein sources for aquafeeds. This study evaluates the feasibility of incorporating blood meal as a partial replacement for fish meal in the diet of butter catfish (Ompok bimaculatus). Five iso-nitrogenous (35.0%) and iso-lipidic (7.0%) diets, designated T₀ (control), T₅, T₁₀, T₁₅, and T₂₀, were prepared by substituting fish meal protein at 0, 5, 10, 15, and 20% levels with blood meal protein, respectively. Fish groups were assigned to each of the formulated diets in triplicate. Each of the 15 glass aquariums (180 L) was stocked with 50 fish (mean±SD 1.5±0.03 g) and fed with experimental diets for eight weeks. The fish fed the T₁₅ diet achieved the highest weight gain (4.61±0.22 g), percent weight gain (305.30±1.20%), and specific growth rate (1.42±0.21% day^–1) compared to fish fed all other diets. The lowest feed conversion ratio (1.85±0.08) was observed in fish fed T₁₀ diet. The highest protein efficiency ratio (1.88±0.02) was also observed in fish fed T₁₅ diet. Replacing fish meal with blood meal positively impacted the haematological profile and whole-body proximate composition. Additionally, the cost of the experimental diets was reduced compared to the control diet. Regression analysis indicated that the optimal replacement level of fish meal protein with blood meal protein ranged from 10.8% to 12.6%. We suggest that blood meal can be effectively used as a partial fish meal substitute in the aquafeed, offering a cost-effective and sustainable alternative.

Current status of blood cockle (Tegillarca granosa) aquaculture off Myeik City, Myanmar

2025-10-01T06:31:29+00:00

Blood cockle aquaculture has played a vital role in the local economy around Myeik City, a major fishing hub in southern Myanmar, in recent years. This study aimed to assess the current state of aquaculture grounds and to contribute to the development of sustainable blood cockle farming. To determine the status of sowing aquaculture grounds, the main fishing sites were identified through boat-based surveys and interviews with local fishermen. Environmental characteristics of these areas were estimated using satellite imagery, along with weather and sea condition data. Additionally, shell length and whole weight of blood cockles purchased from a market in Myeik City were measured, and their digestive tube contents were examined. These results revealed that farming grounds were located around coves and creeks on small islands along the east coast of Kadan Island. These areas were characterised by high turbidity, with salinity remaining stable year-round at over 20 PSU. The annual chlorophyll-a concentration, approximately 4 μg L^–1, indicated a consistent presence of phytoplankton, which was also confirmed by the digestive content analysis. However, compared to data on blood cockles from other regions reported in related studies, those collected after the rainy season were noticeably lighter in weight, indicating a leaner condition. These findings suggested that alternating the use of offshore and coastal aquaculture grounds according to the rainy and dry seasons may enhance farming efficiency and realise sustainable aquaculture practices.