Exploring the reproductive features of Clupisoma garua from Ganges River, Bangladesh: insights into eco-climatic factors for sustainable management and advancements in aquaculture practices.

The Garua bacha, Clupisoma garua, holds considerable commercial and nutritional significance as a fish species. This study investigates the relationships between GSI (gonadosomatic index) and eco-climatic conditions, and provides comprehensive insights into several facets of reproduction, such as size at first sexual maturity (Lm), spawning season, peak spawning period, and proposes sustainable management strategies for C. garua in the Ganges River, northwestern, Bangladesh. Since January to December 2017, 570 female individuals have been gathered from the Ganges River using cast nets, gill nets, and square lift nets on a monthly basis. The total length (TL) of the specimens varied from 3.90 to 26.30 cm. Lm was estimated as 14.30 cm based on the results of the TL vs. GSI, MGSI (modified gonadosomatic index), DI (Dobriyal index), 14.00 cm through TL-FL regressions, and 15.18 cm depending on Lmax for this species. Furthermore, the spawning period was observed from May to August, peaking in June and July, based on greater GSI, MGSI, and DI values. Throughout the peak spawning season, there was not a significant differ from a value of 100 in the relative weight (WR) of the female species. During the spawning season, a substantial association between temperature and GSI (p = 0.0038); rainfall and GSI (p = 0.0043); DO and GSI (p = 0.0043); pH and GSI (p = 0.0002); and alkalinity and GSI (p = 0.0001) was detected. Analyzing a 55-year data series (1964-2018), it became clear that an increase in average air temperature of 0.0289 °C and a decrease in rainfall of 2.988 mm per year might possibly delay the spawning season of this species. As a consequence, the results of this study provide crucial information for developing management strategies to safeguard C. garua populations in the Ganges River and its adjacent ecosystems.

Estimating the growth parameters, exploitation rate, biomass and maximum sustainable yield of long whisker catfish Mystus gulio (Hamilton, 1822) in the coastal waters from southwestern Bangladesh.

The research provides a comprehensive analysis of Mystus gulio including growth pattern, growth parameters, recruitment patterns, mortality rates, biomass, exploitation rate (E), and the estimation of maximum sustainable yield (MSY) within the southwestern coastal waters of Bangladesh. From January to December 2017, fishers provided around 1200 specimens. FAO-ICLARM Stock Assessment Tool and Excel-add-in-solver were used to assess stock status through length-frequency data. Indeed, the research findings indicated that the population of M. gulio displayed negative allometric for both individuals (b = 2.53 for male, b = 2.50 for female), as demonstrated by the calculated allometric coefficient value. Nonetheless, the population's dynamic characteristics revealed an asymptotic length (L∞) of 19.34 cm, 23.28 cm and growth coefficient (K) 0.94 year-1 and 0.81 year-1 for male and female M. gulio. The growth performance indexes (Ø') of 2.55 and 2.64 for male and female and maximum lifespan (tmax) 3.20 years and 3.70 years respectively. This study revealed that the slightly variations in the natural mortality rate (M) for both specimens at 1.55 year-1 and 1.59 year-1. The fishing mortality rate (F) 2.75 year-1 and 1.98 year-1and total mortality rate (Z) 4.30 year-1 and 3.57 year-1 for male and females, respectively. The maximum permissible exploitation rate (Emax = 0.421) was lower than the actual exploitation rate (E = 0.63). The MSY was calculated at 67.968 metric tons. Without a doubt, overfishing stands out as the most critical threat to the wild stock. Therefore, it is clear that the existing fishing approach was not efficiently managed the standing stock in a sustainable manner. The findings would be useful for established proper fishing regulations in coastal waters and the surrounding ecosystems.

First report on population dynamics and stock status of Badis badis in a wetland ecosystem (NW Bangladesh): Insights from new recorded maximum length.

Badis badis (Hamilton, 1822) is a popular ornamental fish species in the world. This study provides valuable insights into some biological indices of B. badis using a sample of 293 individuals. These individuals were captured from June 2021 to May 2022 using several traditional fish harvesting gears and traps in the Babu Mondoler beel, a wetland ecosystem in NW Bangladesh. Biometric data were collected for each individual, contributing to a comprehensive understanding of this species. The recorded results revealed a wide range of total length (TL), varying from 2.30 to 11.33 cm. Notably, we observed a maximum length of 11.33 cm TL and a maximum body weight (BW) of 18.18 g, ranging from 0.20 to 18.18 g, setting a new record and showcasing the diversity in size within the population. The estimated allometric coefficient (b) showed that combined sexes had negative allometric growth (b = 2.67). Growth parameters were assessed as L∞ = 11.93 cm, K = 0.95 year-1 and Ø' = 2.13. The tmax was 3.16 years. The Lm was measured at 7.02 cm TL and tm = 0.89 year. In this study, KF (1.4240 ± 0.3194) was best for the wellbeing of B. badis in the study area. The a3.0 was estimated at 0.0079 and the relative weight WR (100.90 ± 16.994). Physiological status showed that maximum fatty fish were observed at 10.00-12.00 cm TL; lowest at 4.0-6.00 cm TL. Moreover, the Z, Mw, F and E were estimated to be 3.29 year-1, 1.45 year-1, 1.84 year-1and 0.56, respectively. Additionally, the Lopt for this species was found to be 7.91 cm TL. The findings from this study hold great potential for enhancing the assessment and management of the specimen in the study area and its ecological community. These valuable insights into the population parameters, growth patterns, and exploitation rates of B. badis can inform future management strategies, ensuring the sustainable utilization of this fishery resource in Bangladesh and others neighboring countries.