Department of Fisheries, Faculty of Agriculture, University of Rajshahi, Rajshahi, 6205, Bangladesh.
Faculty of Fisheries, Kagoshima University, 4-50-20 Shimoarata, Kagoshima, 890-0056, Japan.
Environ Sci Pollut Res Int. 2019 Apr;26(11):10800-10815. doi: 10.1007/s11356-019-04523-5. Epub 2019 Feb 18.
The Batchwa vacha, Eutropiichthys vacha is commercially important, supporting a viable small- and large-scale fishery throughout the Ganges River, NW Bangladesh. This study provides detail information on reproduction of E. vacha including size at sexual maturity, spawning and peak spawning season, and fecundity based on 734 female specimens through regular monthly sampling using cast net, gill net, and square lift net in the Ganges River during January to December 2016. Also, our study estimated the effects of climate change including temperature and rainfall on reproduction of E. vacha in the Ganges River. For each individual, lengths (total length, TL; standard length, SL) and body weight (BW) were measured with slide caliper and digital balance, respectively. Gonads (ovaries) were collected carefully by ventral dissection of each female specimen and weighed to the nearest 0.01 g accuracy. The gonadosomatic index (GSI % = (GW/BW) ×100), modified gonadosomatic index (MGSI % = (GW/BW - GW) × 100), and Dobriyal index (DI = [Formula: see text]) were calculated to estimate the size at sexual maturity (L) and spawning season. Based on GSI, MGSI, and DI, the L was calculated as 12.5 cm TL for female. The TL, the TL at which 50% of individuals become mature, was calculated by logistic equation as 12.7 cm. Also, on the basis of higher values of GSI, MGSI, and DI, spawning season was ranged from April to August, with the peak in June-July, signifying the peak spawning season for E. vacha in the Ganges River. The total fecundity (F) ranged from 4800 to 77,976 (mean ± SD, 31384 ± 23,747) and was highly correlated with TL and BW. Water temperature during the spawning period ranged from 28 to 34 °C, with an average of 31 °C and there was significant correlation between temperature and GSI. Also, the spawning season coincides with the peak rainfall and there was significant correlation between rainfall and GSI. Additionally, analysis of long data series indicated that annual average air temperature is increasing by 0.0258 °C/year, while the annual average rainfall is decreasing by 3.107 mm/year. Finally, the findings of this study would be very effective to impose specific management for E. vacha in the Ganges River and surrounding ecosystems.
瓦查瓦巴沙鱼，又称瓦查瓦巴沙鱼，是一种具有商业价值的鱼类，在整个恒河（孟加拉国西北部）流域都支持着小型和大型渔业的发展。本研究通过使用刺网、刺网和方型捞网，在 2016 年 1 月至 12 月期间，对恒河中的 734 只雌性标本进行定期每月采样，提供了有关 E. vacha 生殖的详细信息，包括性成熟的大小、产卵和产卵高峰期以及基于 734 只雌性标本的生殖力。此外，我们的研究还估计了包括温度和降雨在内的气候变化对恒河 E. vacha 生殖的影响。对于每个个体，使用滑动卡尺和数字天平分别测量长度（全长，TL；标准长度，SL）和体重（BW）。通过对每个雌性标本的腹部分离仔细收集性腺（卵巢），并以 0.01g 的精度称重。性腺体指数（GSI%=（GW/BW）×100）、改良性腺体指数（MGSI%=（GW/BW-GW）×100）和 Dobriyal 指数（DI=[公式]）用于估计性成熟（L）和产卵季节的大小。根据 GSI、MGSI 和 DI，L 计算为 12.5cm TL 的雌性。TL，即 50%个体成熟的 TL，通过逻辑方程计算为 12.7cm。此外，基于 GSI、MGSI 和 DI 的较高值，产卵季节范围为 4 月至 8 月，高峰期为 6 月至 7 月，这表明 E. vacha 在恒河的产卵高峰期。总产卵数（F）范围为 4800 至 77976（平均值±SD，31384±23747），与 TL 和 BW 高度相关。产卵期间的水温范围为 28 至 34°C，平均为 31°C，且水温与 GSI 之间存在显著相关性。此外，产卵季节与降雨量高峰期相吻合，且降雨量与 GSI 之间存在显著相关性。此外，对长数据系列的分析表明，年平均气温正以 0.0258°C/年的速度上升，而年平均降雨量则以 3.107mm/年的速度下降。最后，本研究的结果将对在恒河及周边生态系统中对 E. vacha 实施特定管理非常有效。
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