Based on a monthly field sampling over a year in the Kochi backwaters (KBW), this study presents the larval ecology of black clam and discusses how an extensive saltwater barrage [Thannermukkom barrage (TB)] impacted the natural black clam resource distribution. Spatial variations in salinity were found minimal during the Southwest Monsoon (June–September) due to the predominance of the freshwater associated with heavy monsoonal rainfall. Conversely, significant spatial changes in salinity were evident during the Pre-Southwest Monsoon (March–May) and Post-Southwest Monsoon (October–February). Monthly sampling exercises revealed that the black clam stock in the KBW breeds throughout the year, as their larvae were found (8 indiv. m^–3–494 indiv. m^–3) in all the locations. This observation is the modification of the traditional belief that black clam in the KBW breeds only twice a year. Mesohaline condition (salinity 5–18) is the most conducive for peak spawning and larval production. There were two peaks of larval production in the KBW over a year, mainly associated with the prevalence of the optimum salinity conditions on different spatial scales. The closing of the TB after the Southwest Monsoon (September) causes shrinkage of the area of the oligohaline and mesohaline conditions, the most conducive environment for the peak spawning and larval production of black clam in the KBW. This study presents a clear case of how human alterations of the natural environment impact valuable biological resources, which may apply to many similar aquatic ecosystems across the globe.

本研究基于高知回水 (KBW) 一年多的每月实地采样，介绍了黑蛤的幼虫生态，并讨论了广泛的咸水拦河坝 [Thannermukkom 拦河坝 (TB)] 如何影响天然黑蛤资源分布。由于与强季风降雨相关的淡水占主导地位，在西南季风期间（6 月至 9 月），盐度的空间变化最小。相反，在西南季风前（3 月至 5 月）和西南季风后（10 月至 2 月）期间，盐度的空间变化明显。每月的抽样活动表明，KBW 中的黑蛤种群全年繁殖，因为它们的幼虫被发现（8 个个体 m ^–3 –494 个个体 m ^–3) 在所有位置。这一观察结果改变了传统观点，即 KBW 中的黑蛤每年只繁殖两次。中盐环境（盐度 5-18）最有利于产卵高峰和幼虫生产。一年内KBW有两个幼虫产量高峰，主要与不同空间尺度上最佳盐度条件的流行有关。西南季风（9 月）之后 TB 的关闭导致少盐和中盐条件的面积缩小，这是 KBW 中最有利于黑蛤产卵高峰和幼虫生产的环境。这项研究提供了一个清晰的案例，说明人类对自然环境的改变如何影响宝贵的生物资源，这可能适用于全球许多类似的水生生态系统。