Although vital in fisheries management, no comprehensive studies on ichthyoplankton have been conducted in Sri Lankan waters in the north central Indian Ocean hitherto. Hence, this study is the first detailed account of diversity and species composition of larval fish based on samples collected during the southwest monsoon in 2018. In total, 80 species belonging to 69 families were identified using morphological and molecular methods targeting the COI gene. The larval fish diversity varied significantly between regions: east (North East, Central East, and South East) and west (North West, South West, and South). In their larval stages, mesopelagic families were associated with the offshore waters whereas demersal and pelagic families were related with shelf regions in the South, South East, and Central East. The larvae of pelagic families are likely dispersed by the South Monsoon Current from the west to the east regions, while demersal fish seem to be confined to the same area as conspecific adults. The most abundant larval species observed were Selar crumenophthalmus, Cubiceps pauciradiatus, and Dipterygonotus balteatus. High abundances of several commercially important larval tuna species were found in the South East, Central East, and South regions indicating that these waters could be important nursery grounds. Furthermore, Callionymus simplicicornis was recorded for the first time in the Indian Ocean, and seven additional species were found new to Sri Lankan waters. The results from this study also highlight the importance of using combined morphological and molecular methods and the need for strengthening fish nucleotide databases in poorly studied areas of the Indian Ocean.

尽管在渔业管理中至关重要，但迄今尚未在印度洋中北部北部的斯里兰卡水域进行鱼鳞浮游生物的综合研究。因此，本研究是根据2018年西南季风期间收集的样本对幼体鱼的多样性和物种组成进行的第一个详细说明。使用针对COI基因的形态学和分子方法，共鉴定了69个科的80种。幼鱼的鱼类多样性在以下地区之间有很大差异：东部（东北，中东部和东南）和西部（西北，西南和南部）。在其幼体阶段，中古生代家族与近海水域有关，而深海和远洋科则与南部，东南部和中东部的陆架地区有关。南季风洋流可能将浮游鱼类的幼虫从西向东散布，而深海鱼类似乎与成年成年仔只局限于同一地区。观察到的最丰富的幼虫种类是浆膜cru眼，Cubiceps pauciradiatus和Dipterygonotus balteatus。在东南部，中部东部和南部地区发现了许多商业上重要的幼体金枪鱼物种，这表明这些水域可能是重要的育苗场。此外，印度洋首次记录到了Callionymus simplicicornis，斯里兰卡水域发现了另外七个新物种。这项研究的结果还强调了在印度洋研究不足的地区使用形态学和分子方法相结合的重要性，以及加强鱼类核苷酸数据库的必要性。