A Century of Ichthyoplankton Research in Indonesian waters: lessons from the past, challenges for the future

We review ichthyoplankton research history in Indonesia, which began when H.C. Delsman conducted studies on fish larvae and eggs in the northern Java region (1921–1938). The Danish 1929 eel expedition net sampling in Indonesian waters discovered an Anguilla bicolor bicolor spawning area off West Sumatra by collecting small leptocephali. After > 45 years of no fish larvae studies in Indonesian waters, the Banda Sea Indonesia-Netherlands Snellius-2 Expedition occurred (1984–1985) before a study on coastal fish larvae at Lombok Island was conducted (1995–1997). Ichthyoplankton research then occurred more frequently in the early 2000s, which started with Indonesia-Japan collaborative Isaacs-Kidd Midwater Trawl (IKMT) surveys for eel larvae (leptocephali), which discovered that some tropical anguillids make short spawning migrations, and that allowed other research, including on marine eel leptocephali. This research was followed by numerous ichthyoplankton surveys in the Indonesian Seas and coastal waters or estuaries. The ichthyoplankton research varied widely in methods, the number of taxa present, and identification levels, with studies being conducted with bongo nets, small beach seines, or push nets. The number of families detected in each region ranged from about 12–90, which included the larvae of several commercially important fish species, and learning about species such as the tunas was an important focus. However, the studies so far are insufficient to guide fisheries management, so we discuss steps to facilitate ichthyoplankton research in Indonesia, which include standardizing survey methodologies, increasing the number of researchers in this field, providing sufficient infrastructure support, and creating data sharing and specimen archiving systems. Graphical abstract