Molecular authentication discloses the species composition of whitebait products in the Taiwanese market

魩仔魚 (in English: whitebait; in Japanese: shirasu), generally encompassing small pelagic clupeoids at early developmental stages, is a popular fishery product in Taiwan. However, it remains controversial as to whether whitebait should be consumed. Although whitebait represents a profitable resource, whitebait fishing can negatively impact high-value fishes by depriving them of food and also through bycatch of their larvae. Such bycatch is a critical issue in the whitebait fishery, but it is problematic to authenticate specimens to species level since fish larvae usually do not exhibit sufficient diagnostic traits for morphological identification. Here, we assessed 735 specimens from 27 whitebait products purchased in the Taiwanese market using DNA barcoding, allowing us to identify most of them (~ 84.4 %) to species level. Clupeoids such as Encrasicholina heteroloba, E. punctifer, E. pseudoheteroloba, Engraulis japonicus, and Sardinella jussieu proved to be the major constituents of our whitebait products, but many economic fishes and shellfishes were also detected. Moreover, crustaceans and toxic pufferfish mixed into the whitebait products destined for human consumption raises health concerns. We speculate that the low bycatch rate (~3 %) detected in our study is likely attributable to whitebait processing, which filters out many non-target specimens. In terms of marine biodiversity conservation and sustainable fisheries, the techniques for whitebait fishery should be improved to reduce bycatch and the annual legitimate catch should be regulated.