Identifying fish eggs and larvae: from classic methodologies to DNA metabarcoding.

Studies involving fish eggs and larvae date back to the end of the nineteenth century. Since then, studies with ichthyoplankton have proved to be an essential tool, generating information for the knowledge of the ichthyofauna and the environmental inventory. Most of these studies reveal the difficulty of obtaining a precise taxonomic identification of the collected materials, making research with ichthyoplankton extremely challenging. With the advent of molecular biology, the use of markers such as COI enabled greater taxonomic precision, helping to understand events involving ichthyofauna. Now we can observe the evolution of the molecular identification tool for ichthyoplankton via DNA barcoding, which has been increasingly used over the last few decades. From 2000 to 2010, we found six publications; from 2011 to 2021, 75 papers were published, and in 2022 four studies. Our survey also showed the accuracy of molecular identification when compared to the taxonomic identification of these. In this review, we show the state of the art of studies that used barcode and DNA metabarcoding to identify fish eggs and larvae in different environments and discuss their importance as the best practice for working with these organisms.