Metabarcoding markers
A total of 22 markers for mitochondrial (COI, 12S, 16S) and nuclear (18S, 28S) barcoding genes were identified from metabarcoding, eDNA, and Sanger sequencing barcoding studies that amplified marine and freshwater fishes and tissue mixtures, including seafood products (Table 1). Most of the tested markers were designed to broadly target bony fish (teleosts), but we also included markers specifically targeting elasmobranchs, crustaceans, and cephalopods, taxonomic groups that are often poorly resolved by universal barcodes. We included markers from five different barcoding genes to account for gaps in database reference sequences and limited sequence variation that can lead to poor species-level resolution for certain taxonomic groups in some genes or conversely, too much sequence variation in primer binding sites that can lead to an inability to detect certain taxa (e.g., Deagle, Jarman, Coissac, Pompanon, & Taberlet, 2014). Only markers that amplified targets <300 bp were selected because minibarcodes are more likely to amplify degraded constituents.