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.