Misidentification of fish larvae: A call for caution and taxonomic reform

The international effort to prevent the collapse of Atlantic bluefin tuna (BFT, Thunnus thynnus, Scombridae) stocks exemplifies the challenges associated with modern marine resource conservation. Rampant mismanagement, under-reporting and IUU fishing led to decades of over-exploitation in the BFT fishery. Surveys of larval abundance in both the Gulf of Mexico and the Mediterranean Sea have been used as a proxy for both spawning biomass and recruitment by researchers attempting to improve estimates of stock abundance. Herein we used both mitochondrial and nuclear genes (CO1 and ITS1, respectively) to barcode larvae (n=188) collected from three spawning areas in the Mediterranean Sea. Our results reveal important differences in the accuracy of the taxonomic identifications carried out by different ichthyoplanktologists following traditional methods. This disparity suggests that the efficacy of the taxonomic techniques employed during the identification of fish larvae is highly dependent on the expertise of the researchers or technicians involved. Misidentification of larvae can lead to uncertainty about the spatial distribution of a species, confusion over life history traits and population dynamics, and potentially disguise the collapse/recovery of localized spawning sites. In an effort to identify the source of these errors, we uncover several weaknesses in modern morphological taxonomy including demographic decline of expert taxonomists, flawed identification keys, reluctance to embrace technological advances and paucity of available user-friendly and modern materials. We advocate a more constructive integration of taxonomy and barcoding in order to strengthen fisheries management and safeguard against stock collapse.