Low Bycatch Rates Add Up to Big Numbers for a Genus of Small Fishes

Nonselective fishing gears extract a great many small marine species, with limited documentation or assessment of their impacts. Among those species, seahorses (genus Hippocampus) are unusual because this genus has been the focus of scientific surveys and international trade regulation. Our review of published and unpublished data sources analyzed data on seahorse bycatch for five gear-type categories and 22 countries. The median catch per unit effort of seahorse bycatch across all five gear types was 0.96 seahorses per vessel−1day−1. Nonetheless, fleet sizes were so large that annual catches were estimated at approximately 37 million seahorses across our sampled countries. Fisher interviews suggested that seahorse catches were declining (although information on changes in effort over time were not available). Furthermore, international export data did not capture the magnitude of seahorses in bycatch. Our work emphasizes the importance of evaluating bycatch, even for taxa where reported daily catch rates are low.