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

Abstract

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 Our review of published and unpublished data sources analyzed data on seahorse bycatch for five gear-type categories and 22 countries.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⁻¹ day⁻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.

ACKNOWLEDGMENTS

This is a contribution from Project Seahorse. We are enormously grateful to our colleagues who conducted the seahorse trade surveys that form the core of this analysis, including Julia Baum, Andrés Cisneros-Montemayor, Brian Giles, Ting-Chun Kuo, Jana McPherson, Jessica Meeuwig, Marivic Pajaro, Allison Perry, Aylin Ulman, and Kate West. We also want to thank Joanna Alfaro-Shigueto and Jeffrey Mangel from ProDelphinus for sharing unpublished data from Peru that was supported by Duke University and the Oak Foundation. We also heartily thank Guylian Chocolates Belgium and anonymous donors for their invaluable support. We appreciate input from Peter Arcese and Rick Taylor and additional readers Lindsay Aylesworth, Kyle Gillespie, Anna Schuhbauer, and Andrés Cisneros-Montemayor.