Genetic diversity, demography and connectivity in the marine snail Thaisella chocolata (Duclos, 1832): implications for sustainable fisheries management along the Peruvian coast

Thaisella chocolata is a marine gastropod (family Muricidae) occurring from northern Peru to central Chile. It is of economic importance in these countries, where hundreds of tons are caught every year. In combination with El Nino-Southern Oscillation events, fishing activity has led to the collapse of Chilean populations, raising concerns about the state of Peruvian populations. The aim of this study is to assess the demography, genetic diversity and connectivity of T. chocolata along the Peruvian coast. This would provide important insights into the resilience of this species to anthropogenic disturbance. In this study, four locations along the coast of Peru were investigated for the first time. Mitochondrial cytochrome c oxidase subunit I (COI) sequences were obtained from 116 individuals and four microsatellites from 95 individuals. Both COI (combined with 156 publicly available sequences) and microsatellite data revealed very low genetic differentiation, despite a few significant phi ST and FST values between population pairs. The most likely gene flow model (MIGRATE-N) is panmixia between all locations, with gene flow occurring equally northwards and southwards. This pattern may be related to the surface currents along the Peruvian coastline combined with the high pelagic larval duration of T. chocolata. Hyperdiversity was found for the COI marker (pi syn > 5%). Microsatellite loci were also polymorphic, with a mean diversity of 12.69 alleles per locus per population. No recent population bottleneck was observed (microsatellite data), while at least one past demographic expansion was suggested (COI data). Given the high genetic diversity and connectivity, T. chocolata is expected to show high evolutionary resilience and can be considered as one management unit in terms of fisheries management. However, further studies, on, for example, the characterization of effective population size (using numerous nuclear loci), are required to confirm this hypothesis. In addition, precautionary fisheries measures should be maintained, given the recent collapse of T. chocolata stocks in Chile.