Patterns and Drivers of Recruitment in Caribbean Amphidromous Fishes

Amphidromous fishes are a major component of tropical coastal and island lotic fish assemblages.  In the amphidromous life-history, adults grow and spawn in freshwater streams, their larvae are transported downstream, larvae grow and develop in the marine environment, and post-larvae recruit to the estuary and undergo metamorphosis during river ingress.  Dispersal during the marine larval phase and subsequent post-larval recruitment allows for population colonization, re-colonization, and replenishment.  Post-larval recruitment also yields valuable ecosystem services such as artisanal post-larvae fisheries and forage for estuarine sport fishes.  Despite the importance of post-larval recruitment for freshwater fisheries and ecosystems, there have been few studies of Caribbean amphidromous fish recruitment and none previously in Puerto Rico.  We quantitatively sampled amphidromous post-larvae at multiple temporal scales in the Río Grande de Arecibo, Puerto Rico, and used periodic regression to model recruitment phenology.  We also sampled post-larvae during peak recruitment times in seven Puerto Rico rivers to explore river discharge, watershed size, and habitat characteristics as physical drivers of recruitment. Our results identify the lunar cycle as a primary temporal driver of amphidromous recruit abundances in Puerto Rico and reveal secondary drivers of recruitment that are crucial for the ecology and management of Caribbean stream fishes.