The Role of Local Retention Versus Subsidies in the Connectivity of Caribbean Spiny Lobster Populations

The spiny lobster (Panulirus argus) commands the most valuable fishery in the Caribbean, yet its management presents an extraordinary challenge.  Spiny lobster have highly mobile larvae that can survive in the plankton for extended periods, theoretically enhancing dispersal potential, hindering local recruitment, and increasing the reliance on subsidies from distant sources.  We simulated lobster reproduction, transport, and recruitment in the Caribbean using a coupled biophysical model to examine recruitment trends and evaluate the roles of local versus distant supply.  The connectivity modeling system (CMS) used here is a LaGrangian individual-based model that combines physical oceanographic models with biological and habitat submodels.  Oceanographic data from multiple sources were incorporated to ensure the highest resolution possible and effectively capture smaller scale hydrodynamic features that may influence larval dispersal.   Surveys distributed to fisheries managers helped determine lobster abundance and fecundity in 10 of the largest lobster stocks in the Caribbean.  These data were used to scale the magnitude and seasonality of the simulated spawning pattern in the model.  Ontogenetic vertical migration behavior was included and was parameterized based on laboratory studies of phyllosome reactions to light, and validated by plankton trawls through the Florida straits.  We present the results from 4 years of larval exchange simulations from monthly spawning production of lobster populations distributed in 261 sites over the Wider Caribbean. Distinct patterns of connectivity emerged within each of the Caribbean basins.   Surprisingly, local retention played a role in each subregion.  While distant subsidies could be substantial in some years and locations, their source and levels fluctuated unpredictably. These results highlight the importance of larval recruits from the local stock for fishery management and suggest that local conservation efforts may be effective even for species with high dispersal potential.