A decade of modeled dispersal of Dungeness crab Cancer magister larvae in the California Current

Abstract

Marine populations are often typified by large annual variations in the number of larvae that return to the adult population. The Dungeness crab Cancer (Metacarcinus) magister is an important economic and ecological species along the western seaboard of the continental USA. Research suggests larval returns of Dungeness crabs vary annually by a factor of 1000, strongly influencing the population dynamics of the species. To understand how hydrographic conditions affect population dynamics, a light trap in Coos Bay, Oregon, was monitored daily during the recruitment season (April to September) from 1997 to 2001 and from 2006 to the present. Using an individual-based biophysical model, we tested the hypothesis that more Dungeness crab larvae recruit during negative-phase Pacific Decadal Oscillation (PDO). The model uses the Regional Oceanic Modeling System to simulate circulation in the California Current and an offline Lagrangian particle-tracking algorithm (Larval TRANSport Lagrangian Model, LTRANS) to model larval dispersal. We validated our model by comparing the model data to the light trap data. Our findings support the hypothesis that more megalopae (pelagic postlarvae) recruit during the negative phase of the PDO. In addition, megalopae appear to spend longer in the water column during positive-phase PDO as a result of faster development rates likely due to warmer seawater temperature. Lastly, our model suggests that the population experiences more self-recruitment than previously thought, albeit not to an extent to suggest there are multiple metapopulations.