RAPID Deepwater Horizon oil spill: Impacts on Blue Crab population dynamics and connectivity.

Tulane University, New Orleans LA

Investigators

Abstract

Intellectual Merit: Blue crabs (Callinectes sapidus) are an ecologically and economically important species in the Gulf of Mexico. In Chesapeake Bay and North Carolina, blue crabs have suffered from unexplained population crashes in recent years, purportedly due to increase fishing pressure and habitat degradation. Despite the importance of this species and the propensity for their stocks to crash, a realistic and predictive population model is still lacking for blue crabs. This RAPID project will use a metapopulation approach to understand and predict the population dynamics of blue crabs. Blue crabs spend their initial, larval, life-stages in the ocean then recruit to estuaries for their juvenile and adult stages. In the metapopulation model to be used, local dynamics in a patch (estuary) will be described and parameterized using fisheries data, remotely-sensed habitat quality estimates, and results from field experiments estimating cannibalism rates. The PIs will estimate connectivity (dispersal of larvae between estuaries) of the population with a particle tracking approach using a fine-scale, spatially-explicit ocean circulation model. When the Deepwater Horizon oil rig exploded on April 20, 2010, and began discharging several million gallons of oil into the Gulf, blue crabs were just beginning their spawning season. In this RAPID, the PIs propose to investigate the impacts of the oil and chemical dispersants on the larval stages, and ultimately on population dynamics, of blue crabs by sampling planktonic larvae at three ocean locations that vary in distance from the oil source. Results will estimate both lethal and sub-lethal effects of oil and dispersants on larvae. They will incorporate the extent and concentration of oil and dispersants into the particle-tracking model and use it to predict the effects of the oil spill on dispersal and recruitment for the entire Gulf of Mexico. To validate model results, the PIs will sample recruitment to estuaries over a wide stretch of the coastline, including areas unaffected, lightly affected and heavily affected by the spill. They will incorporate results into the metapopulation model to explore the long-term effects of the spill on the Gulf of Mexico blue crab population and its fishery. Broader Impacts: The PIs intend that results from this RAPID project will be used to inform fisheries policy so as to prevent collapses of blue crab fishery in the Gulf, especially in light of the recent oil spill. Dispersal information is lacking from current blue crab fishery assessments and may prove especially important now in helping to decide how to not exacerbate the effects of the oil spill. Their sampling will also be useful to document and consider the effects of oil and of dispersants on other commercially and ecologically important species with planktonic larvae, such as menhaden and shrimp. This project will provide interdisciplinary research experiences for several undergraduate and graduate students including field projects as well as computational experience.