In Search of Climate Effects on Atlantic Croaker Stock off the U.S. Atlantic Coast Using Bayesian State-Space Biomass Dynamics Models

Laboratory and field studies support that the winter estuarine water temperature regulates juvenile Atlantic croaker survival and croaker year-class strength and population outbursts on the U.S Atlantic coast. Various croaker assessment review panels recommended exploration of any assessment models including environmental covariates for better understanding the croaker population dynamics and fishery management implications. In this respect, some modeling approaches led to conclusive results. This study attempts to address this issue using Bayesian state-space biomass dynamics models with and without the minimum winter estuarine temperature (MWETE) from the Chesapeake Bay Region, which is the core croaker overwintering nursery area. MWETE is introduced into the intrinsic rate of population increase assuming it largely controls croaker’s productivity via growth and recruitment processes occurring during the pre-recruit stage. Both models lack information on fishing intensity. They only rely on fisheries removals (1973-2008) and are tuned with the fall (September-November) indices developed from the NMFS Northeast Fisheries Science Center (NMFS-NEFSC) multispecies trawl survey (1973-2008) and the Southeast Area Monitoring and Assessment Program (SEAMAP) South Coastal trawl survey (1990-2008). The models fit both indices equally and generate similar estimates. Models goodness-of-fit and comparison indicate that no model outperform the other. Even though MWETE may be driving the croaker population dynamics on the U.S. Atlantic coast, this biomass modeling effort fails to detect MWETE effects. Perhaps this result stems from the noisy nature of the tuning indices that blurs any MWETE impact; and from lack of fishing effort time series, which precludes the partition of any potential roles between fishing intensities, via changes in catchabilities, and MWETE.