Recruitment, Growth, and Mortality of Blue Crabs in Relation to Environmental Factors in the Maryland Coastal Lagoons

Data from 20 years of trawl surveys conducted in the Maryland Coastal lagoons by the Maryland Department of Natural Resources were analyzed to evaluate patterns of recruitment, growth and mortality rates of blue crabs (Callinectes sapidus). Monthly growth rates of 0+ crabs averaged 10.7mm with the highest value being 14.1mm (2008) and the lowest, 6.8mm (1994). Monthly mortality rates of 0+ crabs averaged 0.9; the highest value was 1.33 (1993) and the lowest, 0.52 (2005). Recruitment (peak 0+ CPUE) ranged from 24.9 (1998) to 84.4 (2008) with an average of 52.2. Growth rate was negatively correlated to crab density (r²=0.41, p=0.002), but not to temperature (p=0.33) or salinity (p=0.50). Mortality rate was negatively correlated to temperature (r²=0.32, p=0.012), but not to salinity (p=0.52), or density (p=0.38). Recruitment was negatively correlated to the ENSO Index (r²=0.43, p=0.002). Yearly CPUE and average carapace width were also calculated for four size classes of crab: Age 0+ (<60mm), Age 1+ (>60mm), size 1 Crabs (61-119mm), and size 2 Crabs (>120mm). These indices showed no general trends or correlations to the environmental factors examined. Results from this study are useful as input data in population models for management of blue crabs in the Lagoons.