Evidence for a Male Bias in Atlantic Blue Crab Pot-Based Sampling

The Atlantic Blue Crab Callinectes sapidus is an ecologically- and economically-important species that supports one of the highest valued commercial fisheries in coastal South Carolina, USA. Researchers at the South Carolina Department of Natural Resources conduct multiple surveys to monitor the status of the Atlantic Blue Crab using a variety of gear configurations. Demographic characterizations, however, can often be influenced by sampling gear-related biases. We compared blue crab sex ratios between passive, pot-based, sampling and active, trawl-based, sampling across three estuaries in the fall and for year-round sampling in a single estuary. For fall sampling, the percent of males in pots was 20.1% higher than values observed for trawl-based sampling, while an overall male bias of 22.7% was observed for year-round sampling; however, this bias was only significant in certain months. Our findings suggest that while different sampling gears may offer their own advantages, such as greater suitability to effectively sample specific habitats, the resulting characterizations of population demographics can differ among gear types. Recognizing gear related biases is important for ensuring that field surveys are representative of populations, particularly when sex-specific modeling approaches are used as part of stock assessments to determine population status.