Tidal creeks along the southeastern U.S. and Gulf of Mexico coastlines provide nursery habitats for commercially and ecologically important nekton, including juvenile blue crabs Callinectes sapidus, a valuable and heavily landed seafood species. Instream and watershed urbanization may influence the habitat value that tidal creeks provide to blue crabs. We investigated natural and anthropogenic factors influencing juvenile blue crab occupancy dynamics in eight first-order tidal creeks in coastal North Carolina (USA). An auto-logistic hierarchical multi-season (dynamic) occupancy model with separate ecological and observation sub-models was fitted to juvenile blue crab presence/absence data collected over replicate sampling visits in multiple seasons at three fixed trapping sites in each creek. Colonization and survival are the processes operating on occupancy that are estimated with this formulation of the model. Covariates considered in the ecological sub-model included watershed imperviousness, the percent of salt marsh in each creek’s high tide area, percent salt marsh edge, site-level water depth, and site-level salinity. Temperature, salinity, and dissolved oxygen were covariates considered in the observation sub-model. In the ecological sub-model, watershed imperviousness was a meaningful negative covariate and site-level salinity was a positive covariate of survival probability. Imperviousness and salinity were each marginally meaningful on colonization probability. Water temperature was a positive covariate of detection probability in the observation sub-model. Mean estimated detection probability across all sites and seasons of the study was 0.186. The results suggest that development in tidal creek watersheds will impact occupancy dynamics of juvenile blue crabs. This places an emphasis on minimizing losses of natural land cover classes in tidal creek watersheds to reduce the negative impacts to populations of this important species. Future research should explore the relationship between imperviousness and salinity fluctuations in tidal creeks to better understand how changing land cover influences water chemistry and ultimately the demographics of juvenile blue crabs.

The blue crab Callinectes sapidus is a commercially important crustacean species fished along the Atlantic and Gulf of Mexico coastlines. Cull rings on traps are required to allow for egress of sublegal blue crabs in commercial and recreational fisheries in this region. We undertook a study to estimate contact selectivity (retention probability) of traps with different cull-ring sizes fished for male crabs. We estimated retention probability using logistic models and catch data from 38.1-mm square mesh traps, each affixed with one size of cull rings (58.7, 60.3, or 61.9 mm internal diameter), and fished along with control traps (no cull rings). Each experimental trap type displayed relatively steep retention around its l₅₀, the carapace width at which 50% of individuals are selected. The l₅₀ for traps with 58.7-mm cull rings was less than the minimum legal crab size in North Carolina (127 mm carapace width) while the l₅₀ for traps with 60.3-mm or 61.9-mm cull rings was greater than the minimum legal size. Mean catch rates of legal male crabs were not statistically different among the three experimental trap types; however, catch rates of sublegal males were significantly lower in traps with the two larger cull ring sizes. We conclude that traps with 61.9-mm cull rings are most appropriate for the North Carolina trap fishery because they maintain catch rates of legal males but show the greatest reduction in catch rates of sublegal males. The use of larger cull-ring sizes would reduce rates of fishing mortality resulting from excessive trap confinement, injury during commercial culling, or intentional harvest by fishers who do not cull their catch. Received April 29, 2015; accepted October 22, 2015