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Wire‐mesh traps are extensively used to harvest blue crabs Callinectes sapidusbut also capture over 40 other species. Numerous studies have evaluated bycatch reduction devices (BRDs) to reduce the incidental capture of one species, the diamondback terrapin Malaclemys terrapin, since 1992. Despite decades of research, widespread adoption of BRDs as a conservation action has not occurred, which partly stems from seemingly conflicting results from a multitude of BRDdesigns along the U.S. Atlantic and Gulf of Mexico coasts. In this study, we developed a simple scoring system to assess the probability of trap entry by legal‐sized (≥12.7‐cm carapace width; n= 736) blue crabs as well as trap exclusion of diamondback terrapins (n= 985) based on morphometric measurements for both species. Probability of entry or exclusion for each legal‐sized blue crab and diamondback terrapin was assessed for each of 8,196 theoretical BRDsizes encompassing the range of BRDwidths and heights actually tested since 1992. Predictive relationships for trap entry or exclusion for each theoretical BRDsize were evaluated as a function of three geometric BRDattributes: BRDarea (cm2), diagonal BRDopening (cm), and the ratio of BRDwidth to height. Comparison of observed (35 data sets) versus predicted (entry or exclusion probabilities for BRDs) catches for both species revealed that BRDs have performed as predicted for legal‐sized blue crab catch (slope = 0.99; >81,000 crabs) but have captured considerably fewer diamondback terrapins than predicted based on BRDsize alone (slope = 0.28; 1,430 diamondback terrapins). Analyses also substantiated superior (i.e., >30% better) diamondback terrapin exclusion potential for a BRDwe designed that measured 5.1–6.4 cm (height) × 7.3 cm (width). Increasing the width of this BRDby 0.4 cm would also achieve a 99% capture probability for legal‐sized blue crabs, comparable to other widely tested and marketed BRDdesigns.

Five gear types were fished simultaneously to determine their efficacy at capturing premolt blue crabs Callinectes sapidus of commercial size (= 75 mm carapace width). Peeler pots, crab fykes, bush lines, habitat pots, and baited hard-crab pots deployed at each of nine stations (3 stations/area) in the Ashley River, South Carolina, were fished four consecutive days weekly from 18 April through 16 November 1979. Premolt crabs captured per gear-day (one unit of gear with a 24-hour soak time) were analyzed by 6-week intervals and area for each gear type. Hardcrab pots averaged more than 2.5 early premolt crabs per day during April and May, and habitat pots captured fewer, but consistent, numbers (0.7/day) of late premolt crabs from 18 April through 17 August. Modest peeler-pot success during April-May (over 0.5/gear-day) was attributed to the peak abundance of pubertal-molt females occurring prior to 18 April. Tidal amplitude (mean, 1.5 m) and current velocity (over 1.8 km/hour) limited the usefulness of bush lines and crab fykes throughout the study. Premolt male crabs outnumbered females 2.5:1, 1.6:1, and 1.3:1 in the habitat pot, peeler pot, and hard-crab pot, respectively. Overall, premolt crab catch rates declined from 1.0/gear-day during April-May to 0.4 in June-July, to 0.1 during October-November. Except for hard-crab pot catches during the first 6-week period, catch rates did not differ significantly among upper, middle, and lower river areas. Knowledgeable crabbers fishing habitat pots, peeler pots, and hard-crab pots in the most productive areas and seasons should capture premolt crabs at rates adequate to supply a shedding facility. A viable soft-shell crab industry in South Carolina would have little effect on the current fishery for hard crabs.

South Carolina's blue crab fishery is dominated by commercial landings, although an unknown but large number of recreational crabbers participate. Commercial landings of hard blue crabs average around 2.98 x IOs kg per year. Because of increasing fishing effort and value of blue crab meat, total annual value of the fishery has doubled in the last 5 years, approaching $5 million. Most of South Carolina's landings come from the trap fishery, with modest quantities also coming from trawl fisheries and mariculture. Catch rates in the fishery peak during fall, when most new recruits enter the fishery. Sponge crabs first appear in early April and are proportionally most abundant during summer, producing megalopae that enter the esturaries primarily during fall. Recent analyses of population montitoring data underscore theimportance of tidal creeks as nursery areas and refuges for mating blue crabs. Long-term fishery-independent indices of abundance (trawl and trap data) suggest that blue crab abundance is variable, but stocks seem to be relatively stable. We believe that rainfall (river discharge), disease, and possibly pollution have played varying roles in previous declines in stocks. A high correlation (r = 0.91) exists between annual license sales and commercial landings. suggesting that effort may be the limiting factor in annual harvests. South Carolina iscurrently assessing its blue crab fishery and examining such issues as limiting growth in fishing effort, quantification of fishing effort, under-reporting of catch, trap theft, vandalism of traps, ghost pots, competition between commercial and recreational crabbers, and conflicts with boaters. [ABSTRACT FROM AUTHOR]