Shrimp and Blue Crabs
The Research Vessel Silver Crescent is used to monitor sub-adult and adult shrimp and blue crab on a routine basis in the State's larger creeks, rivers and open waters to provide information on these animals as they begin migrating toward the ocean. This sampling is supplemented by trawling with outboard motorboats in the central and northern coastal zones of the State. Sampling data are important in determining the commercial shrimping season's opening and closing dates for the areas from the beaches to three miles offshore. Catches of white shrimp in 20-ft sample trawls in the fall of 2004 were average through September. Catches then fell below average as tropical storms caused some premature emigration from estuarine locations. In spring 2005, catch rates of white shrimp were close to average, ensuring good numbers for a spring commercial harvest and an average fall crop. Tropical storms curtailed the fall recreational baiting season in 2004. Brown shrimp catches were variable in research trawls in 2005, and commercial harvest was limited by low effort, driven by continued low prices to shrimpers and high fuel costs. Blue crab captured by research trawls rebounded to about average levels in the spring of 2005, an improvement over 2002-03. Although additional sampling and analyses are needed, the decline in blue crab in the open waters appears to be related to severe drought conditions that persisted in 2001-02.
Tidal creeks are sampled biweekly during spring and summer for juvenile shrimp and blue crab, to predict commercial catch and management strategy. Size data are used to predict when shrimp move into areas open for commercial trawling and when they reach a harvestable size. Sampling involves trawling with a 10-ft wide small-mesh net. Sampling in July-August of 2004 indicated above average numbers of juvenile white shrimp in the tidal creeks near Charleston. Creek sampling for juvenile brown shrimp in May and June 2005 produced below average numbers of juvenile brown shrimp, with growth greatly delayed by cool temperatures in April and May. The abundance of blue crab juveniles appeared to be below average in spring 2005, as were catches of adults later in the summer.
Staff have conducted a fishery-independent survey of blue crab stocks using crab pots to determine trends since 1988. The crab pots are fished in a standardized manner in each of the major estuaries. Catch rates in the fall 2004 were near the 16-year average, driven largely by high catch rates of mature female blue crab. Additional pot samples were collected in coastal rivers in FY 04-5 to examine catch rates over longer soak times
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