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Impact of Crab Trapping on Diamondback Terrapin (Malaclemys terrapin) Populations of Kiawah Island, SC

J. Whitfield Gibbons and the SREL Herpetology Lab


Diamondback terrapins (Malaclemys terrapin) occur from Cape Cod to Texas in estuarine environments along the Atlantic and Gulf coasts (Ernst et al, 1994). These small, attractive turtles of the salt marsh are common in many of the tidal creeks bordering Kiawah Island, South Carolina. One of the greatest threats to terrapins may be drowning in crab traps.

By one estimate more than 2,500 terrapins were caught daily by 743 commercial crabbers in the Charleston area during April and May of 1982 (Bishop 1983). Capture mortality amounted to 10% for pots checked daily. Estimates of mortality for abandoned crab traps or those checked at greater than one-day intervals were not made. Since this study, a 20% increase in the number of crabbing licenses has occurred in South Carolina. Whether the incidental take of diamondback terrapins in commercial and recreational pots is sustainable has not been determined. The objective of this study is to determine the potential impact of crab trapping on the population of terrapins on Kiawah Island for which the demographic characteristics are known. Diamondback terrapins have been studied non-destructively using mark-recapture techniques (1204 original captures and 981 recaptures) for 14 years (1983-1996) in the salt marshes, tidal creeks, and river bordering the mainland edge of Kiawah Island (Lovich and Gibbons, 1990; Lovich et al., 1991; Seigel and Gibbons, 1995; Tucker et al., 1995).

To accomplish the research, an experimental field approach will be used in which crab pots are set in tidal creeks having a marked population of diamondback terrapins to determine demographic features of terrapins caught. Commercial and recreational pots in the area will be monitored to assess mortality. These data will be used in population models to determine the effects on terrapin populations and whether or not new management guidelines need to be implemented. A major extension of the research, following the documentation of unsustainability, will be development of a terrapin-excluding crab pot and an extensive environmental education program to alert coastal visitors and residents to the hazards of improperly attended crab pots.


Personnel involved in project:

All SREL Herpetology Lab Personnel
Meg Hoyle, Phil Spivey (master's students, UGA School of Forest Resources)

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