A Contemporary,Sex‐Limited Change in Body Size of an Estuarine Turtle in Response to Commercial Fishing |
| |
Authors: | MATTHEW E. WOLAK GEORGE W. GILCHRIST VICTORIA A. RUZICKA DANIEL M. NALLY RANDOLPH M. CHAMBERS |
| |
Affiliation: | 1. W.M. Keck Environmental Field Laboratory, College of William and Mary, Williamsburg, VA 23187, U.S.A.;2. Department of Biology, College of William and Mary, Williamsburg, VA 23187, U.S.A. |
| |
Abstract: | Abstract: Juvenile growth rate and adult body size are important components of life‐history strategies because of their direct impact on fitness. The diamondback terrapin (Malaclemys terrapin) is a sexually dimorphic, long‐lived turtle inhabiting brackish waters throughout the Atlantic and Gulf coasts of the United States. In parts of its range, terrapins face anthropogenically imposed mortality: juveniles of both sexes inadvertently enter commercial crab traps and drown. For adult females, the carapace eventually grows large enough that they cannot enter traps, whereas males almost never reach that critical size. We compared age structure, carapace dimensions, growth curves, and indices of sexual dimorphism for a Chesapeake Bay population of terrapins (where mortality of turtles is high due to crab traps) with contemporary terrapins from Long Island Sound and museum specimens from Chesapeake Bay (neither group subject to commercial crab traps). We also calculated the allochronic and synchronic rates of evolutionary change (haldanes) for males and females to measure the rate of trait change in a population or between populations, respectively. We found a dramatic shift to a younger male age structure, a decrease in the length of time to terminal female carapace size, a 15% increase in female carapace width, and an increase in sexual dimorphism in Chesapeake Bay. In a new twist, our results implicate a fishery in the selective increase in size of a reptilian bycatch species. These sex‐specific changes in life history and demography have implications for population viability that need to be considered when addressing conservation of this threatened turtle. |
| |
Keywords: | anthropogenic selection haldanes fisheries Malaclemys terrapin rapid evolution sexual dimorphism size‐selective mortality Dimorfismo sexual evolució n rá pida haldanes Malaclemys terrapin mortalidad selectiva por talla pesquerí as selecció n antropogé nica |
|
|