Effects of commercial harvesting on snapping turtle (Chelydra serpentina) populations in the tidal wetlands of Maryland

Background/Question/Methods The global harvest of wild animals by humans for meat and other resources has become more intensive as human populations increase. Models of the life history characteristics of turtles (e.g. extended age to maturity, low annual fecundity, low hatchling survival) have shown that the key to sustaining populations is high annual adult and subadult survival. This combination of life history characteristics makes turtles highly susceptible to the negative effects of commercial harvesting, which usually targets adults. In many mid-Atlantic states, the commercial harvesting of common snapping turtles (Chelydra serpentina) is still a widespread practice. In some states, only a fishing license is required is required to harvest snapping turtles, and many states do not have a limit as to how many individuals are taken. Maryland's Department of Natural Resources (MD-DNR) convened a workgroup in October 2007 to discuss new snapping turtle (Chelydra serpentina) harvest regulations in Maryland. To address concerns of the workgroup, we collected size structure data (body mass, carapace length, sex) on harvested snapping turtle populations in Maryland by accompanying commercial harvesters in the field as well as observing turtles brought to a turtle butchery. We compared these data to data from non-harvested sites at the Patuxent NWR in central Maryland. Results/Conclusions Mean carapace length of males at the harvested site (28.3 cm ± 4.33 SD, n = 147) was significantly smaller (Wilcoxon; p < 0.0001) than males at the non-harvested site (31.9 cm ± 4.39 SD, n = 93), indicating harvests may impact size structure of snapping turtles. The sex ratio at the harvested site was significantly different from a 1:1 ratio (M:F; 2.83:1). At the turtle butchery, we found that a large portion of the snapping turtle harvest in Maryland is confined to a 5-6 week period around May, before the height of the blue crab (Callinectes sapidus) harvest season. In addition, virtually all females purchased by seafood dealers were kept alive and reserved for sale to aquacultures to replenish stocks or immediate sale of eggs.