Human activities have been characterized as the greatest contemporary selective pressure affecting other species.  In coastal ecosystems, commercial fisheries act as a major source of predation for both target and non-target species.  For example, the diamondback terrapin, Malaclemys terrapin, is frequent by-catch in commercial and recreational crab pots.  Crab pots predominantly kill young females and males, which are smaller than mature females.  The effects of crab pots on terrapin population size, age and sex ratio are documented; however, there have been no attempts to document whether crab pots effect terrapin phenotypes.  We used population and size data for 24 tidal creeks along the Georgia coast that vary in the presence of commercial crabbing activity.

Results/Conclusions

We found that the average age and size M. terrapin was greater in creeks with crabbing activity.  We also found that estimated growth rates of both male and female M. terrapin were faster in creeks with crabbing activity.  While we cannot rule out whether increased growth rates are the result of reduced competition associated with reduced population size, we hypothesize that crabbing has selected for the faster growth rates in terrapins. Our results suggest that crab pots function as gape limited predators within estuaries that are having an evolutionary effect on the growth rates and size distributions of terrapins.