The accidental capture of diamondback terrapins (Malaclemys terrapin centrata) in recreational and commercial crab pots has long been documented among biologists. Davis (1942) first described crab pots as a potential threat to diamondback terrapins, and today crab pots are considered the primary threat to diamondback terrapin populations throughout their range (Seigel and Gibbons 1995).

Roosenburg et al. (1997) described 2 levels of terrapin mortality in crab pots. The first being a “constant background mortality” for crab pots that are regularly fished over a long period of time, while the second includes crab pots that have been lost or abandoned (“ghost” or derelict crab pots). Regularly fished crab pots have the potential to consistently capture small numbers of terrapins over time, while derelict crab pots tend to capture more terrapins over a shorter time period. Although both levels have the potential to negatively affect terrapin abundance collectively, only baited crab pots have been shown to be detrimental to diamondback terrapin populations throughout their range (Seigel and Gibbons 1995; Roosenburg et al. 1997; Wood 1997; Hoyle and Gibbons 2000; Roosenburg 2004; Dorcas et al. 2007).

Less well-documented are the effects of unbaited derelict pots on terrapin mortality. Guillory et al. (2001) estimated that 250,000 derelict crab pots are added to the Gulf of Mexico and Atlantic coast annually. Bishop (1983) reported a ghost crab pot in South Carolina that contained the carcasses of 29 terrapins. Roosenburg (1991) found a ghost pot in Chesapeake Bay that contained 49 dead terrapins, which he estimated accounted for 1.6%–2.8% of the local population.

Though many derelict pots are added to coastal habitats annually, a small subset may pose the greatest risk to terrapin populations depending on their specific location within a marsh. Bishop (1983) noted that ghost pots are frequently transported through tidal current action to shallow waters, and pots in shallow water have a higher probability of capturing large numbers of terrapins during the spring months (March, April, and May). Additionally, Roosenburg et al. (1999) observed that larger sized terrapins, generally female, utilize the deep, open water more frequently than the smaller sized males and juvenile females. Therefore, expectations are that abandoned crab pots in shallow marsh habitats have great potential to catch and kill large numbers of male and immature female terrapins during spring periods.

On 4 April 2007, while sampling for diamondback terrapins in a tidal marsh at low tide near St. Simons Island, Georgia, USA (Glynn Co), a crab pot was observed just below the water's surface. The water depth was < 1 m and a mixture of mud, algal and barnacle growth, and turtle carcasses were visible within the trap. The trap was pulled from the water, revealing the carcasses of 94 dead M. t. centrata (Fig. 1). On 4 May, we observed 23 dead and 1 live M. t. centrata in second trap approximately 100 m from the first trap.

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By law, we were prohibited from removing the traps from the water, and during the remainder of our 2-month sampling period, we visited this site 3 additional times. During each visit we observed additional dead terrapins in the derelict crab pots. Over 5 visits between 4 April and 30 June 2008, we documented 133 dead turtles between the 2 derelict crab pots.

During each of our visits we were conducting a mark–recapture study of terrapins, and based on that data, we estimated there were 73 (Standard Error = 15.07) live terrapins still in the creek (White and Burnham 1999). The number of dead turtles documented was nearly twice the estimated remaining live population. We were able to accurately sex and measure carapace lengths for 97 of the dead terrapins. Of these, 83% were male with carapace lengths ranging from 74 mm to 148 mm (x̄ = 119 mm). By comparison, 66% of live turtles captured in the creek were male, with sizes ranging from 97 mm to 133 mm (x̄ = 117 mm). Finally, we used carapace measurements to estimate the mass (g) for dead terrapins. Using methods from Congdon et al. (1986), we estimated the terrapin biomass for this particular tidal creek to be 257.02 kg/ha, consisting of 167.06 kg/ha female and 89.96 kg/ha male. Based on these estimates we determined that 91% of the total terrapin biomass in this tidal creek was lost as a result of neglected crab pots.

The Gulf Coast states have recognized the threats of derelict crab pots and successfully initiated crab-pot cleanup programs, in which they collectively removed 58,611 abandoned ghost pots from 2002 to 2007 (Perry et al. 2008). On the southeast Atlantic coast, North Carolina is the only state that has established a successful crab-pot cleanup program. In 1995, North Carolina began its crab-pot removal program by collecting approximately 4600 crab pots (Guillory et al. 2001). In comparison, in 1996 Georgia attempted to establish a pilot crab-pot recycling program that lasted for just 4 months before being discontinued (Guillory et al. 2001).

Georgia needs to reestablish a crab-pot recycling program in order to remove derelict crab pots from its coastal waters. Further, Georgia needs to develop a more effective soak requirement to identify derelict commercial and recreational crab pots, and enforce state and federal laws governing reasonable soak times and the discarding of pots in public waters. Currently, Georgia has no requirement for how long a crab pot can soak before being checked (Code of Georgia 2008), while North Carolina's soak law requires all pots to be checked every 5 days (North Carolina Administrative Code 2008). Federal law prohibits the discarding of waste, which would include derelict crab pots, in public waters. Providing positive mechanisms to remove derelict crab pots, and developing and enforcing regulations to reduce negligence of crab pots could be a major first step in preventing additional inhumane mortality of terrapins and contributing to the species' long-term conservation.