Examination of effectiveness of Turtle Excluder Devices in crab pots for the prevention of capture of Diamondback Terrapin, Malaclemys terrapin centrata in South Carolina – Year II
The project objectives for this study are as follows:
- Familiarize local commercial crab fishermen with the design, installation, and use of turtle excluder devices in crab pots (=traps).
- Examine catch rates and mortality of diamondback terrapin in commercial crab traps with regard to season and fishing location.
- Compare catch rates of blue crab in pots with and without turtle excluder devices.
- Assess the perceptions of commercial crabbers with regard to turtle excluder devices in crab pots.
- Educate commercial crabbers in the use of excluder devices.
- Compare results in South Carolina with those of studies in other states.
Diamondback terrapin are known to become trapped and in blue crab traps. Studies have shown that turtles caught in South Carolina crab traps have an average mortality of 10%. Another study observed terrapin in crab pots near Kiawah Island, SC and stated that recreational pots are likely to cause more mortalities than commercial pots. They noted that recreational crabbers are often in small creeks where turtles are more abundant. Commercial crabbers have volunteered information suggesting that the only time they see terrapin are during spring at about the time of "peeler season" which is typically late April and May in South Carolina.
Turtle excluder devices or TEDs are typically 2" x 6" metal or plastic rectangular rings that are fixed to the entrance funnels of a blue crab trap. TEDs were first tested on blue crab traps in the mid 1980's in Louisianan and Georgia and in both studies terrapins were effectively eliminated from crab pots while maintaining catch rates of blue crab. In fact, one study determined that catch rates of blue crab actually increased (6.32 crabs per catch day in traps with TEDs vs. 5.52 in standard crab traps). The Georgia study found that traps with vertical TEDs were just as effective for blue crab as were horizontal openings, and that the vertical open may be better at reducing catch rates of turtles.
We believe that fishermen would be accepting of TEDs, at least seasonally, if they are convinced that catch rates of blue crab would not be jeopardized. Compensating crabbers to utilize TEDs should provide the fisherman with first hand evidence that turtles can be protected and blue crab catch rates can be maintained.
For this two year cooperative research study, three commercial blue crab fishermen have been contracted to fish 20 supplied traps in areas where they would typically encounter terrapins. Ten of these traps are not modified while the other ten have TEDs installed. They are required to fill out weekly logbooks which record catch effort, bycatch and socioeconomic data. Once per month DNR personnel accompany the crabbers into the field to record more detailed information, such as length frequency, water quality and GPS location of the gear.