Mitigating by-catch of diamondback terrapins in crab pots

Published source details Hart K.M. & Crowder L.B. (2011) Mitigating by-catch of diamondback terrapins in crab pots. Journal of Wildlife Management, 75, 264-272.
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This study is summarised as evidence for the following.

	Action	Category
	Install exclusion devices on fishing gear: Tortoises, terrapins, side-necked & softshell turtles Action Link

Install exclusion devices on fishing gear: Tortoises, terrapins, side-necked & softshell turtles

A replicated, paired, controlled study in 2000–2004 in coastal waters in North Carolina, USA (Hart & Crowder 2011) found that after rectangular devices were placed at crab pot entrances (a ‘bycatch reduction device’), the unwanted catch of diamondback terrapins Malaclemys terrapin tended to be lower in a commercial blue crab Callinectes sapidus fishery. No terrapins were caught during hard-shell crab fishing and five terrapins were caught during peeler crab fishing in pots modified with excluders (peeler crab 4.3 cm excluder: 0 individuals, 5.0 cm excluder: 2, vertical ties: 3). Hard shell crab catch was lower in pots with smaller excluders (4.0 cm excluder: 1,002 individuals, 4.5 cm excluder: 459) compared to unmodified pots (625–1,270), but similar when pots with the largest excluder were used (365 individuals) compared to unmodified pots (386). Peeler crab catch was similar in modified pots (372–376 individuals) compared to unmodified pots (374). In May–June 2000–2001 and September–November 2000, hard crab were fished for using pots (60 x 60 x 60 cm) in 21 pairs (with and without excluder devices). Three rectangular excluder devices were tested/season: 16 x 4 cm, 16 x 4.5 cm, and 16 x 5 cm (75 fishing days, 3,150 crab pot days). In April–May 2004, peeler crabs were fished in blocks of four pots with either unmodified, or one of three excluders: 16 x 4.3 cm rectangle, 15.2 x 5.1 cm rectangle, or two vertical wire ties/entrance set 7.8 cm apart (19 fishing days, 1,672 total crab pot days).

(Summarised by: Maggie Watson, Katie Sainsbury)