Study

Behavioural interactions of diamondback terrapins with crab pots demonstrate that bycatch reduction devices reduce entrapment

  • Published source details McKee R.K., Cecala K.K. & Dorcas M.E. (2016) Behavioural interactions of diamondback terrapins with crab pots demonstrate that bycatch reduction devices reduce entrapment. Aquatic Conservation: Marine and Freshwater Ecosystems, 26, 1081-1089.

Actions

This study is summarised as evidence for the following.

Action Category

Use a different bait type: Tortoises, terrapins, side-necked & softshell turtles

Action Link
Reptile Conservation

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

Action Link
Reptile Conservation
  1. Use a different bait type: Tortoises, terrapins, side-necked & softshell turtles

    A randomized, controlled study (years not provided) in a brackish water experimental enclosure in South Carolina, USA (McKee et al. 2016) found that using mackerel bait in a crab pot increased catch rates of diamondback terrapin Malaclemys terrapin compared to chicken or no bait. Mackerel bait increased the number of terrapins caught (1.2 entries/terrapin/h) compared to chicken or no bait, which produced similar results (chicken: 0.6; no bait: 0.2 entries/terrapin/h). In total, 25 wild terrapins were caught to participate in three randomly ordered trials: mackerel bait, chicken bait and no bait. A single crab pot with chimney was used to test each bait type. Terrapins were monitored by webcam in 90-minute videos/treatment.

    (Summarised by: Katie Sainsbury)

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

    A randomized, controlled study (years not provided) in a brackish water experimental enclosure in South Carolina, USA (McKee et al. 2016) found that using vertically-oriented rectangular devices to limit the size of entry holes on crab pots (a ‘bycatch reduction device’) reduced the number of entries, increased the time taken to enter and reduced the proportion of successful entry attempts by diamondback terrapins Malaclemys terrapin to crab pots. A vertically-oriented device reduced the number of entries into the pot (2 entries/terrapin) compared to horizontally-oriented devices and no device, which produced similar results (horizontal: 5; no device: 6 entries/terrapin). Vertically-oriented devices increased the average time taken to enter a pot (58 seconds before entry) compared to no device, whereas time to enter horizontally-oriented devices was similar to no device (horizontal: 32; no device: 19 seconds before entry). The proportion of terrapins that entered a pot after investigating it was reduced when a vertically-oriented device was used (0.1 terrapins entered/investigation), compared to a horizontally-oriented device (0.2 terrapins entered/investigation). Both types of device reduced the rate of terrapins entering pots compared to no device (0.3 terrapins entered/investigation). In total, 38 wild terrapins were caught to take part in the study, all of a size where they could enter a crab pot when an opening limiting device was present. Each terrapin participated in three randomly ordered trials: vertically-oriented device fitted to entry holes, horizontally-oriented device fitted to entry holes and no device. Devices were 5.1 x 15.2 cm. Crab pots with chimneys baited with mackerel were used. Terrapins were monitored by webcam in 3 h videos (27 h total footage, 3 h/treatment/study group).

    (Summarised by: Katie Sainsbury)

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