Study

Hook ingestion rates in loggerhead sea turtles Caretta caretta as a function of animal size, hook size, and bait

  • Published source details Stokes L.W., Hataway D., Epperly S.P., Shah A.K., Bergmann C.E., Watson J.W. & Higgins B.M. (2011) Hook ingestion rates in loggerhead sea turtles Caretta caretta as a function of animal size, hook size, and bait. Endangered Species Research, 14, 1-11.

Actions

This study is summarised as evidence for the following.

Action Category

Change hook baiting technique

Action Link
Reptile Conservation

Use larger hooks

Action Link
Reptile Conservation
  1. Change hook baiting technique

    A study in 2004–2005 in laboratory conditions in Texas, USA (Stokes et al. 2011) found that loggerhead turtles Caretta caretta were more likely to attempt to swallow thread-baited than single-baited hooks. The odds that loggerhead turtles would attempt to swallow thread-baited hooks were 2.5 times higher than the odds that they would attempt to swallow single-baited hooks, regardless of bait type used or hook size (results presented as model outputs, see paper for details). Turtle responses to individual baited hooks suspended in their tanks were video recorded (each hook presentation = 1 trial). Sixty 45 cm long captive-reared turtles participated in trials, of which 30 turtles participated again when they reached 55 cm and 65 cm long. Trials were carried out in April and October 2004, and May 2005. Modified circle hooks of different sizes (see paper for details) were baited with whole squid Illex illecebrosus or sardines Sardinella aurita and either single-baited or thread-baited.

    (Summarised by: Katie Sainsbury)

  2. Use larger hooks

    A study in 2004–2005 in laboratory conditions in Texas, USA (Stokes et al. 2011) found that loggerhead turtles Caretta caretta were more likely to attempt to swallow smaller circle hooks than larger circle hooks. All results were presented as model outputs, see original paper. The odds that turtles would attempt to swallow the smallest hook was 97 times higher than the odds that they would attempt to swallow the largest hook size, regardless of size of turtle. Larger turtles were more likely to attempt to swallow larger hook sizes. Turtle responses to individual baited hooks suspended in their tanks were video recorded (each hook presentation = 1 trial). Sixty 45 cm long captive-reared turtles participated in trials, of which 30 turtles participated again when they reached 55 cm and 65 cm long. Trials were carried out in April and October 2004, and May 2005. Modified circle hooks of different sizes were trialled: 14/0, 16/0, 18/0 and 20/0 (20 turtles/hook size, 20/0 was not tested with 45 cm turtles). Hooks were baited with whole squid Illex illecebrosus or sardines Sardinella aurita and either single-baited or ‘thread’-baited (see paper for details).

    (Summarised by: Katie Sainsbury)

Output references
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