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#           Spatial distribution of estuarine diamond-backed terrapins (Malaclemys terrapin) and risk analysis from commercial blue crab (Callinectes sapidus) trapping at the Savannah Coastal Refuges Complex, USA      

      May 1, 2018    

The diamond-backed terrapin (Malaclemys terrapin) is a small estuarine turtle distributed along the Atlantic and Gulf Coasts of the USA. Terrapin populations are declining throughout their range and one of the main causes is mortality by drowning as bycatch in commercially-fished blue crab (Callinetes sapidus) traps (aka pots). We conducted head counts of terrapins and documented the distribution and number of crab pots on the Savannah Coastal Refuges Complex in southeast Georgia, USA. Using an index for representing relative degree of crabbing pressure, we conducted a spatial risk analysis for each of the four refuges surveyed. We fit a series of generalized linear mixed effect models to test hypotheses about the scale (creek scale vs. refuge/island scale) at which terrapin relative abundances respond to crab trapping. Several creeks were found to be at high risk of terrapin mortality from crab pots. Areas with low terrapin head counts may be a result of past crab pot mortality. The best model relating terrapin counts to crab trapping revealed a negative effect of crab pots calculated at the refuge/island scale and included a positive association between cloud cover and terrapin counts. The estimated effect of crab pot number at the refuge/island scale suggests that an increase in crab pot density of one pot per creek is associated with a 74.6% decline in terrapin head counts, underscoring the sensitivity of terrapin populations to crab pot mortality. Mitigation of this mortality factor via redesigned crab traps with bycatch reduction devices may be necessary to maintain healthy terrapin populations on the refuges.

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September 14, 2018

####                 Spatial distribution and risk analysis data for diamond-backed terrapins relative to crab trapping, Savannah Coastal Refuge Complex, USA              

Southwest Biological Science Center

#### Jeffrey E Lovich, Ph.D.

##### Research Ecologist, Co-Deputy Branch Chief, Terrestrial Drylands Ecology Branch

Southwest Biological Science Center

jeffrey_lovich@usgs.gov

928-556-7358

#### Charles B Yackulic, Ph.D.

##### Research Statistician

Southwest Biological Science Center

cyackulic@usgs.gov

928-556-7379

#### Shellie (Michele) R Puffer

##### Wildlife Biologist

Southwest Biological Science Center

mpuffer@usgs.gov

928-556-7344

## Related Content

September 14, 2018

####                 Spatial distribution and risk analysis data for diamond-backed terrapins relative to crab trapping, Savannah Coastal Refuge Complex, USA              

Southwest Biological Science Center

#### Jeffrey E Lovich, Ph.D.

##### Research Ecologist, Co-Deputy Branch Chief, Terrestrial Drylands Ecology Branch

Southwest Biological Science Center

jeffrey_lovich@usgs.gov

928-556-7358

#### Charles B Yackulic, Ph.D.

##### Research Statistician

Southwest Biological Science Center

cyackulic@usgs.gov

928-556-7379

#### Shellie (Michele) R Puffer

##### Wildlife Biologist

Southwest Biological Science Center

mpuffer@usgs.gov

928-556-7344

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2255 N. Gemini DriveFlagstaff, AZ86001United States

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