SLIDE 1 Ryan Gandy , Eric Suarez and Bill Turner
Florida Fish and Wildlife Conservation Commission Fish and Wildlife Research institute Saint Petersburg, Florida
Developing monitoring techniques and management tools to understand the conflict between the blue crab (Callinectes sapidus) fishery and diamondback terrapin (Malaclemys terrapin macrospilota) populations in Florida
SLIDE 2 Investigation into the interaction between terrapins and blue crab traps in Florida
2011
- Investigated the interaction between blue crab traps
and a known terrapin colony on Lanark Reef.
- Developed search methodologies, standardized to
habitat, for terrapin population assessments.
- Developed terrapin ‘hot spot’ maps for management
and targeted research.
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Investigate the interaction between blue crab traps and a known terrapin colony on Lanark Reef
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Introducing the TUBA trap
Terrapin/Crab Trap Interactions
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Methodology
Fall Trapping Study
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Fall Results
0 terrapins in 930 trap days 187 terrapins captured by hand on the island during this
time
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Methodology
Spring Trapping Study
Submerged Traps
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Methodology
Spring Trapping Study
Intertidal traps Placed in vegetation
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Results
Submerged traps
2 terrapins in 1995 trap days First female (104 mm CL) 44 m from shore in 1.83 m water depth Second female (120 mm CL) 136 m from shore in 1.71 m water depth
Intertidal traps
65 terrapins in 330 trap days
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Discussion
Submerged Traps
It is rare for Terrapins at Lanark Reef to enter crab
traps, which was unexpected.
Habitat type, trap type, crab trapping history
may be a factor.
Intertidal Traps
Catch of terrapins in traps set in the vegetated
intertidal zone was high.
This is not a zone where crab traps are placed for
fishing.
Ghost pots that wash up onto intertidal areas
can potentially be harmful to terrapin populations.
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Developed search methodologies, standardized to habitat, for terrapin population assessments
Search Methods
Tide Levels Low Medium High Weather Patterns Clear Partly Cloudy Cloudy Habitat Types Open sand Water near shore Vegetation Vegetation with
tidal wrack
SLIDE 12 Results
Tide Total Captures Man Minutes CPUE Low 273 1020 0.27 (1 terrapin every 3.7 minutes) Medium 107 540 0.20 (1 terrapin every 5.0 minutes) High 126 900 0.14 (1 terrapin every 7.1 minutes)
Kruskal-Wallis Test – H=5.94, DF=2, p = 0.05
A B B
SLIDE 13 Results
Weather Total Captures Man Minutes CPUE Clear 215 900 0.24 (1 terrapin every 4.2 minutes) Partly Cloudy 191 600 0.33 (1 terrapin every 3.1 minutes) Cloudy 100 760 0.13 (1 terrapin every 7.6 minutes)
Kruskal-Wallis Test – H=18.62, DF=2, p<0.001
A B A
SLIDE 14 Results
Habitat Total Captures Open Sand Open water near shore 1 Vegetation 147 Vegetation with tidal wrack 353
Chi-square test: X2 = 84.87, p < 0.001
SLIDE 15 Discussion
Best time to search for terrapin’s is during low tide
- n clear or partly cloudy days.
Terrapins used habitat associated with some form
Primary prey plentiful within vegetation Escape from heat Escape from predators
Very difficult to compare technique to other studies.
Different sampling and trapping techniques
SLIDE 16
Lanark Terrapin population assessment
Methods
Individually marked and PIT tagged each terrapin Upon capture we gathered various morphometric measurements
SLIDE 17
Lanark Terrapin population assessment
We captured a total of 442 new individuals (800 total captures) in 8 months of sampling. Population structure – 5.3 % juveniles (includes yearlings), 53.4 % males, and 41.3 % females. Population estimate for Lanark Reef = 1,124 ± 127 terrapins
A closed model that assumed different mark-recapture
probabilities.
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Terrapin ‘hot spot’ maps for management and targeted research
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Marine Fisheries Trip Ticket Fishing Area Code
SLIDE 20 Databases for Terrapin Populations
Source Terrapin # % of Total Big Bend Survey 63 4.5% Herpetological Atlas 1928-2012 186 13.3% Lanark Reef Study 2011 507 36.3% FWRI FIM Monitoring 2000-2012 641 45.9%
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These maps, data and metadata are available to the public for review and download:
http://atoll.floridamarine.org/Quickmaps/KMZ_download.htm
