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Terrapins, TEDs, and Disintegration Timelines
Willem M. RoosenburgOhio University Center for Ecology and Evolutionary Studies
For the Gulf States Marine Fisheries Commission18 October 2017, Mobile Alabama
The Problem
Years0 10 20 30 40 50 60 70
Num
ber o
f Ind
ivid
uals
103
104
105
106
107
108
Terrapin Life History1) long-lived2) Delayed maturity – 8 yrs3) Low reproductive output4) Low juvenile and high adult
survival
Two Levels of Impact
1. Daily catch rate in actively attended pots.• High impact that
accumulates slowly
2. Ghost pot mortality• Unknown impact,
dramatic perception
Tall Crab
Pots
Terrapin Catch Rates in Crab PotsState and Study CPUE terrapins* crab pot-1 day-1
South Carolina (Bishop 1983)South Carolina (Hoyle and Gibbons 2000)
0.16 -0.240.027
North Carolina (Grant 1997)North Carolina (Hart and Crowder 2011)
0.150.003 – 0.008
Maryland (Roosenburg et al. 1997)Maryland (Roosenburg and Green 2000)Maryland (Jenkins and Roosenburg unpub)
0.17 0.044-0.23
0.19
New Jersey (Wood, 1997a, 1997b) 0.071 -0.49
Alabama (Coleman et al. 2015) 0.0125Florida ( Butler and Heinrich 2007) 0.0 – 0.147Virginia (Upperman et al. 2014 )Virginia (Rook et al. 2010)
0.295 0.201
Texas (Baxter 2013) 1.15
Georgia (Belcher et al 2008) 0.60 – 1.15 /soak
Terrapin Pop Impact of Crab pots
(92 days) (69 piers) (2 CP / pier) = 12,696 CP days
(0.170 terps / CP day) (12,696 CP days) = 2161 terps
Jolly-Seber Estimate of the Patuxent Terrapin Population
2778 - 3730 terps
Assume 100% CP mortality - 58% - 78% of populationAssume 25% CP mortality - 15% - 19% of population
80 terrapins470 crab pot (CP) days = 0.170 terps / CP day
0
5
10
15
20
25
30
Freq
uenc
y
75 80
85 90
95 100
105 110
115 120
125 130
135 140
145 150
155 160
Plastron Length (mm)
Males
Females
Juveniles
Terrapin Sizes in Crab PotsFemales become too big –
male biased impact that skews sex ratio to female bias
BRD Size
No BRA No BRA 4 x 10 4.5 x 12 5 x 10
Num
ber o
f Tur
tles
Caug
ht
0
20
40
60
80
100
1996 1997 1996 1997 1997
BRDs Reduce the number of
Turtles Entering Crab Pots
Impacts of BRDs on TerrapinsState BRD
TypeDimensions
(cm)Terrapin Bycatch
Control:BRDAlabama Wire 5x15 22:2
Delaware Wire 5x10 97:40Delaware Wire 3.8x12 106:0Delaware Wire 4.5x12 106:36Delaware Wire 5x12 106:93
Florida Wire 4.5x12 37:4Georgia Plastic 5x15 136:5Louisiana Wire 5x10 0:0Maryland N/A 4.5x12 1:0Maryland Wire 4.5x12 105:19Maryland Wire 5x10 105:56
Mississippi Wire 5x15 0:0Mississippi Wire 5x10 0:0New Jersey Wire 5x10 40:3New Jersey Wire 4.5x10 3:0New Jersey Wire 5x10 25:4New Jersey Wire 5x10 46:5
North Carolina Wire 4x15; 5x15 13:1North Carolina Wire 5x16 7:0North Carolina Wire 4x16; 4.5x16 1:0South Carolina Plastic 5x15 30:0South Carolina Plastic 4.5x12 75:3
Texas Plastic 4.5x12 2:0Virginia Plastic 4.5x12 2:0Virginia Plastic 4.5x12 69:2Virginia Plastic 5x15 69:0Virginia Plastic 4.5x12 9:0Virginia Plastic 4.5x12 42:0Virginia Plastic 4.5x12 46:2
Data from: Chambers and Maerz 2018 in press
Standard Crab Pots Modified Crab Pots
Ones Twos
MatureFemales
Peelers Ones
Twos MatureFemales
PeelersCrab Type
Num
ber o
f Cra
bs C
augh
t
0
50
100
150
200
250
300
350
No BRD4.5 x 125 x 10
Ones Twos L. F. Peelers Ones Twos L. F. Peelers
Standard Crab Pots Modified Crab Pots
Number of Crabs Caught in Pots with and without BRDs no effect of BRD on number of crabs caught
4.5 cm BRD Impacts on Crab Fishery +5/13
State BRDType
Dimensions(cm)
Change inCrab Size
Change inCrab Number Reference
Delaware Wire 4.5x12 No Change ~14% Decrease Cole and Helser 2001Florida Wire 4.5x12 No Change No Change Butler and Heinrich 2007
Maryland N/A 4.5x12 N/A 29% Decrease Lukacovic et al. 2005Maryland Wire 4.5x12 No Change No Change Roosenburg and Green 2000
New Jersey Wire 4.5x10 No Change 12% Increase Wood 1997North Carolina Wire 4x16; 4.5x16 N/A 23% Decrease Hart and Crowder 2011South Carolina Plastic 4.5x12 N/A 21% Decrease Powers et al. 2009
Texas Plastic 4.5x12 No Change No Change Baxter 2014Virginia Plastic 4.5x12 Slight Decrease ~25% Decrease R. Lipcius, VIMS, pers. comm.Virginia Plastic 4.5x12 No Change 53% Decrease Upperman et al. 2014Virginia Plastic 4.5x12 N/A 17% Decrease Morris et al. 2011Virginia Plastic 4.5x12 N/A 47% Decrease Morris et al. 2011Virginia Plastic 4.5x12 No Change No Change Rook et al. 2010
Data from: Chambers and Maerz 2018 in press
5 cm BRD Impact on Crab Fishery +13/15
State BRDType
Dimensions(cm)
Change inCrab Size
Change inCrab Number Reference
Alabama Wire 5x15 N/A 31% Decrease Coleman et al. 2011Delaware Wire 5x10 No Change No Change Cole and Helser 2001Delaware Wire 5x12 No Change No Change Cole and Helser 2001Georgia Plastic 5x15 No Change ~14% Decrease Belcher et al. 2007Louisiana Wire 5x10 N/A 38% Increase Guillory and Prejean 1998Maryland Wire 5x10 No Change No Change Roosenburg and Green 2000
Mississippi Wire 5x15 No Change No Change Graham et al. 2011Mississippi Wire 5x10 No Change No Change Cuevas et al. 2000New Jersey Wire 5x10 No Change No Change Mazzarella 1994New Jersey Wire 5x10 No Change 10% Increase Wood 1997New Jersey Wire 5x10 No Change 49% Increase Wood 1997
North Carolina Wire 4x15; 5x15 No Change No Change Chavez 2014North Carolina Wire 5x16 N/A No Change Hart and Crowder 2011South Carolina Plastic 5x15 N/A N/A Powers et al. 2009
Virginia Plastic 5x15 No Change No Change Upperman et al. 2014
Data from: Chambers and Maerz 2018 in press
New BRD DesignBRD Type Terrapins
CaughtLegal Crabs
Control 41 48
4.5 X 12 cm 7 51
7.30 X 5 cm 6 36
New 7.30 X 5 cmdesign by Mike Arendt South Carolina DNR
2 7/8 X 2 inches
Ghost pots
Why so few terrapins in ghost pots?
Photos stolen from: Louisiana Fisheries Forward and Louisiana Department of Fisheries
Quantifying Decomposition Rates
Decomposition TimelineMid-Summer
Small Class Size
0 2 4 6 8 10
Rot
ting
Stag
e
2
4
6
8
10
FemaleFemaleFemaleFemaleJuvenile
Medium Class Size
0 2 4 6 8 10
2
4
6
8
10
FemaleFemaleFemaleFemale
Large Size Class
0 2 4 6 8 10
2
4
6
8
10
FemaleFemaleUnknownFemaleFemale
Time (days)0 5 10 15 20 25
2
4
6
8
10
FemaleFemale
Time (days)0 5 10 15 20 25 30 35
2
4
6
8
10
FemaleFemale
Time (days)0 5 10 15 20
Rot
ting
Stag
e
2
4
6
8
10
FemaleFemaleJuvenileJuvenile
Late Summer - Fall
Crab Pot Use in Chesapeake Bay
Davis 1942 –Identified crabs pots
as a threat to terrapins and other
air breathing animals
From: Bilkovic et al, 2016 Ecological and Economic Effects of Derelict Fishing Gear in the Chesapeake Bay
Conclusions• Properly used and ghost pots cause terrapin mortality reducing
or extirpating populations in areas with high crabbing pressure. • By-catch reductions devices or TEDs reduce terrapin mortality. • 5 cm high BRDs have minimal effect on crab catch and size, but
impact varies throughout the range of the fishery.• Terrapin decomposition rates are rapid and thus terrapin remains
are rare in ghost pot clean-ups underestimating terrapin mortality.
• Near shore and shallow water crab pots overlap with terrapin habitat causing a threat to terrapins and therefore a high need for BRDs in gulf region.
• The need for action in many states with commercial crab fisheries indicates that regulation would best be mandated regionally or nationally
Photo By Dave Harp
Thank You!
Olivia BrooksDavid JenkinsScott McGuireWilliam CreskoJason GreeneMichael ModesitteAlayna Tokash