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