Bycatch in the Commercial Blue Crab Fishery in Louisiana

Julie A. LivelyLouisiana Sea Grant and LSU AgCenter

GSMFC Terrapins & Crab TrapsOct. 18, 2017

Research Overview1. Derelict: Removals (Anderson and Alford

2014).2. Derelict: Simulated DFG (Alford and

Anderson Lively in prep)3. Active: Bait testing (A. N. Anderson thesis)4. Active: Bait testing (E. Clowes thesis)

1. Derelict Crab Trap Removal

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Project Objectives

1. Remove derelict traps and other debris

2. Quantify ghost fishing

1. Derelict Crab Trap Removal

2012: Delacroix and Cocodrie2013: Hopedale and Point a

la Hache

New Orleans1. Derelict Crab Trap Removal

Location Ghost fishing (%)Delacroix 67Cocodrie 33Pointe a la Hache 55Hopedale 88

1. Derelict Crab Trap Removal

Delacroix CocodriePointe a la Hache

HopedaleMud crab 5 5 1Stone crab 13 1 1Alligator gar 2Spotted gar 3Hardhead catfish 4 1Gulf toadfish 1 5Flounder 3Bluegill 35 2Pumpkinseed 3Largemouth bass 3White crappie 1Sheepshead 4 15 18Silver perch 3Atlantic croaker 1Red drum 3 1Atlantic spadefish 1Waterfowl unknown 1River otter 1

Delacroix Cocodrie Pointe a la Hache Hopedale

Common Name n = 724 n = 44 n = 149 n = 156Blue crab 325 13 147 386Diamondback terrapin 2 13 14

(Anderson and Alford, 2014)1. Derelict Crab Trap Removal

1. Derelict Crab Trap Removal

• Delacroix: 1957 traps (37%)– 2 terrapins

• Point ala Hache: 492 traps (30%)– 0 terrapins

• Cocodrie*: 747 traps (6%)– 13 terrapins: 3+4+5+1 – 3 brought in only because

terrapin shells and no other data– Equal crab and terrapins

• Hopedale*: 411 traps (38%)– 14 terrapins – Grouped terrapins*biased sampling

• 4 locations: 10 traps at each location• Monthly visits to traps after 5 day initial set• Mark recapture: External marks• Average monthly mortality• Standardized by traps and soak days• Delacroix eliminated after 4 months

2. Simulated Derelict Traps

Site Soak Days Salinity (SD) Temperature (SD) Total CrabGrand Isle 326 18.2 ± 5.7 23.8 ± 5.7 67Cocodrie 251 10.5 ± 5.8 21.4 ± 5.6 127

Rockefeller 334 7.4 ± 4.6 24.2 ± 7.4 405

2. Simulated Derelict Traps

Recaptures Count1 month 502 months 153 months 74 months 1

TOTAL 73

2. Simulated Derelict Traps Recaptures

Species CountSheepshead 25Pinfish 16Hardhead catfish 14Stone crab 11Spadefish 7Black drum 4Speckled trout 4Toadfish 4Flounder 2Alligator gar 1Mullet 1Red drum 1unknown fish skeleton

No terrapins ever caught but seen in the water

2. Simulated Derelict Traps

Baited trap research

3. Anderson Bait TestingMethods• 20 paired traps• 2 field sites:

– Grand Isle – Cocodrie

• 48 h soak • 3 trips• October - November 2013

Type CountHardhead 45

Mangrove Snapper 1Pinfish 29

Sheepshead 3Spadefish 1Stone crab 2

3. Anderson Bait Testing

Site Soak Days TerrapinsGrand Isle 120 0Cocodrie 120 0

• Summer and fall 2014, winter and spring 2015

• 30 traps seasonally• 2 day soak• Rockefeller, Cocodrie, and

Grand Isle• 356 total traps (lost 4)• 847 total landed crabs

4. Clowes Bait Testing

Non-target Bycatch(356 traps; 48 hrs.)

Species Count per trap per soak hr.Hardhead catfish 47 0.13 0.00

Spadefish 18 0.05 0.00 Stone crab** 8 0.02 0.00

Gafftopsail catfish 6 0.02 0.00 Southern flounder 5 0.01 0.00

Pinfish 4 0.01 0.00 Black Drum 3 0.01 0.00

Diamondback Terrapin* 2 0.01 0.0001 Croaker 1 0.00 0.00

Sheepshead 1 0.00 0.00 Shortnose Gar 1 0.00 0.00

White trout 1 0.00 0.00

* Spring Grand Isle, dead

4. Clowes Bait Testing

Petre et al. 2015 (Fig. 1 ) and Selman et al. 2014

Conclusions

Summary• Terrapins in traps

– Derelict: Delacroix: Indefinite time: 0.002 terrapin/trap– Derelict: Hopedale: Indefinite time: 0.3 terrapin/trap*– Derelict: Cocodrie: Indefinite time: 0.09 terrapin/trap*– Baited: Grand Isle: 4 Seasons (Spring Only; 240 days):

0.008 terrapin/(trap x day)

• No terrapins in traps (11,000+ soak days)– Derelict: Point a la Hache: Indefinite time– Sim. Derelict: Delacroix: 4 months (1,200 soak days)– Sim. Derelict: Rockefeller: Year (3,340 soak days)– Sim. Derelict: Cocodrie: 9+ months (2,510 soak days)– Sim. Derelict: Grand Isle: Year (3,260 soak days)– Baited: Grand Isle: Oct/ Nov (120 soak days)– Baited: Cocodrie: Oct/ Nov (120 soak days)– Baited: Rockefeller: 4 seasons (240 soak days)– Baited: Cocodrie: 4 seasons (240 soak days) *biased sampling

Conclusions• Localized• Seasonal• Independent matches what we’ve heard/ seen

with fisheries-dependent• More documentation of bycatch

AcknowledgementsFunding sourceSea Grant College ProgramNational Fish and Wildlife FoundationLouisiana Department of Wildlife & Fisheries

Laboratory / Field HelpAmy AlfordHolly RogersJenessa KayMorgan DucoteJace Hood

Tyler LoebBrandy MalbroughStephanie GrodeskaAngie NguyenEmily SloaneAnna Claire Ferchaud

Additional assistanceSea Grant Oyster HouseLUMCON