Sea Turtles

Field Study 705

Study Type: 

wild

Location: 

Southwest Atlantic

Target catch: 

Tuna

Effect on bycatch species: 

American style longlines - no significant difference in catch rates for blue or porbeagle sharks, seabirds or sea turtles. Spanish style longline - significant decrease in pelagic stingray catch rates on circle hooks, no significant differences in catch

Effect on target catch: 

Albacore catches increased with circle hooks on both types of longline. Shortfin mako shark catch rates increased with circle hooks on the American style longlines.

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Field Study

Study Type: 

wild

Location: 

Chesapeake Bay, United States

Target catch: 

Atlantic thread herring, butterfish, Atlantic croaker, weakfish

Effect on bycatch species: 

Significantly reduced sea turtle interactions

Effect on target catch: 

No difference

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Field Study

Study Type: 

wild

Location: 

Chesapeake Bay

Target catch: 

Finfish

Effect on bycatch species: 

. During the study, 21 sea turtles interacted with the control net, while only 1 interaction with the experimental net occurred, which was a significant difference.

Effect on target catch: 

There was no significant difference in the harvest weight or size selectivity of finfish between the two nets (control and experimental)

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Field Study 637

Study Type: 

wild

Location: 

Baja California Sur, Mexico

Target catch: 

Flatfish and elasmobranchs

Effect on bycatch species: 

Chemical light sticks reduced green turtle bycatch by 60%

Effect on target catch: 

No effect

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Field Study 635

Study Type: 

wild

Location: 

Baja California Sur, Mexico

Target catch: 

Flatfish and elasmobranchs

Effect on bycatch species: 

Reduced green turtle bycatch by 54%

Effect on target catch: 

Reduced target catch by 45% and catch value by 47%

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Field Study 605

Study Type: 

wild

Location: 

eastern Pacific Ocean

Target catch: 

Tuna

Effect on bycatch species: 

Significant differences between J and circle hook size 15 and between J and circle hook size 16 were found in the bycatch species group (all species grouped together). Chub mackerel bait caught the sharks.

Effect on target catch: 

No significant differences in catch rates of the target species were found between hook types. The highest catch rates for tunas were found on circle hooks size 15. Squid and jack mackerel bait had the highest catch rates for tunas.

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Field Study 560

Study Type: 

wild

Location: 

Northern Australia

Target catch: 

Prawns

Effect on bycatch species: 

Upward facing TED's reduced sea turtle bycatch by 99%

Effect on target catch: 

Reduced the proportion of soft and damaged prawns by 35.8% and reduced catches of tiger prawns by 6.3%

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Leatherback Turtle

Species: 

Dermochelys coriacea
Photo: Mass DMF, taken under NOAA 50 CFR 222.310 with authorization of the ESA
Photo: Mass DMF, taken under NOAA 50 CFR 222.310 with authorization of the ESA

Type: 

Reptile

Distribution: 

Circumglobal in tropical to sub-polar waters

Population: 

Decreasing

Bycatch Threat: 

Longlines, gillnets, trawls, pot/traps

IUCN Status: 

Critically Endangered

The worldwide decline in leatherback turtles has been caused, in part, by bycatch in fisheries. Leatherback turtles most often entangled or hooked externally in pelagic longline fisheries (Garrison 2003), but are capable of swimming to the surface to breathe (Witzell and Cramer 1995).  Although not all incidental captures lead to mortality, the number of leatherbacks caught each year is very high and post release mortality rates are unknown. Lewison et al (2004) estimated that the global longlining fleets took 50 to 60,000 leatherbacks in 2000. 

Loggerhead Turtle

Species: 

Caretta caretta
Photo: NOAA
Photo: NOAA

Type: 

Reptile

Distribution: 

Circumglobal, in tropical and subtropical waters

Population: 

Unknown

Bycatch Threat: 

Longlines, gillnets, trawls, traps and pots, and dredges

IUCN Status: 

Globally Endangered

The main cause of the decline of loggerhead turtles, and the current primary threat to global populations is bycatch in longlines, gillnets, trawls, traps and pots, and dredges. Loggerhead can be hooked in the mouth or another part of their body when trying to consume bait, entangled in gillnets or ropes, or caught in a trawl or dredge. Longlines, gillnets, and trawls are responsible for the majority of sea turtle bycatch events around the world (Wallace et al, 2010). Commercial longlines incidentally caught an estimated 200,000 loggerhead turtles in 2000 (Lewison et al, 2004).

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