Modify number of hooks between floats on longlines

Overall effectiveness category Awaiting assessment
Number of studies: 1
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Effectiveness

not assessed
Certainty

not assessed
Harms

not assessed

Calculating overall effectiveness category

Background information and definitions

Using more floats on a longline per hook alters the profile of the longline in the water, which may reduce the opportunities for sea turtles swimming below the surface to become entangled in the line or caught on the hooks.

For studies looking at the effects of different hook designs, see Use circle hooks instead of J-hooks, Use non-offset hooks, Use non-ringed hooks and Use larger hooks.

Study locations

Key messages

One study evaluated the effects of modifying the number of hooks between floats on longlines on reptile populations. This study was in the Atlantic and North Pacific.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

BEHAVIOUR (0 STUDIES)

OTHER (1 STUDY)

Unwanted catch (1 study): One replicated study in the Atlantic and North Pacific found that having fewer hooks between floats did not reduce turtle by-catch in the Pacific but had mixed effects in the Atlantic depending on the species.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A replicated study in 1992–2015 in pelagic longline fisheries in the Atlantic and North Pacific (Swimmer et al. 2017) found that using fewer hooks between floats on a longline did not reduce turtle by-catch in the Pacific but had mixed effects in the Atlantic depending on the species. All data presented as statistical model results. In the Pacific, by-catch of leatherback Dermochelys coriacea and loggerhead Caretta caretta turtles was not affected by the number of hooks between floats. In the Atlantic, the chance of catching leatherback turtles was lower with fewer hooks between floats, whereas loggerheads were less likely to be caught when there were fewer (<3 hooks) or more (>5 hooks) hooks between floats (see paper for details). Pelagic Observer Program data from (1992–2015) was used to determine the number of turtles caught/1,000 hooks, and variation in the number of hooks between floats (majority were 3–5 or 4–5 hooks/float) was used to test its effect on bycatch.
Study and other actions tested
Referenced paper
Swimmer Y., Gutierrez A., Bigelow K., Barceló C., Schroeder B., Keene K., Shattenkirk K. & Foster D.G. (2017) Sea turtle bycatch mitigation in U.S. longline fisheries. Frontiers in Marine Science, 4, 260.

Please cite as:

Sainsbury K.A., Morgan W.H., Watson M., Rotem G., Bouskila A., Smith R.K. & Sutherland W.J. (2021) Reptile Conservation: Global Evidence for the Effects of Interventions for reptiles. Conservation Evidence Series Synopsis. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Reptile Conservation

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