Traplines: A Promising Modification to Reduce Sea Turtle Bycatch in Swordfish Longlines

Area of Science:

• Marine biology
• Fisheries science
• Conservation ecology

Background:

• Fisheries bycatch, particularly of sea turtles, poses a significant threat globally.
• Drifting longlines are highly impactful, and current mitigation strategies have limitations.

Purpose of the Study:

• To assess the conservation value of novel hookless traplines for sea turtles in pelagic longline fisheries.
• To compare the effectiveness of traplines versus conventional J-hooks in reducing sea turtle bycatch.

Main Methods:

• A paired comparison study was conducted using a single vessel in the central Mediterranean targeting swordfish.
• Traplines and J-hooks were deployed alternately along the same drifting longlines across 23 sets.
• Data on turtle and fish catch rates were collected and analyzed.

Main Results:

• Traplines caught significantly fewer loggerhead turtles (1) compared to J-hooks (127).
• Traplines yielded substantial commercial fish catches (6580 kg) compared to J-hooks (9711 kg).
• The ratio of turtles caught per kilogram of fish was significantly lower for traplines, indicating higher conservation efficiency.

Conclusions:

• Traplines show potential to drastically reduce sea turtle bycatch in longline fisheries.
• This hookless gear offers a promising conservation tool with minimal compromise to commercial fish catches.
• Further research across diverse fisheries and environments is recommended to validate these findings.