Investigating weighted fishing hooks for seabird bycatch mitigation

Area of Science:

• Marine Biology
• Fisheries Science
• Conservation Biology

Background:

• Fisheries bycatch, particularly of albatrosses in North Pacific tuna longline fisheries, poses a significant threat to seabird populations.
• Increased annual captures exceeding 1000 albatrosses highlight the urgency of mitigating this bycatch.
• Seabird interactions with fishing gear occur at depths up to 1 meter, influenced by branchline weight placement.

Purpose of the Study:

• To compare the commercial viability of weighted hooks versus conventional gear in reducing seabird bycatch.
• To assess the impact of weighted hooks on catch rates of both retained and discarded species.
• To evaluate the sinking speed of experimental weighted hooks compared to control gear.

Main Methods:

• Experimental fishing comparing weighted hooks with conventional gear (weights 0.75m from hook).
• Bayesian random effects meta-analytic regression to estimate species-specific relative risk of capture.
• Bayesian general linear mixed regression to model hook sinking speed.

Main Results:

• A significant 53% decrease in catch rates for retained species using experimental weighted hooks, indicating potential economic impact.
• No significant effect on catch rates for discarded species.
• Experimental hooks sank approximately 1.4 times faster, reaching 85 cm.

Conclusions:

• Weighted hooks show potential for reducing seabird bycatch and associated risks.
• Current weighted hook designs present economic challenges due to reduced catch rates of target species.
• Prioritizing development of effective weighted hook designs that maintain economic viability is crucial for conservation.