Review of research into drifting FAD designs to reduce species of special interest bycatch entanglement and bigeye/yellowfin interactions

The FAD research plan adopted by WCPFC13 specified that a review be prepared for SC13 on the “design of non-entangling FADs [and designs that lead to] BET or YFT interaction reduction”. This paper reviews available information with a focus on alternative man-made drifting FAD (dFAD) designs that reduce interactions, but minimise impacts on target catch levels.
Unintended mortality of sharks and turtles can occur with dFADs. Both taxa can become entangled on dFAD sub-surface netting, while turtles can also become entangled in netting on the dFAD surface structure. These events have been observed during WCPO purse seine fishing, but resulting numbers are likely underestimates, particularly for sub-surface entanglements which are only identified in the rare event that a dFAD is lifted from the water and the individual has not become detached post-mortem.
Trials of ‘non-entangling’ or ‘reduced entanglement risk’ dFAD designs have occurred in other tropical oceans, with no significant impact on the target tuna catch seen, and best practice guidelines developed (e.g. Figure 1). Trials have not been undertaken within the WCPO, but the effectiveness of designs across other oceans suggests similar performance can be expected. The precautionary approach would suggest the adoption of non-entangling dFAD designs (or at a minimum lower entanglement risk designs) should be considered within the WCPFC to minimise the impact of this mode of fishing on species of special interest and the WCPO ecosystem. Subsequent monitoring of target species catch rates and interaction rates should occur to ensure no unanticipated effects. Noting trials have concentrated on larger industrial fleets, the implications for smaller domestic PICT fleets should be considered.
Evaluation of dFAD designs for reducing juvenile bigeye and yellowfin catch rates is in its early stages. Given the potential impact of oceanographic influences on, for example, bigeye catches in the WCPO, the ability to infer performance of candidate designs from trials in other oceans may be limited. SC13 should consider the prioritisation of at-sea trials in the WCPO to pursue this area of work (see SC13-EB-WP-05).
Adoption of biodegradable dFAD designs would reduce marine debris and the impact of beaching events. However, the efficacy of alternative bio-degradable designs has not been confirmed, although trials of submerged structure material provide some information. To mitigate the risk on habitat of beaching in vulnerable areas (e.g. on coral reefs), dFAD retrieval programmes may be needed.
We invite WCPFC-SC13 to:
• Note available scientific information on alternative dFAD designs for reducing entanglement risk and provide scientific recommendations to the Commission on appropriate WCPO dFAD designs;
• Note the growing body of scientific information on alternative dFAD designs for reducing small bigeye and yellowfin catches and on biodegradable dFADs, in particular the findings for biodegradable submerged structures, but also the limitations of current information; and
• In conjunction with SC13-EB-WP-05, consider potential research activities on and at-sea trials of designs for reducing juvenile bigeye and yellowfin catch rates and trials of biodegradable design options in the WCPO to fill key knowledge gaps.