At‐sea trialling of the Hookpod: a ‘one‐stop’ mitigation solution for seabird bycatch in pelagic longline fisheries

Abstract

Bycatch of pelagic seabird species in longline fisheries is recognized as one of the most important and pervasive sources of mortality, contributing to an increased risk of their extinction. Uptake of mitigation measures to reduce seabird bycatch has not been widespread by the industry. Here, we present the results of 18 at‐sea trials conducted between 2011–2015 onboard pelagic longliners targeting tuna (Thunnus spp) and swordfish (Xiphias gladius) in South African, Brazilian and Australian waters, using a recently designed seabird bycatch mitigation device. The ‘Hookpod’ is a polycarbonate capsule that encases the point and barb of baited pelagic longline hooks to prevent seabirds from becoming hooked and drowning during line‐setting operations. The assessment was based on efficacy (i.e. reducing rates of seabird bycatch without impacting target catch rate) and practicality (i.e. how the Hookpod fitted into fishing operations). We observed 59 130 experimental branchlines over 129 sets and recorded a single seabird mortality on the Hookpod branchlines compared to 24 on the control branchlines, a bycatch rate of 0.04 birds/1000 hooks and 0.8 birds/1000 hooks, respectively. No difference in catch rate of target fish species between Hookpod and control treatments was detected. These findings demonstrate that Hookpods do not negatively affect catch rate of target species and could make an important contribution to halting the decline of many seabird populations if adopted as a mitigation measure by the pelagic longline fishing industry.

Hookpod-mini: a smaller potential solution to mitigate seabird bycatch in pelagic longline fisheries

“…Although not tested statistically due to low sample size, the entanglement rate on Hookpodmini snoods was lower than on control snoods and suggests that the loop formed in the snood when the Hookpod is loaded (see Fig. 2 in Sullivan et al 2018) does not cause an increase in seabird entanglement.…”

“…During line setting, the baited hook is loaded into the Hookpod-mini to encase the point and barb of the hook, preventing seabirds from becoming hooked as they scavenge baited hooks at the stern of vessel. A pressure-release mechanism releases the hook at a predetermined depth (see Sullivan et al 2018 for full operational details). However, the Hookpod-mini does not contain an LED (autonomous light source) and the accompanying electrical circuitry and is therefore 20% smaller and 25% lighter than the original Hookpod-LED ( Fig.…”

“…Due to the continued threat to albatross and other pelagic seabirds posed by longline fishing (Croxall et al 2012, BirdLife International 2015, there is a continuing drive to find new operationally simple solutions to effectively mitigate seabird bycatch in demersal and pelagic longline fisheries. This is best exemplified by recent efforts to design and test new innovative technologies (Ryan & Watkins 2002, Gilman et al 2003, Robertson et al 2013, Sullivan et al 2018). It has proved both technically and politically challenging to take these new technologies from the engineering phase and at-sea testing through to securing regulatory support and widespread uptake onboard vessels.…”

“…These trials demonstrated that the Hookpod-LED (a larger version of Hookpod with a light-emitting diode incorporated in the housing), which released baited hooks at 10 m depth (Fig. 1), was effective at reducing seabird bycatch to low levels, did not reduce catch rates of target species, and was safe, durable, and operationally simple to use (Sullivan et al 2018).…”

“…Here, we describe at-sea trials of a new version of the Hookpod that is smaller, simpler, and cheaper and does not contain an autonomous (LED) light source (sensu Sullivan et al 2018).…”