Comparing results of black petrel capture interactions with bottom longlines using different data collection methods

Refers to a report by the same authors, first published in 2023: New Zealand Aquatic Environment and Biodiversity Report No. 318

Black petrels (Procellaria parkinsoni) are assessed as being the petrel species at greatest risk from incidental captures in New Zealand domestic fisheries. These seabirds breed in north-eastern New Zealand and are caught primarily by bottom longline vessels fishing in that area. To gather additional data on capture rates, a trial camera monitoring programme was undertaken between 2016 and 2022 to these bottom longline vessels. This programme was developed in collaboration with commercial fishers, who volunteered their time and the use of their vessels. The effect of additional observations from the trial camera programme for estimating captures of black petrels was evaluated. In addition to this, the influence of observer and/or camera presence on the reporting of protected species captures was assessed. The results showed that estimated black petrel captures were lower when using observer data and electronic monitoring data combined compared with model fits against observer data alone. Simulating data with different proportions of assessed video footage revealed strong biases of estimated black petrel captures for scenarios that were comparable with the proportion of assessed video footage in the actual data that are used to estimate captures. Hence, current bycatch models seem to overpredict black petrel captures in bottom longline vessels fishing off the north-east coast of New Zealand. When comparing fisher-reported black petrel captures with model estimates there was reasonable alignment between both, even when cameras were present and video footage was not assessed. For fishing events that had neither an observer on-board nor cameras present, the fisher-reported captures were below capture estimates, but as aforementioned these also seem to be overpredicted. Therefore, the results highlight two main benefits from electronic monitoring, which are the ability to increase the proportion of monitored fishing events, thus reducing bias, and more accurate reporting of captured birds when cameras are present.

RECOMMENDATIONS

We recommend that SBWG; 1. note that observer data can be combined with electronic monitoring data to increase the precision of seabird bycatch estimates. 2. note that seabird bycatch estimates may be biased when made using only observer data (e.g. if fishers undertake shorter trips or stay closer to shore when an observer is present on-board). 3. note that when assessing reporting rates for fisher-reported protected species captures there is a need account for potential bias in the data used to fit models to estimate total captures. 4. review ACAP guidance on seabird bycatch data collection and assessment to reflect the conclusions from this study.