Summary

Assessing the bycatch of seabirds is a key step in understanding the impact of fishing on their populations. In this analysis, we used the seabird risk assessment methodology that was developed in New Zealand to estimate the bycatch of 26 albatross and petrel taxa that breed in the Southern Hemisphere. The bycatch estimates were related to population productivity to estimate the impact of surface longline fishing on the populations.

This analysis was based on observer data provided by Japan, South Africa, Australia and New Zealand. These countries all record the seabird species caught during observed fishing, allowing the estimation of seabird bycatch at the species level. The observed captures were related to the overlap between the observed fishing and the distributions of the seabirds (with the latter derived from tracking data where possible). From the fitted risk assessment model, captures were then estimated across all surface longline fishing effort in the Southern Hemisphere (as reported to regional fisheries management organisations). These estimates do not include any estimates of cryptic mortality or survival of released seabirds.

Across all the seabird taxa and surface longline fishing effort included in this study, the total estimated annual captures were 41,078 (95% c.i.: 39,432 to 42,746). Among all the taxa, captures of grey-headed albatross were the highest (8,444; 95% c.i.: 7796 to 9100). The petrel with the highest captures was white-chinned petrel, with estimated annual captures of 5392 (95% c.i.: 2131 to 13,166). There were nine species for which the estimated annual captures in surface longline fisheries exceeded the population productivity: Amsterdam albatross, sooty albatross, Tristan albatross, Gibson’s albatross, grey-headed albatross, Buller’s albatross, black petrel, spectacled petrel and wandering albatross.

The results are preliminary at this stage; however, this analysis demonstrates how distribution information, together with observer data of seabird bycatch, may be used to estimate the impact of fisheries bycatch on seabird populations.