This paper analyses all incidental mortality of seabirds recorded on Argentinian and Chilean vessels fishing for Patagonian toothfish (Dissostichus eleginoides) in Subarea 48.3 during the 1995 season. The data was obtained from the fine-scale reports submitted by each vessel to its national fishing authority and supplemented with the information collected by international scientific observers from each vessel. It was thus possible to evaluate almost all of the incidental mortality of seabirds observed during the season.

The total mortality recorded was 1 428 birds of which white-chimed petrels (Procellaria aequinoctialis) comprised 77.8%, southern giant petrels (Macronectes giganteus) 10.8%, black-browed albatrosses (Diomedea melanophris) 8.1%, wandering albatrosses (D. exulans) 2.0% and grey-headed albatrosses (D. Chrysostoma) 0.7%.  A total of 56 seabirds captured during hauling operations and released alive was also recorded. Within this group, the most abundant were M. giganteus (50%), D. melanophris (14.3%) and P. aequinoctialis (8.9%).

A study of the variables affecting incidental mortality shows that the distance from land, the lunar phase and the use of streamer lines and hook size were important sources of variation, both in vessels' analyses of catch of birds per unit effort (BPUE), as well as of the haul-by-haul data.