Seabird mortality in the Japanese tuna longline fishery around Australia, 1988-1995. (vol 86, pg 37, 1998)

Large numbers of seabirds are killed each year within the Australian Fishin g Zone (AFZ) by Japanese longline vessels targeting tuna. In recent years t he estimated rate of seabird bycatch in the AFZ has been in the order of 0. 15 birds/1000 hooks, translating to mortalities of 1000-3500 birds per year . These estimates are absolute minima because not all birds killed remain o n hooks to be observed hauled aboard the vessels. The observed seabird catc h rate varies annually, seasonally and spatially. Most birds are killed: (a ) during the summer fishing season (October to March), even though most fis hing effort occurs in winter; (b) when longlines are set during the day; (c ) in the waters around southern Australia. Uncertainties in the observed ca tch rates prevent confident assessment of trends, but seabird catch rates d o not appear to be showing a sustained decrease. The process of the inciden tal collection of seabird bycatch data (by observers whose priority is to f ish sampling tasks) renders the seabird bycatch data inadequate for reliabl e assessment of trends in total numbers of birds killed over time. Sixteen seabird species of birds killed on longlines in the AFZ have been identifie d. These include black-browed (Diomedea melanophris), shy (D. cauta), grey- headed (D. chrysostoma), yellow-nosed (D, chlororhynchos) and wandering alb atrosses (D. exulans), flesh-footed shearwaters (Puffinus carneipes) and wh ite-chimed petrels (Procellaria aequinoctialis). Seventy-four per cent of b irds killed were albatrosses and the species composition of the bycatch var ied with seasons and areas. Most species of birds killed were characterised by unequal representation of sex and age cohorts, and these unequal repres entations were not consistent between fishing grounds or seasons. (C) 1998 Elsevier Science Ltd. All rights reserved.