CCAMLR

Satellite telemetry was used to identify the foraging zones of Shy Albatrosses Diomedea cauta breeding at two sites off Tasmania, Australia (Albatross Island in western Bass Strait and Pedra Branca to the south) to assess their level of interaction with longline fisheries. Adult birds from both colonies fed locally both in and outside the breeding season. Breeding birds from Albatross Island foraged over the Australian continental shelf or slope waters off northwest Tasmania, while those from Pedra Branca foraged between the colony and the southeastern edge of the continental shelf. The distances travelled by the birds and the duration of their foraging trips varied during the breeding cycle and tended to decrease as eggs approached hatching. Adults which were tracked near the end of the breeding season (March-April, n = 7 birds) deserted their chicks prematurely, and while dispersing further than incubating or brooding birds, they remained over the continental shelf and slope waters off southeast Australia. Home range analyses indicated 41 % overlap between foraging zones of birds during successive breeding stages. Dispersal during the postbreeding period extended the foraging zones with less overlap between individuals (10% for Albatross Island and 19% for Pedra Branca). The recent contraction of the Japanese Southern Bluefin Tuna longline fishery to the south and east coasts of Tasmania has resulted in extensive overlap with adult Shy Albatrosses from Pedra Branca, but appears to pose a minimal threat to adult birds from Albatross Island. Coupled with the concomitant increase in the Australian domestic tuna longlining industry, adult Shy Albatrosses from southern Tasmania (Pedra Branca and the Mewstone) are vulnerable to incidental capture throughout their annual cycle.

Long term fisheries observer data were used to analyse the influence of a range of environmental variables and mitigation measures upon catch rates of seabirds in the Japanese pelagic longline fishery. In the Australian Fishing Zone (AFZ) seabirds were most likely to be caught on longlines that were set during summer, in southern areas of the zone, and during daylight hours. However, interpretation of changes in catch rates resulting from the use of mitigation measures or from weather effects were problematic due to the interrelationships between the many measured factors. Interpretation and accurate assessment was further complicated by ongoing changes to fishing practices and equipment, and due to changes of the priority that fisheries observers placed on the collection of seabird data. The data relating to factors affecting seabird bycatch which is currently collected incidentally by fisheries observers are not sufficiently robust to allow confidence in statistical assessments alone to examine the efficacy of mitigation measures. Dedicated observations may allow for more confident determination of the reasons why seabirds were or were not caught, and to what degree mitigation measures are effective. The use of these observations in combination with the analyses suggested seabird bycatch rates may be lowered by the use of bird lines, bait throwing machines and thawed baits. However, appropriate use and deployment of these measures are critical if they are to be effective. Further work is required to better understand the effect of these measures, and their effect upon the catch rate of target and non-target species.

Large numbers of seabirds are killed each year within the Australian Fishing Zone (AFZ) by Japanese longline vessels targeting tuna. In recent years the 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 on hooks to be observed hauled aboard the vessels. The observed seabird catch rate varies annually, seasonally and spatially. Most birds are killed: (a) during the summer fishing season (October to March), even though most fishing effort occurs in winter; (b) when longlines are set during the day; (c) in the waters around southern Australia. Uncertainties in the observed catch rates prevent confident assessment of trends, but seabird catch rates do not appear to be showing a sustained decrease. The process of the incidental collection of seabird bycatch data (by observers whose priority is to fish sampling tasks) renders the seabird bycatch data inadequate for reliable assessment of trends in total numbers of birds killed over time. Sixteen seabird species of birds killed on longlines in the AFZ have been identified. These include black-browed (Diomedea melanophris), shy (D. cauta), grey-headed (D. chrysostoma), yellow-nosed (D. chlororhynchus) and wandering albatrosses (D. exulans), flesh-footed shearwaters (Puffinus carneipes) and white-chinned petrels (Procellaria aequinoctialis).Seventy-four per cent of birds killed were albatrosses and the species composition of the bycatch varied with seasons and areas. Most species of birds killed were characterised by unequal representation of sex and age cohorts. and these unequal representations were not consistent between fishing grounds or seasons.

Seabird bycatch arising from longline fishing is known to kill tens of thousands of seabirds each year, and is now acknowledged as representing the most pervasive threat to seabirds, particularly albatrosses, causing widespread declines in populations across the world. However the extent of seabird mortality is poorly known for most of the world's longline fisheries. Information on bird bycatch in the Southern Oceans is best known for the Australian and New Zealand regions. The 10 year evolution of the seabird bycatch issue in the Australian Fishing Zone (AFZ), where the magnitude of the impact of longline fishing on seabirds was first documented, is presented as a case study. Most of the birds killed in the tuna longline fishery operating around Australia are albatrosses, including species recently listed as threatened and endangered. Analyses of the trends of seabird catch rates in the AFZ by Japanese longliners over 10 years show an apparent fall from the 1988 bycatch figure of 0.4 birds/1000 hooks to levels of between 0.1 to 0.2 birds/1000 hooks. Based on current fishing levels, these recent rates equate to between 1000 to 3500 birds being killed year. Although the initial fall in bycatch rate was achieved rapidly, the rate has plateaued, or risen slightly since then, indicating that there may have been changes to fishing practices or equipment which are detrimental to efforts to minimise seabird bycatch and/or adoption of mitigation methods has been slow. This is a cause for concern given that awareness of the seabird bycatch issue has risen rapidly in ten years.
In analysing seabird bycatch data it is important to understand the limitations of observer derived data sets. In particular, large amounts of data are necessary to gain clear insights into the suite of species impacted by a fishery, and the effect of different fishing gear, environmental variables, and the mitigation measures employed. In many cases, it is unlikely that such data will be available for a fishery. To overcome some of these problems, we recommend the retention of all seabird carcases for accurate identification and processing of samples, and also a pragmatic approach to the assessment and implementation of mitigation measures.
The implementation and efficacy of the existing mitigation measures are discussed, together with the approach taken by Australia in preparing a Threat Abatement Plan to mitigate the threat posed to seabirds by oceanic longline fishing. In recognising the need for international action to address the decline in albatross populations, the Australian Government is pursuing such action through international fora such as the Convention for Conservation of Migratory Species of Wild Animals, the Ecologically Related Species Working Group of the Commission for the Conservation of Southern Bluefin Tuna and the IMALF of the Convention for the Conservation of Antarctic Marine Living Resources.