By-catch of Albatrosses and other Seabirds by Japanese Longline Fishing Vessels in the Australian Fishing Zone from April 1992 to March 1995
Data collected by Australian observers, combined with logbook data supplied by all Japanese vessels fishing in the Australian Fishing Zone were used to estimate the total seabird catch and catch rates (and associated variances) within the Australian Fishing Zone by season and area. The species composition of sub-samples of captured seabirds was used in conjunction with the estimates of total by-catch to provide estimates of by-catch by species. The total by-catch of all seabird species by Japanese longline within Australian waters was estimated to be 2981 (coefficient of variation [cv] 17%) for the 1992 fishing year, 3590 (cv 15%) in 1993 and 2817 (ccv19%) in 1994. Because these estimates are based on birds observed hauled on board, they underestimate the total number of seabirds killed by fishing operations. The increase in total seabird by-catch between 1992 and 1993 is partly due to the use of monofilament nylon longline gear by two vessels in 1993, and the decrease from 1993 to 1994 was mainly due to a corresponding reduction in fishing effort. For the three years examined, 78% of the total seabird by-catch was albatrosses, with Black-browed Albatross Diomedea melanophrys and Shy Albatross D. cauta caught in the greatest numbers. Catches of Yellow-nosed Albatross (D. chlororhynchos), Wandering Albatross D. exulans and Grey-headed Albatross D. chrysostoma were also significant. The proportions of individual species caught showed considerable inter-annual variability.