ENVIRONMENTAL, SPATIAL, TEMPORAL AND OPERATIONAL EFFECTS ON THE INCIDENTAL MORTALITY OF BIRDS IN THE LONGLINE FISHERY IN THE CROZET AND KERGUELEN AREAS 2003–2006

During the 2003/04, 2004/05 and 2005/06 seasons, 5883 seabirds were observed to have been killed incidentally in the legal longline fishery operating in the Crozet and Kerguelen EEZs. The estimate of mortality derived from these observations amounts to between 7 766 and 10 541 birds caught. The great majority (between 84 and 91% depending on the season) were white-chinned petrels, the males of which species seem to be more vulnerable to this type of mortality. Grey petrels were also caught incidentally in large numbers (576 individuals) over the same period, and represent between 9 and 16% of incidental catches, depending on the season. No albatrosses were caught during this period. A multivariate analysis has helped to highlight the fact that a complex combination of variables, relating to both the environment and fishing techniques, leads to the incidental capture of white-chinned and grey petrels. Our results suggest that a significant proportion of the mortality of white-chinned and grey petrels can be explained by the effects of season and geographical area. This mortality takes place almost exclusively during the breeding season. The highest mortality of white-chinned and grey petrels occurs during the chick-raising period. White-chinned petrels are mainly caught during the austral summer (from September to April) and grey petrels between April and November. The incidental catch varies according to geographical area, being higher at Kerguelen (where there are geographical disparities) than at Crozet. On the basis of the conclusions of this analysis we suggest a series of recommendations aimed at reducing this cause of incidental mortality in the two main species affected: the white-chinned petrel and the grey petrel. It is imperative that urgent note be taken of the considerable impact of the fishery on the grey petrel and that the Conservation Measures be modified accordingly in order to drastically reduce incidental mortality, failing which the population of grey petrels at Kerguelen will most probably face extinction within thirty years. Also proposed are recommendations regarding incidental catches during hauling.