Fisheries risks to the population viability of black petrel (Procellaria parkinsoni)

Data on the main population of black petrel (Procellaria parkinsoni), which breeds on Great Barrier Island, were analysed. Three types of data were available. The most useful was abundance data, from which it was possible to infer that the population was probably increasing at a rate between 1.2% and 3.1% per year. Mark-recapture data were useful in estimating demographic parameters, like survival and breeding success, but contained little information on population growth rates. Fishery bycatch data from observers were too sparse and imprecise to be useful. The fact that the population is probably increasing shows that there is no evidence that fisheries currently pose a risk to this population. However, this does not imply that there is clear evidence that fisheries do not pose a risk to this population. The mean age of first breeding for black petrel is estimated to be 6.7 y. Before this, new adults spend an average of 1.2 y in the colony as pre-breeders, with only 3% skipping the pre-breeder phase. Of birds that appear in the study area as pre-breeders and survive to breed, only 68% do so in the study area. Once birds start breeding, their annual survival rate is 0.89, 80% breed each year, and of those, 77% are successful (i.e., produce a fledgling). Survival rates before the pre-breeder stage are not well determined because we can’t distinguish mortality from emigration (birds that breed in an area away from where they were hatched). Two recommendations for further monitoring of this population are: periodic repeats of the transect based abundance estimation last done in 2005 (to determine whether the population is increasing or declining); and the use of data loggers to improve our knowledge of the birds’ foraging range and thus help to identify fisheries that might be affecting this population. (New Zealand Aquatic Environment and Biodiversity Report, 51 (2010), ISSN 1176-9440)