A spatially explicit simulation model of the annual movements of the Black Petrel, Procellaria parkinsoni, in relation to commercial fishing operations

Abstract

The Black Petrel, Procellaria parkinsoni is a medium-sized, endemic Procellarid seabird that weighs approximately 700g. Black Petrels are annual breeders, and whilst historically they were established as far south as the Nelson Ranges, they are now found only in two colonies on Great Barrier Island and Little Barrier Island in the Hauraki Gulf near Auckland, New Zealand. With a current IUCN status of ‘nationally vulnerable’, knowledge of the movements and at-sea behaviour of this pelagic seabird is crucial to successfully addressing the major conservation challenge to which it is subjected: the risk of incidental mortality stemming from accidental capture by the intensive in-shore fishing industry. Geo-locator data from twenty-eight birds deployed in the 2007-2008 breeding season and recovered during the 2008-2009 breeding season (with a sampling interval of 1-2 fixes per day) were used to develop a spatially explicit simulation model of the annual movement patterns of the Black Petrels. This primary objective of this model was to provide a means to assess the probability of mortality events over the course of the annual migratory cycle in relation to the spatial-temporal variations (size, timing, location, duration and intensity) of commercial fishing operations, and to see how this affects the population structure of the model species, the Black Petrel. This study found that while there was no significantly sensitive parameter (value > 1), the most interesting result was the sensitivity value of 0 that was generated by the variable ‘size’, this indicates that there is a threshold effect for this variable, and that the size that was chosen as a baseline value was greater than this threshold, hence the no-change result. The results of the pairwise comparisons of treatment were to be expected, with treatment 15 (close to the colony, long duration, high fishing intensity, large size and active over the summer) showing the greatest significance (q = 13.229) when compared to treatment 24 (far from the colony, short duration, high intensity, large size and active over the winter). It is hoped that the results from this study can generate further research into the magnitude of the seabird-fisheries interactions, and hopefully, provide a means for assessing the efficacy of different conservation management strategies of seabirds, including but not limited to this endangered, iconic member of New Zealand’s avifauna.