NIWA, Hamilton

2003-03-17

Room I1.09 (I block, 1st floor) University of Waikato

Southern Buller's albatross (SBA) breeds on only two island groups. During the past thirty years, the Snares Islands' population has approximately doubled in size, whilst the Solanders population may have fallen by ~30%. It has been suggested that birds from the two colonies forage in subtly different areas, and suffer differing levels of fishing-induced mortality in consequence. To address this hypothesis, we require detailed information regarding at-sea distributions relative to fishing fleet distributions. We have two data- sets providing information on the distribution of SBA: counts made from merchant ships (thousands of records, but dominated by zeros, and no information on the origin/sex/age etc. of birds sighted) and satellite tracking data (few birds, but known origin and status). We present an Individual-Based Population Model (IBPM) for SBA. The model's foraging rules are derived from the satellite tracking data. By mimicking the ship-board sampling within the IBPM, we have demonstrated that distributions predicted using the IBPM are consistent with the ship-board observations at scales of 1 degree2 and greater. Thus, despite having tracked very few birds, the rules that we have derived from the satellite-tracking data yield an unbiased at- sea distribution.

(Joint work with J.C. Stahl (Museum of New Zealand, Te Papa Tongarewa) and P.M. Sagar (NIWA, Christchurch)