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NZ sea lion monitoring at the Auckland Islands 2011/12- ground component (PDF, 524K).

NZ sea lion monitoring at the Auckland Islands 2011/12- aerial component (PDF, 1,570K)

Summary

The ground and aerial components of this work was undertaken in the Auckland Islands over January 2012.

Ground component- The pup production estimate for the Auckland Island NZ sea lion population in 2011-12 was 1683 ± 16, the third lowest pup production ever reported for this species. Field sightings of previously tagged, branded and/or passive integrated transponder tagged animals were collected and recorded.

Aerial component- For Sandy Bay we estimate that there were 358 (95% CI 320 – 396), 353 (315-391) and 293 (259 – 339) pups on the 11, 12 and 14 January, respectively. These estimates are based on photographs taken with the 200 mm focal length lens. When photographs of pup piles taken with the 500 mm focal length lens are incorporated in the analysis, the estimate for 14 January is 304 (269 – 339) pups.

For Dundas Island we estimate that there were 1,269 (1,198 – 1,340), 1,207 (1,138-1,276) and 1,222 (1,152 – 1,292) pups on the 11, 12 and 14 January, respectively.

With the exception of one day, the aerial and mark-recapture counts were highly correlated and varied by less than 4% at any one time. For one day, 14 January, the difference between the aerial and ground count was 15%, or 11% if photos of pup piles taken with the 500 mm lens are included in the analysis.

Note: This project underwent review by the CSP Technical Working Group on 21 October 2011 and 28 May 2012. Read the detailed reply to comments from the working group (PDF, 41K).

Publication information

Author: Louise Chilvers, Aquatic and Reporting Unit, Department of Conservation.