NZ sea lion monitoring at the Auckland Islands 2012/13

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POP2012-01 NZ sea lion monitoring at the Auckland Islands 2012/13- ground component (PDF, 764K)

POP2012-01 NZ sea lion monitoring at the Auckland Islands 2012/13- aerial component (PDF, 1,200K)

Summary

The ground and aerial components of this work was undertaken in the Auckland Islands over January 2013.

Ground component- Pup production was estimated for New Zealand sea lion colonies at Sandy Bay (n=374), Dundas Island (n=1,491), Figure of Eight Island (n=75) and South East Point (n=0) with total pup production for the Auckland Islands in 2013 estimated as 1,940 – a 15.2% increase on the estimate from 2012.

Seven hundred and eighty two pups were double flipper tagged at Sandy Bay (n=347), Dundas Island (n=400), Figure of Eight Island (n=33), South East Point (n=0) and elsewhere on Enderby Island (n=2 ).

Over 2,262 tag, brand and micro-chip resightings of individual sea lions were made. All of these resightings are still being verified and validated and, once that is completed, the exact number of resightings and the data itself will be available.

The New Zealand sea lion database was used for the first time, and all of the tagging and resighting data has been entered into it.

It was a very successful trip despite being considerably shorter than previous trips and having fewer personnel. The main difference in outputs being that 67% fewer resightings of individual sea lions were recorded and these were only made in January.

Aerial component- Aerial surveys were conducted to estimate New Zealand sea lion pup production at the Auckland Islands for the 2012/13 breeding seasons, thus reducing the need to access restricted sites where the sea lion colonies occur and minimising disturbance to the colonies. We used aerial photography to count sea lion pups and establish an archival set of photographs that could potentially be used for future trend analysis. This work was to build on a similar photographic survey undertaken in January 2012. 

Specifically, we were tasked to:

1. estimate the New Zealand sea lion pup production at Enderby and Dundas Islands using aerial survey methods established in 2012;
2. provide a detailed comparison of the pup production estimate obtained by aerial survey with ground counts undertaken by the research team led by Simon Childerhouse; and
3. make recommendations for robust, cost-effective estimates of New Zealand sea lion pup production at the Auckland Islands.

In order to verify counts from aerial photographs with ground truthing, we attempted to carry out the aerial photography at the same time as a ground team collected information on marked animals and conducted counts, to gain some level of understanding of the number of pups present in pup piles, and the proportion of pups that weren’t visible from the photographs.

Publication information

This report was commissioned by the Department of Conservation, Project POP2012-01

By Childerhouse SJ, Amey J, Hamer D, McCrone A.