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POP2015-05: New Zealand sea lion monitoring at the Auckland Islands 2015/16 (PDF, 4,409K)

Summary

Pup production was estimated for NZ sea lion colonies at Sandy Bay (n=321), Dundas Island (n=1,347), Figure of Eight Island (n=59) and South East Point (n=0); with total pup production for the Auckland Islands in 2015/16 estimated as 1,727. The estimate for 2015/16 is 10% higher than for 2014/15 and is 15% higher than the lowest ever estimate for pup production in 2008/09.

The steep decline in total pup production seen from 1997/98 until 2008/2009 appears to have leveled off although total pup production is still significantly lower than the peak in 1997/98. 

Estimates of pup mortality to the date of the pup production estimate in mid-January are broadly comparable to previous ‘non-epidemic’ years. However, these figures do not represent full season surveys and are not directly comparable to data collected prior to 2012/13, and so should be viewed as a minimum. Pup mortality estimates to the date of pup count are: Sandy Bay 4% (to 15 January 2016), Dundas Island 9% (to 18 January 2016) and Figure of Eight Island 10% (to 9 January 2016) and overall for all sites 8%.

Mean pup weights at Sandy Bay were 13% and 10% higher than 2014/15 for males and females respectively. Mean pup weights at Dundas Island were 8% and 12% lower than 2014/15 for males and females respectively. Mean pup weights at Figure of Eight Island were 2% lower than 2014/15 for both sexes;

Seven hundred and fifty seven pups were marked at the Auckland Islands including: Sandy Bay – 198 flipper tagged and microchipped, and 110 microchipped only (Note that this was a new protocol implemented in 2014/15 with only approximately 50% rather than 100% of pups being tagged at Sandy Bay); Dundas Island – 400 flipper tagged only; and Figure of Eight Island – 49 flipper tagged only;

Preliminary provisional diagnosis for cause of death of the 33 dead pups in sufficient state for necropsy includes 61% bacterial infection (suspected with Klebsiella pneumoniae), 12% open diagnosis (decomposed, scavenged or no significant findings), 21% starvation, 3% trauma and 3% intestinal perforation.

Between 11 November 2015 and 20 February 2016, there were a total of 6,667 resights of marked NZSLs of which 6,411 were suitable for use (i.e. contained sufficient information allowing positive identification). This season was shorter than the previous two field seasons, and thus fewer represents resight records were collected.

In response to previous pup mortality in holes at Sandy Bay, wooden ramps were installed in 2013/14 and 2014/15 in streams and mud holes. This season no dead pups were found in waterways with ramps and from a limited sample of observations at Sandy Bay, 49 pups were observed exiting or were rescued from streams/holes that represented a high or extreme risk of mortality. Overall this programme of work has been very successful and has led to a direct reduction in NZSL pup mortality;

A considerable amount of additional research was completed including assessment of tag loss, microchip loss, shark scar rates, a preliminary case control study investigating pup mortality and a range of other monitoring projects.

Publication information

Childerhouse, S., Muller, C., Burns, T., French, R., & Kay, E. 2016. Final Report for CSP Project New Zealand sea lion ground component 2015/16. Report prepared by Blue Planet Marine for the New Zealand Department of Conservation, Wellington. 52 p.