NZ sea lion monitoring at the Auckland Islands 2022/23

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POP2022-09 Auckland Islands New Zealand sea lions (PDF, 2,523 K) 

Summary

This report summarises fieldwork undertaken by the Department of Conservation Marine Bycatch and Threats team as part of Conservation Services Programme (CSP) project POP2022-09 ‘Auckland Islands New Zealand Sea Lions’ (DOC 2022).

The field team spent a total of seven weeks at the Auckland Islands (8 December 2022 – 22 January 2023); six weeks at Enderby Island, three nights on Dundas Island, and a half day on Figure of Eight Island. Direct counts of pups were undertaken each day that the team were stationed at the colonies. At Dundas Island, the team conducted a mark-recapture experiment to determine the Dundas Island pup production estimate. All live pups (258 total) at Sandy Bay, Enderby Island, were double-flipper tagged and microchipped, and 200 pups were double-flipper tagged at Dundas Island.

Resights of marked (flipper tagged/microchipped) animals of all age and sex classes were collected daily. Total counts of pups, females, sub-adult males, and adult males were undertaken daily at Sandy Bay, and weekly around Enderby Island.

New Zealand sea lion pup production at the Auckland Islands in 2022/23 was estimated as 1278 ± 23 pups (mean ± 1 SE), 24% lower than the pup production estimate from 2021/22 (1686 ± 51 pups; Young & Manno 2022). This year’s pup production estimate falls below the minimum level set to trigger reviews of both the New Zealand sea lion Threat Management Plan (DOC & MPI 2017) and the Squid 6T Operational Plan (FNZ 2019).

These results describe an unexplained and significant drop from the relatively stable pup production trend over the past decade. This could indicate a temporary reduction in breeding rate or a decline in adult female survival or fecundity. Further research is needed to determine the cause of the decline and the management implications for the species.

These results emphasise the need for continued investment in this monitoring programme, with a view to updating the demographic model for New Zealand sea lions as soon as possible. The change in pup production supports a review of the effectiveness of current management strategies to recover the species.

Publication information

Manno KL, Young MJ. 2023. New Zealand sea lion/pakake/whakahao field research report Auckland Islands 2022/23. Dunedin: Department of Conservation, 27 p.