NZ sea lion monitoring at the Auckland Islands 2023/24

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POP2023-05 Auckland Islands New Zealand sea lions (PDF, 6,738K)

Summary

This report summarises fieldwork undertaken by the Department of Conservation Marine Bycatch and Threats team as part of Conservation Services Programme (CSP) project POP2023-05 ‘Auckland Islands New Zealand Sea Lions’ (DOC 2023).

The field team spent a total of seven weeks at the Auckland Islands undertaking the CSP project (9 December 2023 – 22 January 2024); 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 each of the colonies. At Dundas Island, the team conducted a mark-recapture analysis to determine a pup production estimate. All live pups (297 total) at Sandy Bay, Enderby Island, were double-flipper tagged and microchipped, and 200 pups were double-flipper tagged at Dundas Island.

Resightings of marked (flipper tagged/microchipped) animals of all age and sex classes were collected daily on Enderby Island. 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 2023/24 was estimated as 1457 ± 19 pups (mean ± 1 SE), slightly higher than the historic low of 1278 ± 23 pups reported in 2022/23 (Manno & Young 2023). As was the case in the previous season, 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).

 The past two field seasons have reported 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. The continued lower level of pup production compared to previous seasons supports a review of the effectiveness of current management actions to recover New Zealand sea lions in their subantarctic range.

Publication information 

Manno KL, Whyte J, Young MJ. 2024. New Zealand sea lion/pakake/whakahao field research report Auckland Islands 2023/24. Dunedin: Department of Conservation, 30 p.