Abundance, distribution and status of the New Zealand sea lion, Phocarctos hookeri

Abstract

The abundance of the New Zealand sea lion, Phocarctos hookeri, was estimated using a model that incorporated estimated pup production. Pups are born at only five sites, four of which are at the sub-Antarctic Auckland Islands, which lie to the south of New Zealand. The remaining breeding site is at Campbell Island in the same region. Pup production was estimated during the 1994/95 and 1995/96 breeding seasons from mark–recapture studies at the two largest sea lion rookeries, at the Auckland Islands (Sandy Bay and Dundas Island), which account for almost 90% of total pup production for the species. Pup production for the other sites was estimated from direct counts or, in the case of Campbell Island, from recent tagging data. Total pup production estimates for all sites during the 1994/95 and 1995/96 breeding seasons are 2640 and 2807 respectively. During the four-week pupping season, pup mortality at most sites was estimated to be about 10%. The estimates of absolute abundance based on pup production for the two breeding seasons were 11 700 (95% confidence interval (CI): 10 500–13 100) and 12 500 (95% CI: 11 100–14 000) respectively. This population abundance is among the smallest reported for a species within the Otariidae. The highly localised, and historically reduced distribution make this species vulnerable to impact and warrants particular attention from conservation managers. In particular, the potential impact of the annual bycatch of P. hookeri in a trawl fishery requires close monitoring and, ideally, some mitigation action.