NZ fur seal breeding range and population size have increased since the cessation of commercial sealing and the species is generally considered to still be in the process of recovering. Concern about large numbers of NZ fur seal deaths in the commercial trawl fishery for hoki on the West Coast South Island (WCSI) of NZ in the winters of 1989 and 1990 led to the initiation of a long-term population study of WCSI NZ fur seal breeding rookeries by the Department of Conservation.
This study has operated continuously since the 1990/91 breeding season and has focussed on pups born at Wekakura Point, Cape Foulwind and Taumaka Island collecting mark-recapture observations for population size estimation and individual biometric measurements according to a consistent methodology. These study rookeries comprise approximately one-third of NZ fur seal pup births along the WCSI, including the Fiordland region.
All three of the WCSI rookeries have declined in terms of estimated pup numbers, by ~80% at Wekakura Point, ~70% at Cape Foulwind and ~35% at Taumaka Island within the study period (comparing 2016 estimates with the respective maximum for that rookery). The demographic causes of the protracted decline in pup numbers are unknown.
It is recommended that field observations continue at all three rookeries: Wekakura Point and Cape Foulwind are identified as priority populations due to their poor status and close proximity to commercial trawl fishing grounds. In addition, it is recommended that resighting effort is undertaken of the large flipper-tagged population to determine the demographic causes of population change and to identify marker years when external stressors impacted on the population.
Roberts, J., Neale, D. (2016). Census & individual size of New Zealand fur seal/keneko pups on the West Coast South Island from 1991 to 2016. NIWA Client Report for the Department of Conservation. 28 p.