New Zealand Fur Seals: Summary of Current Knowledge

This outline of available information about New Zealand fur seals (Arctocephalus forsteri) identifies the primary studies that contribute to knowledge of fur seals, in particular in relation to their incidental capture in commercial fisheries, as a resource for fishery managers. Some information is available to describe pup production and dietary and foraging characteristics, but this information is colony specific and often represents a small number of seasonal surveys. Although the life history is generally well understood, there is less information available on the basic population parameters of this fur seal. The current estimate of population numbers for the entire region is unknown; however, since the mid 1970s, there appear to be increases in numbers at some breeding colonies and expansion of areas colonised by these fur seals. Where several time series of data exist, such as the annual pup production data for three colonies on the west coast of the South Island over the last 20 years, the results are yet to be published.
The interaction between commercial fishing activity and fur seals has been described and quantified annually for major fisheries, especially trawl fisheries in which larger factory trawlers operate, but information that could describe the likelihood of fur seal interactions with the fishing activities of smaller vessels that operate in inshore fisheries is lacking. This report summarises the main body of literature relating to fur seal life history, distribution and abundance, diet and foraging, marine and terrestrial habitat, and fisheries interactions including factors affecting capture and mitigation methods. The main knowledge gaps identified include fur seal population dynamics, population numbers throughout New Zealand (or at least for those breeding colonies which are located close to fishing grounds), interactions between fur seals and fisheries for which observer coverage is moderate, low, or non-existent, proportion of the sex and life stages that are removed by fishing each year, and the provenance of the fur seals caught in fishing gear. The main recommendations are for a coordinated approach to define the best strategy for obtaining population parameters and determining comparable population estimates; the data from the west coast South Island main rookeries be published or released for analysis; and that the observer coverage of commercial fisheries, particularly those that are operated close to fur seal breeding colonies, is increased to provide improved estimates of the incidental captures.