Population changes and diet preferences of the New Zealand fur seal Arctocephalus forsteri in eastern Cook Strait

Abstract

1.1 History of New Zealand Fur Seal: During the late 18th and 19th centuries the New Zealand fur seal, Arctocephalus forsteri (Lesson, 1828), was brought close to extinction by the unregulated activities of sealers from several nations (Cawthorn et al., 1985; Mattlin, 1987; Crawley, 1990). The species was saved from biological extinction only by the increasingly poor economics of sealing, and by the imposition of a system of limited open seasons under fisheries regulations in 1875. Since that time, only small numbers of animals have been legally killed during occasional limited open seasons, and for scientific research (Street, 1964; Sorensen, 1969; Crawley and Wilson, 1976; Crawley, 1990). All marine mammals in New Zealand territorial waters are now totally protected by the Marine Mammals Protection Act 1978. This Statute was formerly administered by the Ministry of Agriculture and Fisheries (MAF) but has been administered by the Department of Conservation (DOC) since that department's formation in 1987. 1.2 Current Population Recovery: Much evidence has now been compiled indicating that the New Zealand fur seal population is undergoing a steady recovery. Successive studies in the South Island and outlying islands have documented increasing numbers of animals at known haulouts (hauling grounds or nonbreeding colonies), and the formation of new haulouts and rookeries (breeding colonies) as established colonies become saturated (Falla, In Sorensen, 1969; Crawley, 1972; Wilson, 1981; Cawthorn et al., 1985; Anderson, 1990; Taylor, 1992; Dix, 1993). An average rate of increase of approximately 2% per annum has been suggested as a likely figure (Cawthorn et al., 1985; Crawley, 1990), but a rate of up to 6% per annum has been suggested in areas on the periphery of the species' range (Crawley, 1990; Taylor, 1992). Fur seals first made a reappearance on the Wellington coastline in about 1950, at Cape Turakirae (Turakirae Head) (Gibb and Flux, In Williams, 1973). Other haulouts (nonbreeding colonies) developed at Cape Terawhiti, Tongue Point, Sinclair Head, and at Cape Palliser (Taylor et al., Unpubl. ms.). These haulouts were populated only during the winter months (i.e. between June and September) by mature males (bulls) as they migrated north from rookeries (breeding colonies) to restore the condition they had lost during the breeding, or pupping season (Gibb and Flux, 1973; Cawthorn et al., 1985).