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Fur Seals Flourish

When Polynesians first arrived in New Zealand, fur seals were present on virtually all areas of rocky coast. By the end of the pre-European period, Maori harvesting had confined fur seal breeding populations to the western and southern coasts of the South Island and to outlying southern and subantarctic islands. European sealers drastically reduced fur seal numbers in the southern parts of New Zealand during the late 18th and 19th centuries.

In 1894, they became protected, and since that time the population has gradually recovered, although there has been some debate as to whether seal numbers have increased or whether the apparent increase was due to redistribution of an otherwise stable population. The estimate commonly quoted for the total population of fur seals in New Zealand waters today is 50,000, but this is largely based on data collected during a nationwide survey carried out between 1971 and 1974.

In 1991, Rowley Taylor, Kerry Barton and a team of researchers from Landcare Research began a study of fur seals at the northern limit of their breeding range. Over 1,500km of coastline in the Nelson-Marlborough region was searched looking for sites used regularly by seals.

Four breeding rookeries were identified in the region, established during the 1970s and 80s. There were also 17 hauling grounds with 25 or more seals ashore in winter, and about 50 other sites where lesser numbers hauled out regularly. The summer population appears to have increased from about 70 in 1973 to about 1,000 in 1995.

Fur seal populations are best estimated from pup numbers. Young pups are easily recognised and confined to the shore. Counts of older seals are less reliable, as the number of seals ashore changes with season, time of day, and weather conditions. In 1995, about 500 pups were born, and the population breeding or born at the four rookeries was assessed as 2,410. The number of pups produced has increased at a mean annual rate of 23% since 1970, when only three to four pups were produced in the region. This rate of increase is much higher than can be accounted for by local reproduction, implying that immigration of females from other rookeries is occurring.

Taylor and Barton's study indicates that fur seal numbers are increasing and they estimate that the total number of fur seals in New Zealand waters is approximately 100,000. They predict that without further direct human impacts, fur seals should fully recolonise their previous breeding range in Nelson-Marlborough and the North Island.

Kerry Barton works for Landcare Research in Nelson