THE IMPACT OF THE FUR SEAL INDUSTRY ON THE DISTRIBUTION AND ABUNDANCE OF CAPE FUR SEALS ARCTOCEPHALUS PUSILLUS PUSILLUS ON THE EASTERN CAPE COAST OF SOUTH AFRICA

Abstract

SUMMARY The present paper provides a review of the former distribution and abundance of Cape fur seals, Arctocephalus pusillus pusillus, off the Eastern Cape coast of South Africa based on available historical records. It identifies the distribution of Eastern Cape seals before commercial sealing began; documents sealing activities off the Eastern Cape coast during the 19th and 20th centuries, and discusses current population trends in relation to past exploitation regimes. The importance of the Eastern Cape population is discussed in relation to the total population. Cape fur seals were valued primarily for their fine quality furs. Other products included oil from the blubber; leather from skins of old seals; and vitamin A from the liver. Exploitation by Europeans began near the Cape of Good Hope in 1610. By the end of the 19th century more than 20 colonies had been extirpated. On the Eastern Cape coast, Cape fur seals inhabited six islands in Algoa Bay (Stag, Seal, Black Rocks, St. Croix, Jahleel and Brenton) and two sites in Plettenberg Bay (Seal Point on the Robberg Peninsula and Beacon Island). Soon after British settlement of Algoa Bay in 1820, the St. Croix and Bird Islands were leased to individuals by the governor of the Cape Colony (Lord Charles Sommerset) at an annual rental, for fishing and sealing purposes. More than 18 000 seals were killed by commercial sealers in Algoa Bay between 1822 and 1825; > 2 935 between 1831 and 1850; c. 3 516 between 1851 and 1876; > 1 763 in 1907 and 1908; and > 500 between 1943 and 1949. Harvest figures for Plettenberg Bay are unknown. Available evidence suggests that seals had been extirpated from St. Croix, Jahleel and Brenton Islands in the late 1850s; Seal Point between 1857 and 1890; Stag Island in the mid/late 1800s; Seal Island in the early 1900s; and Beacon Island in the late 1800s/early 1900s. Black Rocks was the only colony on the Eastern Cape coast to survive commercial sealing operations. Access to Black Rocks is difficult and for that reason sealing activities were irregular. Sealing operations on Black Rocks were terminated in 1949. At present, Black Rocks supports c. 700 seals. In the last 12 years the population has decreased by 82%. By destroying seal herds through commercial harvesting, and confining the population to Black Rocks, the population is unable to build up its numbers sufficiently to stimulate colonisation on neighbouring islands. Limited space for breeding seals on Black Rocks, and the influence of storms (gale force winds and high swells) restricts the number of pups that can be reared successfully. It is unlikely that the Black Rocks population can increase quickly enough to flow onto Seal and Stag Island, without being depleted by storms. The effect of man on the Seal, Stag and Black Rocks population is therefore a permanent one. Approximately 23 000 Cape fur seals may have occupied the Bird Island group before European exploitation. The current population for the Eastern Cape coast is considerably less than its historical size.