Right whales Eubalaena australis at Tristan da Cunha— A clue to the ‘Non-recovery’ of depleted stocks?

Abstract

Exploitation of the right whale Eubalaena australis population at Tristan da Cunha began about 1819/20, and an estimated 2500 animals were taken by French and American whalers from 1830/31 to 1834/35. Despite obvious depletion, catches continued to be taken from this stock throughout the remainder of the 19th century. Right whales began to reappear at the islands in the 1890s, and by the 1940s and 1950s were numerous enough to be considered a nuisance. Three episodes of illegal exploitation of right whales in Tristan waters by foreign fleets in the 1960s are reported. Shipboard and aerial surveys of the archipelago from 1971 to 1986 indicated that the population was greatly reduced from the level reported in the 1950s. The apparent recovery of right whales at Tristan da Cunha in the 1940s and 1950s seems to have been possible because, unlike nearly all other southern hemisphere stocks, this population was not subjected either to a shore-based fishery in the late 19th century or to a phase of coastal modern whaling in the early 20th century. An estimated 1217 right whales were killed in modern whaling in the southern hemisphere between 1904 and 1936. The apparent failure of other right whale stocks to recover under protection may have been the result of extreme depletion in 1935, so that any subsequent recovery was initially undetectable.