The case of the Pedder galaxias

Lake Pedder in south-western Tasmania was the largest glacial outwash lake in the Southern Hemisphere (Plate 25.1). In 1972 the Tasmanian state government submerged it under 50 m of water to create a huge dam to generate hydro-electricity. They also sanctioned release into the dam of brown trout (Salmo trutta), a non-native predator, for recreational fishing. These controversial actions contributed to the emergence of the environmental movement in Australia and may even have spawned the first green political party in the world.

The Pedder galaxias (Galaxias pedderensis) (Plate 25.2) was endemic to the original Lake Pedder. Following impoundment it initially increased in abundance before declining dramatically in the 1980s, probably because of predation and competition from climbing galaxias (G. brevipinnis) and trout. In 1992 the Pedder galaxias was formally recognised as ‘endangered’ and likely to become extinct in 5 years if no action was taken.

The Inland Fisheries Commission of Tasmania studied the life history, diet, conservation status and management of the Pedder galaxias and found the species in only three of 117 creeks in the area and only 68 individuals in the two creeks surveyed intensively.

Three management options for saving the species were (1) protection of existing populations from ‘threatening processes’ (predation and competition from brown trout and climbing galaxias), (2) captive breeding or (3) moving a portion of the wild population to a place without the threatening processes.