Upstream migration by young pigmented freshwater eels (Anguilla australis australis Richardson) in Tasmania

Abstract

During late spring and summer, upstream migrations by young pigmented freshwater eels (elvers) can be seen at stream barriers in Tasmania. The elver runs at two major hydro-electric dams, Trevallyn and Meadowbank, were sampled regularly during the period 1977-1981 and migrations at a number of smaller stream barriers throughout Tasmania were also investigated. Migrating elvers were found to be short-finned eels, A. a. australis; only a single specimen of the long-finned eel, A. reinhardii Steindachner, was recorded. Elvers sampled at inland stream barriers were both larger and older than those found nearer the sea, indicating that eels migrate farther upstream for several years in succession. Eels involved in upstream migration were found to be shorter than 25 cm, having spent up to 10 years in fresh water. Day length, water temperature and river flow may all contribute to the initiation and control of elver migrations. The numbers of elvers involved in annual migrations at major hydro- electric dams in Tasmania are substantial: the largest migration occurs at Trevallyn, where between 3 × 10⁶ and 5 × 10⁶ elvers take part each year. These elvers represent a considerable stocking poterltial and could be used to expand the local wild-eel fishery.