Impacts of alien salmonids on freshwater biota in Australia: background, review of impacts, and defining the issues

• Published in: New Zealand journal of marine and freshwater research 2004-08, Vol.38 (3), p.567-567
• Main Authors: Raadik, T A, Lintermans, M, Jackson, J, Hammer, M
• Format: Article
• Language: English
• Subjects: Freshwater
• ISSN: 0028-8330

Salmonids, mainly brown and rainbow trout (Salmo trutta and Oncorhynchus mykiss) were introduced into Australia in the mid 1860s and mid 1890s respectively, and now support economically valuable recreational fisheries. These alien species have established self-sustaining populations in many aquatic environments in south-eastern and south-western Australia, and stocking of hatchery-produced fish in larger systems is undertaken when fisheries targets are not met (e.g., fish numbers or appropriate size). Salmonids have established self-sustaining populations in many waters not targeted or managed as fisheries, colonising the entire catchment in cooler upland areas of Australia. These populations usually consist of a high abundance of fish in small first to third order tributaries. These waters are infrequently targeted by anglers, and populations may not contribute individuals to downstream fisheries. Negative impacts of alien salmonids on native aquatic fauna (e.g., fish, frogs, spinycrays), mainly through direct predation, and to a lesser degree competition for resources, have been noted for over 140 years. Impacts on some faunal groups have been so severe as to eliminate entire populations and severely fragment species across their range. Despite these impacts, salmonid management is focused largely on providing improved recreational angling opportunities, whereas management of their impacts is almost non-existent. Management of the symptom of salmonid impacts, declining native species, begins only after native species have become imperiled. This presentation, part one of two, describes salmonid origins and distribution in Australia, reviews their impacts on native aquatic fauna, and outlines issues and challenges in current management, which are dealt with in part two.