Research aims at rejuvenating Australian Bass populations in the Snowy River

Note Number: FN0550
Published: 29 May 2003

Wayne Fulton, Marine and Freshwater Resources Institute

The Department of Sustainability and Environment and the former Department of Primary Industry have committed $400,000 over two years to fund research into native freshwater fish in the Victorian section of the Snowy River system.

The study will assess fish populations and habitats in general and also focus on the Australian bass, an icon species in the Snowy River. This note describes progress to date with work on the Australian bass.

The Snowy River was a highly regarded and productive recreational Australian bass fishery, but in recent years the fishery has declined from its former levels. Recreational anglers report that, while good size bass are still available in some sections of the river, the numbers of bass caught have declined considerably.

Adult bass live in the freshwater reaches of the river, often a considerable distance upstream from the estuary. Bass migrate to estuaries from July to November to spawn before they move back upstream. Larval bass and small juvenile bass spend some time in estuarine habitats before migrating upstream.

The timing of spawning and of both adult and juvenile migrations is determined by certain environmental cues, including river flow.

Spawning and/or recruitment success in  Australian bass is known to be highly variable with typical populations having good years - in which a lot of young fish join the population - and poor years in which very few young fish are produced.

The reasons for these variations are not known but it is thought that conditions in the river may not always be favourable for either adult or juvenile bass migration and/or spawning.

To better understand these mechanisms, this project will study Australian Bass populations in the Snowy and closely related Brodribb River and compare these with populations in a nearby reference area such as the Bemm River.

The research will provide a basis for future management of the resource and will generate valuable baseline information to examine the impact of future flow restoration on fish fauna and its habitats.

This project is being undertaken by the Marine and Freshwater Resources Institute (MAFRI) at Snobs Creek.

Mr Wayne Fulton, MAFRI's Deputy Director and Project Leader, is encouraging anglers to become actively involved in this research.

"We are looking to see if there are links between successful breeding and environmental variables such as river flow."

"Over the past six months, MAFRI scientists and anglers have been catching, tagging and releasing bass, with the aim to determine their movements and breeding patterns in the Snowy River," Mr Fulton explains. "Anglers can assist by reporting the capture, including the locations and tag numbers to the researchers on the contact number printed on the tag."

Preliminary results indicate that few small (and probably young) bass are present in the Snowy River. The bass population appears to be dominated by large individuals measuring 30 to 50+cms (total length).

Analysis of the ages of the fish also confirms the field data that few young bass are present in the Snowy River. Though only preliminary, it appears that most fish are about 15 or 16 years old.

Initial field sampling indicates spawning, successful larval development and/or migration did not occur in the 2002 breeding season, as no bass larvae were detected.

These preliminary data confirm that successful recruitment for Australia bass in the Snowy River is episodic. The last good year for recruitment of Australian bass to this river appears to have been in 1987.

"As we suspected, successful recruitment appears to be a problem for the Australian Bass populations in the Snowy River." Mr Fulton says. "By the completion of the project we hope to have a handle on what part of the Australian bass's reproductive strategy is failing and why, and the factors environmental or otherwise that are contributing to that failure."

The results of the project will be a better understanding of the fish resources and the fishery, which should lead to better management and increased economic and social benefits to the local community.

The project is funded by Fisheries Victoria and the Catchment and Water Division of the Department of Sustainability and Environment.

For more information about the project please contact Wayne Fulton at MAFRI on 5774 2208

ISSN 1329-8062

Published and Authorised by:
Department of Environment and Primary Industries
1 Spring Street
Melbourne, Victoria

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