Issue 111, 23 January 2004

Co-operative Response to Native Fish Kill in the Goulburn River

On 14th January, Goulburn Murray Water (GMW) reported to Fisheries Victoria that there had been a fish kill on the Goulburn River, below the Goulburn Weir at Nagambie. Dead trout cod, carp, trout and galaxias were identified. GMW collected dead fish and water samples along with the EPA for testing.

GMW immediately undertook measures to improve water quality in the affected reach by releasing water from higher in the water column using a different set of gates on the weir. Previously water had been released lower in the water column that can have lower dissolved oxygen (DO) levels.

Samples of dead fish were analysed and disease or chemical poisoning were not identifiable as a cause. GMW water quality monitoring suggests that very low dissolved oxygen levels was a likely contributor, however the reason for the low DO levels is unknown. Fish become stressed at DO levels less than 5 mg/L. DO levels in Lake Nagambie and immediately downstream in the Goulburn River were reported to be less than 1 mg/L – levels that are lethal to fish. Nevertheless information collected by various agencies remains insufficient to confirm the cause of the fish kill, -further investigations and monitoring of DO is continuing. A fish survey to determine the remaining fish population is planned.

On the 16th and 20th January, Fisheries Officers, GMW and EPA staff discovered more dead fish up to 7 to 8 kilometres downstream from Nagambie Weir. These included several golden perch, trout cod, redfin, silver perch, carp and over 90 Murray cod, the largest of which was estimated to weigh 110lb. These fish appear to have been dead for some time and may have been killed in the initial incident.

GMW increased water flow down the Goulburn River to 800mg/day to flush and clean the affected reach.

A number of the species, namely trout cod, Murray cod and silver perch are recognised in State and Federal legislation as having conservation significance.

Today, teams from Fisheries Victoria and GMW are working to remove dead fish from the river using boats to access floating fish. This should reduce the likelihood of Australia Day holiday makers encountering decomposing fish carcasses. GMW is arranging for dead fish disposal.

Anglers and holiday visitors to the area should not take dead fish and should avoid swimming in areas where dead fish are observed.

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