Fish surveys continue to show positive results

Recent fish surveys in the Thomson River have seen the highest catch rates of Tupong since targeted surveys began in 2004.

“This is another good result and continues the increase we’ve seen in fish populations over a number of years,” said Dr. Stephanie Suter, Environmental Water Resource Officer with the West Gippsland Catchment Management Authority (WGCMA).

Fish surveys in the Thomson were conducted by teams from the Authur Rylah Institute and Austral Research in early February and saw increased numbers of both Tupong and the Australian Grayling, which is listed nationally as a vulnerable species, compared to previous years.

“Wet conditions combined with multiple years of targeted environmental flows from the Thomson Dam has certainly played a large part in allowing this lift in numbers. The maintenance of baseflows and large freshening flows, mimicking those that would have occurred naturally provides an environment more conducive to all sorts of aquatic life, including these particular fish.”

Of note from the WGCMA perspective are the fish numbers in and above the recently constructed fishway at the Horseshoe Bend Tunnel site.

The fishway was completed in 2019 to allow migratory fish, particularly the Grayling to move up the Thomson to its upper reaches.

“Seeing a return of Tupong above the fishway is evidence the fishway is enabling fish passage upstream, particularly for native migratory species.

It’s a strong signal that river conditions and environmental flows are providing both the upstream connection and the flow cues favourable to our native species.

It’s very encouraging and we look forward to seeing further number increases, in species such as grayling, turning up in fish surveys in coming years,” said Steph.

The survey team found three Tupong above the fishway and one passing through the fishway. Record numbers were also found in the lower section of the river, bolstered by migration of a large number of juveniles into the river.

Nineteen Australian Grayling were found in the mid to lower sections of the river also.

“So, what we see here is encouraging on a number of fronts,” said Steph.

“Overall, the numbers of fish like the Tupong and the Australian Grayling are up, indicating good conditions and the likelihood of more fish found throughout the river system in coming years.

“We’re also seeing fish being caught in more than one location, indicating a diversity and breadth of the population and another positive indicator that we will see more upward migration, through the fishway in coming years.

More information including videos of the Thomson River Fishway project can be found at wgcma.vic.gov.au

A survey team from the Authur Rylah Institute and Austral Research on the Thomson River.
One of the surveyed Tupong from the Thomson River.