River

Understanding freshwater catfish breeding helps with environmental flow planning

Recent research indicating freshwater catfish in Tahbilk Lagoon spawn between November and December will help shape future Goulburn River environmental watering activities.

Goulburn Broken Catchment Management Authority (CMA) Environmental Water Manager Simon Casanelia said
the freshwater catfish population in Tahbilk Lagoon on the Goulburn River was particularly significant because it
is the largest and most southerly remnant population of the species in Victoria, where it is listed as an endangered species.

“We knew that freshwater catfish generally breed sometime between September and February, but until now,
the timing of freshwater catfish breeding at Tahbilk Lagoon was unknown,” Mr Casanelia said.

“As changes in water level during the breeding season can impact on breeding success, we wanted to get better,
more reliable information to make sure water levels are not significantly changed during the critical breeding
period.”

Goulburn Broken CMA worked with Arthur Rylah Institute researchers Wayne Koster and David Dawson
between October 2015 and February 2016 to determine the timing of breeding at Tahbilk Lagoon.

Dr Koster said they used a range of trapping and netting techniques for the project that was funded through the
Victorian Government’s Threatened Species Protection Initiative - Critical Action and Strategic Partnerships
Project.

“Ten-to-15-day-old freshwater catfish larvae were collected in late November indicating they had spawned
earlier in the month,” Dr Koster said. “Bigger freshwater catfish - from 55-60mm long - were collected in mid-February and based on their length it is
most likely they also spawned in November or December. Strategies to maintain stable water levels between
November and December therefore are likely to be important in conserving populations of freshwater catfish.
Further sampling would also be valuable to better understand the timing of breeding in other years.”

A range of other native fish species were also collected, including Murray River rainbowfish, Australian smelt
and for the first time, an unspecked hardyhead. Unspecked hardyhead are now rare in the southern part of the
Murray Darling Basin.

Mr Casanelia said Goulburn River flows often increased during November and December to meet demand from
irrigators and other users.

“We will continue to work closely with the river operator Goulburn-Murray Water, Tahbilk Winery and other
water users to ensure the freshwater catfish and other native species in Tahbilk continue to flourish,” Mr
Casanelia said.

View the 2016/17 Seasonal Watering Plan for the Goulburn River here.