Fisheries biologist Matt Moore of Catchment Solutions, which built the fish ladder, said the results told a compelling story.

“Fourteen years of fish surveys in the Bremer Catchment have not detected Freshwater mullet, so to catch more than 1,000 in a week is an incredible result,” Mr Moore said.

“Over the years, man-made barriers to fish migration have reduced populations of Freshwater mullet and many other native species.

“The fact that we are finding Freshwater mullet now means the Bremer’s 90m long, rock-ramp fish ladder is really starting to show results.

“It is helping our native fish move easily upstream to complete their life cycle.”

Berry’s Weir was built in the 1960s to impound water for power generation and formed a major barrier to fish migration.

The fishway provides a series of steps and pools in a ‘natural’ rock formation that allow fish to easily ascend over the barrier, in this case the weir, by swimming, stopping for a rest and swimming again.

Across two monitoring days held since the fish ladder was completed, more than 16,000 fish were captured at a rate of 4,075 per day.

Of 15 different species captured, only one was not native. The median size of fish passing through the fish ladder was 34mm.