31,000 fish all in a day’s work

Two men with a net box next to a river.Tens of thousands of fish have been recorded flowing through constructed fishways in Mackay.

Fisheries ecologists say the soaring numbers are proof the fishways are playing a vital role in providing clear passage through a formerly disconnected aquatic ecosystem.

Recent monitoring (funded by local NRM Reef Catchments and the Australian Government) show huge numbers of fish streaming through the underwater environment.

The fish count is above published figures for previous fishway monitoring in the Murray and Burnett rivers, prompting researchers to ask if it could be among the highest recorded in Australia.

“The results have shown unbelievable numbers of fish migrating through the system,” said fisheries ecologist Matt Moore, from Catchment Solutions (fisheries research consultancy contracted to deliver the monitoring).

“We thought our initial catch was pretty good, with 3,653 fish recorded successfully ascending the fishway at the Mackay Gooseponds wetlands.

Evening scene of a river and embankments.“However, this was trumped the following day at the same site with over 18,000 fish captured in four hours in the morning, and over 13,000 fish in the afternoon – bringing the total to over 31,000 in 8 hours.

“This is by far the most fish we have ever recorded in any local fishway, and would be up there with the highest ever recorded in Australia that we know of – fishways in the Murray River have recorded up to 4,415 fish per day and in the Burnett River 4,500 fish per day.

“These are exciting results that demonstrate the importance of facilitating connectivity past fish barriers, particularly the first barrier located upstream from the estuary, even on small ordered streams.”

Thanks to the fishway, the Mackay Gooseponds constructed wetlands (located in the Mackay urban area) is now better connected to Janes Creek and the wider Pioneer River Basin.

Some of the species recorded included juvenile barramundi, red scat, crescent perch, sea mullet and empire gudgeon – all valuable environmental and socio-economic species.

Significantly, further monitoring at Boundary Creek wetlands captured 43 barramundi fingerlings, including the smallest barramundi ever monitored locally at 30 mm.

“These little guys must have moved out of their coastline habitats behind the mangroves and then migrated upstream to the wetland via the fishway,” Mr Moore said.

A disembodied hand next to water and plants.“This is extremely significant because small fish possess weaker swimming abilities than larger fish… at 30mm they have only just started swimming, as opposed to hitching a ride with the currents and tides prior to this”.

“This demonstrates that the fishways provide suitable conditions for weaker swimming juvenile fish species. This is great news for Queensland’s most important commercial inshore net fish species.”

Reef Catchments general manager Katrina Dent said it was essential organisations like Reef Catchments could continue to fund environmental monitoring.

“These are fantastic results that really contribute to our knowledge of the aquatic ecosystem, both in Mackay and nationally.

“Reef Catchments is pleased to have helped drive this research. These are the kind of figures we need to continue to secure funding to construct more fishways in priority areas.”

This project was supported by Reef Catchments and delivered by Catchment Solutions, through funding from the Australian Government’s National Landcare Programme.