“We are losing a couple of hundred million fish every single year,” Mr Hansen said. “Native fish numbers have dropped by between 70 and 90 per cent since European settlement. We have done a great job of even making some of those species extinct, and making a number of them threatened.”
Industry representative group Cotton Australia held its event on Wednesday in Sydney to address concerns around the industry’s social licence to operate, inviting questions from environmental advocates, fishers, farmers and scientists.
A mass fish kill on the lower Darling River in Far Western NSW early last year sparked public outcry after images of 30 year old Murray cod belly up in a stagnant pool of shallow water were published.
State governments are responsible for regulating the volume of water extraction for human, industrial and agricultural use. But after the Darling River fish kill many in the general public pointed their finger at the cotton industry, which is the dominant water user in northern NSW and southern Queensland.
Cotton Australia chief executive Adam Kay said the industry is “always open” to working with recreational fishers, industry and government to protect fish.
“Today we had very productive conversations with representatives from the recreational fishing industry and we have agreed to work together to achieve a common goal,” Mr Kay said.
“We accept that over the recent past, we have not engaged with the broader community well enough about what we do and why we do it.”
Mr Hansen said it was “unacceptable and insane” to invest recreational fishing funds in restocking up to three million native fish to rivers each year and not stop them being “macerated” in pumps.
“In the United States fish screening on pumps has been everyday practice for 100 years. It’s legislated in many states.”
Estimates of fish killed by irrigation pumps includes biomass from all stages of their life cycle – eggs, juvenile and mature fish.
Mr Hansen said the screens used in typically more predictable US rivers were not suitable because the Murray Darling demanded heavy-duty screens to cope with the logs and debris carried along by its sporadic torrents.
“There’s trials under way, but the pebble hasn’t quite rolled off the hill when a full industry acceptance and a big drive from all the irrigation sectors,” he said.
Native fish are also under severe pressure from feral European carp, which have exploded across the entire Murray Darling Basin since their introduction in the 1950s. Carp make up more than 80 per cent of the Murray Darling’s aquatic biomass – hoovering up the eggs of native fish and out-competing them for food and habitat.
Mr Hansen said inland rivers were “almost a complete reversal” of early explorers’ accounts.
“Sturt described it as shoals of fish floating like birds in mid-air, the bottom visible at great depths. Now we’ve got weirs, dams, willows, cold water pollution, carp and gambusia [a feral US fish also known as plague minnow].”
Mike is the climate and energy correspondent for The Age and The Sydney Morning Herald.