Climate change, Fish Die-offs, algal blooms, drought and water mismanagement in the Murray Darling Basin

Rob McBride and Menindee resident, Dick Arnold stand in the Darling river, holding Murray cod that have lived through decades of droughts and floods, but could not survive this human-made disaster. Image: Kate McBride

NSW Primary Industries Minister Niall Blair revealed the latest fish die-off has occurred at Lake Hume on the NSW-Victorian border. The numbers of dead fish are much smaller than at Menindee: perhaps about 1800 according to the NSW Department of Primary Industries. Cause of the deaths are still being investigated. Lake Hume is controlled by the Murray Darling Basin Authority and is currently 30 per cent full.

Niall Blair is trying to divert blame to drought and heatwave conditions rather than ongoing corruption (water theft) and mismanagement of water flows and over-allocation of water to upper Murray Darling basin irrigators (especially cotton), at the expense of environmental flows, to ensure the health of the Murray Darling river ecosystem through drought periods. The Australia Institute have now researched and published a discussion paper which holds the NSW Government and Murray Darling Basin Authority water mismanagement as culpable for the massive fish kill in the Darling river near Menindee.

Rapid Indian Ocean warming affecting marine plankton, fish stocks

The ocean heat uptake has doubled since 1997 resulting in warmer surface layers of the oceans, as well as increasing ocean warming at greater depths. One of the symptoms of this can be seen in the rapid warming of the Indian Ocean. This ocean has the largest warming trend in sea surface temperatures in the tropics over the past century. This has resulted in a 20 per cent reduction in primary plankton productivity for the period 1998 to 2013, contributing to reduced fish stocks and adding a threat to food security.

Climate change driving California native Freshwater fish species to extinction

Eighty two percent of native freshwater fish species in California, including salmon, are likely to become extinct on present trends within the next century due to climate change, reports a study lead by Professor Peter Moyle from University of California Davis.

The study - Climate Change Vulnerability of Native and Alien Freshwater Fishes of California: A Systematic Assessment Approach - found that, of 121 native fish species, 82 percent are likely to be driven to extinction or very low numbers as climate change speeds the decline of already depleted populations. In contrast, the study reported that 19 percent of the 50 non-native fish species in the state face a similar risk of extinction. Many non-native fish are likely to thrive in changed aquatic conditions, mostly at the expense of native species.

"If present trends continue, much of the unique California fish fauna will disappear and be replaced by alien fishes, such as carp, largemouth bass, fathead minnows and green sunfish," said Peter Moyle, a professor of fish biology at UC Davis who has been documenting the biology and status of California fish for the past 40 years.

"Disappearing fish will include not only obscure species of minnows, suckers and pupfishes, but also coho salmon, most runs of steelhead trout and Chinook salmon, and Sacramento perch," Moyle said.