Archives for March 21, 2007

The World Wildlife Fund (WWF) has just released a report entitled ‘World’s Top 10 River’s at Risk’.

Australia’s Murray-Darling is included in the top 10. But it’s two rivers, so maybe the title should be ‘World’s Top 11 River’s at Risk’?

The report goes onto state that, “The Murray and Darling Rivers have great variability in year to year flows, and their ecology is driven by large floods covering their extensive flood plains and intervening dry periods.”

This may be the case for stretches of the Darling River, but the Murray is now a completely regulated system which, has even during this worst drought, been mostly full of water.

Anyway, this new report which has generated much publicity for WWF has identified the “key threat” to the Murray-Darling as “invasive species, especially from aquarium trade”.

But, interestingly, key invasive fish species identified in the report were not introduced recently or from the aquarium trade.

According to the new WWF report, native fish species such as the Silver Perch, Freshwater Catfish and the large Murray Cod are all “in rapid decline” while numbers of invasive species have significantly increased.

The report cites a government report, Barrett 2004, and a World Resource Institute website, WRI 2003, to support the contention that numbers of native fish are in decline and another government report, but also on the native fish strategy, MDBC 2005, as evidence numbers of invasive species are on the increase.

But none of these reports included good credible data on changes in numbers of invasive or native fish species.

The government’s native fish strategy was written by ecologist Jim Barrett. I contacted Mr Barrett when I was writing ‘Myth & the Murray: Measuring the Real State of the River Environment’ back in 2003.

Based in part on information provided by Mr Barrett, I wrote in that report that, “Since the 1980s, carp numbers [a key invasive species in the Murray River] have been observed to decline and downstream of Yarrawonga, numbers are thought to be about half what they were in 1997 and are now estimated to represent 21 per cent of total fish numbers. According to the Murray Darling Basin Commission (MDBC) a likely explanation for the decline in carp numbers is that the initial population boom resulted in an overutilization of available resources and subsequent reduction to equilibrium carrying capacity for this species. In contrast, local fishermen attribute the observed reduction in carp numbers to predation from an increasing Murray cod population.”

The WWF report acknowledges that, “since 1996 A$2 billion has been allocated to recover water to increase environmental flows and restore fish passage for the lower 1,800 km of Murray River.”

But in the next paragraph, without providing any data, falsely concludes that “despite these worthy initiatives, the ecological health of the rivers continues to decline.”

But even the typically pessimistic head of the Murray Darling Basin Commission (MDBC) Dr Wendy Craik recently described the “visionary Native Fish Strategy” as a success with “solid evidence” that native fish are using the new innovative fishways built as a part of the sea to Hume Dam fish passage program. Furthermore, Dr Craik claimed another success in the “resnagging” project in which large tree stumps, or snags, are placed strategically into rivers. The snags provide refuge from fast-flowing water and help to recreate original river habitats for native fish.”

But when is the MDBC, or WWF, or someone else, going to start collecting some good credible data on fish numbers?

In summary, the WWF report ‘World’s Top 10 River’s at Risk’ which is making news today, is about 20 years out of date at least with respect to the Murray River. Indeed while numbers of native fish have on average, probably declined since European settlement, with a crash in Murray Cod populations in the early 1960s, there is evidence to suggest numbers of native fish, including the Murray Cod, are now on the increase while invasive species are on the decline. So the WWF has got it all the wrong way around. Then again, they are perhaps more interested in ‘hand-waving’ than river ecology.