Science saves small fish

Science saves small fish

23 Nov 2010

Critical to the health of our wetlands, the Murray hardyhead has escaped extinction, thanks to the efforts of La Trobe University fish ecologist Iain Ellis and the National Murray hardyhead Recovery Group.

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Transcript

Narrator:

Australia has about eight species of small native fish called Hardyhead, which are critical to the life and health of our rivers and lakes. Probably the most threatened is the Murray hardyhead. This fish has managed to escape extinction during the recent drought due to the efforts of La Trobe University fish ecologist Iain Ellis and the National Murray Hardyhead Recovery Group.

Iain Ellis:

As a small bodied fish they forage on zooplankton and small invertebrates, particularly mosquito larvae so they help control those numbers, those animals, and they're also a valuable food source for some larger fish which can survive in these saline environments and particularly for some of the birds that migrate and often breed around these saline environments. So they are quite an important food source particularly when they are abundant.

Narrator:

The fish live on the fringes of the flood plain in more saline environments, which were common throughout the Murray-Darling river system before European settlement.

Iain Ellis:

In the late 1990s there were probably about eight or nine known populations of Murray hardyhead surviving in Victoria alone and probably another half dozen in South Australia. It was known to be extinct in NSW, with only three remaining populations in Victoria and only a handful in South Australia. The extinction of each population causes a severe dent in the long-term viability of this species.

Narrator:

He says the species is in big trouble due to the recent extended drought and regulation, for Riverboat navigation and irrigation.

Iain Ellis:

Prior to regulation, the river would flood every three or four years and a lot of these outlying areas that contain Murray hardyhead would reconnect, the fish would be able to wash downstream or swim upstream and occupy new habitats. With the instigation of river regulation we seem to have a lot of wetlands directly upstream of the weir system, which remain too fresh because they are constantly full of fresh water, or wetlands downstream of the weirs that have dried out due to the drought or reduced water inflows.

Narrator:

Mr Ellis and his team at the Mildura Murray Darling Freshwater Research Centre were contracted to salvage the fish from dwindling wetlands including Lake Hawthorn, which has since dried up completely. They brought the fish to their Mildura campus laboratory, and nurtured them back to health. Here the fish lay their eggs suspended from sticky filaments on the fronds of artificial plants. After a few days, the eggs are transferred to a larval rearing tank where they hatch and develop into adults. Ian Ellis: In collaboration with the Victorian and South Australian governments we have managed to salvage fish from seven different locations, which are all the known locations where the species still survives, and that's important because we can then maintain the genetic diversity of this species across its current range, which will really be beneficial for the long-term survival of the Murray hardyhead.

Narrator:

So far around 300 fish have been released back into the wild, in Victoria and South Australia. Additional wetlands are being investigated as potential new translocation sites for the Murray hardyhead.

Iain Ellis:

To get them back to the status they had prior to European occupation we would need the system to flood quite regularly so these isolated populations could be connected through floodwaters back to the river system and the fish could then spread back out into hundreds of fringing wetlands along the Murray system. The research we've conducted on Murray hardyhead has probably served as a good example of how to better understand threatened species and their management required to both conserve these species and to recover them, so down the track we are better equipped to conserve some of the other threatened species in the aquatic environment.

Narrator:

All of which, he says, is important, not just for the fish, but for local communities along the river striving for long-term viability of their ecosystems, as well their tourism and agricultural industries.

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