Small native fish in danger

Small native fish in danger

13 October 2010

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Australia —  So it makes a change to be able to report the ATF and the Department of Sustainability and Environment are working together in an effort to save Victoria’s only endemic freshwater fish the barred galaxias from extinction.

This endangered species has only 12 known populations worldwide – all in a small area of Victoria.

The barred galaxias is a small scaleless, orange-coloured fish with dark, vertical bars, and is one of 41 species of native freshwater fish in the state.

Arthur Rylah Institute’s senior scientist Tarmo Raadik has spent 15 years researching barred galaxias, including the more widespread mountain galaxias, and is in the process of describing 13 new species.

“Taxonomically the barred and mountain galaxiids were thought to be the same species but with genetic technology we have found they are separate species and that there were many more species out there,” Tarmo said.

The terms used by fish biologists can be confusing so before going further, here is an explanation as to why galaxias and galaxiid are used.

Galaxiids is plural for a number of species. Galaxiid is a single species.

Galaxias is used when referring to a single species (barred galaxias) and is plural and singular.

There are currently 50 species of galaxiids, all in the Southern Hemisphere, occupying similar habitat to salmonids in the Northern Hemisphere.

As well as Australia, galaxiids are found in South Africa, New Zealand and South America.

Australia’s mountain galaxias is unique in that it is found at the highest altitude of any galaxiid, more than 2000m to the top of Mt Kosciuszko.

Galaxiids generally have a disproportionate representation on the Australian national threatened species list.

Tarmo said that of the 35 freshwater species listed in the highest categories, 12 (more than a third) are galaxiids.

It is introduced predators such as trout, which continue to threaten some galaxiids, mostly in very small high mountain streams.

The smaller galaxiids (up to 14cm) are a natural meal to a trout as it makes its way into the tiny spring headwater streams where it can thrive.

Galaxiids were the top predators here before trout arrived and did not evolve any natural defence to avoiding being eaten.

Many remaining populations are now only found upstream of natural barriers which keep the trout away.

Tarmo’s major concern is the fragmentation and reduction of galaxiid populations in the mountains, with fire and drought further raising the extinction risk.

“In the past there have been larger galaxiid populations nearby to recolonise affected populations,” he said.

“Unfortunately, this does not now apply to the barred galaxias and other upland galaxiids, which live out their lives in small upland waters and do not migrate. If a small population, isolated by trout, is wiped out, there is now no chance for it to naturally re-establish.”

In larger, lowland waters, redfin and trout can feast on galaxiids but the populations of galaxiids are not as threatened.

Tarmo said that in some lowland streams where there is increased habitat, mountain galaxias survived better, and even cohabitated with trout.

However, of the 13 upland galaxiid species he is identifying, nine have been seriously affected by trout predation.

Last December, 70 barred galaxias were released into a creek in an area burnt in the February 2009 bushfires. The fish were rescued from the small creek near Toolangi in the aftermath of the fires.

The recovery action was vital for the survival of barred galaxias because 90 per cent of its known habitat was affected by either the 2006 or 2009 fires.

Tarmo said the barred galaxias were held in aquaria at ARI Heidelberg until the creek and its associated vegetation recovered. Bushfires create serious problems for fish.

Former Victorian Fisheries and Wildlife officer Jack Rhodes’ memoir Heads and Tales, tells how during the 1939 bushfires, the suffocating effects of ash and silt soiling the normally clear rivers in North East Victoria wiped out most native fish, including trout cod, Macquarie perch and river blackfish, in the Kiewa, Mitta Mitta and Big rivers.

The recovery of the barred galaxias continued in June when the ARI, ATF and Marysville Youth Incorporated took part in restoring vegetation along Leary’s Creek at Marysville, which was affected by the 2009 bushfires. The fires also damaged the predator barrier but this has since been repaired.

This is the Year of Biodiversity and as Tarmo said: “The management of trout and native galaxiids is one of balance and the challenge is finding ways to facilitate co-existence”.

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