Life is still hard in the Murray

Posted on Posted in finned, Mallee, South Australia

Heavy flows have finally funnelled their way down to the Coorong, topping up waterholes and filling the floodplains of the Murray along the way.

Many iconic plants and animals have been revelling in their newly restored habitats, refreshed by the flows. Perhaps none so much as the Murray Hardyhead (Craterocephalus fluviatilis). This small, native fish is truly hanging by a thread.

The Murray Hardyhead is a small silvery fish, reaching 8cm in length (Photo courtesy of Ian Ellis MDFRC)

Extinct in NSW, and on its way to being critically endangered in VIC and SA, the hardyhead has all but disappeared from the entire catchment. Despite being in trouble now, these fish are actually extremely tolerant and can withstand salinities close to seawater! Historically they ‘boomed’ in isolated, drying waterholes, and then redispersed once the floods came. But as the floods disappeared, so did the fish.

Relict populations of the fish are restricted to a few lakes in NW Victoria, and SE South Australia. These lakes are the only areas left that provide the fish with the salty conditions they thrive in, and the vegetation they need to lay their eggs on.

Here, for the past few years of the drought, the hardyheads were literally competing with irrigators for every drop of water. Lucky for this precious species, scientist Ian Ellis whisked a few fish away to a captive egg laying paradise, where juveniles are now being reared to protect against complete extinction.

Salvaging hardyheads from a wetland in NW Victoria
Salvaging hardyheads from a wetland in NW Victoria. (Photo courtesy of Ian Ellis MDFRC)

Scientists are waiting for the ideal time to release the next batch of fingerlings, in the hope that they will boost population health. Recent flooding has provided access to key wetlands, giving the species a chance to recolonise previous habitats and shake things up a bit in terms of genetics!!

Although long term threats such as intense flow regulation and competition from vicious exotic fish such as Redfin and Mosquitofish, are likely to remain; the recent floods have provided some long awaited relief, and a well deserved life-line for this species in distress.

Murray hardyheads thrive in Boggy Creek, near Lake Alexandrina. Photo courtesy of SA Natural Resource Management Board
Murray hardyheads thrive in Boggy Creek, near Lake Alexandrina. (Photo courtesy of SA Natural Resource Management Board)

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