Endangered native hardyhead fish are making a run across borders in search of a better life.

Thousands of the rare native fish are being relocated from South Australia's Riverland to a waterway in Victoria to help the population recover.

The once-common Murray hardyhead has dwindled drastically in number since European settlement, and it is now considered endangered.

Several previous initiatives have seen growth in hardyhead populations in SA’s Riverland.

Around 200 of the fish were released into the Causeway Lagoon near Berriin 2010 to help save it from extinction.

This project was backed up by an effort in 2013 to build a 2.5 kilometre drain to catch irrigation drainage at Berri and deliver it closer to the hardyhead’s home in the Katarapko floodplain.

At that time, there were only about seven known populations throughout the Murray-Darling Basin.

Now, wetlands ecologist Lara Suitor has told the ABC that moving fish to Mildura would build on these successes.

“We'll be continually monitoring those fish to determine how successful the translocation has been and to see if they establish at that site within the next couple of years or so.

“We had some pretty amazing results this February in our seasonal monitoring round.

“We caught Murray hardyheads in the thousands of from both those sites - more than 10 times the usual abundance that we catch and certainly more than anything that's been caught in the recent past,” she said.