Australia's tuna fishers have defended a $320,000 donation to the Liberal Party, rejecting any link to an abrupt Abbott government policy shift.

The donation, $250,000 of which was made before the last federal election, was the first to be made to any party by the Australian Southern Bluefin Tuna Industry Association.

Tuna caught in Port Lincoln to be packed and shipped to Japan. Credit:Quentin Jones

The officially "overfished" tuna species is subject to high stakes international negotiations about the size of the quota. Australia and Japan have long argued over their shares of the quota and the accuracy of counts of the catch each other takes in the $1 billion fishery.

Nearly all the bluefin in the 5000-tonne Australian quota is netted live to be grown in sea cages at Port Lincoln, South Australia, before being sold to Japan's sushi and sashimi market.