Fisheries

Search for tuna blood fluke diagnostic test

In Japan, tuna is a very popular fish, and those caught in the near seas are rushed to the market, but those caught in the ocean are frozen on board and stored in a freezer.

RMIT researchers are working with Australia’s tuna industry to develop a test for two parasites that threaten ranched stocks of Southern Bluefin Tuna.

The first findings from the collaboration, published in the Journal of Aquaculture, revealed the effectiveness of targeted treatments and fewer parasites.

The parasitic blood flukes, Cardicola forsteri and Cardicola orientalis, asexually reproduce in a worm found on the sea floor before emerging to infect tuna. The parasite lays eggs that enter the fish’s blood stream and lodge in the gills, causing respiratory failure that can be fatal.

Though naturally occurring in approximately five percent of wild tuna, the parasites are of particular concern for fishers ranching in areas where the host worm is more common.

RMIT lead researcher Dr Nathan Bott said current diagnostic testing methodology is fatal and involves taking samples from the tuna’s gills, blood and internal organs.

“We’re hoping to develop a new test that would only require a mucus swab from the gill of a live fish to test for the presence of the parasite. The aim is for this to be a portable diagnostic test,” he said.

The parasite found in tuna is restricted to the fish’s circulatory system and cannot transfer to humans.

The research will also make recommendations on best practice for managing the handling of fish once caught to reduce any effects the parasite may have.

The study is being undertaken by researchers at RMIT University in collaboration with the Australian Bluefin Tuna Industry Association (ASBTIA) and the Fisheries Research and Development Corporation.

Source: RMIT