Southern Bluefin Tuna stocks are unlikely to recover to pre-1980 levels by the year 2020 if current catch rates continue, a CSIRO scientific report says.

The study found there was a less than 50% chance of the stocks recovering under current catches within the next 25 years.

The results from the report indicate that large recent increases in catch by countries outside the Commission for the Conservation of the Southern Bluefin Tuna (CCSBT) are further reducing the chances of stock recovery.

The CSIRO models were based on a variety of data which measures catch levels and fishing pressures. CSIRO's Dr Ian Poiner says the models aimed to predict the effect on tuna populations of different fishing pressures and the likelihood of the stock recovering in the long-term.

CSIRO has carried out stock assessments on Southern Bluefin Tuna annually since 1982. The CSIRO assessments reflect the research results of Australian scientists and differ from those accepted by Japan and New Zealand, the other signatory nations to the CCSBT.

According to the 1996 CSIRO assessments, the probability of the stock reaching 1980 levels by the year 2020 was only 36% if known catches for 1995 continued into the future, he says.

At that time, global catches were estimated to be 14,350 tonnes. Since the study, global catches are estimated to have increased to greater than 16,000 tonnes. The increase is due to increased catches by non-CCSBT nations.

The CSIRO findings were presented to the CCSBT last year as the Australian assessment of the status of the fishery, and have been the focus of a recent Greenpeace media release.

"The research is essential for providing the rigorous scientific information about the state of the stock necessary for sound management," says Dr Poiner.

However, he says the Greenpeace media release was not correct in its claim that the CSIRO models predicted that Southern Bluefin Tuna are faced with "extinction".

Dr Poiner says that while the computer simulations do give probabilities of the stock reaching "zero", this is a simplified presentation of the results for comparative purposes. The term "zero" in the report should be interpreted as referring to the probability of the population reaching very low levels.

At such very low levels, new processes may come into play that are not included in the models. These processes can result in the fish population being maintained at low levels or being further reduced.

"The models are not structured to predict the probability of extinction," says Dr Poiner.

The CCSBT met in Canberra last week to consider quota levels for 1997-1998. The meeting adjourned without finalising this year's global Southern Bluefin Tuna quotas.

More information
Dr Ian Poiner, CSIRO Marine Research 041 970 2652