Government shark tally queried by scientists

Scientists have criticised Government shark number estimates.
Scientists have criticised Government shark number estimates.

‘I think it’s very unprofessional and inappropriate because they are making inferences from inappropriate data sources using computer models,’ University of Queensland principal research fellow Jennifer Ovenden said.

The two-year study conducted by Dr Ovenden and four others from the university’s Molecular Fisheries Laboratory was peer-reviewed, after it found a separate great white population from Bass Strait to WA with an estimated 693 mature animals, including about 350 females.

Last week, the Government recognised the Queensland study of a separate population from Bass Strait to WA, but not the estimated numbers in its draft report based on computer modelling for current and future great white numbers, to be used in a Public Environmental Review (PER) of the cull’s extension.

‘I think it would have been prudent to have at least one model where they used our mature individual estimates,’ Dr Ovenden said.

The Government’s report said 25 great whites and 1000 tiger sharks could be killed over three years, after 16 scenarios estimated WA great white numbers were 834 to 9700 animals, of which 50 to 100 may be commercial fishing by-catch each year.

The report said median estimates of 3400 to 5400 great whites had a ‘high likelihood’ because they conformed with initial data sources put into the modelling, including other population surveys, divers’ sightings and attack records.

However, when gauging populations, if 10 females were culled annually for three years, the report removed scenarios with the lowest populations of 834 and 1046 animals, and those closest to the Queensland study’s estimates, because they were not ‘consistent’ with at least four of the data sources.

Dr Ovenden said killing 10 per cent of 350 breeding females each year would affect the population.

The Department of Premier and Cabinet did not respond to questions.