Conservationists say the death of three dolphins in Queensland's Moreton Bay last week should not be blamed on a fertiliser and oil spill in March.
The Pacific Adventurer lost 31 containers of fertiliser in rough seas off Cape Moreton, damaging the ship which leaked thousands of litres of oil.
But Simon Baltais from the Wildlife Preservation Society says the dolphins' deaths are more likely to have been caused by south-east Queensland's booming population.
"Dispersion of that fertiliser would have been fairly quick and I think you'll find most scientists would agree with that," he said.
"I think what we're seeing is a symptom of a bigger problem and that's the health of Moreton Bay going backwards - we're seeing increased loads of nutrients entering the bay through stormwater pollution and that could be one of the major drivers."