The trust said similar stranding levels were being reported across Europe, raising concerns about population impacts.
“Cornwall Wildlife Trust is calling on government and regulators to introduce the long-overdue management measures needed to better protect dolphins and porpoises and is urging concerned public to raise the issue with their MPs,” it said.
Fishermen in Mevagissey have taken their own steps to tackle the issue, including reducing the time nets are in the water.
Nick West, chairman of Mevagissey Fisherman’s Association, said: “We are fully committed to excluding the likelihood of bycatches completely.”