Ruth Williams, Cornwall Marine Officer, said there was strong evidence that pair trawling was to blame.
"A lot of them have got signs that they have been trapped in big trawl nets.
"They have broken beaks and damaged skin particularly on the fin areas which give you some idea of their distress in the nets."
London Zoo normally collects all the carcasses for post-mortem, but it has been inundated and says it cannot take any more.
That means that bodies are now being left to rot, or taken to landfill.
Environmentalists warned earlier this year that dolphins off the South West coast are in danger of being wiped out by pair trawlers.
Local fishing representatives say the local fleet is not responsible and have blamed industrial foreign vessels looking for bass.