Underwater dolphin detectors have been installed along the Cornish coastline.
The seven audio recording devices, known as CPODS (Cetacean and Porpoise Detectors), were installed by the Cornwall Wildlife Trust.
It hopes that by learning more about where dolphins, whales and porpoises congregate, it can reduce the number killed by fishing nets.
The CPODs are attached to offshore buoys in locations recommended by local fishermen.
An eighth CPOD is due to be floated from a site near St Agnes in the next week.
Abby Crosbie, a conservation officer with the trust, said: "It's essential that we get information from fishermen about the seabed and where to place the CPODS.
"We're protecting these species, unfortunately they are affected by accidental bycatch.
"No-one, not us nor the fishermen, want that to happen."
The 1m-long CPODS hang about 10m (33ft) down from the sea's surface.
They record the special "clicking" sound that dolphins and porpoises make.
According to the trust, about 1,100 dolphins, porpoises and whales were washed up dead on Cornish beaches between 2005 and 2008.
About 70% of the animals were victims of bycatch - getting accidentally caught up in fishing gear.
In December, the trust published the results of a 12-month trial, where different audio devices, known as "pingers", were fitted to nets on four fishing boats based in Newlyn.
It found there was a 48% reduction in the amount of harbour porpoises near the fishing boats when the devices were fitted.
Harbour porpoises are the most common victims of bycatch in inshore waters, the trust said in its report.
But the number of dolphins counted was too low to conclude whether the "pinger" was effective in keeping them away from boats.