A biologist believes the death of a Hector's dolphin in Canterbury could only be from a fishing net.

The male Hector's dolphin was found dead in Akaroa Harbour yesterday.

Those that found the mammal reported it to the Department of Conservation.

The Banks Peninsular's a designated marine mammal reserve, but set nets can be used from April to September.

Marine Biologist Steve Dawson examined the dolphin and says it's obvious how the mammal died.

"It's got sharps nicks and cuts all over it's flippers, tail flukes and dorsel fin. There's a series of criss-cross marks around the snout of the animal, which shows very clearly that it's been killed in a set net."