A 10-metre (33-foot) whale died on Sunday after becoming tangled in a Tunisian fisherman's nets off the coast of Sidi Bou Said town north of the capital Tunis.
"At first, I thought it was a car bumper. Then I saw the whale's tail," the 24-year-old Bilel Jerbi told AFP.
He said the whale, whose species has yet to be identified, was already dying when he found it in his nets, although it was unclear what had killed it.
Jerbi then towed the carcass to port in Sidi Bou Said.
The marine mammal was around 10 metres in length and weighed "seven or eight tonnes", according to an official from the Tunisian coastguard.
"We have seen three- or four-metre-long whales before. But it's the first time for one of this size or weight," the official said, speaking on condition of anonymity.
On Sunday afternoon, fishermen and members of the coastguard, surrounded by onlookers, were still trying to drag the whale from the water, Jerbi said.
The fisherman said he had suffered financially because of the loss of the nets torn by the oversized catch, but said he was hoping to sell the whale for meat.
But the coastguard official said it would be down to the "national institute for sciences to examine it and to see what to do with it".
The institute was not immediately available for comment.
The International Fund for Animal Welfare said whales "can find ropes and nets wrapped around their fins and flukes... The whales might drown and die quickly, or live for weeks or months with the deadly gear tightening around them, leading to eventual infection, illness and often death".
Explore further: Colored lobster rope could be safer for whales