Seals on a beach. (Olivier Hoslet/EPA-EFE/REX/Shutterstock)

It's a grim little mystery: Seals are winding up dead on the shores of northern France.

Since January, at least three seals have been found dead on the Cote d'Opale, a burst of shore near the Netherlands. An animal conservation group is offering about $12,000 to anyone with information about the killings.

The weapons used have varied. According to the French newspaper Nord Littoral, two of the seals had bullet wounds. Autopsies revealed that the bullets were most probably fired using a hunting rifle. The third seal may have suffocated or been strangled.

Sea Shepherd, the group offering the reward, worries that other seals also have been killed but that their carcasses haven't been found. “We don’t always find the carcasses, and there’s not always an autopsy,” Lamya Essemlali, the regional head of Sea Shepherd, told the paper. “But as far as we know, there aren’t similar cases on the other beaches in France. This is specific to the northern shore.”

Who is behind these gruesome deaths is not known. But there are some suspects. Chief among them: local fishermen, who have formed an anti-seal collective. The seamen say the seals deplete the local fish supply, making it harder for them to do their jobs.

Fabrice Gosselin, president of the collective, dismissed as ridiculous the accusation that fishermen might be responsible for the killings.

“What nonsense,” he told Europe 1, a French radio station.

“I find it hard to believe that this is the work of a fisherman,” he said. “Trying to accuse us of killing the seals is utter folly. The reward should go to the penniless migrants in Calais. They need the money more than the seals do.” The coastal city of Calais has become the symbolic epicenter of France's migrant troubles. The migrants in Calais, most of whom are focused on making it across the border into Britain, are often stuck in stateless limbo and squalid conditions.

But Essemlali isn't so sure that the fishermen are blameless. “This anti-seal collective may or may not be directly responsible for poaching, but it is certain that it is responsible for a climate of hatred and resentment toward these animals,” she said, according to Europe 1.