An army of sea lions has invaded deserted Bentenjima island off Cape Soya in Wakkanai, Hokkaido. (Provided by Wakkanai Fisheries Research Institute)

WAKKANAI, Hokkaido--An army of seal lions has invaded a deserted island here, much to the consternation of local fishermen who fear damage to their nets.

About 1,500 of the big-bellied animals have staked a claim to Bentenjima, a rocky outcrop about 1.2 kilometers off Cape Soya, Japan's northernmost point.

“In winter, not many fishing boats move near the island and also there has been less stormy weather in recent years that causes rough seas. These might be the reasons the sea lions have settled on the island,” said Yoko Goto of the Wakkanai Fisheries Research Institute.

Local fishermen have been worried about the rise in numbers of the animals in recent years.

Until just five years ago, around 100 sea lions were spotted on the island. But numbers have shot up and reached a high of 2,000 or so in June last year, according to the institute.

The sea lion, renowned for its loud honking bark that sounds like a dog with influenza, is classified as “near threatened” on the Environment Ministry’s Red List, but the mammals cause serious damage to the fishing industry.

They rip through fishing nets to feast on favored food such as octopus and herring.

An unmanned drone was flown over the island by the Wakkanai Fisheries Research Institute on March 11 to gauge the number of sea lions, a figure that is believed to have mushroomed further in subsequent weeks.

Sea lions head south in search of food from the eastern part of Russia's Sakhalin island to the coasts of Hokkaido each October and then move back up north in May.

Bentenjima island is a stopover on the journey.

The Fisheries Agency removes a limited number of sea lions each year.