BioEd Online

The death of another critically endangered western grey whale (Eschrichtius robustus) in Japanese fishing nets has scientists and conservationists concerned for the safety of the species — and confused as to why the deaths are happening.

In January, fishermen found the dead body of a juvenile female in fixed fishing nets in Yoshihama Bay, northeastern Japan. It was the fourth such whale to be found trapped, entangled and drowned off the Pacific coast since 2005; all of them have been female.

"We are extremely concerned at the loss of this female, which belonged to one of the most endangered whale populations in the world," said Carl Gustaf Lundin, head of the Global Marine Programme of the World Conservation Union (IUCN), in a press release on 1 February.

The population of western grey whales, which migrates along the Pacific coasts of Asia, was driven to almost extinction by whaling and other factors in the early 1900s. It has been slowly recovering since the 1960s, but is still very vulnerable. The population of grey whales at the other end of the Pacific, off the west coast of the United States, is doing fairly well thanks to strict protection measures there. But in the western population it is estimated by the IUCN that there are only about 120 individuals left, of which just 20 to 25 are reproductive females.

For a decade, until 2004, Japan recorded only two carcasses of western grey whales off their shores. Both had been stranded, and so perhaps died of natural causes, Lundin says.

That situation has changed — but no one is sure why, not even the chair of the IUCN's Western Grey Whale Advisory Panel, Randall Reeves. "I don't know whether there's a change in fishing traps and the behaviour of fishermen," says Reeves.

Some grey whales have been released alive from fishermen's nets, but others have been dead by the time they were found.

Aware of the problem

The Japanese government is well aware that whales are occasionally trapped in fishing nets. In 2001, Japan's Fisheries Agency decided to allow fishermen to sell the meat of trapped whales, partly to let them earn money to compensate for the damaged nets.

The agency advised fishermen that they could not do the same with western greys, says Ryoichi Nakamura, an official with the agency's whaling section in Tokyo, although technically there is no law to enforce this policy.

In 2006, the agency again issued a statement again advising fisherman not to sell the meat from trapped grey whales, and considered revising the law to make such action illegal. But such a change has not yet been made.

The Fisheries Agency will conduct a detailed analysis on the latest death, and present the results at the next meeting of the International Whaling Commission. But it is unlikely to take further action immediately. "We think we need measures to prevent such accidental entrapments, but we have yet to discuss any concrete actions," says Nakamura.

Toshio Kasuya, a retired researcher in Tokyo who specialized in marine mammals, says the government should take more initiative. They should call for a greater effort to get whales out of traps alive, he says, and develop technologies to prevent whales from getting trapped in the first place. Kasuya says nets that produce warning beeps may be one way of doing this.

"So far, we don't have technologies that could work effectively," Kasuya says. "And the government's efforts are far from enough."