Massive Die-Off of Rare Sea Lions

New Zealand's Minister of Conservation, Nick Smith, formally closed the Auckland and Campbell Islands to visitors last Thursday "in response to potential risks to human health from the mystery illness that has caused mass fatalities of New Zealand sea lions," the department said in a press release.

"It is wise to take a cautious approach, given that scientists have not yet identified the cause of the sea lion deaths. I have sought and received advice on the potential risks to humans. The advice [from public health authorities]" Smith said, "is that the risk is iow, particularly if the cause of death is a virus or biotoxin. There is a greater uncertainty however, if the cause is bacteria. They have recommended that until more information is known, access for all non-essential persons be restricted."

Scientists hope to reduce the mystery of the vast sea lion mortality rate in the area with preliminary autopsy results that are due Monday.

Although emphasizing that it was impossible to accurately estimate the total loss, New Zealand Department of Conservation (DOC) marine mammal expert Mike Donoghue revealed that the death rate of the sea lion pups -- left close to shore while the mothers foraged for food for three to five days before returning -- was already 48 percent, and was likely to increase.

It was difficult to know when, or if, the mothers would return, Gales said.

Some 95 percent of the sea lions breed on Dundas and Enderby, two small islets in the Auckland and Campbell island groups. Located about 250 miles south of New Zealand's South Islands, the two islands collectively occupy the land area of perhaps a few football stadiums.

A virus, a bacteria or a biotoxin were listed by Donoghue and echoed by Smith as the three most likely causes of death, although it could be weeks before any definite results were available, he said.

"We don't know how many adult females we've lost," Donoghue explained. The only way to measure this is to keep track of how many sea lion pups are born over the next few years and make a comparison." In addition to the females and pups already lost, the loss of females, who attend to the pups after birth, signifies the likelihood of an additional loss of pups.

On Enderby Island, Gales noted, the pups appeared to be mainly dying of starvation, with some disease deaths still occurring, while on Dundas the main cause remained a mystery. At Davies Point on Campbell Island, two of six adult females appeared to have symptoms and there were 24 dead pups.

Once distributed throughout New Zealand from the tip of North Island to the deep sub- Antarctic at Campbell Island, the mammals were nearly brought to extinction by early 19th Century commercial sealers. A more recent concern has been the accidental killing of sea lions in the trawl fishery for squid around the Auckland Islands.

New Zealand's only endemic seal species, the sea lions have been protected since the late 19th century. Ministers of Conservation and Fisheries have set a catch limit for sea lions for each of the past four years, and last year closed early because the catch limit of sea lions was exceeded.

DOC scientists arrived at Enderby Island in mid-January and noticed nothing abnormal. However, when weather conditions permitted a return visit to Dundas on January 26, the team found some 700 recently dead pups. Dying pups often showed spasms and paralysis, with symptoms including ulcerated anuses and vaginas and head lesions.

"Fewer adults than usual were on the beach, but at that time there were no signs that the older animals had been affected," Donoghue said. "Returning to Enderby, the team soon found that the pups were beginning to die there also. In addition, adult females started showing signs of paralysis. Afflicted animals also had small raised lesions on the belly and neck," he added.

Smith, before closing the isalnds to tourists, had announced that a decision to review the sea lion bycatch from the squid fishery would be made later in the month following further information on the cause of death.

"If the population is at risk following this incident," Smith added, "there may be further steps that the Government needs to take to ensure the sea lion's protection."

Other sources have indicated that the Massey University team has ruled out the distemper virus that 10 years ago killed some 17,000 harbor seals in Europe.

Although initially it was believed that a virus may have caused the deaths, so far they have found no evidence to support that. Cetacean Investigation Center director Per Madie acknowledged that after initial studies they were still no closer to understanding the cause of the sea lion fatalities.

Madie added, however, that it is "highly unlikely" that the entire sea lion population would become extinct, since a threatening organism would first destroy itself by killing off its host.

The already endangered species of sea lions face problems in many parts of the world from accidental trawler catches, "kill" policies, competing fishermen, depletion of their food supply in various locations, and apparently, in some areas, from the impact of El Nino, which has spread warm-water currents and disrupted fishing seasons as fish migrate elsewhere.