By Margaret Bauman
Alaska Journal of Commerce

A fisheries scientist who has spent hundreds of hours researching beneath the sea says trawling was not the lone culprit in the collapse of Bristol Bay red king crab stocks in the 1980s.

It was a combination of increased commercial fishing and bottom trawling, and a once successful reproductive strategy that is now simply a migration of the most prolific female king crab into the most heavily trawled region of the eastern Bering Sea, said Braxton Dew.

Dew has studied the demise of the Bristol Bay red king crab for the National Marine Fisheries Service for much of the last 13 years. He discussed his findings Aug. 24 at a public meeting in Kodiak attended by an eclectic group of fishermen and fisheries scientists.

"I think it was relatively new information for the bulk of the people there," said Theresa Peterson, Kodiak outreach coordinator for the Alaska Marine Conservation Council.

Following the demise of the crab, "there was an overall concern from the community to figure out what had happened, why the Japanese had it closed and what we can do to be better stewards of this area," she said.

"Braxton's research has significant implications for the future of fisheries management and the need to safeguard the long-term viability of marine ecosystems," she said. "It is important to share this research within our coastal community so that we all may gain a better understanding."

Dew, who presented a slide show followed by a question-and-answer session, said his conclusions were influenced by hours and hours of scuba diving to study red king crab in their natural habitat.

By doing some night diving, he found that the typical dome-shaped pod of crab observed resting on the ocean floor during daytime became an actively foraging aggregation at night. "It didn't take long to realize that the behavior of these crab was very organized, and that their intention was to stay together," he said. "It was also obvious that the resting crab, which were the same as the foraging crab, formed the same pod, or aggregation."

Detailed trawl sampling in Bristol Bay shows that multiple-age, mixed-sex aggregations may cover several dozen square miles in Bristol Bay, he said. While most crab species form dense aggregations while mating and then disperse, the red king crab podding occurs continuously throughout the year, he said.

"It is their intensely gregarious social structure that make red king crab especially vulnerable to man's fishing," he said.

In a paper written with NMFS colleague Robert McConnaughey, to be published by a professional journal in 2005, the scientists concluded that the population's most prolific females migrate into the most heavily trawled region of the Eastern Bering Sea. It is likely this is one factor that has kept the Bristol Bay red king crab population at depressed levels for two decades, they said.

Back in the late 1940s and 1950s, the Japanese were the only active fishing fleet in the Eastern Bering sea, he said. "The Japanese knew better than to trawl on broodstock aggregations, so in 1959 they implemented the pot sanctuary, prohibiting their fleet from trawling there. American crab managers and fishermen also recognized the area off Unimak and Amak islands as the reproductive center of the population, and lobbied in the mid-1960s to keep trawling away," Dew said.

The 1976 Magnuson-Stevens Fishery Conservation and Management Act effectively eliminated the no-trawl zone in the southeastern Bering Sea.

In the 1980s, groundfish trawling began in the pot sanctuary, which had served as a reproductive refuge for red king crab for more than 20 years. The broodstock disappeared from the Unimak area, and mature males disappeared from previously occupied regions to the southwest, Dew said.

Fishermen also became aware that several thousand crab were being caught incidentally in the groundfish nets. The so-called red bags, trawl nets plugged with red king crab, were discarded at sea without being recorded, and observer-estimated bycatch numbers remained deceptively low, he said.

A reversal in the sex ratio from a female-dominant to a male-dominant population in just four years, from 1982 to 1986, is the end product of a process that was killing off mature females 70 percent faster than mature males, he said.