The fighting king salmon hatched in Alaskan rivers is prized for its size (15 to 90 pounds) and rich, flavorful meat. When the summer run begins on Kenai Peninsula, fishermen are shoulder to shoulder on some riverbanks, a human weir for the salmon to navigate as they return to their spawning grounds.

What makes the king quite a catch for Alaskan fishermen makes it equally valuable to the Japanese who fish the North Pacific and Bering Sea where the salmon grow up before heading home. The king's origin and destination are at the core of the U.S. argument that it should not end up in Japanese nets, as did an estimated 200,000 of them in 1983.

Months of negotiations between the State Department and Japanese government resumed this week in Seattle -- and broke down again today -- in what had been billed as a final effort to avert threats brandished by both sides.

The United States has threatened to cut Japan's allocation of bottomfish -- flounder, yellowtail sole and cod -- from the 200-mile fishery conservation zone off Alaska's coast. Japan has threatened to ban U.S. seafood imports, which totaled more than $700 million in 1984.

"The people in bush Alaska have really had their economies trashed by the Japanese interceptions," said Harold Sparck, director of Nunam Kitlutsisti, a group representing 56 western Alaska Eskimo and Indian villages. "Salmon is the most essential ingredient in our economy."

The United States allows salmon fishing in a carefully regulated coastal zone to insure that enough fish escape from each spawning area to propagate the next generation. University of Washington biologists estimate that Japanese interceptions cut Alaska's 1983 king salmon harvest by as much as 20 percent -- to 830,000 -- and aggravated an intramural fight among the state's sports, commercial and subsistence fishermen over which group is entitled to how many of the king salmon that make it home.

Sports and commercial fishermen are concentrated in south-central Alaska. Subsistence fishermen in the less populous west, most of them Eskimos and Indians, use their catch to supplement typically meager incomes and as food for their families. The only thing all three groups agree on is that they do not need the interceptions.

"They're clobbering us out there," said Henry Mitchell, executive director of the Bering Sea Fishermen's Association, a commercial group.

Official estimates place the dollar loss to Alaska fishermen at between $20 million and $40 million. But Sparck thinks the Japanese are taking far more fish than official estimates, and places the dollar loss at more than $70 million, a figure the Japanese reject.

The Japanese cite a 1952 treaty, revived in 1978, ceding them the right to fish for salmon on the high seas and within small areas of the U.S. conservation zone. "People can't understand why the U.S. is taking such a strong stance against the high-seas fishery," said Hidehiko Hirai of the Japan Fisheries Association, the country's national fishing industry group.

Besides the king salmon, the dispute involves steelhead trout and silver and red salmon, among others, that spawn in the American Northwest. The Japanese disagree with the U.S. estimate that they intercept as many as 1 million fish annually and put the figure closer to 400,000. Even the higher figure, they note, represents less than 1 percent of Alaska's record 1985 catch of 145 billion salmon of all kinds.

Japan's annual North Pacific harvest is about 30 million fish, more than 95 percent of them of Asian origin. Nevertheless, with the backing of their congressional delegations, fishermen from Alaska, Washington and Oregon have joined in demanding that the Japanese fishermen stay closer to Asia.

Japan says as many as 50,000 fishermen make their living in the North Pacific, and their trade groups have united in a powerful lobby against reducing their bottomfish allocation. The retaliatory step was first proposed in a December vote by the North Pacific Fishery Management Council as leverage in resolving the salmon dispute. "We felt it was time to fish or cut bait," council Chairman James O. Campbell said.

Three days after the vote, Japanese fishermen demonstrated at the U.S. Embassy in Tokyo. The Japanese Diet denounced any link between the salmon dispute and the bottomfish allocation, according to H. Stetson Tinkham, a State Department official.

The State Department has given the Japanese 10,000 of the 525,410 metric tons of U.S. bottomfish promised for their fleets in 1986. "It will be difficult to release any further allocations . . . if this [interception] issue is not resolved," U.S. State Department negotiatior Edward Wolfe said.

Sparck, representing Eskimo and Indian fishermen, wants to retaliate against the Japanese interception by sending U.S. salmon boats to the Aleutian Islands to intercept salmon before they migrate back to Japanese and Soviet spawning grounds. The state's fish and game board will consider Sparck's proposal at a March meeting.

Any move by Japan to ban U.S. seafood imports would hit Alaska especially hard. In 1984, Japanese bought $271 million worth of the state's seafood products. But the ban would also hurt Japanese interests, since much of the seafood is bought from Alaska- and Seattle-based processors owned by Japanese companies.

A seafood import ban also would hurt the fledgling U.S. trawler fleet, which is rapidly expanding its share of the bottomfish catch and sells much of it to Japan.

"The Japanese are a very, very patient people and don't want to express an opinion," said Yoshimi Suenaga, a fishery officer with the Japanese consulate in Anchorage. "But . . . Japanese opinion has gotten big. This is a very emotional issue."