Biologists look to ocean for clues in Alaska king salmon collapse
Source: Craig Medred. Alaska Dispatch
What scientists know about the working of the ecosystem beneath the storm-swept waters of Alaska is a lot and almost nothing. Because for all that is known, no one has a clue as to the latest fishery mystery that has so many in the 49th state talking: Where have all the king salmon gone?
"Gone to graveyards everyone," to quote the old song "Where Have All the Flowers Gone?" Well, not quite every king is gone to the graveyards, but a bunch of them clearly left Alaska rivers as young fish never to return. This is known from the work of state fisheries biologists who track spawning numbers and monitor smolt migrations.
"We're adequately seeding the spawning grounds," said Jeff Regnart, director of the Alaska Department of Fish and Game's Division of Commercial Fisheries, "but they're not coming back."
What both state and federal fisheries biologists studying in Alaska have seen, in general, is good numbers of king salmon on spawning beds followed by good numbers of smolt going to sea. Smolt are young king salmon. The salmon lifecycle is a bit complicated: Adult fish bury eggs in gravel. Over winter, the eggs hatch into alevins that live in the gravel. By spring, the alevins are ready to wiggle out of the river bottom as fry. The fry begin feeding on various forms of insects and crustaceans. Young kings will do this for one or two summers, depending on the river system, before they began to "smolt up" as fisheries biologists like to stay.
A study commissioned by the U.S. Fish and Wildlife Service on the Anchor River, a small stream near the southern tip of the Kenai Peninsula, estimated 75,000 smolts left that one little stream in 2011. If Alaska was witnessing the sort of ocean survival seen back in the 1990s, about 4,500 of those smolts would be expected to return as adults. If Alaska were to see the sort of survival rate witnessed by Washington and British Columbia hatcheries in the mid-70s -- when they averaged 11 percent -- more than 8,000 kings would return.
State fisheries biologists figure they need a minimum of 3,800 spawners to seed the Anchor. A return of 4,500 would provide about 700 fish for anglers. A return of 8,000 and anglers would be in fat city. But 8,000 doesn't seem likely. The Anchor closed to fishing almost as soon as it opened this year. Only 3,455 kings reached the river's spawning grounds in 2009. The next year was better with 4,417, but there were only 3,547 last year despite the early closure of the stream to all fishing. Instead of a 6 or 7 percent return adults to smolts, there was a return of less than 5 percent. This year could be worse.
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