State biologists and the Takshanuk Watershed Council believe “engineered log jams” placed at the head of sand bars can create overwintering habitat and drive up the number of kings returning to the Chilkat as mature fish.
“If you put more kings out in the ocean, hopefully more will come back. Given a constant for marine survival, the more you put out there, the more come back,” said Rich Chapell, area sportfish biologist for Alaska Department of Fish and Game.
Chapell supports an idea to put up to four such structures in the river, tentatively in the vicinity of 20 Mile. Shrinking returns of king salmon to the Chilkat have resulted in restrictions on sport, commercial and subsistence fishing in the past two years.
Kings spawn in Chilkat River tributaries each August, with eggs hatching the following spring. Juveniles that are produced migrate in late fall from tributaries to larger river sections, like the Chilkat River’s main channels, spending a winter before heading into the ocean the next spring.
But the winter before entering the ocean can be a killer, Chapell said. “Overwintering mortality can be as high as 75 percent depending on ice and cold.”
Juvenile kings like protected pools in the river that are near moving water, where they can find food. Beached logs naturally create such pools. The watershed council wants to stitch several logs together to create new, large pools.
The structures are engineered to withstand high-water flows and to trap additional wood, building on themselves, said Meredith Pochardt, executive director of the watershed council.
Manmade log jams have been used in Juneau and Haines, but the planned ones would be the first used for king salmon in Alaska, Chapell said. Naturally-occurring log jams appear to be on the decline between 12 Mile and 21 Mile, where an annual juvenile-trapping effort is seeing fewer fish.
“You still have the river taking down cottonwoods, producing real habitat, but we’re just seeing – over time – fewer of the log jams that we’ve seen in the past,” biologist Chapell said. “There are fewer places to catch king salmon smolt on the Chilkat.”
Chapell said he’s confident the structures would have no negative impact, as similar ones have enhanced coho salmon habitat in Washington state. There is a chance that when the river switches channels, a logjam might be left high and dry.
“The risk is very small. In a worst-case scenario, you just end up with more trees in the river, which is a perfectly natural thing. They wouldn’t do any harm,” Chapell said.
The watershed council received Fish and Game funding to design four logjams, three of which would cost about $26,000 to install and a larger one, $48,000. The council is seeking grant funding for construction and about $20,000 for five years of monitoring of the new logjams.
“We want monitoring to be able to see if (engineered log jams) are doing what they’re supposed to be doing,” Pochardt said at a recent meeting of the Upper Lynn Canal Fish and Game Advisory Committee.
The advisory committee hasn’t taken an official position on the log jams, but member Randy Jackson, a commercial fisherman, likes the idea.
Jackson compared log jams to manmade chum-spawning channels already in place in the Chilkat. “It’s the next level of the least intrusive things we can do to enhance our salmon runs.”
Jackson thinks that proceeds from a fisheries enhancement tax or from a king salmon stamp could help pay for the project. “Compared to chum channels, these are small-site projects. (The funding) is still kind of fuzzy but I think the direction for us to go in is to support in-river enhancement with the engineered log jams.”
The Haines Sportsman’s Association, representing king salmon anglers, has not taken a position on the log jams.
Biologist Chapell called the structures “kind of experimental but worth trying.”
“This is a way of protecting the Chilkat king run without reducing harvest,” Chapell said.