It’s been an oddly large year for chum and pink salmon in Upper Cook Inlet’s commercial fisheries.

Odd-numbered years are usually pretty thin ones for pink salmon in the area — a two-year fish, the stream systems of Upper Cook Inlet usually see their big plumes of pinks on even-numbered years. Likewise, not many chum salmon run into Upper Cook Inlet, and those that do are usually headed for west side streams and the Susitna River.

This year, the catches of both have been larger than expected. As of Monday’s fishing period, all the commercial fishermen in Upper Cook Inlet had cumulatively harvested about 163,000 chum salmon and 137,975 pinks. That’s not a lot on the scale of other pink and chum salmon fisheries around the state — for example, Kodiak’s commercial fishermen have harvested more than 6 million pinks already this year and Prince William Sound fishermen have harvested more than 22.3 million — but on even years, the commercial fishermen usually harvest fewer than 100,000 pinks, said Alaska Department of Fish and Game commercial area management biologist Pat Shields.

It’s especially odd that because during the times when the pink salmon would be running most strongly, the east side set gillnet fishermen and the central district drift gillnet fleet have only had three fishing periods, he said.

“Through (July) 31, we’re at (nearly) 150,000, and that is without much fishing at all,” he said. “This would have likely been a very large odd year.”

Both those species are of less significance in Cook Inlet than in other areas of the state — there are not as many of them and there is not as much pressure on them, and Fish and Game doesn’t run any sonar or abundance assessments on the two species in the area.

The pink salmon abundance this year has also messed with Fish and Game’s counting of sockeye on the inriver sonar on the Kenai River, according to the daily commercial fishing recording Thursday. Because the sonar counts all salmon and the biologists have to distinguish the sockeye from the pinks, they use a secondary assessment method in fish wheels, where they adjust the sonar count for how many pinks versus how many reds they see. This year, there are more pinks than they expected on an odd year, Shields said.

That sometimes happens, Shields said. There’s not a great explanation other than something about ocean conditions potentially favoring pink salmon from that brood year, but it’s happened before that one odd-year run out of a handful will be larger than the average odd-year run. The last time it happened, based on commercial harvest, was in 2009, he said.

“I can’t really explain why that happens,” he said. “I would just chalk it up to we see this occur every once in awhile.”

The other fish showing up in larger numbers in the commercial fishery is coho salmon. During the Monday period, drift gillnetters harvested nearly 40,000 coho, more than the approximately 31,000 sockeye they harvested on the same day. That’s not an unusual size historically, and may actuall be a good indication of abundance for coho salmon headed to the Matanuska-Susitna Valley streams at the head of Cook Inlet, Shields said.

“Those coho at that time of year are headed north,” he said. “That was actually a good sign to see it that way. I’m hearing that drifters are seeing a fair amount of coho again today. We believe it’s going to be a fairly good coho run this season.”

The sockeye run to the Kenai is beginning to taper off, based on sonar counts. Shields said Fish and Game manager sbelieve the run will continue to “bleed” into the river in small numbers, probably between 15,000 and 30,000 fish per day, for the remainder of the run. Current projections still show the final escapement reaching somewhere between 1 million and 1.1 million fish, he said.

Fish and Game maintains the sonar in the river until three consecutive days after Aug. 15 show less than 1 percent of the cumulative run each day, he said.

Reach Elizabeth Earl at elizabeth.earl@peninsulaclarion.com.