Despite the Columbia River’s record-shattering run of fall chinook salmon, Yakama Nation fishermen may not see a much larger harvest because steelhead and coho returns are below average.

Steelhead, considered threatened under the federal Endangered Species Act, are sometimes caught accidentally by chinook fishers. Treaty rights allow tribal members to keep such steelhead, but “tribes have to count all the steelhead caught, and once they get to the limit, they stop all chinook fishing,” said Kathryn Kostow, a fish analyst for the Columbia River with the Oregon Department of Fish and Wildlife.

The Yakama Nation decided Friday to postpone its decision on whether gillnet fishing in the stretch of the Columbia between Bonneville and McNary dams will be open next week until the catch data from this week is in, said Emily Washines, spokeswoman for the Yakama Nation Fisheries. Things are on hold while they do the math.

“That’s why we set 48-hour notices and sometimes have to make emergency closures,” Washines said. “Mostly, the fishermen are pretty used to it.”

The fishery managers use the run forecasts to adjust the season lengths and catch limits. When fish are fewer than expected, fishing is ratcheted back. While it’s more fun to scale up a season in response to fish exceeding expectations, Kostow said the management adapts either way to keep harvest at healthy levels for the fish populations.

The main steelhead run was 27 percent below its forecast and a smaller steelhead run came back with only about a third of the numbers predicted, according to data collected by a technical advisory committee that tracks salmon and steelhead numbers in the Columbia. The early coho run in September was also about a third of the forecast numbers, but no data was available yet for the late coho run.

Meanwhile, fall chinook have almost doubled the numbers predicted — 893,862 fish have been counted at Bonneville so far this year.

Kostow said that it’s not uncommon for a good chinook year to coincide with a bad coho year because the fish face very different environmental conditions. They migrate out during different seasons and then live and feed in different parts of the ocean.

The low steelhead and coho numbers aren’t that alarming, Kostow said. She said that some of the low numbers might be because the steelhead from Idaho hatcheries are coming back much smaller than usual, and since catch limits and counts are based on fish size, they aren’t being counted.

“Somewhere in their life cycle, that group of fish did not grow as big as they should have,” said Kostow.

They may never have an exact answer why. But, she added, it would be nice to know why the chinook run was so good, so they can do it again.