Was it hungry birds, bad math, disease or something else?
That’s unclear but state fishery managers are confirming they can’t account for a high percentage of hatchery summer-run steelhead smolts and sea-run cutthroat trout reared for release last year into a very popular Southwest Washington river.
They say that 70 percent of the fish they expected to turn loose in the Cowlitz River in spring 2016 were “unaccounted for.”
Instead of 625,900 steelies and 90,600 cutts that were scheduled to go out, only 202,000 total fish did, according to the Washington Department of Fish and Wildlife.
That means 2018’s summer-run season will probably be less productive than usual, though it could also be an average fishery, depending on how the steelhead fair in the ocean, the agency claims.
The Cowlitz is the last system in the state where sea-run cutts are reared and they provide another option to salmon in fall.
It’s the latest blow for Western Washington’s premier consumptive steelhead fishery, a river which saw its early-returning winter-run program cut several years ago because it relied on out-of-basin stocks, and the death of an estimated 200,000 in-basin fry raised for return later this winter due to bacterial coldwater disease.
As for the most recent loss, a Jan. 9 fact sheet prepared by WDFW’s Vancouver office says a number of potential causes have been identified, with bird predation, counting error and disease and/or environmental causes the chief suspects.
WDFW says it has contracted with USDA Wildlife Services for hazing services for two decades but has not seen this level of predation before, nor had it been expected to increase.
“Unfortunately masking effects from predation make it difficult to quantify each factor,” the fact sheet says.
Part of the problem is that with the way fish are currently reared there’s no way to run a count and see something’s amiss, meaning a loss wouldn’t be realized until release when it’s too late to correct anything, according to WDFW.
However, the counting device is also apparently “prone to error” as well “due to its technical limitations.” It’s regularly checked and calibrated to minimize errors, the fact sheet states.
Going forward, WDFW says three corrections are being explored — improving the netting around the rearing ponds and increased hazing during all daylight hours; considering nightly patrols and installing covers to try and keep blue herons away; and Tacoma Power looking into contracting for “some level of lethal hazing,” which could be in place later this year.
WDFW operates the trout hatchery which is owned by Tacoma Power as mitigation for dams on the Cowlitz.
Both the agency and utility are also looking into ways to better estimate rearing losses in hopes of becoming more proactive about problems.
“The long-term strategy is to install full bird netting on the rearing lakes,” the fact sheet states. “This will be part of the hatchery remodel that Tacoma Power is planning and should be completed in three to six years from now. Tacoma Power is working with WDFW and hatchery design experts to explore a variety of options to meet current and future production challenges. The remodel project is in its early stages so timelines have not been finalized.”
The local fisheries biologist said it did not affect winter-run smolts, and that so far predation on the next crop of fish actually seems to be lower than average.