Limiting Factors For Columbia River Smelt? Climate Change, Ocean By-Catch, Smaller Ocean Plume

Biologists know that the number of eulochon entering the Columbia River this year, as well as over the last few years, is relatively low. But harvest management of the fish, better known as smelt, suffers from a deficiency of run size and run timing data, according to a recent report to the Northwest Power and Conservation Council.

That makes it difficult to set recreational smelt dipping harvest on either the Cowlitz River in Washington or the Sandy River in Oregon, according to Laura Heironimus, biologist with the Washington Department of Fish and Wildlife. She outlined the recovery efforts for eulochon by the states of Washington and Oregon at the April 9 Council meeting in Portland.

A limited conservation-level commercial research fishery in 2018 designed to help evaluate run strength caught just 110 pounds of smelt (a measurement of spawning stock biomass) and that, she said, signaled another poor run of smelt to the Columbia River. Because of that low test catch, both Washington and Oregon chose to forego recreational smelt dipping for yet another year.

The research fishery, run each year between 2014 and 2018, generally yields about 9,000 pounds of smelt. This year’s forecasted smelt run size is even smaller than in 2018, so the two-state Columbia River Compact staff this year recommended not to initiate the test fishery and alerted recreational smelt dippers that a smelt fishery on the Sandy and Cowlitz river in 2019 would be unlikely.

(See CBB, March 26, 2019, “Due To Low Numbers Fishery Managers Say No Smelt Dipping This Year,” http://www.cbbulletin.com/442352.aspx)

After two to five years growing in saltwater, eulochon move into rivers in early spring where they spawn in very cold 4 to 10 degree Celsius water (39 to 50 degree Fahrenheit). They typically move into the Columbia River in late February and March and, although they were thought to once have traveled as far up river as Celilo Falls, the largest runs now are into the Cowlitz and Sandy rivers. As semelparous fish, they die after spawning and the eggs incubate while traveling downstream on river currents.

The Columbia River run of the fish, as well as other smelt runs that are a part of the Southern DPS eulochon, went into decline in the mid-1990s and that prompted action that resulted in the Washington-Oregon Eulochon Management Plan in 2001. The fish was listed as threatened under the federal Endangered Species Act March 18, 2010. NOAA’s Eulochon Recovery Plan for the threatened species is at https://www.westcoast.fisheries.noaa.gov/publications/protected_species/other/eulachon/final_eulachon_recovery_plan_09-06-2017-accessible.pdf

Both recreational and commercial fishing was allowed over the years. In fact, according to a 1978 creel survey, the recreational dip net harvest was about the same in pounds of fish as was the commercial harvest.

Recently, recreational harvest of the fish, typically using dip nets from the shore, has been spotty, with a one day harvest on the Cowlitz River in 2016. But the popularity of smelt fishing was evident in that fishery with an estimated 16,700 angler trips and 141,000 pounds of smelt harvested. The size of smelt runs has been in significant decline since.

However, according to Heironimus, harvest in the Columbia River system doesn’t make the top five list of limiting factors in the river’s eulochon population, as determined by a 2010 study. At the top of the list is climate change’s impact on ocean conditions.

Second on the 2010 list is ocean by-catch, particularly by the pink shrimp fishery, but that, she said, saw significant improvement when boats began illuminating the front of the nets with LED lights. It is a change that reduced bycatch by 90 to 95 percent in the pink shrimp trawl harvest. An added benefit to the trawlers is that they have a “cleaner” product having to separate out so many smelt.

Following bycatch on the list of limiting factors is climate change impacts on freshwater habitats where eulochon spawn and also where their eggs incubate while drifting to the estuary and into the ocean.

Dams and water diversions are next on the limiting list. It’s not that dams block a significant amount of habitat – although they do – it’s how they have changed the Columbia River hydrograph and how that impacts the estuary and the Columbia River plume, Heironimus told the Council.

“The plume pushes the larval smolts from the estuary into the ocean and a small plume doesn’t do that well,” she said. “The plume has been reduced in size, shape and intensity.”

More obvious, Bonneville Dam is a physical barrier and there is some evidence that smelt had traveled as far upriver to spawn as the Hood River in Oregon and Klickitat River in Washington.

At number five on the limiting list is water quality in the river.

Each year Washington conducts a commercial test fishery, yet very little is known about the life history of smelt. A Eulochon Technical Recovery and Implementation Team that oversees the fish from Cape Blanco to Grays Harbor is trying to gain more information using, among other methods, NOAA Fisheries research trawl surveys and sampling in the Columbia by WDFW and the Oregon Department of Fish and Wildlife, but there has been little funding for the river surveys. Other research partners are the Cowlitz, Quileute and Yakama tribes.

Among the findings from this research is that the sex ratio of the fish is roughly one to one, and that the age of runs varies. For example, in 2013 the age of spawners was two and three-year old fish, changing to four and five-year old fish in 2016 and two and four year old fish in 2018.

NOAA plans a pilot study in 2020 to explore potential acoustic biomass, a technique Heironimus said is a proven method to manage forage fish stocks (like smelt). That, she said, could give biologists a better inkling of run size and timing, and whether a fishery should be allowed.

WDFW has proposed several smelt related amendments to the Council’s Fish and Wildlife Program. Those include:

— Update the F&W Program measures and language to reflect NOAA’s eulachon recovery plan.

— Include eulachon spawning stock biomass as the first high-level indicator for this species, and fund annual monitoring of eulachon spawning stock biomass.

— Add eulachon in the emerging program priorities and address critical uncertainties/questions for this species.

Heironimus’ presentation to the Council is at https://www.nwcouncil.org/sites/default/files/2019_0409_4.pdf

Also see:

— CBB, February 1, 2019, “For 2019 Columbia/Snake Spring Chinook, Sockeye Returns Forecasted To Be Well Below Average,” http://www.cbbulletin.com/442083.aspx

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