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White Sturgeon Populations Hold Steady In Columbia River Reservoirs, Spawner Abundance A Concern
Posted on Friday, October 16, 2015 (PST)

Despite the die-off of 169 white sturgeon this summer – which is nearly 2 percent of the spawning population –in Columbia River reservoirs, the white sturgeon population in the Columbia River is healthy and holding steady.

 

In fact, the Bonneville pool remains home to one of the largest populations of white sturgeon in the world, second only to the population in the lower river, according to an update of the Columbia River’s white sturgeon status by Tucker Jones, Oregon Department of Fish and Wildlife. Jones spoke Tuesday to the Northwest Power and Conservation Council’s Fish and Wildlife Committee at its meeting in Vancouver, Wash.

 

Although not listed under the Endangered Species Act as is the Kootenai white sturgeon along with its anadromous cousin, the green sturgeon, found in the lower Columbia River and Pacific ocean (both listed as threatened), white sturgeon are still faced with threats to their existence, not the least of which are warm water and dams in the mid-Columbia and Snake rivers.

 

Other threats are predation by sea lions, vessel traffic collisions and poaching for caviar (there can be as much as 100 pounds of eggs in a large mature sturgeon that sells for about $200 per ounce on the market. The extent of the poaching is unknown, Jones said).

 

This year’s die-off in The Dalles, John Day and McNary pools was caused by “high and rapidly increasing water temperatures that occurred much earlier this year than past years,” Jones said. “And, it was mostly mature fish that died, the sexually mature fish.”

 

He said the only thing fisheries managers could do was to shut down harvest of the sturgeon even though there was no evidence that had anything to do with sturgeon dying. A similar but much smaller die-off occurred in 2013 in The Dalles pool for the same reason when 25 sturgeon died.

 

With climate change expected to bring warmer air and water temperatures in the future, sturgeon will experience hot summers more often, Jones added.

 

(For more information, see CBB, July 17, 2015, “Heat-Stressed Large Sturgeon Dying; States Close Sturgeon Fishing From Bonneville to Mid-Columbia,” http://www.cbbulletin.com/434540.aspx)

 

Historically, sea lions have been reported as far upstream as Celilo Falls but, to some degree, Jones  said, the hydrosystem has become a series of chokepoints in the river for sturgeon and sea lions.

 

Sturgeon gather near a dam’s tailrace and sea lions pick them off. In 2005, the river began to see a resurgence of Steller sea lions that target sturgeon. This year the average daily presence of the combined Steller and California sea lions was 35 at Bonneville Dam.

 

At the peak in 2011, the states estimated that sea lions consumed over 10,000 sturgeon in one season throughout the 145 miles of the lower Columbia River, according to Jones’ presentation. However, pinniped predation is way down the last couple of years, even with the rising number of sea lions in the lower river.

 

For a report of pinniped predation at Bonneville dam of sturgeon, salmon, steelhead and other fish, go to www.nwdwc.usace.army.mil/tmt/documents/fish/

 

(Also see CBB, October 9, 2015, “Report: California Sea Lions This Year Take Big Chunk Out Of Willamette River Spring Chinook Run,” http://www.cbbulletin.com/435197.aspx and CBB, June 19, 2015, “Final 2015 Sea Lion Predation Report: 8,474 Salmonids Taken Below Bonneville, Twice 10-Year Average,” http://www.cbbulletin.com/434287.aspx)

 

At least one of the direct hydrosystem impacts on sturgeon is being addressed by the U.S. Army Corps of Engineers. Sturgeon enter turbine draft tubes, penstocks and other orifices and without some type of deterrence they can be exposed to blade strikes, blunt force injuries or barometric trauma, according to Jones’ presentation. In addition, fish are vulnerable during dewatering activities as turbines shut down and ramp up. This is being addressed with what is called a slow-roll startup that waters the turbine draft tubes first and slowly ramps generation up to speed.

 

Despite its issues with warm water, turbines, pinnipeds and poachers, white sturgeon have a large, healthy and somewhat static population in the Columbia River, Jones said.

 

However, harvest has been tailing off the last few years, largely due to the abundance of spawning-sized fish. Harvest in 1998 was near 55,000 fish, but has trailed off and in 2013 about 10,000 fish were taken by tribal and recreational fishers. 

 

Harvest can be a factor, especially at the higher harvest rates of the late 1980s. Jones said fish managers would like to see adult abundance – the spawning sized fish that are generally over 60 inches long – to be around 3,800 throughout the lower Columbia River reservoirs. It’s near that number now, but managers are prudently holding harvest steady.

 

The Bonneville pool has about a quarter-million sturgeon, but just 1,000 mature adults. “Growth and productivity in the pool are down (in all the size categories) and the fish don’t grow well,” Jones said.

 

Consequently, the population is intensively managed, with recreational and tribal fishers taking 1,000 to 2,000 fish annually the last two years

 

The Dalles pool has about 100,000 sturgeon and, like the Bonneville pool, about 1,000 are mature fish. Due to low recruitment in the pool, harvest was down to about 500 in 2014.

 

“The further away from the ocean, the fewer fish there are,” Jones said. The John Day pool has 30,000 to 40,000 sturgeon, but it has a higher proportion of sub-adults and mature adults than in the downstream pools.

 

“There aren’t that many young adults. Tribes and the states are planning a hatchery in the near future in this pool.” Recruitment is down due to lower than needed flows from McNary Dam upstream. Better recruitment would come with average annual flows greater than 250,000 cubic feet per second, but that hasn’t happened recently.

 

“It looks like 2015 again will be another year without measurable recruitment,” Jones said, even though the John Day pool has a greater proportion of brood fish than in the other pools.

 

Harvest in the John Day pool is in the 1,600 to 1,800 fish range with about two-thirds of that going to tribal harvest.

 

The Council has included sturgeon measures as one of its seven emerging program priorities, calling on the region to add passage and research for both white sturgeon and lamprey in its 2014 Fish and Wildlife Program. See the Investment Strategy chapter of the Council’s 2014 Fish and Wildlife Program at http://www.nwcouncil.org/fw/program/2014-12/program/partsix_implementation/ii_investment_strategy/

 

The presentation at the Council on Tuesday to the Fish and Wildlife Committee was also by Brad James, Washington Department of Fish and Wildlife, and Blaine Parker, Columbia River Inter-Tribal Fish Commission. Information can be found on the Council website at http://www.nwcouncil.org/media/7149600/f1.pdf

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