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Juvenile Sturgeon Below Bonneville Dam Still Show Reduced Abundance, Legal-Size Fish Numbers Down In
Posted on Friday, February 08, 2019 (PST)

The number of legal-sized white sturgeon (38 to 54 inches in fork length) in the Columbia River downstream of Bonneville Dam declined in 2018 while the number of sturgeon large enough to spawn (over 65 inches FL) – adults – remained steady from 2017 numbers, according to a 2018 report by the Oregon Department of Fish and Wildlife.

 

Legal-sized sturgeon – those large enough but not too large to fill a legal slot allowed for fishing – declined 19 percent from 2017 and was 28 percent lower than the peak abundance in 2016. In 2018, biologists say there were 162,182 legal-sized sturgeon (63 percent of the conservation status level) in the river downstream of Bonneville and 6,108 adult-sized fish (3-year average is 7,493 fish and the desired abundance is 9,250 fish, while the conservation status threshold abundance is about 3,900 fish).

 

Both sizes of sturgeon, however, have abundances that are “firmly above conservation status,” the report says (https://www.dfw.state.or.us/agency/commission/minutes/19/02_Feb/Exhibit%20B/Attachement%201_Agenda%20Item%20Summary.pdf), an abundance that could allow fishing this year.

 

“When considered in a broader time scale the trend in sub-adult abundance has been, and continues to be, positive since 2012,” the report says.

 

The conservation status of white sturgeon was set in 2011 by both Oregon and Washington Commissions when they adopted the Lower Columbia River and Oregon Coast White Sturgeon Conservation Plan that sets long-term management goals for the sturgeon that would constitute healthy and harvestable numbers.

 

Tucker Jones, Ocean/Salmon Columbia River Program Manager for ODFW, is briefing the Oregon Fish and Wildlife Commission today (Feb. 8) at its meeting in Portland, on the status of white sturgeon in the lower Columbia River and lower Willamette River.

 

Ultimately, there could be fishing for white sturgeon in 2019 similar to the last couple of years’ sport and commercial fishing set by the Commission, “but that’s somewhat dependent on Commission guidance – which I hope we may get Friday,” Jones said.

 

However, there is a “reduced relative abundance of juvenile and sub-legal sized fish, an extended period of low young-of-year (YOY) recruitment, as measured by catch per net (CPN), and a leveling out or downturn year-over-year in most metrics,” the report says. “Taken together these signs point to ongoing low productivity over the last several years, and indicate that the precautionary approach to fisheries management we have used over the last several years should continue.”

 

Jones said he’s not certain why young of year recruitment is down, but one thought is predation by steller sea lions.

 

“We don’t have a causative relationship worked out, but there is growing evidence that, irrespective of predation, the abundance of steller sea lions appears to be negatively correlated with successful white sturgeon recruitment, that is to say, the more stellers are around the lower recruitment we measure,” he said.

 

Still, the lower Columbia River white sturgeon population cannot be considered truly healthy, the report says, unless abundance targets are met and it has a balanced, sustainable stock structure across life history stages. Large abundance estimates with a stock structure dominated by juveniles indicates successful recruitment is occurring regularly, assuring replacements for mortality at older life stages.

 

The desired percentage of juveniles that make up the entire population would be 95 percent, but in 2018 the percentage was about 63 percent. That’s still above the conservation status in the Plan (60 percent).

 

“The reduced relative abundance of juvenile and sub-legal sized fish over time indicates ongoing productivity issues,” the report says. “We do not anticipate this trend changing in the immediate future; however, if future recruitment is more like that witnessed in pre-2009 or 2017, this trend may, with time, reverse itself.”

 

Sturgeon retention fisheries were closed 2009 through 2016, although in the latter year catch and release was allowed. Retention fishing resumed in 2017 and continued in 2018, but fishing was allowed in three areas and the slot size was reduced to 44 to 50 inches to dampen catch rates and lengthen the season, the report says. Anglers were allowed 2,960 white sturgeon in the estuary, 1,230 in the mainstem Columbia River upstream of the Wauna power lines at river mile 40 and 740 in the lower Willamette River.

 

The estuary fishery was scheduled for ten days during mid-May through early June in 2018, and was ultimately extended for an eleventh day with an estimated catch of 2,412 white sturgeon from 18,294 angler trips. The main-stem fishery was scheduled for two Saturdays during September and produced a catch of 1,049 white sturgeon from 11,031 trips.

 

Along with recreational retention, commercial harvest also continued in 2018 with a guideline of 1,230 44 to 54-inch FL white sturgeon available. In off-channel and fall mainstem Zone 4/5 commercial fisheries, a combined 826 of the 1,230 commercial guideline was harvested, the report says.

 

Also see:

 

-- CBB, October 27, 2017, “Sturgeon Fishing Day Added, Mainstem Night Fishing Ban Lifted, Wild Steelhead Passage Still Very Low,” http://www.cbbulletin.com/439783.aspx

 

-- CBB, October 13, 2017, “States Set Two Days For Sturgeon Retention Fishing Downstream Of Bonneville Dam; Fish Over 66-Inches,” http://www.cbbulletin.com/439717.aspx

 

--CBB, June 16, 2017, “With More Fish Caught Than Expected, States Close Lower Columbia Sturgeon Fishing,” http://www.cbbulletin.com/439103.aspx

 

--CBB, February 10, 2017, “Harvest Managers Extend Tribal Sturgeon Gillnetting For One Week,” http://www.cbbulletin.com/438300.aspx

 

-- CBB, Feb. 26, 2016, “Lower Columbia River White Sturgeon Overall Numbers Continue To Grow, ‘Ongoing Productivity Issues' ” http://www.cbbulletin.com/436114.aspx

 

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