Sockeye salmon

Sockeye salmon, like this adult spawning male, are not returning to Idaho in the numbers that hatchery personnel expected.

BRETT FRENCH, GAZETTE STAFF

Hard water at a new sockeye hatchery in southeastern Idaho is proving to be an unforeseen obstacle for smolts and fisheries managers.

Idaho Fish and Game officials believe juvenile sockeye salmon are having a difficult time adjusting from the mineral-rich water they are raised in at the Springfield Hatchery to the extremely soft water in Redfish Lake Creek, where they are released to begin their journey to the Pacific Ocean.

The young salmon are surviving at lower-than-expected rates.

“A portion of them actually die within visual sight of the release before they even start their out-migration,” said Paul Kline, assistant fisheries chief for the Idaho Department of Fish and Game at Boise.

Others are dying before they make it to the Columbia River estuary below Bonneville Dam. Starting in 2015, biologists recorded poor in-river survival rates for the juvenile fish released from the hatchery. Only about 37 percent of them that reached Lower Granite Dam west of Clarkston survived all the way to Bonneville Dam on the lower Columbia River. Biologists would expect to see survival rates of 50 percent to 60 percent.

The poor performance of the juvenile fish that year wasn’t a shock, Kline said. It was one of the lowest water years on record, and water temperatures quickly reached dangerous levels for juvenile and adult salmon and steelhead. Juvenile sockeye from the upper Columbia River also survived poorly that year.

The following year saw more normal flows and water temperatures. Survival of sockeye from the upper Columbia returned to expected levels, but the sockeye from Springfield Hatchery struggled even more, with only 13 surviving between Granite and Bonneville.

Kline said hatchery managers and fisheries biologists looked at several possible causes before settling on the hardness of the water. Kline said the water at Springfield is fairly hard, but the fish don’t have any trouble at the hatchery itself. The water in Redfish Lake, which feeds Redfish Lake Creek, is so soft that Kline compared it to distilled water.

Biologists found that the fish produced high levels of the blood hormone cortisol, an indication of stress, after going from the hard water to soft.

Softening the water at the hatchery likely would be too expensive — Kline estimated the price tag in the millions. Instead, the department will try a handful of approaches to fixing the problem.

Smolts are trucked from the hatchery to the creek when they are ready to be released. During the trip, the department will slowly soften the water in the trucks so the change is less pronounced when they are released. Kline said sockeye smolts raised at the Sawtooth Hatchery, which has medium water hardness, don’t have any trouble adjusting to the soft water in the creek.

The department also will raise a portion of the smolts at the Sawtooth Hatchery, and it will house others at the hatchery for a short time prior to release as a sort of halfway house between the hard water at Springfield and the soft water in the creek.

Kline said the department expected to have challenges during the first few years of the hatchery.

“It’s growing pains associated with operating a new hatchery,” he said. “We are fairly confident that we are on to the smoking gun in respect to these observed water hardness differences.”

Sockeye were listed under the Endangered Species Act in 1991 when the run nearly blinked out. In the nine years following listing, only 23 sockeye returned to Idaho, including two years when no fish made the 900-mile trip.

But the numbers improved modestly, with more than 900 adults passing Lower Granite Dam in 2008 and a high of 2,786 in 2014, just as the state was completing the $13.5 million Springfield Hatchery.

The hatchery releases hundreds of thousands of smolts per year and is working toward a target of 1 million. Fisheries officials expected adult returns to increase when the hatchery came online. Instead they have turned south — just 228 adults were counted at Lower Granite this summer.

Salmon advocates said in a news release that sockeye need more than ramped-up hatchery production and said the best thing for the fish and for threatened runs of spring and summer chinook, steelhead and fall chinook would be to breach the four lower Snake River dams.

“Fish and game biologists are to be commended for saving sockeye salmon from the brink of extinction, but increased focus on hatchery production is failing,” said Kevin Lewis of Idaho Rivers United at Boise. “Until we address main-stem survival we’re missing the biggest opportunity for these amazing fish.”

0
1
0
0
0