Press Release

Biologists think they've found answers to low survival of sockeye salmon

Sockeye runs have improved since the 1990s, but biologists want better survival of young fish and more returning adults

Idaho Fish and Game’s sockeye recovery program has overcome many challenges in preserving the species, and scientists are continuing to learn and improve as they transition from staving off extinction to growing Idaho’s sockeye population. 

Fish and Game’s Assistant Fisheries Chief Paul Kline said F&G biologists think they’ve answered a nagging question about its relatively new sockeye hatchery in Springfield. The hatchery succeeded in raising lots of young sockeye, but the fish have survived poorly after being released to migrate to the Pacific. 

A hard journey made harder

Biologists found differences in water hardness between Springfield Hatchery in Southeast Idaho where the fish are raised from eggs and Redfish Lake Creek near Stanley where they’re released.  Differences in water chemistry between the two waters may be adding stress to fish that are already stressed from “smoltification” - a period when they migrate downstream and their bodies transition from freshwater to saltwater. 

Biologists are investigating higher-than-expected mortality that started in 2015, the first year Springfield Hatchery’s sockeye were released for migration. That year, about 37 percent of the young sockeye survived the trip between Lower Granite Dam about 30 miles downstream from Lewiston and Bonneville Dam on the Columbia River, which is the last dam the fish cross enroute to the Pacific. 

But the spring of 2015 was a low water year for migrating young salmon, which need high flows to flush them to the ocean. Upper Columbia River sockeye, Idaho’s closest geographic cousins, also had poor survival. 

However, river conditions and survival of Upper Columbia River sockeye improved in 2016, but survival of Idaho’s sockeye dropped, signaling Idaho’s fish were facing other challenges.

Solving the mystery through science

Biologists explored potential causes and improved or eliminated some possibilities, such as additional stress associated with high levels of dissolved gas, and stress from loading fish on trucks and transporting smolts from the hatchery to the release site. 

Unlike other salmon species that Fish and Game has decades of experience raising in hatcheries, sockeye production is relatively new. Sockeye hatcheries are common in Alaska and Canada, and over 20 years ago, Idaho biologists followed guidance from these programs to establish rearing and fish-health protocols for the Eagle Hatchery Sockeye Salmon Captive Broodstock Program. That program likely saved Idaho's sockeye from extinction. 

The same protocols are also being followed at the Springfield Hatchery.  Kline pointed out most of Alaska and British Columbia hatcheries are in the same river systems where the fish are released, not raised off site with a different water source like at the Springfield Hatchery. 

The water at Springfield comes from wells with a hardness of about 200 milligrams per liter of calcium carbonate, compared with Redfish Lake Creek at less than 20 milligrams per liter. Kline described Redfish Lake Creek as “almost like distilled water” Whereas, Springfield’s water is typical for Southeastern Idaho. 

Kline pointed out water hardness is not an issue for raising sockeye from eggs, and the young fish do well in the Springfield Hatchery. There is little to nothing in the scientific literature regarding water hardness in relation to rearing sockeye in hatcheries, however big changes in water chemistry can spell trouble for any species of fish. 

“We’re treading on fresh ground here,” he said.

Biologists theorized that when young salmon enter the smolt phase of their life and transition from freshwater to saltwater, the additional stress of going from hard water to soft water may contribute to higher-than-expected mortality. 

Biologists at Idaho Fish and Game’s Eagle Fish Health Laboratory experimented with a few young sockeye, testing their response after being trucked and transferred to tanks filled with hard water from Springfield, soft water from Redfish Lake Creek or Salmon River water with hardness roughly between those two. 

A smoking gun? 

They found young sockeye transferred from Springfield well water to Redfish Lake Creek water had elevated cortisol levels, which is an indicator of stress, and those levels increased over time. Whereas fish that were transferred to water taken from Springfield’s well, or the Salmon River, quickly began to recover from the stress of the road trip. 

Spreading the risk and learning

Biologists are developing several strategies to test their theory and ease young sockeye's transition from hard water to soft water. This fall, some fish were released directly into Redfish Lake as pre-smolts, and they will spend the winter in the lake before naturally migrating downstream through Redfish Lake Creek and into the Salmon River. 

Others will be raised at the Sawtooth Hatchery in raceways that would normally be used for young Chinook salmon, but a low 2017 Chinook return means there’s temporary space available.

The remaining fish will continue to be raised at the Springfield hatchery, and biologists are continuing to refine protocols to help 2018 releases go more smoothly, including gradual water softening during trucking, mixing water in trucks before fish are released, and acclimating fish for a few days in Sawtooth Hatchery’s moderately hard water before release.  

Fish will be released in Redfish Lake Creek and the Salmon River near the Sawtooth Hatchery. Kline said if water hardness is the problem, the test groups should provide some answers without further endangering the entire group of young fish. 

“We’re getting closer to long-term solutions, but in the mean time, we are spreading our risk,” he said.

Biologists want to solve the problem, but it’s a constant challenge considering there are many other variables beyond their control, including weather, river and ocean conditions. Young sockeye only migrate downstream once per year, and it takes another year to see how many return as adults.  

“We want to be sure we’re checking off probable causes accurately,” Kline said. “Between 2018 and 2019, we’re going to learn a lot.” 

Another bump in a long road

It can be a frustrating setback for Fish and Game biologists who’ve devoted their careers to saving sockeye from the brink of extinction, and then boosting annual adult returns from single digits, to dozens, and now to hundreds. Kline said the goal is to increase that to thousands of adult sockeye in the future. 

He also tries to keep the current smolt survival in perspective. He remembers when Idaho sockeye were listed in 1991 under the federal Endangered Species Act, only four adults returned to the Sawtooth Basin. The total annual returns to Idaho between 1991 and 1999 were 23 sockeye, which included two years when none returned. 

By comparison, 157 adult sockeye returned to the Sawtooth Basin in 2017, which was a down year. The 10-year average from 2008 through 2017 is 690 sockeye annually, which you can read about in this September sockeye article explaining the 2017 return.  

Biologists expect more sockeye will return to Idaho each year if they can raise and release more young fish and improve their survival through the Salmon, Snake and Columbia rivers to the Pacific. If Springfield’s water hardness situation proves to be the culprit, Kline sees solving it as a hurdle, not a wall. 

“It’s not a disaster, it’s part of what you experience when you open a new hatchery,” he said. “It’s disappointing, but we’re not going to let it get us down.”