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Study: Variability In Hatchery Rearing Has ‘Profound Abilities’ To Impact Salmon Smolt Performance
Posted on Friday, May 05, 2017 (PST)

Hatchery salmon smolts are not all equal, according to a recent study that examined the same Hood River broodstock but reared a portion – a third – at each of three different spring chinook hatcheries in the Columbia River basin before releasing the smolts back into their native river.


One hatchery stood out: the Pelton Ladder hatchery, operated by the Oregon Department of Fish and Wildlife on the Deschutes River just downstream of Portland General Electric’s Pelton-Round Butte Complex of dams. The hatchery is funded by PGE and the Bonneville Power Administration.


The Pelton Hatchery smolts migrated to Bonneville Dam and the Columbia River estuary faster than the others and they came back in higher relative numbers (better smolt-to-adult returns) than the other two hatcheries used in the experiment – Parkdale Hatchery on the Hood River and the Carson National Fish Hatchery on the Wind River in Washington.


The Parkdale Hatchery is operated by the Confederated Tribes of the Warm Springs and the Carson Hatchery is operated by the U.S. Fish and Wildlife Service and is supported by Mitchell Act funds.


“Different environments and different rearing protocols at different locations created smolts that performed quite differently,” said Brian Beckman, a research fisheries biologist with the Northwest Fisheries Science Center, NOAA Fisheries, Seattle, and one of the study’s authors. “Smolt development, size at release, speed of smolt out-migration, age of maturation and smolt to adult survival varied widely among smolts of the same genetic stock reared under different protocols in different hatchery environments but released at the same place and experiencing the same out-migration gauntlet.


“Variability in hatchery rearing has profound abilities to influence post-release smolt performance,” Beckman concluded.


“The Impact of Different Hatchery Rearing Environments on Smolt-to-Adult Survival of Spring Chinook Salmon,” was published online March 30, 2017, in Transactions of the American Fisheries Society (


Its authors are Beckman, Deborah Harstad, Dina Spangenberg, Rua Gerstenberger, Chris Brun and Donald Larsen, all research fisheries biologists with the Northwest Fisheries Science Center, NOAA Fisheries, Seattle.


After rearing at Pelton Ladder and Carson, biologists brought the smolts back to acclimation pens before releasing those smolts, plus the smolts reared at Parkdale, into the Hood River. From 2010 to 2012 they released over 40,000 PIT-tagged spring chinook smolts into the river over the same three day period each year.


The average migration rate of the juveniles after release was 3.9 to 10 kilometers per day (2.4 to 6.2 miles/day), but the migration rate for the Pelton fish was significantly greater than that for either the Carson or the Parkdale fish. “Rearing location was a significant predictor of migration rate to Bonneville Dam, but BY (brood year) was not,” the study says. Migration rates to the estuary had similar results.


“On its own, migration rate to Bonneville Dam was the best predictor of age 3-5 SAR,” the study concludes.


On return, the smolt-to-adult return rate of the fish reared at the Pelton Ladder hatchery was 1.55 percent, while the SAR from the Carson Hatchery was just 0.36 percent and the SAR from the Parkdale Hatchery was 0.49 percent.


However, the proportion of fish that were two-year fish, or minijacks, was “highly variable across brood years and rearing locations,” the study says.


“These results demonstrate the significant effect prelease rearing practices can have on postrelease performance of spring Chinook Salmon smolts,” the study says.


Smolts from the Pelton Ladder hatchery were the largest at the time of release, had the greatest degree of smolt development, the lowest loss as a result of early male maturation (proportionally fewer minijacks, 2-year early maturing males) and they returned in greater numbers as adults.


So, what is it about the Pelton Ladder hatchery that it would produce better returning adults? The study says that the “overall rearing regime and growth trajectory for fish reared at Pelton Ladder represents a template for producing smolts with a combination of favorable smolt attributes.”


Smolts at the Pelton Ladder hatchery are actually reared in an abandoned fish ladder below Pelton Dam, a facility, the study says, that would be “prohibitively expensive to replicate elsewhere.”


The difference between the hatcheries could be what the authors call the “wild fish template.”  It’s a phenomenon that is similar to naturally-reared spring chinook in the Yakima River.


“The wild fish template is notable for the strong anabolic to catabolic shift in the autumn that results in a cessation of growth and depletion in lipid stores through the winter. In the early spring, there is another physiological shift, from the winter catabolic phase to a spring anabolic phase, with the reinitiation of growth,” the study says.


In another study from the year 2000, Beckman suggested that the catabolic–anabolic shift in the spring could be important for priming smolt development and be related to the typically high smolt survival found in naturally-rearing fish.


In 2006, Larsen suggested that the summer–autumn shift from an anabolic state to a catabolic state had important implications for modulating the stimulation of male maturation that results in minijacks. Wild fish were found to undergo a strong catabolic shift in the autumn and had a low rate of minijack production, while hatchery fish maintained a positive anabolic phase through the autumn and typically had enhanced levels of minijack production.


According to Beckman, managers from the Confederated Tribes of the Warm Springs has since the study changed their rearing protocols at the Parkdale Hatchery “to reduce the abundance of early maturing males (age 2 minijacks) and increase the number of full-size anadromous adults.”


Still, he said, the wild fish template, although it provides a useful way to assess hatchery fish development, is not a one size fits all route to better SARs and fewer minijacks.


“Natural selection has molded the physiological responses of juvenile salmon to environmental variation to optimize smolt survival,” he said. So, naturally-reared salmon from one river basin differ widely in traits from those in another basin.


“I don’t think developing a single template for spring chinook salmon smolt rearing across all populations and all rearing environments is possible” because of the variations among populations and environments.  “Our goal is to develop a mechanistic understanding of how interactions among water temperature, feeding rate, photoperiod and resulting growth rates influence age/size of smolting, smolt to adult survival and age of maturation of chinook salmon smolts and thus help optimize smolt rearing for different populations in differing hatchery environments.”


Some strategies for replicating the wild fish template, according to the study, are:

--shaping water temperature regimes to produce the anabolic-catabolic shifts seen in the wild;

--using winter feeding regimes that include weeks to months of fasting.


These changes can be made without expensive facility changes, the study concludes.


“One of the biggest implications of our study is that the choices managers make about such things as seasonal growth rates (feeding rates) may have large impacts on subsequent smolt performance,” Beckman said. “Our goal is to help managers understand the implications of some of the rearing choices they have to make.”


For additional information from NOAA Fisheries about this study, see a feature story by Al Brown at


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