of stored energy in steelhead differ according to sex, the amount of time spent
in freshwater before spawning and whether the fish is of wild or hatchery
origin, according to a recent study of steelhead that spawn in the Kalama River
in Washington state.
study, which based energy levels on the amount of somatic lipids in a fish,
found that the lipid content depended on whether the steelhead was a summer –
stream maturing – or winter (ocean maturing) fish.
run fish, which return to freshwater months before spawning and mature while in
the freshwater environment, had twice the lipid content than did winter
steelhead, and, further, within each run the lipid level declined with arrival
addition, summer run females had 19 percent more lipid content than males and
wild fish had 21 percent more than hatchery fish, but the difference was
greater for summer run fish than it was for winter run fish,
findings highlight a fundamental difference between summer-run and winter-run
steelhead that reflects the freshwater energetic demands of the two ecotypes
and further describes steelhead diversity,” said James Lamperth, fish and
wildlife biologist with the Washington Department of Fish and Wildlife. “Energy
storage is likely part of a suite of adaptations associated with timing of
return, rigors of migration, duration of freshwater residency, and spawning.”
of this is not new information. 2014 and 2015 studies found that chinook that
arrive in freshwater long before spawning (premature migration) tend to have
more stored energy, as do fish that migrate long distances to spawning grounds.
But fish that differ in timing often migrate different distances, “confounding
the ability to differentiate the importance of each factor on energy storage
needs,” the study says.
with all populations – wild summer and winter runs and hatchery summer and
winter runs – present in one river, the Kalama River, the authors were able to
tease out the certainty of such statements about energy levels.
interacting variables, including return timing, rearing origin, and sex, were
connected to levels of energy storage, as indicated by somatic lipid content,
of steelhead returning to the Kalama River, WA, according to Lamperth.
controlling for migration distance, summer steelhead had more stored energy
then winter steelhead; earlier arriving fish had more stored energy than those
arriving later regardless of ecotype; wild fish tended to have more energy than
hatchery fish; and levels of stored energy differed between the sexes and
depended on the ecotype and most likely reflected future energetic demands of
maturation,” Lamperth said. “Stable isotope analysis suggested these
differences were not related to marine foraging.”
of stored energy but not marine foraging patterns differentiate seasonal
ecotypes of wild and hatchery steelhead (Oncorhynchus mykiss) returning to the
Kalama River, Washington” was published online in the Canadian Journal of
Fisheries and Aquatic Sciences (http://www.nrcresearchpress.com/doi/abs/10.1139/cjfas-2016-0018#.WJt4EPkrLIU).
co-authors are Dr. Mara Zimmerman, research scientist, Washington Department of
Fish and Wildlife, and Dr. Thomas Quinn, professor, School of Aquatic and
Fishery Sciences, University of Washington.
are a diverse lot with most spending one to four years in freshwater before
migrating to the ocean and then another one to three years in the ocean growing
to size. While they return to freshwater at all times of year, summer steelhead
return from spring through fall and are relatively immature reproductively.
They will overwinter as they mature and spawn the next spring.
steelhead that return in late fall to early spring are relatively mature
reproductively. They spawn weeks to a few months after returning to fresh water.
addition, steelhead can spawn, survive the breeding season, return to the ocean
and come back to spawn up to four times. Most of those that spawn more than
once are females.
steelhead need to reserve sufficient energy for postspawning survival,” the
steelhead are not allowed to return to the ocean after spawning and may
“inadvertently select for reduced energy storage because artificial spawning
eliminates selection for dominance displays, nest preparation, and other
energetically demanding behavior patterns associated with spawning,” the study
says. Since they are killed before they can spawn, “there is no selection to
store energy to spawn multiple times in a single year or to spawn in multiple
years as occurs in wild fish.”
also “might be part of the complex of traits that cause hatchery-origin
salmonids to produce fewer offspring when breeding in rivers compared with
sympatric wild fish,” the study concludes.