As many as 7 percent of the steelhead in the ocean are
preparing for their second, third or even fourth trip to spawning grounds in
coastal and inland rivers, according to a recent study.
Of those fish, 71 percent had spawned once, 21 percent twice
and 8 percent three times. One fish in a 1992 study had spawned four times.
After spawning in the spring, steelhead kelts (returning
steelhead) move downstream and eventually back to the ocean where they spend
one to two summers, re-mature and then return to freshwater as repeat spawners.
Location makes a difference in a kelt’s downstream
migration. About 17 percent of kelts from coastal streams which have few dams
will return to spawn. But the farther a steelhead kelt must travel and the more
obstacles it encounters on its migration, the lower the chance it would
eventually return all the way to its spawning grounds.
Repeat spawning rates for interior Columbia River steelhead
populations range from 0.5 percent to 1.2 percent in the Snake River to 1.6
percent to 3.4 percent in the Yakima River, according to the study, which was
recently published in the North American Journal of Fisheries Management.
“Due largely to low energy reserves after spawning and a
difficult downstream migration journey through the hydrosystem projects,
mortality on kelts returning to the ocean is very high and consequently only a
small number of kelts successfully complete the trip as repeat spawners,” said
Jeffery Trammell, a fish biologist with Yakama Nation Fisheries and one of the study’s authors. “In the Yakima River repeat spawners make up
about 3 percent of the steelhead spawning run yet over half of the run is seen
moving downstream as kelts.”
In fact, mortality rates for migrating kelts from the
mid-Columbia River range from 20 percent to 40 percent of the fish that begin
the downstream journey, and mortality is as much as 84 percent to 96 percent
from the lower Snake River, the study says.
Mortality rates reflect the fact that kelts are often
emaciated, having survived a prolonged freshwater migration of up to 1,500 km
(932 miles), but which is also a function of energetically costly migration
delays, accumulated physiological stress, delayed effects of injuries sustained
during dam passage, and susceptibility to opportunistic pathogens, the study
Poor emigration survival to the ocean appears to be the
limiting factor “in a steelhead’s ability to successfully exhibit iteroparity,”
or repeat spawning, according to the study.
Still, there is some evidence that emigrating kelt survival
has improved in recent years due to actions at hydroelectric dams, such as
removable spillway weirs and mandated spill, the study says.
The co-authors evaluated several management actions that
could be used to increase the abundance of repeat spawners by improving
survival of kelt steelhead.
Those management actions ranged from very low intervention
(collect and transport to Bonneville Dam), to high intervention (collect kelts,
culture them for 6 months, and then release them back to the river), Trammell
said. “We termed this long-term
reconditioning. The long-term
reconditioning option resulted in significantly higher benefits (at least 5
times better than the next best scenario) to the steelhead populations than any
of the other management actions.”
Return rates for fish subject to long-term reconditioning
were 11 to 18 percent, while return rates for the other treatments were 1 to 3
The study, “Evaluating Steelhead Kelt Treatments to Increase
Iteroparous Spawners in the Yakima River Basin,” was published online July 15,
Trammell’s co-authors are Dave Fast, senior research
scientist, William Bosch, data manager, Joseph Blodget, hatchery manager, and
Chris Frederiksen, research scientist, all with Yakama Nation Fisheries;
Douglas Hatch, senior fisheries scientist, Ryan Branstetter, fisheries
biologist, and Andrew Pierce, fisheries scientist, are all with the Columbia
River Inter-Tribal Fish Commission.
What they found was that reconditioning helps to preserve
the diversity of life history pathways in steelhead and can be used as a
restoration tool for at-risk steelhead populations. Trammell said.
“Kelt steelhead utilizes wild fish that have already
contributed to the spawning population.
The timing of their release allows them to select their own mates, spawn
timing, and spawning location, so the potential for negative effects is very
low,” he said. “Therefore, kelt
reconditioning helps to preserve the diversity of life history pathways in
steelhead and can be used as a restoration tool for at risk steelhead
Ensuring more kelts return to spawn could provide abundance
and diversity benefits to threatened steelhead populations. One study in 2010
found lifetime reproductive success (the total number of progeny produced over
the entire life span of a fish) for repeat-spawning steelhead was more than
double that of one-time spawners, and some male fish only contributed in their
second spawning year. In addition, repeat spawners grew substantially between
their first and second breeding seasons, resulting in an estimated average
increase in female fecundity of about 400 eggs per fish, or 10 percent, the
In addition, the long-term kelt reconditioning treatment is
relatively inexpensive in the Yakima River because existing irrigation and
hatchery infrastructure allows for the capture and rearing of a substantial
number of kelts, the report concludes.
“Thus the only costs incurred for our study were the rearing
tanks (about $12,000–$16,000 per circular tank), feed (about $4,000/year), and
some staff time. Costs could be substantially greater in river systems where
traps, weirs, and hatchery infrastructure need to be constructed to capture and
rear kelts,” the study says.
The final results of the study show that long-term steelhead
kelt reconditioning is far more successful than either transportation or
in-river migration treatments at increasing repeat spawner abundance and
providing recovery, the study says.
“Indeed, long-term reconditioning has the potential to
contribute hundreds of repeat spawners in any given brood year in river systems
where kelts can be readily collected for treatment,” it concludes.