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Repeat Spawners:Study Looks At How Improving Steelhead ‘Kelt’ Survival Could Aid At-Risk Populations
Posted on Friday, July 22, 2016 (PST)

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 says.


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 percent.


The study, “Evaluating Steelhead Kelt Treatments to Increase Iteroparous Spawners in the Yakima River Basin,” was published online July 15, 2016 (


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 populations.”


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 study says.


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.


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