Anglers don't typically care about the genetics of the fish they catch. They're more interested in length, size and the fight. But sometimes fishermen like to argue about whether rainbow trout, a favorite of anglers in Idaho waters, are native to the state.
The issue is more complicated than it sounds, and the simple answer is: Yes they are, and no they're not.
A genetically pure strain of rainbow, commonly referred to as "redbands," existed in Idaho waters long before Europeans came to the area. But for at least the past 100 years, other varieties of rainbow, typically referred to as "coastal rainbow," have been introduced into Idaho waters, giving us today a hodgepodge in the rainbow gene pool. Nonetheless, the introduction of new genes has likely resulted in the vibrant rainbow trout population found today in Idaho waters.
An exception to that statement may be the steelhead, sometimes thought to be a salmon, but in reality a trout originally genetically identical to the original Idaho redbands. But the Idaho Department of Fish and Game believes that even the steelhead, which migrates to the Pacific Ocean before returning to spawn in its original home waters, may have been genetically altered over the years by the influx of introduced outsiders.
Adding to the rainbow gene pool, even today, are various strains of hatchery-raised fish, planted in Idaho waters to appease the trout-hungry fishing community. Though hatchery-raised rainbow are now sterilized before introduction, Fish and Game estimates that about 2 percent of them remain fertile.
Also influencing the rainbow genetic equation are cutthroat trout, a separate species that is also native to Idaho. However, rainbow and cutthroat are genetically close enough that sometimes they interbreed.
Redband rainbow
Most experts agree that redband rainbow trout have lived in Idaho for thousands of years, likely dating back to the end of the last ice age. But they never fully populated Idaho's waters. Doug Megargle, regional fisheries manager for Fish and Game in Jerome, said migration of redbands into eastern Idaho, where cutthroat were the original predominant trout species, seems to have been blocked by Shoshone Falls.
Megargle said isolated communities of genetically pure redbands can still be found in some areas of the state, but that Fish and Game has been unable to document a non-hybridized redband population in the Big Wood River drainage.
Skooter Gardiner, a fly-fishing guide for Silver Creek Outfitters in Ketchum, said that although it has not been genetically proven, he has encountered what he believes to be pure redband populations in the headwaters of the Little Wood River.
"You have to go to some pretty remote areas to find a native rainbow," Gardiner said.
Megargle and Gardiner agree that pure redband rainbows tend to be smaller, less stocky fish than their hybridized cousins.
An exception would be the steelhead, which Megargle said over the millennia chose a different "life strategy." Instead of remaining in their original waters, steelhead migrate down the Snake, Salmon and Clearwater rivers to the Columbia River and then to the Pacific Ocean. Steelhead stay in the ocean one or two years before returning to their original waters to spawn. If they stay in the Pacific for two years, some of them return weighing up to 20 pounds.
So why didn't other redband populations chose to swim to the ocean? Megargle refers to the situation as "species diversity" and likens it to the human population. Some humans live in civilized areas, others live in tribal villages and still others remain nomads.
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Big Wood drainage
Anglers in the Big Wood River drainage catch two basic color variations of rainbow trout and numerous combinations of the two.
The first basic variation is a greenish backed fish with a diminutive rainbow pattern, a reddish band on its side, a belly that is reddish and yellow and with brilliant orange fins. Fishermen often refer to this color variation as a redband, and though the fish may show redband characteristics, it is still a hybrid.
The other basic color variation, typical of coastal or hatchery raised rainbow, has more of a steel color on its back, has a brilliant rainbow pattern, little or no red on its belly and whitish-colored fins.
However, Megargle said that it is an oversimplification to state that the reddish-colored trout are more closely related to the original redbands. Because of "genetic diversity," fish from the same parents could exhibit either basic color pattern or a combination of the two.
Megargle said fish coloration can be influenced by factors other than genetics, including water conditions, amount of sunlight, health and diet.
"What you see is not necessarily what you get," he said.
In the Big Wood River below Magic Reservoir, rainbow trout tend toward the green and reddish color. Megargle said some anglers have suggested that the population is a unique variety of rainbow. However, he said, they're still just hybrids like the rest of the rainbow trout in the drainage system. But he did acknowledge that the fish do have a cutthroat look to them.
The story goes, he said, that years ago a truck headed north with a planter load of cutthroat trout had mechanical problems. Rather than just let the fish die, the crew dumped them into the Big Wood below the reservoir thinking it would do no harm. To anglers it didn't, but if the story is true, then it further complicated an already complex gene pool.
Megargle said fish below Magic are also genetically influenced by rainbow that spill out of the reservoir, which is heavily stocked with coastal rainbow varieties.
Coastal rainbow
Rainbow trout introduced into Idaho waters for at least the past 100 years are typically referred to as "coastal rainbow." That's because multiple strains have been brought to the state from western areas of northern California, Oregon, Washington and even British Columbia.
Megargle said original stocking methods involved hauling fish in water jugs on the backs of mules.
Today, two types of rainbow of coastal origins are introduced annually in the waters of the Big Wood River drainage. One type, from the private Troutlodge company headquartered in Washington and with rainbow hatcheries throughout the Pacific Northwest, are called "triploid Troutlodge Kamloops." The other, from the Fish and Game Hayspur hatchery in south Blaine County, are called "Hayspur rainbow triploid."
Megargle said Troutlodge keeps the genetics it its rainbow stock secret, while the Hayspur trout have been developed over the years from numerous genetic stocks to develop a fish with brilliant colors, stamina, growth potential and fighting ability.
"Some people refer to it as a junkyard dog," Megargle said. "But it has still proven to be an effective strain."
For about the past 10 years, Fish and Game has tried to make sure that hatchery fish are sterilized before being introduced to wild waters. However, Megargle acknowledged that a process called "power shocking" is only about 98 percent effective.
Planters have a high mortality rate during their first year of introduction, both from heavy harvesting and from failure to adapt to wild conditions. However, Megargle estimated that for every 1,000 fish planted, perhaps five survive that are able to pass their genes into an already complex gene pool.
Native or not?
Fish and Game lists rainbow trout as a native Idaho species in its literature.
Gardiner said he doesn't consider rainbow as native because of the heavy genetic influence of coastal rainbow into the population. He does acknowledge that many of the rainbow trout in Idaho have some genes that they got from the original pure redbands.
So the questions of whether rainbow trout are native to Idaho remains a complex issue. And depending upon one's perspective, either answer is true.
Terry Smith: tsmith@mtexpress.com
Fishermen in the Big Wood River drainage catch two basic color variations of rainbow trout. The fish at top shows coloration typical of the original “redband rainbows” that are native to Idaho, while the fish below shows coloration typical of “coastal rainbow,” which have been introduced into Idaho waters for at least 100 years. However, the Idaho Department of Fish and Game considers rainbow trout in the Big Wood drainage with either color variation, or a mix of the two, to be hybrids. Courtesy photos by Bob Knoebel
