Nature Notes by Dr. Frank Lang
We have heard a lot lately about fish species at risk, especially Rogue and Columbia River salmon. Recently, some eastern Oregon endangered suckers were shipped to a New Mexico fish hatchery to be propagated for replanting. These aren’t the only fish in trouble. The western brook charr better known as the bull trout, Salvelinus confluentus, is rapidly slipping into oblivion as its Oregon habitat diminishes.
For a long time, we considered bull trout a non-sea running, inland form of the better-known Dolly Varden trout, S. malma. In 1978, TM Cavender, after serious study, decided that there were enough anatomical and behavioral differences to consider bull trout a distinct species. One dependable feature is the number of bony rib-like structures that give shape and support to tissues in the throat beneath the head. Bull trout have 25 to 31, while Dolly Varden have 19 to 26. Other differences probably gave rise to its common name. Bull trout have a wide, long head with a big mouth and prominent jaws, and a fleshy knob and notch on the nose. They are voraciously piscivorous, fish-eating. Bulldog-like, I suppose, though I have yet to meet a fish-eating bulldog.
The Dolly Varden was named for a character in Charles Dickens’ novel Burnaby Rudgebecause of her pink-spotted dress.
Bull trout are members of the charr genus, characterized by few teeth on the roof of the mouth and light spots on a dark background. Other charrs in Oregon include lake trout and brook trout. Bull trout do not have the deeply-forked tail of lake trout, nor the white-edged pelvic and anal fins of brook trout.
Bull trout were formerly widespread from Alaska south to the McCloud River in northern California. The Columbia Basin is the center of distribution for bull trout.
During the Miocene and Pleistocene, there was a connection among the Columbia, Klamath and Sacramento Rivers that allowed establishment of bull trout in these areas. They were never known in Oregon coastal streams, including the Rogue.
As with many species, the bull trout is becoming extinct over much of its former range. It now exists in isolated pockets, although substantial populations still thrive in the Pend Oreille and Priest Lake basins of northern Idaho and the Flathead River of northern Montana.
In the 1950s, bull trout started disappearing from many of its former haunts – gone also from California and from former habitat in Washington State. What has gone wrong?
Well, big surprise. It’s us again, human beings, agents of the largest extinction event since the asteroid did in the dinosaurs. Disappearance may be due to changes in water quality caused by dams, agriculture, logging, livestock. It may be due to competition with imported eastern brook trout or hybridization with it. What hope is there for remaining bull trout populations? Existing populations are preserved in the few remaining undisturbed streams, especially those within public lands managed by government agencies. Remember, bull trout streams are happy streams, clear and clean and healthy, unless of course, you are a fish of another color and food for a hungry bull trout.
— Dr. Frank Lang