Mountain whitefish
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| Prosopium williamsoni (Girard, 1856) |
The mountain whitefish Prosopium williamsoni is one of the mostly widely distributed salmonid fish of western North America.
The body shape is superficially similar to the cyprinids, although it is distinguished by having the adipose fin of salmonids. The body is slender and nearly cylindrical in cross section, generally silver with a dusky olive green shade dorsally. The short head has a small mouth underneath the snout. The short dorsal fin has 12-13 rays, with 11-13 for the anal fin, 10-12 for the pelvic fins, and 14-18 for the pectoral fins. The tail fin is forked. Size has been recorded at up to 70 cm in length and a weight of 2.9 kg.
It is a fish of mountain streams and lakes, favoring clear cold water and large deep pools of at least a meter depth; the Lake Tahoe population lives just above the bottom in deeper water. Mountain whitefish are bottom feeders, stirring up the substrate with pectoral and tail fins to expose insect larvae and other invertebrates, including snails, crayfish, and amphipods. Their main feeding time is in the evening, but they will also take drifting prey during the day.
The spawning season is from October to early December, when water temperatures are 2-6 °C. The fish seek out areas of coarse gravel or cobble at depths of at least 75 cm, and scatter the non-adhesive eggs so that they sink into the interstices. The eggs then develop slowly through the winter (6-10 weeks), hatching in the early spring.
They are found throughout the western half of North America, as far north as the Mackenzie River and the drainages of the Hudson Bay, in the Columbia River, upper Missouri River, upper Colorado River, and so forth.
Although once important in the subsistence fisheries of the Native Americans, they seem to have become less common in modern times, although as of 2002 detailed surveys had not been conducted.
[edit] References
- Prosopium williamsoni (TSN 162009). Integrated Taxonomic Information System. Accessed on 18 April 2006.
- Peter B. Moyle, Inland Fishes of California (University of California Press, 2002), pp. 243-245
- "Prosopium williamsoni". FishBase. Ed. Ranier Froese and Daniel Pauly. April 2006 version. N.p.: FishBase, 2006.
