Wildlife
Rainbow Trout (Oncorhynchus mykiss):
Rainbow trout were historically distributed from the northern coast of Mexico north to the Kuskokwim River in Alaska. Rainbow trout can be found in many of the streams and lakes throughout the Togiak National Wildlife Refuge, and are prized by many sport anglers.
 Rainbow trout have an elongated, moderately compressed body shape with a rounded snout. Overall body shape varies due to genetic and local environmental factors and different food habits. Rainbow trout body colors can vary as well, but generally the upper portion of the body is dark green to brown, while the lower sides and the belly can be silver to whitish. The tail and back are covered with black spots that may continue down the sides to the belly in some populations. A broad pink to vibrant red band can be seen running the length of the mid-body in most rainbow trout populations. The colors are most pronounced during and after the spring spawning period and give the rainbow trout its common name. Rainbows can attain weights up to 40 pounds (steelhead) in Alaska. Rainbow trout within the Togiak Refuge generally do not weigh above 7 pounds, but weights vary throughout the year depending on food availability.
Rainbow trout have a diet that varies depending on the time of year and the size and availability of prey. Prey items range from zooplankton to small mammals, with insects providing the base diet in most populations. Despite the cool water temperatures in Togiak Refuge rivers, the availability of high energy foods such as salmon eggs, juvenile fish, and decaying flesh of salmon allows some rainbow trout to attain large sizes.
Rainbow trout have two life history strategies: some populations will migrate to saltwater as do salmon (anadromous) and are called steelhead. Other rainbow trout populations remain their entire life in freshwater and are known as resident rainbow trout. Rainbow trout populations present in the Togiak Refuge are all thought to be resident.
Studies conducted on resident rainbow trout in Togiak Refuge have documented two life history patterns. Some rainbow trout populations may spend their entire life in stream or large river systems, while other populations reside primarily in lakes, using streams for spawning and seasonal feeding.
Rainbow trout spawn in streams during the spring when water temperatures are from 5oC to 13oC. The male courts the female through contact and rubbing against her sides and belly. The female prepares for spawning by turning on her side, and by strong flips of her tail cleans the gravel of fine particles. This process eventually results in a redd with an upstream pit and downstream mound of gravel. The male defends his territory against other males while the female prepares the redd. Eggs are deposited in the redd and covered by gravel from subsequent upstream diggings. Fertilized eggs hatch in about four to seven weeks, depending on the water temperature, and juveniles emerge within several weeks and begin to feed.
After spawning the adults spend the rest of the summer feeding. Depending on the life history pattern, the individual fish may return to a lake, travel great distances within their spawning stream, move to a new stream, or remain in the same area for the remainder of the year.
Resources:
Morrow, James E. 1980. The freshwater fishes of Alaska. Alaska Northwest Publishing Company. Anchorage Alaska.
For more information, visit the Alaska Department of Fish and Game's wildlife notebook pages.
Last updated: July 24, 2008
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