Cutthroat Trout
(Onchorhynchus clarki)
The Idaho State Fish

Description
Cutthroat trout are named for the bright red-orange streak in the fold under the jaw. Cutthroat are native to mountain streams, lakes and rivers throughout Idaho. This is the primary reason for its designation as Idaho's state fish. They are great indicators of water quality, since they prefer very clean, pristine waters. They have been introduced into many of the high mountain lakes. Cutthroat prefer colder water than do the closely related rainbow trout.

Life History
Spawning takes place in the late spring in small tributary streams. The female digs a redd in the gravel with her tail. Cutthroat may spawn more than once and with different partners. Both the male and female are aggressive if other fish try to spawn too close to their redd. Once spawning has been completed, the female will use her body and tail to displace gravel upstream of her redd to cover it. They may spawn during the day or night. The eggs will hatch in about five weeks, early in the summer. The small cutthroat trout may live in the stream where they were born, migrate to another stream, or migrate to a lake. In many Idaho rivers, cutthroat will migrate in the fall, over-winter, and move back to their summer home. You may find yourself angling for cutthroat during only one season in order to find cutthroat large enough to catch. Like the rainbow, their size and age of sexual maturity varies. Cutthroat are usually three years old when they spawn for the first time.

Feeding Habits
Cutthroat trout will feed on aquatic and terrestrial insects. They feed along the surface, but may take insects at any level in the water. Larger cutthroat may feed on smaller fish when available.

Brown Trout
(Salmo trutta)

Description
Brown trout are golden brown in color with large black spots, red spots with pale halos. They are the only trout with both red and black spotting. Young browns have an orange adipose fin.

Brown trout are native to Europe. They were introduced into Idaho waters in 1892. It was not until 1948 that introductions were successful. The brown trout is more tolerant of silt and warm water than native trout and, therefore, has been stocked in areas disturbed by man.

They may be found in rivers, streams, lakes, and reservoirs in the southern part of the state, particularly in the Henry's Fork River Basin. There are small populations in the Clark Fork River, Lake Pend Oreille, and other waters in the north.

Life History
Spawning occurs in October and early November. With her tail, the female digs a shallow depression in which eggs are deposited. After spawning, she covers the eggs with gravel. The eggs hatch the following April. The juvenile brown trout grow quickly for the first three years. As they reach maturity, growth slows. An adult brown might be 4 to 15 years old.

Feeding Habits
The brown trout is aggressive and territorial, chasing other species away from good cover. It feeds on many different varieties of invertebrates and small fish, both on the bottom and on the surface. Browns forage freely on the surface when mayflies, caddis flies and stone flies are emerging. They will also eat other fish.

Rainbow Trout
(Oncorhynchus mykiss)

Rainbow spawn in streams from mid-April to late June. They use areas of gravel, or cobble, depending on the size of the fish. The female rainbow selects a place in a riffle area below a pool to dig a redd (nest). The female displaces the gravel with her body and tail, and the male fertilizes the eggs as they are deposited. The female covers the eggs with gravel by continuing upstream and the current carries the gravel over the eggs.

The eggs hatch in early to midsummer. The young fish may live in the stream a few months, several years, or their entire life. The growth of those that remain in the stream varies with the amount of food and temperature of stream.

When they mature and are ready to spawn, the rainbow migrate back to the place they were born. The age of sexual maturity depends on the type of rainbow and where it lives. Most rainbow require 3 to 5 years to mature.

 

© 2007  Idaho Fish and Game