aracterized by a bright red lateral stripe, hooked jaw, and a slightly, humped back. Both sexes have small black spots on the back, dorsal fin, and upper lobe of the caudal fin. The gums of the lower jaw are gray, except the upper are at the base of the teeth which is generally whitish (Fry, 1973). Parr have 8-12 narrow parr marks centered along the lateral line. The marks are narrow and widely spaced. The adipose fin is finely speckled, imparting to it a gray color, but the other fins lack spots and is tinted orange.
Coho salmon are one of five species of Pacific salmon (Oncorhynchus) found in California. They do not appear to have the genetically distinct, temporally segregated runs that characterize the more abundant chinook salmon and steelhead trout. However, the strong homing abilities of coho salmon make it likely that each coastal stream has a distinctive strain of coho adapted to local environmental conditions. For the purposes of this section, the coho populations are divided into big-river coho salmon and short-run coho salmon. Big-river coho are those that migrate up large river systems 65-130 miles or more to spawn in the river tributaries. They typically start entering the streams in September or October, somewhat earlier than short-run coho. In the Klamath River and some other systems, much of the production of the big-river fish takes place in hatcheries.
Short-run coho salmon occupy the smaller coastal streams and the tributaries of the lower reaches of the big rivers and rarely migrate more than 65 miles upstream. These populations in any one stream system are typically small and highly dependent on natural reproduction. Overall, coho populations in California are the southernmost for the species and have adapted to the extreme conditions (for salmon) of many coastal streams. From Mendocino County south, the conditions in California are even more extreme. The physical, climatic, and hydrologic factors make coho salmon survival in the southern end of the range even more rigorous.
The life history of the coho salmon in California has been well documented by Shapovalov and Taft (1954) and Hassler (1987). Most coho salmon return to their parent streams after spending two years in the ocean (up to three years in Alaska). Jack males may, however, return after one growing season in the ocean (at age 2 years), but most fish in California return after two growing seasons in the ocean (age 2 years). In California, spawning migrations begin after heavy late fall or winter rains breach the sand bars to the mouths of coastal streams, allowing the fish to move into the streams. However, migration typically occurs when stream flows are either rising or falling, not necessarily when streams are in full flood.
In the Klamath River, the coho will run between September and late-December, with peak runs occurring during October and November. Spawning itself occurs mainly in November and December (U.S. Fish and Wildlife Service, 1979). In Waddell Creek, peak spawning is between January 15 and February 15 and spawning migrations often do not begin until late November or December (Shapovalov and Taft, 1954). In Oregon and south of San Francisco streams, spawning can occur as late as March, if drought conditions delay rains or runoff (Sandercock, 1991, Smith, 1991).
Coho salmon migrate and spawn mainly in small coastal streams that flow directly into the ocean or in the tributaries of large rivers. Females choose the spawning sites (redds), usually near the head of a riffle (at the tail of a pool) at, or slightly upstream of the hydraulic control, where the water changes from smooth to turbulent flow and there is a medium to small gravel substrate (1/2 to 4.4). The flow characteristics at the location of the redd usually ensure good aeration, and the circulation facilitates fry emergence from the gravel. Each female builds a series of redds, moving upstream as she does so she deposits a few hundred eggs in each. Thus, spawning may take about a week to complete and a female can lay between 1,400 to 7,000 eggs. There is a positi