ore an important coastal economy, and improve drinking water quality and recreational opportunities for the citizens of the State.
SPECIES DESCRIPTION AND BIOLOGY
COHO SALMON Oncorhynchus kisutch
Coho Salmon are widely distributed in steams along the California coast and are important to sport and commercial fisheries. Their life history is well known from numerous studies that have been conducted over the years, including the classic life history study by Shapovalov and Taft, 1954. They have adapted to the unpredictable conditions present in most California coastal streams. Coho salmon, nevertheless, have demanding habitat requirements and are most abundant in least disturbed, heavily forested watersheds. They move upstream in response to an increase in stream flows caused by fall storms, especially in small streams when water temperatures are 39-57 degrees F. Spawning sites are typically at the head of riffles or tail of pools where there ideally are beds of loose, silt free gravel and where cover exists nearby for adults. Optimal temperatures for development of the embryos in the gravel are 43-50 degrees F. Juveniles prefer deep (greater than 3 feet) well shaded pools with plenty of overhead cover. Juveniles prefer water temperatures of 50-59 degrees F and demand high oxygen and food (invertebrates) levels. High turbidity is detrimental to emergence, feeding and growth of young coho.
Description: Coho are fairly large salmon, with spawning adults typically attaining 22 to 28 inches in length and weighing 6.5-13.2 pounds. They have 9-12 dorsal fin rays, 12-17 anal fin rays, and 9-11 pelvic fin rays. Lateral line scales number from 121-148 and the scales are pored. There are 11-15 branchiostegal rays on either side of the jaw. Gill rakers are rough and widely spaced, with 12-16 in the lower half of the first arch (Moyle 1976).
Spawning adults are dark and drab. The head and back are dark green, the sides are dull maroon to brown, and the belly is gray to black. Females are paler than males. Spawning males are characterized 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