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By Harvey Thommasen, with Photography by Nick Didlick As salmon and sea-run trout enter the streams and rivers during the spawning season, they change in both color and form. Each species develops its own characteristic spawning colors and patterns. Color patterns and shapes have several functions including protection (against the harmful effects of sun's radiation), camouflage (allowing them to blend in with the bottom and sky), spawning and territoriality (to allow males and females to recognize each other in the parings and forming of redds, and in enforcing territorial control of spawning zone).
The spawning act is remarkably similar among all oncorhynchid (salmon and trout) species. Male and female fish pair up. The female builds a nest (redd) in the gravel by turning on her side and scooping out a depression in the gravel using her tail. The gravel is moved not by the tail beating down on the bottom, but by the upwelling caused as the tail sweeps up. The female repeatedly arcs her body, until a shallow, saucer-shaped depression is cleared of silt, sand and smaller gravel. When she is ready to deposit her eggs into the redds, the male moves up beside her. They will often brush gently against one another. Simultaneously they release egg and sperm, indicating that in their courtship they have transmitted information to one another, and helped stimulate one another. The fertilized eggs settle to the bottom of the redd, where a slight tackiness helps them stick to the bottom. The female then moves immediately upstream of the redd, turns on her side and begins to loosen up gravel using her tail again. She is building a new redd, and at the same time covering the one she’s just filled with eggs. After completing the spawning act the exhausted Pacific salmon all die, usually within a few days. Many trout and steelhead also die, although some do survive. The death rate is higher among the males, apparently because they have exhausted themselves through fighting. Although hundreds to thousands of eggs are laid by each female only 5 to 10% will survive until hatching time. Some eggs will be frozen in ice, others smothered by silt, some will be ground to death by shifting gravels during floods, others washed away by flood waters of spring and winter or by spawning activity of other fish, and yet others will dry in stream beds.
Some will be eaten by insects, birds, snakes, raccoons. . . The eggs which do not hatch, either because of poor fertilization, development, or natural disaster, are not wasted. They provide important food directly for larger fish - which pounce on them when they drift down with the current - or indirectly, by feeding the insects which feed small fish. The alevin that hatch from the eggs in the spring are tiny fish with big eyes and an attached yolk sac. When the nourishing yolk sac is absorbed these tiny fish will emerge from the gravel as 2.5-3.5 cm long fry and begin a life history typical of each fish species. In each stream, each oncorhynchid species has its own time of emergence, generally separate from others, maximizing the food available for each. Depending on the species, the emerging fry will live in freshwater for varying lengths of time before heading downstream to the ocean. Pink and chum fry leave almost immediately for the sea. Chinook fry may migrate to the salt water immediately or wait up to 15 months to do so. Coho fry remain in fresh water for a year or two before migrating to salt water. Sockeye fry spend one to three years in a freshwater lake before heading to salt water. Cutthroat and rainbow trout spend 2-3 years in freshwater streams before heading to saltwater. It’s important, when fishing in the spring, to know what species spawned in a river system the fall previous. That way you can fish a fry imitation that matches the hatch. In early spring, look along the shore margins for the tiny fry....if they are still carrying their yolk sacs, a fly with a touch of orange on the underside can do wonders. The fry from different species generally prefer different rearing habits. Steelhead juveniles are found in the riffles and fast running glides. Chinook juvenile prefer slightly slower waters, and are more likely to be found along the margins of the deeper pools. Sockeye salmon fry rear in freshwater lakes. Pink and chum fry rear in the estuary, and that is why they migrate downstream shortly after emerging from spawning gravels. Cutthroat fry and coho fry are commonly found in the small tributary streams, beaver ponds, or off channel sloughs of the lower river. The coho prefer the slower pools, whereas the cutthroat are more likely to be found in the faster riffle habitat. If you are fishing salmon streams this fall and winter, pay attention to the species you see spawning. It will be valuable information when you return in the spring, to fish the fry hatch.
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