=Anadromous Fishes.=--Many fresh-water fishes, as trout and suckers, forsake the large streams in the spring, ascending the small brooks where their young can be reared in greater safety. Still others, known as _anadromous_ fishes, feed and mature in the sea, but ascend the rivers as the impulse of reproduction grows strong. Among such fishes are the salmon, shad, alewife, sturgeon, and striped bass in American waters. The most remarkable case of the anadromous instinct is found in the king salmon or quinnat (_Oncorhynchus tschawytscha_) of the Pacific Coast. This great fish spawns in November, at the age of four years and an average weight of twenty-two pounds. In the Columbia River it begins running with the spring freshets in March and April. It spends the whole summer, without feeding, in the ascent of the river. By autumn the individuals have reached the mountain streams of Idaho, greatly changed in appearance, discolored, worn, and distorted. The male is humpbacked, with sunken scales, and greatly enlarged, hooked, bent, or twisted jaws, with enlarged dog-like teeth. On reaching the spawning beds, which may be a thousand miles from the sea in the Columbia, over two thousand in the Yukon, the female deposits her eggs in the gravel of some shallow brook. The male covers them and scrapes the gravel over them. The female salmon does as much as the male in covering the eggs. Then both male and female drift tail foremost helplessly down the stream; none, so far as certainly known, ever survive the reproductive act. The same habits are found in the five other species of salmon in the Pacific, but in most cases the individuals do not start so early nor run so far. The blue-back salmon or redfish, however, does not fall far short in these regards. The salmon of the Atlantic has a similar habit, but the distance traveled is everywhere much less, and most of the hook-jawed males drop down to the sea and survive to repeat the acts of reproduction. [Illustration: FIG. 123.--Tide-pools of Misaki. The Misaki Biological Station, from the north side.] _Catadromous_ fishes, as the true eel (_Anguilla_), reverse this order, feeding in the rivers and brackish estuaries, apparently finding their usual spawning-ground in the sea. [Illustration: FIG. 124.--Squaw-fish, _Ptychocheilus oregonensis_ (Richardson). Columbia River.]