The absence of the fine spring salmon in the streams of Japan is the cause of the relative unimportance of the river fisheries of the northern island of Japan, Hokkaido. It is not likely that either the quinnat or the red salmon can be introduced into these rivers, as they have no snow-fed streams, and few of them pass through lakes which are not shut off by waterfalls. For the same reason neither of these species is likely to become naturalized in the waters of our Eastern States, though it is worth while to bring the red salmon to the St. Lawrence. The silver salmon, already abundant in Japan, should thrive in the rivers and bays of New England.
The Parent-stream Theory.—It has been generally accepted as unquestioned by packers and fishermen that salmon return to spawn to the very stream in which they were hatched. As early as 1880 the present writer placed on record his opinion that this theory was unsound. In a general way most salmon return to the parent stream, because when in the sea the parent stream is the one most easily reached. The channels and runways which directed their course to the sea may influence their return trip in the same fashion. When the salmon is mature it seeks fresh water. Other things being equal, about the same number will run each year in the same channel. With all this, we find some curious facts. Certain streams will have a run of exceptionally large or exceptionally small red salmon. The time of the run bears some relation to the length of the stream: those who have farthest to go start earliest. The time of running bears also a relation to the temperature of the spawning grounds: where the waters cool off earliest the fish run soonest.
The supposed evidence in favor of the parent-stream theory may be considered under three heads:[[9]] (1) Distinctive runs in various streams. (2) Return of marked salmon. (3) Introduction of salmon into new streams followed by their return.
[9]. See an excellent article by H. S. Davis in the Pacific Fisherman for July, 1903.
Under the first head it is often asserted of fishermen that they can distinguish the salmon of different streams. Thus the Lynn Canal red salmon are larger than those in most waters, and it is claimed that those of Chilcoot Inlet are larger than those of the sister stream at Chilcat. The red salmon of Red Fish Bay on Baranof Island are said to be much smaller than usual, and those of the neighboring Necker Bay are not more than one-third the ordinary size. Those of a small rapid stream near Nass River are more wiry than those of the neighboring large stream. The same claim is made for the different streams of Puget Sound, each one having its characteristic run. In all this there is some truth and perhaps some exaggeration. I have noticed that the Chilcoot fish seem deeper in body than those at Chilcat. The red salmon becomes compressed before spawning, and the Chilcoot fishes having a short run spawn earlier than the Chilcat fishes, which have many miles to go, the water being perhaps warmer at the mouth of the river. Perhaps some localities may meet the nervous reactions of small fishes, while not attracting the large ones. Mr. H. S. Davis well observes that "until a constant difference has been demonstrated by a careful examination of large numbers of fish from each stream taken at the same time, but little weight can be attached to arguments of this nature."
It is doubtless true as a general proposition that nearly all salmon return to the region in which they were spawned. Most of them apparently never go far away from the mouth of the stream or the bay into which it flows. It is true that salmon are occasionally taken well out at sea, and it is certain that the red salmon runs of Puget Sound come from outside the Straits of Fuca. There is, however, evidence that they rarely go so far as that. When seeking shore they do not reach the original channels.
In 1880 the writer, studying the salmon of the Columbia, used the following words, which he has not had occasion to change:
"It is the prevailing impression that the salmon have some special instinct which leads them to return to spawn in the same spawning grounds where they were originally hatched. We fail to find any evidence of this in the case of the Pacific-coast salmon, and we do not believe it to be true. It seems more probable that the young salmon hatched in any river mostly remain in the ocean within a radius of twenty, thirty, or forty miles of its mouth. These, in their movements about in the ocean, may come into contact with the cold waters of their parent rivers, or perhaps of any other river, at a considerable distance from the shore. In the case of the quinnat and the blue-back their 'instinct' seems to lead them to ascend these fresh waters, and in a majority of cases these waters will be those in which the fishes in question were originally spawned. Later in the season the growth of the reproductive organs leads them to approach the shore and search for fresh waters, and still the chances are that they may find the original stream. But undoubtedly many fall salmon ascend, or try to ascend, streams in which no salmon was ever hatched. In little brooks about Puget Sound, where the water is not three inches deep, are often found dead or dying salmon which have entered them for the purpose of spawning. It is said of the Russian River and other California rivers that their mouths, in the time of low water in summer, generally become entirely closed by sand-bars, and that the salmon, in their eagerness to ascend them, frequently fling themselves entirely out of water on the beach. But this does not prove that the salmon are guided by a marvelous geographical instinct which leads them to their parent river in spite of the fact that the river cannot be found. The waters of Russian River soak through these sand-bars, and the salmon instinct, we think, leads them merely to search for fresh waters. This matter is much in need of further investigation; at present, however, we find no reason to believe that the salmon enter the Rogue River simply because they were spawned there, or that a salmon hatched in the Clackamas River is more likely, on that account, to return to the Clackamas than to go up the Cowlitz or the Des Chûtes."
Attempts have been made to settle this question by marking the fry. But this is a very difficult matter indeed. Almost the only structure which can be safely mutilated is the adipose fin, and this is often nipped off by sticklebacks and other meddling fish. The following experiments have been tried, according to Mr. Davis:
In March, 1896, 5000 king-salmon fry were marked by cutting off the adipose fin, then set free in the Clackamas River. Nearly 400 of these marked fish are said to have been taken in the Columbia in 1898, and a few more in 1899. In addition a few were taken in 1898, 1899, and 1900 in the Sacramento River, but in much less numbers than in the Columbia. In the Columbia most were taken at the mouth of the river, where nearly all of the fishing was done, but a few were in the original stream, the Clackamas. It is stated that the fry thus set free in the Clackamas came from eggs obtained in the Sacramento—a matter which has, however, no bearing on the present case.