THE GROWTH OF SALMON.
SEEKING- the salt water, the spent salmon of the Dee were stopped at Chester. The drought had made the river so• low that the weir there blocked the way, Accordingly, the Conservators lifted the fish over in nets ; and the sea now holds a good many salmon with tickets on their tails. As a, fish of the salmon kind always goes back to the place of its birth, it is hoped that, by-and-bye, some of the ticketed salmon will be caught again; and it is assumed that in that event we shall have trustworthy information as to the length, of the period during which the salmon lives in the sea, and as to the rate at which it grows. The results, if there be any, will be interesting ; but they will not be conclu- sive. There is reason for believing that the fish recover very rapidly when they have reached the sea, and that in some cases they go back into the river whenever a flood comes down, even if that is within a month after they had left it. On the other hand, there is reason for believing, also, that there are exceptions to the rule. There are always "clean fish" in Loch Tay, for example ; which proves that salmon are not uniform in their habits, and, as Mr. James Hannay would have phrased it, "lends colour " to the local belief that that water has two tribes of fish, each of which spawns not once a year, but once in two years. As regards the part of it with which we are now dealing, then,- the experiment on the Dee cannot lead to a general con- clusion, It may enable the Conservators to find out how long a few of the Dee salmon take to recover "condition." It will give us no more than a suggestion as to the habits of salmon generally. Indeed, the experiment will be incomplete, even as regards the Dee itself. It is not likely that the Conservators, or they and the netters and the anglers together, will catch all the ticketed fish. What are we to say if half of them are not seen again this year P Shall we not be entitled to conclude that the absentees are spending the year at sea ?
We shall; but if we are wise, we shall not come to any con- clusion at all. The absence of half the ticketed salmon will support a suspicion on the strength of which we purpose show ing that as regards the other and more important half of it, the experiment on the Dee must be a complete failure. Let us suppose that a month hence a salmon, which the other day weighed 12 lb., is found to have become a 20-pounder. Will that warrant us in adopting or in forming any opinion as to- the rate at which salmon grow ? It will not. The fish which weighs 20 lb. in July, 1893, may, for all we know, have weighed 20 lb. in July, 1892. Perhaps it may have weighed even more in 1892 ; for it may be a fish which had reached its utmost maturity, and, like most other creatures, salmon fall off in weight when they have passed their prime.. The fish which has gained 8 lb. in a month may be smaller than the average fish of the river ; but that will not be a safe reason for assuming that it is adolescent and a fair test. In certain waters, such as the Hampshire chalk-streams, a trout which is old and declining bears certain signs of its age; it is black, lanky, and often blind of an eye, the eye towards the bank near which it is reposing; but no man can have more than a guess at a salmon's age. Its years are always more dubious than those of the celebrated ladies of whom popular sixpenny magazines give portraits, representing them at seven, seventeen, twenty-five, and "the present day." Thus, all that will be proved by the fact that a Dee salmon has grown 81b. heavier in a month, is that that is probably the rate at which a spent fish recovers. We shall not have gained any knowledge as to the rate at which, from year to year, a salmon grows. We shall know nothing more about him than his appearance and stature at " the present day," a date which, in so far as his appearance and stature are concerned,. has no scientific relation to any other date whatever.
There are other reasons for expecting that the experiment will be inconclusive. We have not been told what the tickets on the tails are made of. If they are of cloth, or of parch- ment, they will rot in the sea, and be heard of no more. If they are of metal, they will either kill the fish as their tails endeavour to expand, or prevent them from growing as they might grow if there were nothing to impede their growth. The Conservators, of course, may have realised all that, and made a precautionary compromise. Perhaps the tickets -" bearing date this week " are of metal, which will endure, attached by india-rubber bands, which will yield. What then P Let a Conservator put an elastic band round his wrist, or, still better, round his waist, on retiring for the night; and he will be able to make answer in the morning, perhaps long before cock-crow. He will be very sore indeed; for, even as the constant dropping of water wears a stone, an elastic band, gentle as it is for a minute or two, makes a strenuous impression if you give it time. If it did not kill the Conservator in a month, it would certainly make him pine; and what reason have we for assuming that the sensi- bility of a salmon is less than that of a Conservator P Saving that when you knock him on the head, a fish quivers as terribly as a man in his extreme agony, we know nothing about the sensibility of fish. What we do know is that a salmon is mar- vellously adapted to the conditions amid which it lives. It can cleave through tons of water falling perpendicularly ; yet its fins and its tail, which seem to hold the propelling power, are not less fragile than the wings of a bat. It can be killed without injury to its contour, and a plaster cast of it can be made ; yet no mechanician can devise an instrument which will lie in the water, and move, as it does, and no theory of dynamics has explained either its postures in the water or its motion. Softer and more pliable than any woman, it has the strength of a mole, which, proportionately, is greater than that of an elephant ; simple in its organisation as it seems, its movements are as inimitable by any human contrivance as the flight of a bird has proved to be. Is it not obvious, then, that the movements and the very life of a salmon depend upon its delicate adjustment to natural conditions, and that the tickets on the tails of the Dee fish are sure to destroy, or to falsify, the very phenomena which they are designed to connote scientifically ? If, not being lost, they do not kill the fish, they will certainly add to the conditions of their life a con- dition artificial in the extreme, and incompatible with their natural growth.
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