NATURAL HISTORY OF SALMON AND SEA-TROUT.
[On the Growth of Grilse and Salmon. By Mr Andrew Young, Invershin, Sutherlandshire. (Transactions of the Royal Society of Edinburgh. Vol. XV. Part III.) Edinburgh, 1843.]
[On the Growth and Migrations of the Sea-Trout of the Solway. By Mr John Shaw, Drumlanrig. (Ibid.) Edinburgh, 1843.]
The salmon is undoubtedly the finest and most magnificent of our fresh-water fishes, or rather of those anadromous kinds which, in accordance with the succession of the seasons, seek alternately the briny sea and the "rivers of water." It is also the most important, both in a commercial and culinary point of view as well as the most highly prized by the angler as an object of exciting recreation. Notwithstanding these and other long-continued claims upon our consideration, a knowledge of its natural history and habits has developed itself so slowly, that little or nothing was precisely ascertained till very recently regarding either its early state or its eventual changes. The salmon-trout, in certain districts of almost equal value with the true salmon, was also but obscurely known to naturalists, most of whom, in truth, are too apt to satisfy themselves rather by the extension than the increase of knowledge. They hand down to posterity, in their barren technicalities, a great deal of what is neither new nor true, even in relation to subjects which lie within the sphere of ordinary observation,—to birds and beasts, which almost dwell among us, and give utterance, by articulate or intelligible sounds, to a vast variety of instinctive, and as it were explanatory emotions:—what marvel, then, that they should so often fail to inform us of what we desire to know regarding the silent, because voiceless, inhabitants of the world of waters?
But that which naturalists have been unable to accomplish, has, so far as concerns the two invaluable species just alluded to, been achieved by others with no pretension to the name; and we now propose to present our readers with a brief sketch of what we conceive to be the completed biography of salmon and sea-trout. In stating that our information has been almost entirely derived from the researches of practical men, we wish it to be understood, and shall afterwards endeavour to demonstrate, that these researches have, nevertheless, been conducted upon those inductive principles which are so often characteristic of natural acuteness of perception, when combined with candour of mind and honesty of purpose. We believe it to be the opinion of many, that statements by comparatively uneducated persons are less to be relied upon than those of men of science. It may, perhaps, be somewhat difficult to define in all cases what really constitutes a man of science. Many sensible people suppose, that if a person pursues an original truth, and obtains it—that is, if he ascertains a previously unknown or obscure fact of importance, and states his observations with intelligence—he is entitled to that character, whatever his station may be. For ourselves, we would even say that if his researches are truly valuable, he is himself all the more a man of science in proportion to the difficulties or disadvantages by which his position in life may be surrounded.
The development and early growth of salmon, from the ovum to the smolt, were first successfully investigated by Mr John Shaw of Drumlanrig, one of the Duke of Buccleuch's gamekeepers in the south of Scotland. Its subsequent progress from the smolt to the adult condition, through the transitionary state of grilse, has been more recently traced, with corresponding care, by Mr Andrew Young of Invershin, the manager of the Duke of Sutherland's fisheries in the north. Although the fact of the parr being the young of the salmon had been vaguely surmised by many, and it was generally admitted that the smaller fish were never found to occur except in streams or tributaries to which the grown salmon had, in some way, the power of access, yet all who have any acquaintance with the works of naturalists, will acknowledge that the parr was universally described as a distinct species. It is equally certain that all who have written upon the subject of smolts or salmon-fry, maintained that these grew rapidly in fresh water, and made their way to the sea in the course of a few weeks after they were hatched.
Now, Mr Shaw's discovery in relation to these matters is in a manner twofold; first—he ascertained by a lengthened series of rigorous and frequently-repeated experimental observations, that parr are the early state of salmon, being afterwards converted into smolts; secondly,—he proved that such conversion does not, under ordinary circumstances take place until the second spring ensuing that in which the hatching has occurred, by which time the young are two years old. The fact is, that during early spring there are three distinct broods of parr or young salmon in our rivers.
1st, We have those which, recently excluded from the ova, are still invisible to common eyes; or, at least, are inconspicuous or unobservable. Being weak, in consequence of their recent emergence from the egg, and of extremely small dimensions, they are unable to withstand the rapid flow of water, and so betake themselves to the gentler eddies, and frequently enter "into the small hollows produced in the shingle by the hoofs of horses which have passed the fords." In these and similar resting-places, our little natural philosophers, instinctively aware that the current of a stream is less below than above, and along the sides than in the centre, remain for several months during spring, and the earlier portion of the summer, till they gain such an increase of size and strength as enables them to spread themselves abroad over other portions of the river, especially those shallow places where the bottom is composed of fine gravel. But at this time their shy and shingle-seeking habits in a great measure screen them from the observance of the uninitiated.
2dly, We have likewise, during the spring season, parr which have just completed their first year. As these have gained little or no accession of size during the winter months, owing to the low temperature both of the air and water, and the consequent deficiency of insect food, their dimensions are scarcely greater than at the end of the preceding October: that is, they measure in length little more than three inches.—(N.B. The old belief was that they grew nine inches in about three weeks, and as suddenly sought the turmoil of the sea.) They increase, however in size as the summer advances, and are then the declared and admitted parr of anglers and other men.
3dly, Simultaneously with the two preceding broods, our rivers are inhabited during March and April by parr which have completed their second year. These measure six or seven inches in length, and in the months of April and May they assume the fine silvery aspect which characterizes their migratory condition,—in other words, they are converted into smolts, (the admitted fry of salmon,) and immediately make their way towards the sea.
Now, the fundamental error which pervaded the views of previous observers of the subject, consisted in the sudden sequence which they chose to establish between the hatching of the ova in early spring, and the speedy appearance of the acknowledged salmon-fry in their lustrous dress of blue and silver. Observing, in the first place, the hatching of the ova, and, erelong, the seaward migration of the smolts, they imagined these two facts to take place in the relation of immediate or connected succession; whereas they had no more to do with each other than an infant in the nursery has to do with his elder, though not very ancient, brother, who may be going to school. The rapidity with which the two-year-old parr are converted into smolts, and the timid habits of the new-hatched fry, which render them almost entirely invisible during the first few months of their existence,—these two circumstances combined, have no doubt induced the erroneous belief that the silvery smolts were the actual produce of the very season in which they are first observed in their migratory dress: that is, that they were only a few weeks old, instead of being upwards of two years. It is certainly singular, however, that no enquirer of the old school should have ever bethought himself of the mysterious fate of the two-year-old parr, (supposing them not to be young salmon,) none of which, of course, are visible after the smolts have taken their departure to the sea. If the two fish, it may be asked, are not identical, how does it happen that the one so constantly disappears along with the other? Yet no one alleges that he has ever seen parr as such, making a journey towards the sea "They cannot do so" says Mr Shaw, "because they have been previously converted into smolts."