Volume 53 — NATURAL HISTORY OF SALMON AND SEA-TROUT.
Reading edition
[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."
Having now exhibited the progress of the salmon fry from the ovum to the smolt, our next step shall be to show the connexion of the latter with the grilse. As no experimental observations regarding the future dimensions of the détenus of the ponds could be regarded as legitimate in relation to the usual increase of the species, (any more than we could judge of the growth of a young English guardsman in the prisons of Verdun,) after the period of their natural migration to the sea, and as Mr Shaw's distance from the salt water—twenty-five miles, we believe, windings included—debarred his carrying on his investigations much further with advantage, he wisely turned his attention to a different, though cognate subject, to which we shall afterwards refer. We are, however, fortunately enabled to proceed with our history of the adolescent salmon by means of another ingenious observer already named, Mr Andrew Young of Invershin.
It had always been the prevailing belief that smolts grew rapidly into grilse, and the latter into salmon. But as soon as we became assured of the gross errors of naturalists, and all other observers, regarding the progress of the fry in fresh water, and how a few weeks had been substituted for a period of a couple of years, it was natural that considerate people should suspect that equal errors might pervade the subsequent history of this important species. It appears, however, that marine influence (in whatever way it works) does indeed exercise a most extraordinary effect upon those migrants from our upland streams, and that the extremely rapid transit of a smolt to a grilse, and of the latter to an adult salmon, is strictly true. Although Mr Young's labours in this department differ from Mr Shaw's, in being rather confirmatory than original, we consider them of great value, as reducing the subject to a systematic form, and impressing it with the force and clearness of the most successful demonstration.
Mr Young's first experiments were commenced as far back as 1836, and were originally undertaken with a view to show whether the salmon of each particular river, after descending to the sea, returned again to their original spawning-beds, or whether, as some supposed, the main body, returning coastwards from their feeding grounds in more distant parts of the ocean, and advancing along our island shores, were merely thrown into, or induced to enter, estuaries and rivers by accidental circumstances; and that the numbers obtained in these latter localities thus depended mainly on wind and weather, or other physical conditions, being suitable to their upward progress at the time of their nearing the mouths of the fresher waters. To settle this point, he caught and marked all the spawned fish which he could obtain in the course of the winter months during their sojourn in the rivers. As soon as he had hauled the fish ashore, he made peculiar marks in their caudal fins by means of a pair of nipping-irons, and immediately threw then back into the water. In the course of the following fishing season great numbers were recaptured on their return from the sea, each in its own river bearing its peculiar mark. "We have also," Mr Young informs us, "another proof of the fact, that the different breeds or races of salmon continue to revisit their native streams. You are aware that the river Shin falls into the Oykel at Invershin, and that the conjoined waters of these rivers, with the Carron and other streams, form the estuary of the Oykel, which flows into the more open sea beyond, or eastwards of the bar, below the Gizzen Brigs. Now, were the salmon which enter the mouth of the estuary at the bar thrown in merely by accident or chance, we should expect to find the fish of all the various rivers which form the estuary of the same average weight; for, if it were a mere matter of chance, then a mixture of small and great would occur indifferently in each of the interior streams. But the reverse of this is the case. The salmon in the Shin will average from seventeen pounds to eighteen pounds in weight, while those of the Oykel scarcely attain an average of half that weight. I am, therefore, quite satisfied, as well by having marked spawned fish descending to the sea, and caught them ascending the same river, and bearing that river's mark, as by a long-continued general observation of the weight, size, and even something of the form, that every river has its own breed, and that breed continues, till captured and killed, to return from year to year into its native stream."
We have heard of a partial exception to this instinctive habit, which, however, essentially confirms the rule. We are informed that a Shin salmon (recognized as such by its shape and size) was, on a certain occasion, captured in the river Conon, a fine stream which flows into the upper portion of the neighbouring Frith of Cromarty. It was marked and returned to the river, and was taken next day in its native stream the Shin, having, on discovering its mistake, descended the Cromarty Frith, skirted the intermediate portion of the outer coast by Tarbet Ness, and ascended the estuary of the Oykel. The distance may be about sixty miles. On the other hand, we are informed by a Sutherland correspondent of a fact of another nature, which bears strongly upon the pertinacity with which these fine fish endeavour to regain their spawning ground. By the side of the river Helmsdale there was once a portion of an old channel forming an angular bend with the actual river. In summer, it was only partially filled by a detached or landlocked pool, but in winter, a more lively communication was renewed by the superabounding waters. This old channel was, however, not only resorted to by salmon as a piece of spawning ground during the colder season of the year, but was sought for again instinctively in summer during their upward migration, when there was no water running through it. The fish being, of course, unable to attain their object, have been seen, after various aerial boundings, to fall, in the course of their exertions, upon the dry gravel bank between the river and the pool of water, where they were picked up by the considerate natives.
For example, in the spring of 1837, Mr Young marked a great quantity of descending smolts, by making a perforation in their caudal fins with a small pair of nipping-irons constructed for the purpose, and in the ensuing months of June and July he recaptured a considerable number on their return to the rivers, all in the condition of grilse, and varying from 3lbs. to 8lbs., "according to the time which had elapsed since their first departure from the fresh water, or, in other words, the length of their sojourn in the sea." In the spring of 1842, he likewise marked a number of descending smolts, by clipping off what is called the adipose fin upon the back. In the course of the ensuing June and July, he caught them returning up the river, bearing his peculiar mark, and agreeing with those of 1837 both in respect to size, and the relation which that size bore to the lapse of time.
The following list from Mr Young's note-book, affords a few examples of the rate of growth:—
List of Smolts marked in the River, and recaptured as Grilse on their first ascent from the Sea.
Period of marking. Period of recapture. Weight when retaken.
1842. April and May. 1842. June 28. 4 lb.
July 15. 5 lb
15. 5 lb.
25. 7 lb.18
25. 5 lb.
30. 3½ lb.18
Mr Young commenced marking grilses, with a view to ascertain that they became salmon, as far back as 1837, and has continued to do so ever since, though never two seasons with the same mark. We shall here record only the results of the two preceding years. In the spring of 1841, he marked a number of spawned grilse soon after the conclusion of the spawning period. Taking his "net and coble," he fished the river for the special purpose, and all the spawned grilse of 4 lb. weight were marked by putting a peculiarly twisted piece of wire through the dorsal fin. They were immediately thrown into the river, and of course disappeared, making their way downwards with other spawned fish towards the sea. "In the course of the next summer we again caught several of those fish which we had thus marked with wire as 4 lb. grilse, grown in the short period of four or five months into beautiful full-formed salmon, ranging from 9 lb. to 14 lb. in weight, the difference still depending on the length of their sojourn in the sea."
In January 1842, he repeated the same process of marking 4 lb. grilse which had spawned, and were therefore about to seek the sea; but, instead of placing the wire in the back fin, he this year fixed it in the upper lobe of the tail, or caudal fin. On their return from the sea, he caught many of these quondam grilse converted into salmon as before. The following lists will serve to illustrate the rate of growth:—
List of Grilse marked after having spawned, and re-captured as Salmon, on their second ascent from the Sea.
Period of marking. Period of recapture. Weight when marked. Weight when retaken.
1841. Feb. 18. 1841. June 23. 4 lbs. 9 lbs.
18. 23. 4 lbs. 11 lbs.
18. 25. 4 lbs. 9 lbs.
18. 25. 4 lbs. 10 lbs.
18. July 27. 4 lbs. 13 lbs.
18. 28. 4 lbs. 10 lbs.
March 4. July 1. 4 lbs. 12 lbs.
4. 1. 4 lbs. 14 lbs.
4. 27. 4 lbs. 12 lbs.
1842. Jan. 29. 1842. July 4. 4 lbs. 8 lbs.20
29. 14. 4 lbs. 9 lbs.20
29. 14. 4 lbs. 8 lbs.
March 8. 23. 4 lbs. 9 lbs.
Jan. 29. 29. 4 lbs. 11 lbs.
March 8. Aug. 4. 4 lbs. 10 lbs.
Jan. 29. 11. 4 lbs. 12 lbs.
During both these seasons, Mr Young informs us, he caught far more marked grilse returning with the form and attributes of perfect salmon, than are recorded in the preceding lists. "In many specimens the wires had been torn from the fins, either by the action of the nets or other casualties; and, although I could myself recognise distinctly that they were the fish I had marked, I kept no note of them. All those recorded in my lists returned and were captured with the twisted wires complete, the same as the specimens transmitted for your examination."
Leaving the country of the Morer Chatt (the Celtic title of the Earls of Sutherland) we shall now return to the retainer of the "bold Buccleuch." We have already mentioned that Mr Shaw, having so successfully illustrated the early history of salmon, next turned his attention to a cognate subject, that of the sea-trout (Salmo-trutta?) Although no positive observations of any value, anterior to those now before us, had been made upon this species, it is obvious that as soon as his discoveries regarding salmon fry had afforded, as it were, the key to this portion of nature's secrets, it was easy for any one to infer that the old notions regarding the former fish were equally erroneous. Various modifications of these views took place accordingly; but no one ascertained the truth by observation. Mr Shaw was, therefore, entitled to proceed as if the matter were solely in his own hands; and he makes no mention either of the "vain imaginations" of Dr Knox, the more careful compilation of Mr Yarrell, or the still closer, but by no means approximate calculations of Richard Parnell, M.D. In this he has acted wisely, seeing that his own essay professes to be simply a statement of facts, and not an historical exposition of the progress of error.
It would, indeed, have been singular if two species, in many respects so closely allied in their general structure any economy, had been found to differ very materially in any essential point. It now appears, however, that Mr Shaw's original discovery of the slow growth of salmon fry in fresh water, applies equally to sea trout; and, indeed, his observations on the latter are valuable not only in themselves, but as confirmatory of his remarks upon the former species. The same principle has been found to regulate the growth and migrations of both, and Mr Shaw's two contributions thus mutually strengthen and support each other.
The sea trout is well known to anglers as one of the liveliest of all the fishes subject to his lure. Two species are supposed by naturalists to haunt our rivers—Salmo eriox, the bull trout of the Tweed, comparatively rare on the western and northern coasts of Scotland, and Salmo trutta, commonly called the sea or white trout, but, like the other species, also known under a variety of provincial names, somewhat vaguely applied. In its various and progressive stages, it passes under the names of fry, smolt, orange-fin, phinock, herling, whitling, sea-trout, and salmon-trout. It is likewise the "Fordwich trout" of Izaak Walton, described by that poetical old piscator as "rare good meat." As an article of diet it indeed ranks next to the salmon, and is much superior in that respect to its near relation, S. eriox. It is taken in the more seaward pools of our northern rivers, sometimes in several hundreds at a single haul; and vast quantities, after being boiled, and hermetically sealed in tin cases, are extensively consumed both in our home and foreign markets. But, notwithstanding its great commercial value, naturalists have failed to present us with any accurate account of its consecutive history from the ovum to the adult state. This desideratum we are now enabled to supply through Mr Shaw.
Having narrated the result of Mr Shaw's experiment up to the migratory state of his brood, we shall now refer to the further progress of the species. This, of course, we can only do by turning our attention to the corresponding condition of the fry in their natural places in the river. So far back as the 9th of May 1836, our observer noticed salmon fry descending seawards, and he took occasion to capture a considerable number by admitting them into the salmon cruive. On examination, he found about one-fifth of each shoal to be what he considered sea-trout. Wisely regarding this as a favourable opportunity of ascertaining to what extent they would afterwards "suffer a sea change," he marked all the smolts of that species (about ninety in number) by cutting off the whole of the adipose fin, and three-quarters of the dorsal. At a distance, by the course of the river, of twenty-five miles from the sea, he was not sanguine of recapturing many of these individuals, and in this expectation he was not agreeably surprised by any better success than he expected. However, on the 16th of July, exactly eighty days afterwards, he recaptured as a herling (the next progressive stage) an individual bearing the marks he had inflicted on the young sea-trout in the previous May. It measured twelve inches in length, and weighed ten ounces. As the average weight of the migrating fry is about three and a half ounces, it had thus gained an increase of six and a half ounces in about eighty days' residence in salt water, supposing it to have descended to the sea immediately after its markings were imposed. In this condition of herlings or phinocks, young sea-trout enter many of our rivers in great abundance in the months of July and August.
On the 1st of August 1837—fifteen months after being marked as fry, on its way to the sea—another individual was caught, and recognised by the absence of one fin, and the curtailment of another. This specimen, as well as others, had no doubt returned, and escaped detection as a herling, in 1836; but it was born for greater things, and when captured, as above stated, weighed two pounds and a half. "He may be supposed," says Mr Shaw, "to represent pretty correctly the average size of sea-trout on their second migration from the sea." In this state they usually make their appearance in our rivers, (we refer at present particularly to those of Scotland,) in greatest abundance in the months of May and June. This view of the progress of the species clearly accounts for a fact well known to anglers, that in spring and the commencement of summer, larger sea-trout are caught than in July and August, which would not be the case if they were all fish of the same season. But the former are herlings which have descended, after spawning early, to the sea, and returned with the increase just mentioned; the latter were nothing more than smolts in May, and have only once enjoyed the benefit of sea bathing. They are a year younger than the others.
From these and other experiments of a similar nature, which Mr Shaw has been conducting for many years, he has come to the conclusion, that the small fry called "Orange-fins," which are found journeying to the sea with smolts of the true salmon, are the young of sea-trout of the age of two years;—that the same individuals, after nine or ten weeks' sojourn in salt water, ascend the rivers as herlings, weighing ten or twelve ounces and on the approach of autumn pass into our smaller tributaries with a view to the continuance of their kind;—that, having spawned, they re-descend into the sea, where their increase of size (about one and a half pound per annum) is almost totally obtained;—and that they return annually, with an accession of size, for several seasons, to the rivers in which their parents gave them birth. In proof of this last point, Mr Shaw informs us, that of the many hundred sea-trout of different ages which he has marked in various modes, he is not aware that even a single individual has ever found its way into any tributary of the Solway, saving that of the river Nith.