Although, as we have said, salmon soonest ascend the warmest rivers, they are alleged to spawn earliest in the colder ones. Thus Mr Scrope informs us, that in the shallow mountain streams which pour into the Tay, near its source, the fish spawn much earlier than those in the main bed of that magnificent river, and he quotes the following sentiments of the late John Crerar, head fisherman and forester to the Duke of Athole, on the subject:—
"There are," said John, "two kinds of creatures that I am well acquainted with—the one a land animal, the other a water one—the red-deer and the salmon. In October the deer ruts, and the salmon spawns. The deer begins soonest, high up among the hills, particularly in frosty weather; so does the salmon begin to spawn earlier in frosty weather than in soft. The master hart would keep all the other harts from the hind, if he could; and the male salmon would keep all the other males from the female, if he was able."—P. 60.
We do not think, however, that Mr Scrope's comparative reference to the upper and lower portions of the Tay affords a satisfactory or conclusive test. The higher parts of almost all rivers (including, their tributaries) constitute the favourite spawning places, from other causes than "by reason of the cold;" and the question should be tried, not by comparing two different districts of the same river, but all the portions of one river, with the entire course of another of dissimilar character. The exceptive clause in Mr Loch's proposed act in flavour of the river Ness, certainly stood upon the supposition of that river being an early one for the breeding salmon, as well as the new-run winter fish; for it enacts not only that the Ness should open more than a month earlier than its neighbours, but also that it shall close more than a month before them. This latter restriction would of course be useless and impolitic, if the parent fish were not conceived to be about to spawn. But it should also be borne in mind, that the same causes (such as the extent and depth of feeding lakes) which produce a higher temperature in winter, cause a lower one in summer and the earlier part of autumn, and that shallow upland streams are warmer during the latter periods than those which flow from deeper and more affluent sources. We believe that the fish of all rivers spawn soonest on the higher portions of their water courses, whether these be comparatively warm or cold. The earliest individuals are in general such as have escaped the nets and other accidents below, and have made their watery way in good time to proper spawning places. In several rivers with which we are acquainted, a great majority of the breeding fish ascend in August and September. But many of those which make their appearance in July, would be early spawners if they were allowed to escape the various dangers which beset their path in life—almost all the salmon of that month being captured by one means or another. Mr Young, in our MS. notes already quoted, states, in regard to the range of the breeding season, that he has seen salmon perfectly full of spawn, ascending the rivers in October, November, December, January, and February. Now the fish of the last-named month may have spawned as late as March, although our correspondent adds that he has never seen fish on the spawning beds later than February, nor earlier than September. He has seen them in the act of spawning in these and all the intermediate months.
As we have said above, the greater part of these breeders ascend in August and September, and the throng of the spawning process takes place in November and December. The earlier spawning begins in September with only a few pairs, generally grilse; and from that period the numbers increase till the first week of December, when the operation has attained its height. It then gradually decreases until February, when perhaps only a few pairs are seen at work. Mr Young informs us that sea-trout are seen spawning a week earlier than grilse, and grilse a week earlier than salmon. He does not mean that all grilse spawn before salmon begin, but that they are observed working a week before the latter have commenced.
Mr Shaw informs us, (in his last letter,) that it is an exceedingly rare occurrence to find an unspawned fish in the rivers of Dumfriesshire in the month of March. On one occasion, however, about twenty years ago, he observed a female salmon spawning in the Nith about the 10th or 12th of March, but unaccompanied by any male. He can also call to mind a pair of salmon having been observed spawning in the Ettrick so late as Selkirk March fair, which is held during the first week of April. This, however, we believe to be a very rare occurrence, notwithstanding Mr Scrope's statement, that he has in the Tweed "caught full roaners as late as May." These seem to be anomalous or accidental instances, and we are not aware that any evidence has been brought forward to prove that they still seek the spawning beds in pairs at that period, or produce what may be called autumnal fry.
The usual spawning period in the south-west of Scotland extends from about the middle of November till the middle of February; but the busiest months of that period are December and January, when the salmon spawn in great numbers in the Nith, about Drumlanrig. From the circumstances of the largest salmon visiting the rivers at that season, Mr Shaw is induced to think that they are likewise the oldest; and that, as they increase in years, they desire to remain the longer in the sea, visiting the fresh waters only during the breeding season. The spawning period of sea-trout, he informs us, is from about the middle of October until the middle of December, the principal period being the whole of November, when the various streams and tributaries are taken possession of both by sea-trout and herling, spawning in deep or shallow water, according to their individual size.
But in reference to the point in question, that cold accelerates the spawning process, let us take for a moment the general basin of the Oykel waters into view. We know that for several seasons back, the earliest spawning in that quarter has occurred in the Carron, in September. Now, it is certain, that during that month the Carron waters are warmer than those of the Shin. So also the Oykel (properly so called) is itself two degrees warmer in October than the Shin, and yet the latter is the later of the two. It thus appears that warmth may be advantageous both as inducing early spawning in autumn, and an early entrance of fresh-run fish in winter; although a single river may not possess both attributes for the reason hinted at—the deepest waters, though protected from winter's cold, being also screened from summer's heat. Mr Scrope may therefore be regarded as right in his facts as to the earlier season of the upland streams, although his theoretical explanation of them is not conclusive.
The lateness of the spawning season in the Shin may, in some measure, be owing to the early breeding fish going up into the loch, from whence, after a time, they fall back upon the spawning places in the fords of the river. The same thing happens in the lower regions of the Tay—the fish fall back from the loch, and the ford between Taymouth Castle and Kenmore is by far the latest in that river. Salmon have been seen to spawn there in February. In regard to the general influence of the atmosphere, we may here remark that frosty weather is good for spawning; because the fish go then into the deeper or central portions of the fords, by which procedure the spawning beds are never dry,—whereas, in time of spates, salmon are apt to deposit their spawn along the margins, and thus the roe is frequently destroyed by the subsiding of the waters.
However, the real importance of an early river has little or no connexion with the periods of the spawning process; because it is not so much the breeding fish that are of individual value in winter, as those which, having no intention or requirement to spawn until the following autumn, enter the fresh waters because they have already completed the days of their purification in the sea. Although, when viewed in the relation of time, they may seem to form the continuous succession of spawning fish which have come up gravid from the ocean during the later months of autumn, they are in truth rather the avant-couriers of the newer and more highly-conditioned shoals which show themselves in early spring. We believe that fresh-run fish may be found in all our larger rivers during every month throughout the year, though we cannot clear up their somewhat anomalous history, nor explain why the breeding season, as among land creatures of identical natures, should not take place more uniformly about the same time. It is by no means improbable, however, that, as grilse seek our fresh waters at different periods from adult salmon, so salmon of a certain standing may observe different periods of migration from those of dissimilar age.
If, as many suppose, the earliest fish are those which have soonest spawned during the preceding autumn, and have since descended towards and recovered in the sea,—then a precocious spawning would necessarily lead to the speediest supply of clean fish in mid-winter; but the fact referred to has not been ascertained, and it may therefore still be as reasonably alleged that the winter fish (an opinion supported by the fact of their unusually large size) have continued in the sea since spring. At least a majority of them, (for they differ somewhat in their aspect and condition,) instead of having spawned soonest in autumn, have probably rather spawned last of all during the preceding spring, and so required for their recovery a corresponding retardation of their sojourn in the sea. The reasons why grilse seldom show themselves till the summer is well advanced, are very obvious, now that we have become conversant with their true history. They were only smolts in the immediately preceding spring, and are becoming grilse from week to week, and of various sizes, according to the length of their continuance in the sea. But they require at least a couple of months to intervene between their departure from the rivers in April or May, and their return thither;—which return consequently commences, though sparingly, in June, and preponderates in July and August.