Salmonia; Or, Days of Fly Fishing / In a series of conversations. With some account of the habits of fishes belonging to the genus Salmo

by Sir Humphry Davy

Poiet.—It may have been a fish imported from the continent, and carried to a number of rivers, only a few of which may have suited its habits, and has remained there and multiplied.

Hal.—There may be truth in what you are now imagining, for the grayling requires a number of circumstances in a river to enable it to increase.

Poiet.—What circumstances are these?

Hal.—A temperature in the water which must be moderate—neither too high nor too low. Grayling are never found in streams that run from glaciers—at least near their source; and they are killed by cold or heat. I once put some grayling from the Teme, in September, with some trout, into a confined water, rising from a spring in the yard at Downton; the grayling all died, but the trout lived. And in the hot summer of 1825, great numbers of large grayling died in the Avon, below Ringwood, without doubt killed by the heat in July.

Poiet.—But I have heard of grayling being common in Lapland—at least so says Linnæus.

Hal.—I think it must be another species of the same genus; the same as Back’s grayling found by Captain Franklin and his companions in North America, and distinguished by a much larger back fin. Having travelled with the fishing-rod in my hand through most of the Alpine valleys in the south and east of Europe, and some of those in Norway and Sweden, I have always found the char in the coldest and highest waters; the trout, in the brooks rising in the highest and coldest mountains; and the grayling always lower, where the temperature was milder: and if in hot countries, only at the foot of mountains, not far from sources which had the mean temperature of the atmosphere,—as in the Vipacco, near Goritzia, and in the streams which gush forth from the limestone caverns of the Nordic Alps. Besides temperature, grayling require a peculiar character in the disposition of the water of rivers. They do not dwell, like trout, in rapid shallow torrents; nor, like char or chub, in deep pools or lakes. They require a combination of stream and pool; they like a deep still pool for rest, and a rapid stream above, and a gradually declining shallow below, and a bottom where marl or loam is mixed with gravel; and they are not found abundant except in rivers that have these characters. It is impossible to have a more perfect specimen of a grayling river than that now running before us, in this part of its course. You see a succession of deep still pools under shady banks of marl, with gentle rapids above, and a long shelving tail, where the fish sport and feed. Should there be no such pools in a river, grayling would remain, provided the water was clear, and would breed; but they cannot stem rapid streams, and they are gradually carried down lower and lower, and at last disappear. You know the Test, one of the finest trout streams in Hampshire, and of course in England; when I first knew this stream, twenty years ago, there were no grayling in it. A gentleman brought some from the Avon, and introduced them into the river at Longstock, above Stockbridge. They were for two or three years very abundant in that part of the river; but they gradually descended, and though they multiplied greatly, there are now scarcely any above Stockbridge. There were, four years ago, many in the river just below; but this year there are very few there, and the great proportion that remains is found below Houghton. I ought to mention, that the water is particularly fitted for them, and they become larger in this river than in their native place, the Avon,—some of them weighing between 3 and 4lbs. The trout, in all its habits of migration, runs upward, seeking the fresh and cool waters of mountain sources to spawn in: the grayling, I believe, has never the same habit of running up stream; I never saw one leaping at a fall, where trout are so often seen. Their large back fin seems intended to enable them to rise and sink rapidly in deep pools; and the slender nature of the body, towards the tail, renders them much more unfit for leaping cataracts than trout and salmon. The temperature of the water, and its character as to still and stream, seem of more importance than clearness; for I have seen grayling taken in streams, that are almost constantly turbid,—as in the Inn and the Salza in the Tyrol. This fish appears to require food of a particular kind, feeding much upon flies and their larvæ, and not usually preying upon small fish, as the trout. It has a very strong stomach, in texture like that of the gillaroo trout, and is exceedingly fond of those larvæ which inhabit cases, and are usually covered with sand or gravel. I once caught a grayling in the Wochain Save, that weighed about a pound and a half, the stomach of which equalled in size a very large walnut, and contained some small shells, and two or three white round pebbles as large as small beans. In accordance with their general habits of feeding, grasshoppers are amongst their usual food in the end of summer and autumn; and at all seasons, maggots, upon fine tackle and a small hook, offer a secure mode of taking them,—the pool having been previously baited for the purpose of angling, by throwing in a handful or two a few minutes before.

Poiet.—You just now said, that you thought the Lapland fish, considered by Linnæus as grayling, was the same as Back’s grayling; but I find, in the Appendix to Captain Franklin’s narration, two graylings described as belonging to the northern regions,—one the Coregonus Signifer, and another, which appears to differ very little from it, except being small in size. This seems to agree as nearly as possible with our grayling, with a difference of at most one spine in the back fin. May not this in fact be the same fish as the grayling of the Alps, only rendered in a succession of generations fit for a colder climate?

Hal.—This is certainly possible: there is no doubt, that, in many successive generations, animals may be fitted to bear changes, which would have destroyed their progenitors. It is said by Bloch, that graylings are found in the Caspian Sea, and in the Baltic,—masses of saline water; though, as I have proved, the grayling of England will not bear even a brackish water, without dying. And notwithstanding the severity of the winter in high northern latitudes, streams under the ice may retain a temperature not much lower than some of the Alpine rivers. I have seen grayling in Carniola, in a source at the hottest season not quite 50°; and as, in large bodies of water, the deepest part, in frost, is generally the warmest—about 40°, the degree at which water is heaviest—I see no reason why grayling may not be habituated to such a temperature—coolness being generally favourable to their existence. But see, the fog which had filled the valley and hid the mountains from our sight is clearing away, and I fear it will be a hot day. Before the sun becomes too bright is the best time for fishing, in such a day as this. As soon as the fog is fairly off, the water-flies will begin to appear, and fish to sport.

Phys.—I see the fog has already disappeared from the deep water in the meadow, where I suppose the warmth of the air from the considerable mass of the water, is greater; and which is further removed from the hills sending down currents of cold air, from the mixture of which with the moist warm air above the river this phenomenon is produced. I see some yellow flies beginning to come out; they have already felt the influence of the warm air: and look! a fish has just risen opposite that bank, and he rises again: let us prepare our tackle.

Poiet.—What flies shall we employ?