for some twelve years i have been trying experiments on lochs on my ground in the north of scotland, and have written what follows mainly because i hope and believe that the result of these experiments may prove useful to some of those who love trout-fishing as i do, and have the means at hand, possibly without fully realising their opportunities, of increasing their sport and that of their friends. i have spent much labour and a good deal of money in attempting to improve the fishing in various lochs. in some cases these efforts have proved useless; in others the labour and money expended in stocking the lochs and increasing the food supply have been altogether[183] out of proportion to the results obtained, but in one case, and one case only, the results have been phenomenal, not only in my own experience, but also in that of my keeper, who, like myself, has all his life been keenly interested in and familiar with trout-fishing in the north. in the case of those lochs where no good result has been achieved, i have at least learnt something from my failure. the loch upon which i experimented with such wonderful results must have been a veritable larder of food for the trout when i put them into it, for there was a large quantity of water lizards, leeches, frogs, and above all, fresh-water shrimps; there were also various kinds of insect life, water beetles, notably the coch-y-bundhu, and a smaller beetle with a silver body which moves with a swift darting movement. it is impossible for the trout to spawn effectively, as there is no burn coming into or going out of the loch and no water continually moving over a shingly bottom. the loch is not more than six acres in extent, and is about 500 feet above the level of the sea. at the time, just thirteen years ago, when i began to put fish into it, there were no fish in it, and so far as i know there never had been any, except some years ago when a few trout were put in,[184] but these had no doubt been caught or died long before i began my experiments. i am also quite certain, for the reasons already mentioned, that they had left no descendants. every year, in may or june, about 2½ acres of the loch are covered with a common kind of rush, the “horse-tail,” equisetum maximum, and about one-quarter of an acre with grass, which, i believe, is a species of scirpus. in the rushes and round them are patches of a kind of surface weed which is common in highland lochs, and which, as every fly-fisher in the highlands knows, is a great danger to him. this weed, the scientific name of which is, i am told, potamogeton polygonifolius, covers an area of some 20 square yards. lastly, and most important of all, there is in the loch a considerable quantity of the well-known water milfoil or shrimp-weed, myriophyllum verticillatum, which in this water produced quantities of fresh-water shrimp.
by august and september the rushes have, of course, largely increased, and extend to nearly four acres, leaving a comparatively small part of the loch which can be fished. the depth of the loch is about 3½ feet all over with the exception of two places, a very small part of it, where it is[185] about 5 feet. its bottom is for the most part fairly hard ground, but on one side there is soft mud, and on another side, for about an acre and a half, the bottom is rocky. i began stocking the loch in 1910, and during the first three years put into it small trout from burns and other lochs on my ground, but in 1913 and 1914 put into it 150 and 200 loch leven yearlings respectively. these yearlings were supplied from one of the well-known hatcheries. in 1915 i put no trout into the loch, but since, and including 1916, i have put in every year on an average about eighty small trout taken entirely from burns—one of which runs into the sea and contains the young of sea-trout as well as small brown trout. the following table shows the exact numbers of fish put into the loch, showing a total of 1062.
1910. aug., sept., oct 62 (20 fair size)
1911. july, aug., sept 61 (16 fair size)
1912. july, sept., oct 20
1913. april 150
1914. april 200
1916. june, july 104
1917. june, july 105
1918. june, july 96
1919. august 74
1920. july 96
1921. july, august 44
1922. july 50
[186]
i have taken care that the loch should not be fished too much, and nothing has been used but the wet fly. it has only been fished in may and june and in august and september. in may and june, which are, of course, the best months of the year, it has only been fished for two or three weeks, and in august and september it is very difficult to persuade the trout to rise, and a rare experience to catch one. it has been suggested to me that i should introduce rainbow trout into the loch, as they would rise freely in august and september, when the large brown trout will not do so.
in may and june there is a hatch out of flies from the weeds on the loch and from the heather on the adjoining moorland. in particular there is a hatch out of a large fly, of which i have caught specimens. these i have sent south for examination, and am told that they are all sedges, the largest being the large red sedge, phryganea grandis, those next in size being cinnamon sedges. i have had flies dressed in imitation of these, and if one is fortunate enough to be on the loch when the sedges are hatching out, there is grand sport to be had, and sport which is greatly increased by the presence of so many troublesome weeds. the loch was not fished until 1913, three years[187] after trout were first put into it. every fish caught under a pound, with very few exceptions, has been returned to the loch, but it is a curious fact that the fish rise very little until they reach about a pound in weight, and so we have not been troubled much by catching the smaller fish which would have to be returned to the loch.
the following is the record of fish caught, showing a total of 216, weighing 482 lb. 1 oz., and averaging nearly 2¼ lb.
1913. 6 trout, weighing 8 lb.; average 1⅓ lb.; largest 2 lb.; smallest ½ lb.
1914. 19, weighing 29 lb.; average slightly over 1½ lb.; largest 2½ lb.; smallest ¾ lb.
1915. 14, weighing 29 lb. 11 oz.; average just over 2 lb.; largest 3½ lb.; smallest 1 lb. 1 oz.
1916. 20, weighing 58 lb. 9 oz.; average nearly 3 lb.; largest 4 lb. 7 oz.; smallest 2 lb.
1917. 18, weighing 58 lb. 11 oz.; average about 3¼ lb.; largest 4 lb. 10 oz.; smallest 2 lb.
1918. 44, weighing 98 lb. 5 oz.; average nearly 2¼ lb.; largest 6 lb.; smallest ¾ lb.
1919. 13, weighing 28 lb. 4. oz.; average over 2 lb.; largest 4¼ lb.; smallest 1 lb.
1920. 20, weighing 59 lb. 6 oz.; average very nearly 3 lb.; largest 7½ lb.; smallest 1 lb. 2 oz.
1921. 30, weighing 48 lb. 13 oz.; average about 1⅝ lb.; largest 4¾ lb.; smallest ¾ lb.
1922. 32, weighing 73 lb. 6 oz.; average slightly over 2¼ lb.; largest 5 lb. 2 oz.; smallest 1 lb.
the exact weights of the 20, 18, 20, and 32[188] fish caught respectively in 1916, 1917, 1920, and 1922 (in which years the highest average was reached) were as follows:
1916. 1917. 1920. 1922.
lb. oz. lb. oz. lb. oz. lb. oz.
4 7 4 10 7 8 5 2
4 1 4 1 4 10 5 1
3 13 4 0 4 8 4 8
3 10 3 14 4 7 4 4
3 9 3 14 4 4 3 4
3 6 3 10 3 10 3 4
3 1 3 9 3 10 3 4
3 0 3 8 3 0 3 0
3 0 3 8 2 9 2 12
3 0 3 5 2 8 2 8
2 12 3 1 1 12 2 4
2 12 3 ½ 1 10 2 2
2 9 2 13 1 10 2 1
2 8 2 8 1 10 2 0
2 8 2 8 1 8 2 0
2 4 2 4 1 8 2 0
2 3 2 4 1 8 3 of 1 12
2 2 2 0 1 4 7 of 1 8
2 0 ∙ ∙ 1 4 5 of 1 4
2 0 ∙ ∙ 1 2 1 0
the fish caught have been remarkable not only for their weight but also for their extraordinary beauty and condition. those of us who have seen them have seen many trout in our time, but have never seen trout to compare with those caught during the first four or five years after[189] we began fishing the loch. several of these, which we measured, were as much in girth as in length from the gills to the point of the tail where the flesh ends. they had small heads and were most beautifully coloured. their flesh was in colour a deep red—no doubt due to the pigment in the fresh-water shrimps which, as i have said, abound in the loch.
it is an interesting fact that, although the loch was very little fished by ladies, they secured the two largest fish, one of 7½ lb., which took over three-quarters of an hour to land and gave splendid sport, the other 6 lb. the former was a most extraordinary fish. it was 22 inches in length, 16 inches in length from the gills to the point where the flesh ends at the tail, and 16 inches in girth. there is, however, no doubt that, with the exception of this particular fish, the fish caught during the last four or five years, whilst in excellent condition and comparing very favourably with the ordinary large brown trout caught elsewhere, have not been so extraordinary in their girth as in the first few years after the loch was stocked.
these experiments show the correctness of the opinion expressed by one of the most experienced of writers on the subject of trout culture, mr.[190] p. d. malloch, who says in his well-known work on the life history and habits of the salmon, sea-trout, trout and other fresh-water fish[31] (p. 186): “when a farmer rents a piece of land for grazing he knows how many sheep or cattle it will pasture, and that if he puts on more than the proper number they will not grow. he also knows that if he introduce too few they will become fat and too lazy to eat up all the pasture, and he will thus lose part of the money paid for the pasture land. if the proprietor or the tenant of a loch would consider the matter in the same way as the farmer, he would obtain full value out of his lochs, be saved a deal of grumbling, and find life more pleasant.” the same writer also says (p. 157): “many naturalists maintain that there are different species of trout in the british islands—loch leven trout, gillaroo trout, tidal trout, and many others—but from a close study of all these trout for the last forty years, i have come to the conclusion that there is only one species of trout in great britain, and that in the different varieties the differences are caused by the nature of the water in which they are found and by the food they eat.” thus, as would be expected,[191] there is no apparent difference between the so-called loch leven trout which were put into the loch from the hatcheries and the little trout from my own burns. numbers of these splendid trout running up to 5, 6, and 7 lb. must be the brothers and sisters of the little fingerlings of the same age in the burns. the best authorities are apparently agreed[32] that the average life of trout is about ten years (although there are authenticated instances in which they have lived for a much longer period), that they reach their prime in six or seven years, that they remain in their prime for a few years longer, and then begin to lose condition and weight as old age creeps on. those of the trout put into the loch in 1910 and 1911 which i have described as of fair size were about three to the lb., some rather larger and could not then have had many years to live. those from the burns were probably of different ages, but it is highly likely that in 1913 and 1914, when the yearlings from the hatcheries were put into the loch, there were very few of such other trout[192] as were still there that could live more than three or four years longer.
so far there has been little indication that any of the trout caught have been cannibals—probably because they can obtain plenty of other food, and since their transfer to the loch have not been in the hungry condition in which they certainly were when they lived in the burns. on one occasion we found when carrying some of the little brown trout from one of the burns to the loch that one of the captives on the journey in the small can in which they were being carried had caught and succeeded in half swallowing another little trout half its own size.
both mr. malloch (see pp. 130-132 of his work mentioned above) and mr. hamish stuart (the book of the sea-trout,[33] p. 240) agree that the young of the sea-trout, if confined in a loch, grow rapidly if the feeding be good, and are as silvery as sea-trout that are fresh run.
my experience in regard to the young of the sea-trout put into this loch confirms this view, as i have caught sea-trout up to nearly 2 lb. in the loch, which are in no way distinguishable from the ordinary fresh-run sea-trout. it is curious,[193] however, that so far no sea-trout larger than 2 lb. have been caught in this loch.
to summarise the results of these experiments, it seems clear that in order to obtain the best results the following conditions should be fulfilled:
1. there must be a sufficient supply of the right kind of food for the fish in the loch in order that they may grow to a large size.
in order to attain this object, it is desirable that the loch should not be too high above the level of the sea. as mr. malloch says in the work to which i have already referred (p. 179): “lochs over 1000 feet above sea-level, fed from snow from surrounding hills, produce little feeding until may, and owing to the cold fall off in september, thus giving the trout only four months of good feeding. on the other hand, lochs at or near sea-level produce good feeding in march, and continue to do so for three months more than their highland brethren. it will be seen, then, that this extra time for feeding, when extended over the seven or eight years which constitute the life of a trout, easily accounts for the difference of size.” moreover, as the same writer points out, in a loch which is very high above the sea-level, not only[194] is the feeding-time shorter, but the food is much scarcer.
on the question of food supply it is worth while to recall the words of mr. f. h. halford:[34] “food supply generally is ... chiefly dependent on the presence of the weeds in which the best forms of food for the fish are to be found.... it must not, however, be forgotten that, in marryat’s terse words, ‘while floating food is caviare, sunk or mid-water food is beef to the fish.’ hence, when engaged in his examination of the weeds and the animal life contained therein, the fisherman should remember that he can only expect well-fed, good-conditioned, healthy, and consequently game trout in a (loch) which contains a bountiful supply of crustaceans, such as fresh-water shrimps and mollusks such as snails of the genera limnaea, planorbis,” etc., etc.
further, it is of the utmost importance that the number of fish in the loch should be regulated in such a way that the food supply may be sufficient to enable the fish to grow to a large size.
where the fish cannot spawn effectively, and it is therefore necessary to renew the stock,[195] experience alone can decide the number of fish which should be put into the loch every year. spring is the best time to do this. the number of fish which should be put in will obviously depend chiefly upon the amount of food in the loch and the number of fish caught, and destroyed by their enemies, during the preceding year. in many lochs there are stones under which the small trout can find protection from the large ones, but where there is no protection it is worth while to put stones or small drain tiles round the edge of the loch.
in lochs where, as is usually the case, the fish can spawn effectively the fish increase so rapidly that there is not a sufficient supply of food, and the result is that the loch is filled with hungry small trout. when it is remembered that it is reckoned that every spawning trout produces 800 to 1000 eggs for every pound of its weight, some idea is obtained of the rapidity with which fish increase. in many lochs nature intervenes and the enemies of trout—divers, herons, ducks, otters, etc.—keep the numbers down, sometimes to the point of extinction; in other lochs, owing to the severe frosts and other causes, it is only occasionally that the eggs are hatched out.
[196]
2. the lock must not be too deep or the trout will not rise or will not rise well.
this, i believe, is the cause of my failure in several of the lochs upon which i have been making experiments. as mr. malloch truly says:
“when a loch is more than 12 feet deep the supply of food soon becomes scarce and the trout small, while shallow lochs produce plenty of food, therefore large trout.... in constructing new lochs, one should endeavour to have as much shallow water as possible.... the best depth is from five to nine feet; beyond twelve feet food becomes scarce and trout do not rise well in deep water.”
