THE BREEDING AND GROWTH OF SALMON CONFINED TO FRESH-WATER LAKES.

Otago Daily Times, Issue 1119, 22 July 1865, Page 6

THE BREEDING AND GROWTH OF SALMON CONFINED TO FRESH-WATER LAKES.

We (Australasian) direct the attention of our acclimatising readers to the subjoined important and interesting communication, extrae'ed from a recent number of the Field* upon the question, whether salmon can be propagated and attain their full growth though confined to fresh water only. If the lacts detailed in this Utter may be taken as deciding the question affirmatively, it is clear that we have open to us a sure and easy method of increasing the number of our young salmon without exposing them to the accidents and dangers of a sea voyage. The following is the letter:—

Sm—ln the ■Norwegian Shjltertidende, No. 13, January 1,5, 1865, 1 gave an answer to the qufstion, "Can salmon {_Salmo salar) and sea trout (JSulmo Irutla) become full-grown fish in fresh water?" This question, which, as far as I knew, had not un»il then been satisfactorily answered, is now set at rest by the experiments which have been made in this country since the Norwegian Government besran, some years ago, to employ me in adopting measures for the improvement of the freshwater fisheries. By propagation it is not only shown that the aforesaid kinds of fish can live both in ponds and lakes longer than is generally supposed—that is to say, from their being hatched until the time they get down to the sea—but that even, under favourable circumstances, they can in the lakes grow to a size larger than grilse, and are saleable; and further, that they can propagate without having been in the sea. But the account in the Shjttcrtidende on this subject was translated, without my knowledge, Isy an Englishman who has resided some yearn in this country, and has been »iven to the public in a work of which he is the author.

As I imagine that the.=e facts have not been proved in any other country, and will interest the readers of the Field, I take the liberty to forward you them. I send them to your journal m preference, because you have subscribers iv this country who will be able to inquire into the truth of the statements, and therefore there will be a greater opportunity to verify them.

It is generally known that these kinds •of fish are spawned in fresh water, where they remain for a year or tw>, after which time they go down to the sea, whence they return to the same river in which they were spawned. The statement that these kinds of fish can, under certain circumstances, become full-grown in fresh water without going to the sea, has hitherto been generally denied. Several Englishmen with whom I have conversed nre of the opinion that it i.s necessiry for the growth of the salmon that they should remain for a time in salt water, and in order that they may be a' le to propagate. It has been even affirmed that salmon die if they do not get to the sea within two years and two months. Probably this has arisen from want of experience in the matter, and too great a reliance on books. When I undertook to conduct the system of improvement of the fresh-water fisheries in this country, I determined to make an attempt to acclimatise these kinds of fish in ponds and lakes •where previously "there had been no large fish ; but before* I begin to speak of these attempts I will'draw your attention to the iact, wjiich was known here long before any improvement of the fisheries was thought of, that tlie sea-trout thrives in ponds and lakes without yoing to the sea; that it propagate*; and that the second or third generation is in every respect, both as to size and shape, precisely similar to the fresh water trout.

The pond in which the attempt was first made is ou the property of Vefferstad, in the parish of Lier, mar Draratnen. In the spring of 1857 a number of fry were taken from a hatching apparatus close by, and were let out there; they developed themselves, however, very slowly, after having grown to srnolts, not having attained a greater weight th;in ono pound and a-half by the summer of 1862, when they were five years old; but this is more to be ascribed to tlie scarcity of food in the pond, ■which was only 1200 fqusire alen (about ■533 square yards'), than to the want of s;ilt water. Their flavour was, notwithstanding, good, though inferior to that of the sea-trout which were bred with them in the same pond, and also to fresh wiittr trout from other pieces of water The flesh of both the salmon and the sea trout was white, like thnt of all pond fish.

On the other hand, the experiments which have been made by letting out salmon fry into lakes and large pieces of •water, where there is more food to be found than in a pond, had better results. They attained a larger size, and had a much finer flavor than the pond-salmon at "Vefferstad, which shows that want of food,, and not of salt water, was the cause of the difference. These experiments have, therefore, a greater scientific interest, and are more important, in a practical view. One of these places consists of two lakes called Siljevandene, situated in Laurdal, in the district of Laurvik. These lakes are in connexion with a river, and are about four English miles in length. In the spring oi 1856, 2000 salmon fry and a number of sea-trout fry, which had been taken from a hatching apparatus at Laurdal, were Jet out here, and some time afterwards 200 or 300 salmon fry. In these lake", which are at an elevation of about 1000 feet above the level of the sea, there was at that time no other kind of fish than minnow. There were, however, a great many ■ insects, and also numerous frogp, as U the case in all shallow water. All these animals have served as food for the fry. These lakes are now full of fish, both kinds having propagated. In the summer of 1863, the largest which were caught were four pounds and a-half in weight, and last summer one was caught weighing eight pounds; but the largest sea-trout that has been caught in these lakes weighed only two pounds and a-half. The second place selected for experiments is the large lake of Holtsfjord, in Ringerike, which is ra connexion with Tyrifjord, These lakes are not more than thirty English miles in length, and before the experiment took place abounded in fresh-water trout (Salmo fario), lavaret (Coregonus lawretus), char (Salmo alpinus), perch (Perch fluviatilis), pike (Esox lucius), bream (Abramis brama), and several other kinds of smaller fresh-w.ater fish, which serve as food for the larger. In the springs of 1857 and 1858, from 15,000 to 16,000 salmon-fry were let out jnto this lake from a batching apparatus

on the spot. Three or four years after Small (grilse) were caught, but in 1863 and last year salmon of from 9lb to 111b were taken. '

Tb.3 third experiment was maiie some years ago by a peasant in the district of Storen, in the Sondre Throndhjttm Amt. He caught salmon and sea-trout fry in the neighbouring river Guul, and tooki'them to two small lakes on the property of jSoranes, in which there had previously been no fish. These lakes now abound in fish, and a number of small salmon and sea-trout have been caught there of late years.. Both kinds of fish have propagated, not only in the pond, but also in the small lakes. In the pond, which is supplied b3f a small brook, the process of propagation has been observed, and also the fry have been seen. In the small lakes propagation must likewise have taken place, as they abound in fish, and as these fish are of different sizes. The number of salmon in the Hottffjord will probably alro increase, but a longer time must elapse before it caa be" ohfervtd, on account of the greater extent of water.

It must be allowed that these facts sufficiently prove that these kinds of fish, if let out aa fry into fresh water, will no"t only attain the size of full-grown fish— although their development, as seen, will be much slower than if they had been able to go to the sea, where food is more plentiful—but their spawn will mature without the necessity of their going into salt water. And if it be taken into consideration that they are quite as much fresh-water as salt-water fish, inasmuch as they remain as long iv rivers as in the sea, and in come places even longer ; that they resemble so closely several kinds of fresh-water fish (for instance, Salmo furio, Salmo ferox, Salmo alpinus) that it is possible to cross the bieed of these with salmon or sea-trout; and, further, that the experiments which are made in other countries for acclimatising fish, under circumstances of still greater difficulty and deviation from nature than in this country—the results which I have arrived at cannot be called improbable.

Having communicated these facts, I have only to remark, that whilst the flavor of the sea-trout more closely resembles that of the fresh-water trout than any other fish (which is also the case when caught in the sea), the flesh of the lake salmon has also the same red colour and the same flavour as of those caught in salmon rivers, though the fish have been somewhat leaner than salmon generally are when they first arrive from the sea. But, at all events, they would have been saleable in any market. Whether the lake salmon will keep its original qualities through several generations, or degenerate, time must prove. There will be an international exhibition of fish in Bergen, from August 1 to September 16 this year, where it is my intention to produce specimens of lake salmon. In another letter I will send you particulars of the salt water apparatus for salmon and sea. trout. M. G. Hjetting. Christiania, March 31, 1865.

The ' Courier of Algeria ' reports that a fresh insurrection has broken out in Morocco, in the neighbourhood of Rabat. The Emperor of Morocco is stated to be marching to the scene of the insurrection at the head of his array.