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XXVII.—Account of Experimental Observations on the Development and Growth of Salmon-Fry, from the exclusion of the Ova to the age of two years

Published online by Cambridge University Press:  17 January 2013

John Shaw
John Shaw
Affiliation:
Drumlanrig.
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Extract

That the facts which I communicate regarding the natural history of the salmon in its earlier stages, may not appear altogether undeserving of consideration, I may premise that my remarks have not proceeded from hasty or imperfect observation, but from the experience of many years sedulously devoted to the subject, the whole of my life, with the exception of a few seasons, having been spent on the banks of streams where salmon are in the habit of depositing their spawn, and where of course the parr is likewise abundant. My opportunities of observation have thus been as ample, as my efforts have been unremitting and laborious, to discover the true history of this invaluable species. I shall here present a brief abstract of my earlier proceedings in relation to the subject.

Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 14 , Issue 2 , 1840 , pp. 547 - 566
Copyright
Copyright © Royal Society of Edinburgh 1840

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References

page 547 note * My first paper, entitled “An Account of some Experiments and Observations on the Parr, and on the Ova of the Salmon, proving the Parr to be the young of the Salmon,” was published in the Edinburgh New Philosophical Journal for July 1836, vol. xxi. p. 99Google Scholar. My second paper, under the title of “Experiments on the Development and Growth of the Fry of the Salmon, from the exclusion of the Ovum to the age of six months,” was read before the Royal Society of Edinburgh on the 18th December 1837, and was published in the Edinburgh New Philosophical Journal for January 1838, vol. xxiv. p. 165Google Scholar. My third and concluding communication, which the Society now honours by its reception, contains an account of the continuance and confirmation of these experiments, with an introductory reference to the papers above named.

page 556 note * I have transmitted a series of the specimens referred to, from the ovum to the smolt, and including the ordinary and transitionary state of the parr, to be exhibited when my paper is read.

page 559 note * On the approach of autumn, the whole of the Salmonidæ, resident as well as migratory, while in fresh water, acquire a dusky exterior, accompanied by a considerable increase of mucus or slime. The fins also become more muscular. However, on the return of spring, they resume their wonted beautiful colouring, and the fins, the cartilaginous portions of which are frequently damaged during the winter floods, grow up and acquire their former outline.

page 559 note † “Pinks in the river Hodder, in the month of April, are rather more than three inches long, and are considered to be the fry of that year; at this time smolts of six inches and a half are also taken.”— See Yarrell's Supplement to British Fishes, page 6. The fry of the same year, in mild winters, are only quitting the gravel in April, at which stage they measure not more than one inch.—J. S.

page 560 note * One or two of each of the three broods assumed the migratory or smolt dress at the age of twelve months. This circumstance I am disposed to attribute to the high temperature of the spring-water ponds, which I have no doubt has hastened the change. I am greatly strengthened in this opinion by the fact of no instance of a similar change having occurred with individuals reared in similar ponds supplied with water from a rivulet, the temperature of which throughout the year ranges pretty nearly with that of the River Nith.

page 561 note * Edinburgh New Phil. Journ. for January 1838 (vol. xxiv. p. 172,Google Scholar note).

page 561 note † Ibid. same page.

page 562 note * As I believe it has been objected to my views, or rather practice, regarding this mode of impregnation, that the generative influence may have been in some other way effected than through the medium of the parr, I therefore took every means to prove the truthful results of my experiments by varying in some measure their conditions. Thus, in two instances, I took a portion of the ova from a female salmon, and placed them, without impregnation, in a stream of pure water. The result was as I anticipated:—up to the termination of the general hatching season they exhibited no appearance of vitality. The female from which one lot of ova was taken, and placed in water without impregnation, was the female with which the four parrs above alluded to were spawned. They were placed in the same stream but in a separate vessel from the four lots impregnated. The other lot was taken from the female with which the male from pond No. 3. was spawned. The unimpregnated lot was placed in the same stream with the former. The impregnated lot was placed in the stream of pond No. 3. To avoid contact the unimpregnated lots were in each case taken first, and removed to a distance.

page 564 note * Solitary instances have occurred of large female parrs having been found in salmon rivers with the roe considerably developed, and I find, by detaining the female smolts in fresh water until the end of the third winter, that individuals are found in this comparatively mature condition. From this fact, therefore, it may be inferred, that the large parr, either male or female, of nine and ten inches in length, which are occasionally found in rivers, are the young of the salmon, which, for some natural reason, had not been prepared to migrate at the ordinary period, and had, therefore, remained for another year in the fresh water.

page 564 note † Recent experiments having been made on the young of the salmon by very competent individuals, it is now admitted that they “remain one year in the river before they go to the sea as smolts.” However, owing to these fishes having escaped the observation of those individuals during the intermediate stage, that is, from the ovum up to the length of three inches, they were actually twelve months old at the commencement of the experiments referred to by Mr Yarrell, in place of being the “fry of that year.” —See Mr Yarrell's Supplement to British Fishes.

page 565 note * I am aware it has been a matter of dispute amongst observers as to which of the two extremities of the fish is employed in the formation of the spawning-bed. However, from late opportunities of observation, which rarely occur, owing to the turbid state of the river in the spawning season, I am now satisfied that it is by the action of the caudal extremity alone that the gravel is removed.