26 SA^LMONID^ OF BEITAIN. 



changed daily. At the end of this period I measured each ovum, and found 75 

 were 0"25 of an inch in diameter, three were 0'20 of an inch, one was 0"175 of an 

 inch, and one 0"15 of an inch. Looking through the hatching-troughs at Howietoun 

 it appeared that from 4 to 5 per cent, of the eggs are less tlian the noi'mal size of 

 the remaining 95 or 96 per cent. 



It has been observed that the offspring from large eggs are superior to such 

 as are reared from small ones ; consequently fish-culturists should be careful to 

 obtain their stock from the best sources, unless the water in which they are 

 going to be transferred is deficient in amount or in food when the source from 

 whence the supply is obtained becomes of little practical moment.* 



The immediate and possibly remote result of employing eggs from young fish 

 for stocking purposes is one which requires the earnest consideration of the fish- 

 culturist. For it is evident that by selection a more rapidly growing race may be 

 I'eared, and I now purpose demonstrating that small eggs from young parents- may 

 give bad resultsf as to the number hatched or the quality of the young. In 

 short the great mortality from the eggs of young mothers appears to be during 

 the incubating stage, while from the progeny of young males one season older it 

 seems to show itself among the fry ; passing over another year, there is not so great 

 a mortality among the eggs nor disease of the offspring. Bearing on this I may 

 allude to the ova of American chars having been milted from a Scotch char in 

 November, 1882 ; one of the progeny gave 146 eggs on November 12tb, 1884, or a 

 little under two years of age. Only six feeble little ones hatched on February 3rd, 



* Two batches of Lochleven trout were spawned November 2, 1882, at Howietoun, the parents 

 of one lot having been hatched in 1875, and of the other in 1876; the eggs were similarly treated, 

 and the young came out during January and February, 1883. At Craigend are two ponds, which 

 have been constructed for the reception of young fish, each of the same width and 100 ft. long ; 

 one is nearly on a level with the other, and the identical stream passes through both. Into these 

 two ponds the two lots of fry were turned, those from the older (1875), or seven-year-old parents, 

 having the lower pond; those from the younger, or six-year-old fish, having the upper pond, 

 while they were fed and otherwise similarly treated. At the end of November, 1883, those in the 

 lower pond were about one-fourth larger than those in the upper pond, and it seemed as if the 

 produce of the older parents, or larger eggs, were decidedly superior to those from the younger 

 parents, or smaller eggs. A second experiment was tried in the same two ponds, which were 

 stocked with young Lochleven trout bred from parents of the same age, spawned the same day, 

 and hatched in the same room. I saw these fish both in August and also in November, 1881, but no 

 difference in size or appearance was perceptible between them. It would, consequently, seem 

 that the larger eggs from older parents produce fry which grow faster than do those from the 

 smaller eggs furnished by younger parents. Also, Mr. Francis Francis {Fis]i Culture, Appendix, 

 p. 309), when alluding to the salmon fishery at DoohuUa, in Ireland, noted that big smolts make 

 big fish. One that was peculiarly fine was marked, and on the shoals returning from the sea 

 this very fish was caught, and as he was the largest smolt, so he was the largest grilse, and 

 weighed 7ilb. 



t For several seasons it had been remarked at Howietoun that eggs from young mothers were 

 subject to a greater percentage of deaths than those taken from older fish. On November 13th, 

 1881, about 500 eggs, having a diameter of 0-17 of an inch, were obtained from a rising two-year- 

 old Lochleven trout, and they were impregnated from another of the same race of the usual size. 

 Out of these eggs only about a dozen hatched on January 28th, and seven lived to be turned into 

 the rearing-pond. In this instance the immaturity was on the mother's side. On November 29th, 



1883, 4500 eggs of the Lochleven trout (of the season of 1875) were milted from the par of a 

 salmon raised at Howietoun, and which had been hatched in March, 1881, and consequently were 

 a little over 2| years of age. The mortality during incubation was only about 2 per cent. ; but 

 this by no means gave a true index of the experiment, for when the young hatched January 15th, 



1884, nearly all were seen to be suffering from what has been termed dropsy or blue swelling of 

 the yelk-sac. (Day, Proc. Zool. Soc. 1884, p. 376.) Among these 4000 dropsical fish only about 

 100 lived out the year. As the same cross had been made December 24th, 1881, but with older 

 parents, and that without occasioning dropsy, one is irresistibly led to the conclusion that 

 hybridization had nothing to do with these results, but that they might reasonably be attributed 

 to the immaturity of the male pars. As a further confirmation of this view, pars in 1884 taken 

 from the same lot were found prolific, but with comparatively few cases of dropsy occurring. 

 On November 11th, 1884, about 12,000 Lochleven trout eggs were milted from a salmon smolt 

 hatched in March, 1881, and though about 8000 hatched on January 28th, 1885, by March 12th 

 about 1000 had died, they having mostly shown signs of dropsy. Subsequently the mortality 

 ceased. In this case the male was one season older than in the last experiment. Dropsy did not 

 set in so rapidly, neither were so many affected ; but it must be clear that there was deficiency of 

 vitality in one of the parents, and that would most probably have been in the male, which was 

 thirty-one months old. 



