90 SALMONID^ OP BRITAIN. 



another season consisted of fish, of both sexes, consequently females do not migrate, 

 as had heen suggested, one year earlier than the males.* The statement of 

 Dr. Davy, Physiological Researches, -p. 221, that when kept in confinement the milt 

 of these fishes is shed prior to their assuming the smolt livery was not found to be 

 generally correct at Howietoun. 



Having now traced the produce of salmon eggs up to and through their par 

 stage, it is necessary to follow out their further progress towards attaining the 

 condition of becoming a salmon. The par on assuming the smolt livery, as it does 

 as a rule when commencing its seaward journey, changes from its brilliant golden 

 and spotted colours with its brilliant finger-marks, which have been described 

 (p. 55), to take on a bright silvery appearance, both on its opercles and body. 

 As Howietoun fish showed this change without leaving the ponds, it is clear that 

 such must precede or be coincident with, but not consequent on, migration seawards.f 

 This silvery colour is not owing to their acquiring an additional coating of 

 scales, as has been asserted, but due to the deposition of a silvery pigment on the 

 under surface of the scales and opercles, J which latter could not be so overlaid 

 because of being scaleless. 



These silvery smolts, at least after they have been some time so, may be turned 

 directly and without injury into sea water, while the scales are not nearly so 

 adherent as when the fish had the par livery, and the fish itself seems more 

 susceptible of injury. 



Although the great seasonal migration of smolts is during April, or May and 

 June,§ this is not the only period at which they descend seawards, as some do so 

 during the autumn months, as well as probably throughout the year. As the 



exclusion from the ova, the pinks begin to assume the silvery coat prior to their migration. At 

 this period their transverse bars and pink spots gradually disappear and give place to bright 

 silvery scales. In three or four weeks the change is completed. With the variation of their 

 external appearance a striking alteration in their habits also takes place. Pinks are invariably 

 solitary previous to their transmutation into smolts. After that event they are gregarious, and 

 assemble in numerous shoals shortly before the commencement of their descent to the sea." 



* Mr. W. Brown, Stormontfield Experiments, 1862, p. 7, observed upon having in February, 

 1836, caught a dozen and a half of par in the Tay. He kept them confined in a stream of running 

 water, and by the month of May the whole of them had become smolts ; but some had leaped out 

 of their confinement in their struggle to find their way to the sea, and were found dead upon the 

 side of the pond. It has also been remarked that whether a river is an early or late one, the 

 descent of the smolt generally occurs during the spring, between March and June. Mr. Dunbar, 

 who annually hatched about 500,000 in the Thurso river, in the county of Caithness, informed 

 Mr. Young that about eight per cent, became smolt at the end of the first year, and about 

 60 per cent, at the end of the second year, and the remainder, or 32 per cent., at the end of the 

 third year. 



t There seems reason to believe that occasionally par ascend rivers, being found in localities 

 above where any breeding salmon have been seen. I have received one of a large size which was 

 taken in Wales above a cascade up which sea-trout were known to ascend, but where salmon had 

 never been seen. 



t Davy, Physiological Besearches, 1843, p. 250, suggested " that the young remain in fresh 

 water until they have acquired not only a certain size and strength, but also additional scales, 

 fitting them in their smolt stage to endure without injury the contact of the saline medium." 

 Dr. Davy considered the scales of the smolt to be new productions, not mere alterations of the 

 former scales {Angler in the Lake District, p. 209). Couch, in 1865, demurred to such an opinion, 

 observing that the silvery colour of smolts is not due to their acquiring additional scales, but 

 owing to a deposit of bright soft matter which shines through the transparent scales. Dr. Giinther 

 (Introduction to the Study of Fishes, 1880, p. 632) remarked, respecting the river-trout, that they 

 "frequently retain the par-marks all their lifetime ; at certain seasons a new coat of scales over- 

 lays the par-marks, rendering them invisible for a time, but they reappear in time, or are distinct 

 as soon as the scales are removed. When the Salmones have passed this par-stage ... a new 

 coat of scales overlays the par-marks." It was likewise stated in one of the conference papers 

 read at the " Great International Fisheries Exhibition " in 1883, that the young of the true Salmon 

 " do not venture into the sea tiU another skin of glistening scales has been formed over their first 

 skin. They then receive the name of smolts. If put into salt water before getting this silvery 

 dress they die " (Salmon and Salmon Fisheries, by D. Milne Holme, p. 4). 



§ We are told that in the exodus of the smolts from Stormontfield in 1857 of the fry of 1856, 

 the first shoal left the 12th of April, a week earlier than the first hatching in 1854, which appeared 

 to be owing to the winter of 1856-57 having been much milder than that of 1854-55 (Stormontfield 

 Experiments, pp. 61-63). 



