SEA TROUT— LIFE HISTORY OF. 177 



tlie sea and in several distinct localities all were females; it is not so, however, in 

 the rivers. 



The questions of sterility, limits of reproduction and monstrosities, will be 

 discussed along with hybridism. 



lAfe history. — That of the sea trout, so far as it has been observed and 

 recorded, appears to be very similar to what occurs in the salmon, having its par 

 stage, in which it has been asserted on insufficient evidence, that the anadromous 

 may be distinguished from the fresh-water forms by the number of transverse 

 bands or finger marks along their sides. But this method of recognition appears to 

 fail when carried into actual practice* (see p. 171, 172 ante). The par goes through 

 the smolt and grilse stage as whitlings or herlings in the north {see p. 159) or 

 white fish and peal in the south (see p. 160) : while the young are equally or 

 more voracious than young salmon, for when artificially brought up they will 

 consume pond snails as Limnea or Ancylus which salmon appear to reject. 



I have already adverted to the opinion held by others and personally believed 

 in that our sea and fresh-water trout are merely local races of one species. That 

 anadromous or fresh-water habits may simply result from local circumstances, and 

 colours be consequent upon immediate surroundings. In tracing up these fish 

 then we may well begin by the question. What is an orange fin ? The very term 

 speaks for the colour which is, as a rule, seen staining the outer quarter or half of 

 the adipose dorsal fin, or else in the form of distinct orange spots. 



The rate of growth in sea trout has been investigated by several observers, but 

 as already remarked (see p. 146 ante), in some instances the marked par or smolt 

 has developed into an undoubted fresh-water form of trout. I have, therefore, in 



* Mr. Shaw, of Drumlanrig, observed to the Eoyal Society of EdirHmrgh in 1843, that having 

 shot a pair of salmon-trout while spawning in the Nith, he incubated and hatched the eggs, the 

 young becoming par the first year and orange fins the second year. At eighteen months the males 

 have the milt developed : at two years, when about 7J in. long, many assume the smolt dress. 

 At this period they are as follows : — " Dark brown on the back, passing gradually into a white 

 silvery appearance on the sides and belly : the pectoral fins are white, with the extremities (J) 

 orange : ventral fins pure white : anal fins white, with a iaint dusky mark on each side : dorsal 

 fin light brown, inclining to black at the extreme points of the anterior rays, which are tipped 

 with a very little white : posterior rays have a faint tinge of orange, and the whole fin is much 

 spotted : adipose fin dark brown, margined with red : caudal rays of a light colour near the base, 

 running into a dark orange, terminated by a faintly marked double margin of black. The spots 

 on the back and sides vary much, prevailing principally along the back, with a few below the 

 lateral-line. Each spot is surrounded by a circle of a lighter colour than the general surface of 

 the body, and this appears to be a prevailing character of the trout species, and one which the 

 sea trout exhibits, even after having assumed the migratory dress, when every other feature 

 of resemblance to the conmion trout has disappeared." 



But "a certain number of the individuals of both sexes (probably about one-fourth of each 

 brood) never assume the silvery exterior, or migratory dress ; and even if those which have 

 assumed that appearance be detained in fresh water for a month or two, they will re-assume the 

 dusky coating; and in the ensuing autumn both sexes have their reproductive organs fully 

 developed." He observed that " it is by no means improbable that portions of each brood are 

 permanent residents in fresh water, as they are never observed to migrate in a dusky state along 

 with the shoals of silvery fry." Having marked some of these young fish he concluded that the 

 " orange " or " yellow-fins" became hirlings of six or seven ounces after a sojourn of about ten 

 weeks in the sea the first season and ascend their native rivers to spavm : and that they return 

 the next and each subsequent season as salmon-trout, with an increase of about IJ lb. per annum. 



Dr. W. M'Intosh, Scottieh Naturalist (July, 1872, vol. i, no. 7, pp. 227-233) contributed a 

 paper "on the 'yellow-fins ' of the Allan-water." At p. 227 he observed upon some "yellow-fins" 

 which he thought to be.young whitlings (Salmo albm or brachypoma) which had from 43 to 44 

 ccBcal appendages and a second variety or species possessing from 49 to 57, while he stated that 

 in the common trout of the Tay, Erioht, Allan-water, and the mill-stream at Stormontfield these 

 appendages ranged from 38 to 56. He also thought that the tail fin of the yellow-fin was more 

 deeply cleft than seen in the brook trout. The important question of the number of par-bands 

 along the sides is omitted, while it must be evident that if the smolt had the maxillary compara- 

 tively slender and the vomerine teeth in a single series they were peculiar. He contrasted the 

 young yellow-fin smolt with the young burn trout as follows : — " The dark back of the ' yellow- 

 fin,' its silvery sides and cheeks, and the silvery and whitish belly, stand in strong contrast with 

 the young river trout. The red spots on the sides are much more developed in the latter than in 

 the ' yellow-fin.' " . . " In a ' yellow ' trout (S. fwrio) and a ' yeUow-fin ' of the same length, 

 there is a very appreciable difference in the position of this (dorsal) fin, which is decidedly 

 further forward in the latter, the same variation occurring in the fatty, ventral and anal as 

 noticed in the first glance at the fish," {See page 198.) 



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