96 



Appendices to twenty-second Annual Report 



the present we do not know if a fish having, as it were, embarked upon 

 the habit of short migration, continues this habit through life, while 

 another in like manner adopts the long-migration-habit, or whether 

 short and long migrations may be alternated, or, indeed, whether any- 

 particular system or regularity of habit in this matter exists, although 

 we have in 7298 an indication that a fish may possibly spawn in 

 three consecutive seasons. It is clear that, while we refer to the short 

 migration as being a return in the summer of the year of descent as a 

 kelt, we must include in this short migration a great mass of breeding 

 fish which ascend through autumn and early winter. Also in regarding 

 the long migration we must not overlook the clean run so-called spring 

 fish which may enter our large rivers one, two, or even three months 

 before the end of the calendar year. The individual fish representing 

 those separate migratory habits are of course in the river at the same 

 time, yet although mixed together may be, without difficulty, allocated 

 to their positions as breeders or " springers." 



By selecting what appear to be well-defined cases in the kelt-to-clean- 

 fish series I have attempted to construct a diagram which shows the 

 Duality of Migration. I have, for the sake of clearness, restricted the 

 number of recaptures shown, and have not attempted to display either 

 the autumn and winter fish which form the great mass of breeders and 

 which are of the same class as the summer fish, or the very early clean- 

 run fish which belong to the spring class. If attention be turned to the 

 diagram it will be seen that excepting the two first diverging and 

 unnumbered black lines, three groups are represented, each group 

 containing three recaptures. The three numbers of the first group 

 are printed in blue, those of the second group in red, and those 

 of the last group in black. The black lines representing these 

 recaptures are drawn straight from point to point, each lower point 

 being on the horizontal level which gives the weight of the kelt when 

 marked, the higher being the weight on recapture. It will be under- 

 stood, therefore, that in each case the sea- ward migration and the re- 

 ascent have taken place in the period over which the lines are drawn. The 

 fish in the kelt stage are placed according as their weights seem to be in 

 proper proportion to the weights of previous unspawned fish. The 

 seasons and years of the fish's life are indicated horizontally. Com- 

 mencing at the left hand low corner we have the newly hatched embryo 

 of practically no weight, and, following the indications of the Stormont- 

 field and other experiments, we may fix the point B in the spring, 

 when the fish is about 26 months' old, as representing the time when the 

 smolt migrates to the sea. (Dahl's observations concerning Norwegian 

 smolts incline him to consider that only a year and a quarter is 

 spent in fresh water before the first seaward migration). The 

 thin line from A to B represents, therefore, the two years and 

 two months which it seems to me the great majority of young 

 salmon spend in the river of their birth before the first migration 

 seawards. For the smolt to grilse stage, represented by the first 

 diverging and unnumbered black lines, we are indebted to two early 

 Tweed recaptures. The lower of the two was marked in the spring of 

 1854, and recaptured in July 1855 at Wilford, a grilse of 3| lbs. It 

 was marked by means of a wire in the tail fin. (A similar case was that 

 of a smolt of 1857, recaptured at Hallowell on 9th August 1858, a grilse 

 of 3| lbs., marked with silver wire in the upper jaw.) The other, or 

 higher line, represents a smolt marked in May 1855, recaptured on 6th 

 August 1856 at Meadowhaven, a grilse of 6 J lbs., marked with silver 

 wire in the operculum. We have no data to show any other seasonal 



