24 



Appendices to Twenty -eighth Annual Report 



We are still very ignorant of what happens in the sea, and in which 

 parts of the ocean smolts and kelts increase in weight so rapidly. 

 Dr. Dahl has, I understand, obtained some young salmon in mackerel nets, 

 and the North Sea investigations promise to help us by indicating when 

 and where the food supply is abundant. Any definite knowledge as to the 

 marine haunts of the salmon might not prove an unmixed advantage, as 

 their sanctuary would be sure to be invaded to the probable detriment of 

 our home fisheries. The latter are within territorial limits and subject to 

 our laws, ancient though they be and much in need of amendment ; but 

 any attempt to protect salmon in the ocean would be dependent on 

 international agreement, not always easy to arrange and often difficult to 

 enforce. 



Salmon that have Spawned. 



Now that we know that many of the older salmon are on their first 

 return to the river, it is evident that, even if they manage to evade the 

 nets and other dangers that threaten to terminate the course of their 

 natural life, their opportunities of reproducing their species must be 

 limited in number. In the Twenty-third Report (p. 77) I gave particulars 

 of the scales of one or two fish that had spawned twice before they were 

 netted, while on their third journey to the redds. So far I have not come 

 across any scale bearing more than two spawning marks, but as this mark 

 is not defined until after the fish descends to sea as a kelt and adds new 

 growth to the circumference of the scale, it follows that a salmon may have 

 spawned three times, and yet only show two indications of having done so. 

 Such a case, however, implies that we lose trace of it after its third 

 appearance as a kelt. 



We have confirmation of the possibility of a third spawning in an 

 instance from the Helmsdale, where a kelt marked early in 1905 was 

 recaptured and artificially spawned both in 1906 and 1908, so that it yielded 

 ova in three seasons though the scale only recorded two spawning marks 

 up to the time the fish was last handled. It seems fairly safe to conclude 

 that only a few salmon get the chance of breeding three times. 



From the marking experiments on the Tay, it would appear clear that 

 many of the heavier autumn fish which spawn for the first time when in 

 their fifth year, do not repeat the operation until their seventh year, which 

 is probably near the close of their reproductive life. We would expect 

 that a grilse (so-called) spawning in its fourth year might exhibit a greater 

 generative frequency, but there is little evidence on this point. There 

 does not seem any room for doubt that the restocking of our rivers largely 

 depends on the maiden fish of the different seasonal runs, for although 

 some salmon that have previously spawned contribute their share of ova, 

 they are in the minority, 



DESCRIPTION OF PLATE. 



Scale (magnified) of a 351b. spring salmon (male), captured in March, 1900. 



This fish had migrated as a smolt shortly after the completion of its second year, 

 and had remained nearly three years in the sea before returning to fresh water. 



Towards the middle of the scale a small point is visible, which is called the centre 

 of growth and marks the initial formation. This is surrounded by the tine lines 

 added in the river during two years of infancy, and these again are bordered on the 

 anterior (or concealed) portion of the scale by the better-developed ridges representing 

 three years' growth in salt water. 



During the three summers this fish spent in the sea its scales increased rapidly in 

 size, as denoted by the distance between the numerous ridges ; but in the winter 

 months the rate of growth was diminished, and the lines put on were comparatively 

 few and close together, forming a band indicating approximately the end of a year in 

 salt water. Two of the winter bands are distinct, and the third is in course of 

 formation on the periphery of the scale where the ridges approach each other more 

 closely. 



The break in the scale outside the second winter band is not a spawning mark, but 

 is caused by the unequal action of the cells on the resumption of activity in the 

 beginning of the last summer. 



