of the Salmon in Fresh Water. 3 



feeding they should have been lighter. (Fourteenth Annual Report, Part 

 //., ,>. 12.) 



If salmon do feed in the sea it is perhaps curious that food should be 

 found in so small a percentage of those captured at the mouths of 

 rivers. But it must be remembered that the estuary of the river is not 

 the natural feeding ground of the salmon, and it is probably only by chance 

 that food is still in the stomach of fish captured there. 



SCOPE OF PRESENT INVESTIGATION. 



The present investigation was undertaken with the following 

 objects : 



1. To throw light upon the influences determining the migration of 

 salmon from sea to river and from river to sea, and to study more fully 

 than has hitherto been done the course of the migrations. 



2. To investigate whether salmon in fresh water require or use food; 

 and whether fish which do nob leave the sea till late in the autumn 

 continue to feed while their genitalia are developing ? 



o. To study the relative rate of growth of genitalia in salmon in fresh 

 water and in the sea. 



4. To investigate more fully the nature of the changes in the flesh 

 (muscle) and genital organs throughout the year. 



5. To determine the source of the material used in the construction 

 of the genital organs, and to study the chemical changes which the 

 various substances undergo. 



6. To elucidate the source of the energy required by the fish in 

 ascending the river. 



METHOD OF INVESTIGATION. 



To cany out this enquiry, it was necessary to have a supply of fish at 

 all possible seasons of the year. Further, it was desirable to have fish 

 from different sources at these various times some from the sea at the 

 mouth of the river, some from the upper reaches so that the changes of 

 the fish in their passage up the river, and in their sojourn in the upper 

 waters, might be thoroughly studied. 



It is known that through the spring, summer, and autumn there is a 

 more or less constant procession or stream of salmon passing from the 

 sea into the rivers. Our plan, then, was to take samples of the fish just 

 leaving the sea, and similar samples of those which had reached the 

 upper parts of the livers, and, by comparing the latter with the former, 

 to investigate the changes which had taken place during the sojourn of the 

 fish in fresh water. The method may be compared to that of taking 

 samples of water from two parts of a river in order, by examination of 

 them, to ascertain what changes have taken place in the water 

 between these points. 



MATERIAL FOR INVESTIGATION. 

 () Supply of Fish. 



The observations were commenced in June 1895 at the request of Mr. 

 Archer, Inspector of (Salmon Fisheries for Scotland. 



At this time Mr. Tosh was stationed at Berwick-on-Tweed investi- 

 gating the growth of the genitalia in Tweed salmon, and it was arranged 

 that he should send the viscera, with portions of the flesh, to the 

 Laboratory. 



It was soon found that to make the investigation satisfactory it would 



