Manchester Memoirs, Vol. Ivii. {\C)\l\ No.Vi. 5 



shire Avon, the Dorsetshire Stour (3), and some were from 

 La Creuse (4) and La Vienne. Although specimens of 

 scales were not collected from a sufficient number to make 

 it worth while to quote figures, it is significant that almost 

 without exception the fish had remained in the river for 

 only one year. Scales of salmon taken in the Hampshire 

 Avon have been examined by Mr. Johnston (5), and he 

 records similar results. 



This regular series of decreasing lengths of time spent 

 in the river noticed in fish from Finmark, Trondhjem, the 

 Wye and the Avon, Stour, Vienne and Creuse raises a 

 very interesting point. What influences the length of 

 time spent in the river? From the results mentioned 

 above it would naturalK' be supposed that the tempera- 

 ture of the rivers must be an important factor. There are 

 no data to hand of the temperatures of the rivers in the 

 localities named, but from their geographical positions it 

 would be safe to saj' that the temperature of the Stour, 

 Avon and Vienne would be higher on the whole than 

 that of the rivers of Finmark. It would therefore seem 

 that the temperature of the water may have a considerable 

 influence on the length of time the fish remain in the 

 river. With the higher temperature there might be 

 quicker growth and possibly a more rapid approach to 

 the stage at which the young salmon are ready to go to 

 the sea. In order to settle this point satisfactorily, care- 

 ful investigations should be made in different localities, 

 ascertaining the avei'age size of the young salmon at the 

 time of migration and the average size of the fish on their 

 return to the river to spawn. We should then fully 

 understand whether the young salmon in the north of 

 Norway leave the rivers when approximately the same 

 size as the young salmon in the Wye. It might be th;it 

 those from Finmark are t\pically larger than those of the 

 Wye, thus necessitating a longer life in the river. 



