36 BRITISH FRESHWATER FISHES 



In the open sea, as has recently been proved by a 

 Norwegian, Dahl, the smolts pursue the young 

 Herring, Sand-eels, etc., and this diet suits them so 

 well that they grow rapidly, so that when they 

 return in May or June, after spending about twelve 

 months in the sea, to the river from which they 

 went, they rarely measure less than 16 inches 

 in length, or weigh under i-J- Ibs., whilst some are 

 much larger, and those which ascend later in the 

 season, and which have been feeding for a longer 

 time, may weigh as much as I 2 to 14 Ibs. 



These fish on their first return from the sea, at an 

 age of three to three and a half years, are termed 

 grilse ; one of about 4 Ibs. is shown on PI. II, 

 Fig. 2. Exceptionally small grilse are sometimes 

 captured in February or March, but as a rule they 

 do not appear until April, and only in large 

 numbers in June, July, and August. 



Salmon intermediate between smolts and grilse 

 are not often captured, and mention may therefore 

 be made of a specimen in the British Museum from 

 Yarrell's collection, which that writer described as 

 the smallest Salmon he had ever seen that had been 

 to the sea. It measures only 1 1 J inches in length, 

 and was captured in the Solway Firth on the 8th 

 of June, when it had probably been in the sea not 

 more than two or three months. 



Grilse have the coloration already described as 

 characteristic of the adult fish, and all trace of the 

 parr-marks has disappeared. They are of a more 

 graceful form than the parr; the fins are relatively 

 much smaller and the anal is differently shaped, the 

 longest ray, when laid back, not reaching so far 

 as the last, whilst the caudal is less strongly 



