242 BRITISH FRESH-WATER FISHES 



were retaken in the same river as they were first captured in: 

 the other five were as follows : — 



Three salmon captured in the Helmsdale were retaken in the Brora.* 

 One „ „ „ Spey was „ „ Dee.t 



One „ „ „ Spey „ „ „ Deveron. 



Out of ten fish marked in rivers and recaptured in salt 

 water, all were retaken near the mouths of these rivers, except 

 one fish marked in the Deveron, retaken at Cove (Aberdeen),, 

 about seventy miles to the south-east, and another marked in 

 the Brora, retaken in Bighouse Bay, one hundred miles to the 

 north-west. It is easy to suppose that salmon may be lured 

 to great distances from their native rivers by the movements 

 of shoals of herring or other fish on which they are known to 

 subsist. In Norway a fish marked in the Aaensira River was 

 retaken two years and a half later in Trondjhem's Fjord, 

 fully five hundred miles to the north. 



As to the rate of growth and increase in weight, some very 

 instructive tables have been prepared by Mr. Calderwood, both 

 from the observations and markings conducted on the Tweed 

 between 1851 and 1873, and from those of the Scottish Fishery 

 Board initiated by Mr. Archer. Of the fry hatched from ova 

 deposited in winter, it has been ascertained beyond doubt that 

 some descend to the sea as smolts in their second spring, being 

 then about fifteen months old ; others delay their migration 

 till their third spring, when they are about twenty-seven 

 months old. In neither case will they exceed two ounces in 

 weight ; let them but reach the salt water in safety, and their 

 rate of growth is amazing, if reliance may be placed upon the 

 results of marking in the Tweed.J 



* The mouths of these two rivers are only about twelve miles apart. 

 t This fish had travelled about ninety miles. 



X This was sometimes done by fin-cutting, a very untrustworthy 

 method ; in the cases cited, silver wire in the gill-cover was used. 



