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 rs »  Dee.t 
One a 9 »  spey 3 ny », 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, onethundred 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.t 
* The mouths of these two rivers are only about twelve miles apart. 
+ This fish had travelled about ninety miles. 
~ This was sometimes done by fin-cutting, a very untrustworthy 
method ; in the cases cited, silver wire in the gill-cover was used. 
