DURATION OF SEA LIFE AND WEIGHT INCREASE AFTER SPAWNING. 71 



they have to spend nearly a whole year in the river before they get back to the sea as 

 kelts, during which time they are practically starving.' 



Dahl (1910, p. 37-38) evidently did not regard effects of the spawning operation as 

 the only cause of the mortality. He says : 'and this is easily understood when one thinks 

 of all the dangers the fish has to pass through during its spawning journey, and among 

 which by no means the least are the snares and traps of mankind. The violent changes 

 of conditions to which it is subjected during its long journey, during the long fast in 

 fresh water, and during the labours in the actual act of spawning, are bound to be fatal 

 in their effects.' 



Duration of Sea Life and Rate of Increase in Weight After Spawning. 



In the Scottish, English, and Irish salmon reports, Calderwood (1907, p. 59-66) 

 regarded the demonstration of what was called the divided migration of the salmon, 

 i.e., the habit of the fish after spawning to remain short periods (less than one year), 

 and long periods (one year or over), in the sea, as the most outstanding feature. A sum- 

 mary of these Irish and Scottish reports shows the following: 



The Irish short-period fish (from three to eight months, averaging 5Vio months) made 

 monthly gains of one-quarter to 23^ pounds, averaging three-quarter pounds. 



The Irish long-period fish (11-17 months, averaging 14 months) made monthly gains 

 from one-seventh to P/v pounds, averaging about two-fifths pounds. 



The Scottish short-period fish (two to nine months, averaging 5.14 months) made 

 monthly gains from one-quarter to nearly two pounds (PV25 pounds), averaging about 

 iVe pounds. 



The Scottish long-period fish (11 to 24 months, averaging about 15.6 months) made 

 monthly gains of Vis to P/n pounds, averaging shghtly over Vs pounds. 



Calderwood (1907, p. 71-72) says: 'It may be asked whether grilse kelts, which are 

 subsequently found as summer salmon, continue to be annual spawners, or whether one 

 fish may be at one time an annual breeder and at another a fish of long absence in the 

 sea — a long period feeder. Two Brora records which show remarkably small increase 

 of weight in two years' interval seem to indicate that in both cases the greater part of 

 the time between marking and recapture must have been spent in fresh water, and that 

 annual spawning had prevented any very substantial increase.' 



Both fish were kelts when marked and when recaptured. One female, when marked, 

 weighed b}/2 pounds and was 28 inches long March 15, 1902. When retaken in the same 

 waters, March 28, 1904, weighed eight pounds and measured 34 inches in length, showing 

 an increase in weight of only 23^2 pounds and sLx inches in length in a little over two years. 

 Another, a female grilse kelt when marked in the same waters (Loch Brora), April 20, 

 1901, weighed four pounds and measured 25 inches in length. When retaken in the 

 same Loch, March 18, 1903, weighed 63<t pounds and measured 303^ inches in length, 

 having gained only 23^ pounds and b}/2 inches in length in about one year and 11 months. 



On the other hand, Calderwood (1907, p. 73-75) shows records of rapid growth in a 



