Evolution Going On 197 



The Story of the Salmon 



In late autumn or in winter the salmon spawn in the rivers. 

 The female makes a shallow trough in the gravel by moving her 

 tail from side to side, and therein lays many eggs. The male, who 

 is in attendance, fertilises these with the milt, and then the female 

 covers them deeply with gravel. The process is repeated over 

 and over again for a week or more till all the eggs are shed. For 

 three to four months the eggs develop, and eventually there 

 emerge the larva? or alevins, which lurk among the pebbles. They 

 cannot swjm much, for they are encumbered by a big legacy of 

 yolk. In a few weeks, perhaps eight, the protruding bag of yolk 

 has disappeared and the fry, about an inch long, begin to move 

 about more actively and to fend for themselves. By the end of 

 the year they have grown to be rather trout-like parr, about four 

 inches long. In two years these are double that length. Usually 

 in the second year, but it may be earlier or later, the parr become 

 silvery smolts, wfrich go out to sea, usually about the month of 

 May. They feed on young herring and the like and grow large 

 and strong. When they are about three and a half years old they 

 come up the rivers as grilse and may spawn. Or they may pass 

 through the whole grilse stage in the sea and come up the rivers 

 with all the characters of the full-grown fish. In many cases the 

 salmon spawn only once, and some (they are called kelts after 

 spawning) are so much exhausted by starting a new generation 

 that they die or fall a victim to otters and other enemies. In the 

 case of the salmon of the North Pacific (in the genus 

 Oncorhynchus, not Salmo) all the individuals die after spawning, 

 none being able to return to the sea. It must be remembered that 

 full-grown salmon do not as a rule feed in fresh water, though 

 they may be unable to resist snapping at the angler's strange 

 creations. A very interesting fact is that the salmon keeps as it 

 were a diary of its movements, which vary a good deal in different 

 rivers. This diary is written in the scales, and a careful reading 

 of the concentric lines on the scales shows the age of the fish, and 



