ATLANTIC SALMON 



Salmo salar salar Linnaeus 



The Atlantic salmon was originally distributed on both sides of the Atlan- 

 tic Ocean from Portugal in Europe and from the Hudson River north on this 

 continent. The number of rivers along the Atlantic Coast which the Atlantic 

 salmon originally ran on their spawning migrations varied from 28 to 34. 



The majority of the Atlantic salmon enter the rivers in the spring taking 

 advantage of the freshets occurring at this time. Stragglers however continue to 

 run through to October and November. Since most of the adults ascend the 

 streams in early summer a good salmon river must have deep, cool pools for 

 these fish to maintain themselves during the summer months before spawning 

 time. Although the Atlantic salmon do not necessarily die after spawning it 

 is apparent from an examination of the fish running the streams that by far the 

 greater majority of them are "maiden fish" making the spawning journey for the 

 first time. Roughly 90 per cent of the runs each year are fish returning to spawn 

 for the first time. The spawning run is made up of fish from four or five years 

 old although variations from this age occur. Some of the fish running the rivers 

 are much smaller than the others and represent the "grilse" which have re- 

 mained in the sea for only one year. These grilse are nevertheless sexually 

 mature. The fish spawn from October through November with the peak of 

 spawning during the last week in October. The Atlantic salmon river must have 

 extensive spawning areas of large gravel or rubble in riffles. 



The female, ready to spawn, seeks out a suitable area at the head of a 

 riffle or the tail of a pool which will insure a good flow of water over the eggs. 

 The nesting area of a salmon is properly called a redd and each redd is 

 composed of several ^gg pits. The female digs the individual ^gg pits by turn- 

 ing on her side and flapping vigorously with her caudal fin and peduncle. The 

 pectoral fins are usually held out to retard forward motion. Digging takes place 

 every few minutes with a rest of 10 to 15 minutes. The male during this time is 

 either attending the female or escorting smaller bucks from the nesting area. 

 The actual act of spawning takes place with the male and the female side by side 

 eggs and sperm being extruded into the tgg pit. Natural fertilization is more 

 efiicient than was formerly recognized because of the small eddy currents set up 

 in the ^.gg pit. These eddy currents circulate the eggs and sperm insuring ferti- 

 lization and hold them in the pit preventing them from being washed down- 

 stream. The only parental care of the eggs is the covering of the pit with gravel. 

 Much of this covering is done while the female is digging the next ^gg pit 

 when the gravel is carried downstream to the former pit. The number of pits 

 dug by the female depends on the number of eggs which she may contain and 

 how many she deposits in each pit. The completed redd of an Atlantic salmon 

 may measure from 8-20 feet in length and 2 to 3 feet in width with the eggs 

 buried as deep as 10 inches. 



19 



