Fishes of the Western North Atlantic 



487 



less destructive today than under primitive conditions has not been determined. Their 

 relative effect on Atlantic Salmon populations now as compared with those in earlier 

 times may be due to either or both of the changes that affect the ability of the predators 

 to reproduce or to prey on the fish {142 ; 143). 



Overfishing has often been blamed for the decline noted. Anadromous fish are 

 more vulnerable to overfishing than species that remain at sea throughout their entire 

 life because they concentrate within a small area when they run up rivers to spawn; 

 thus it is much easier for fishermen to take a high percentage of the stock. The high 

 price that Atlantic Salmon command encourages intense exploitation of the fishery. 

 However, present evidence indicates that the fishery as now permitted by law does 



ATLANTIC SALMON 



1870 leeO 1890 1900 1910 1920 1930 1940 1950 



Figure 123. Commercial landings of Atlantic Salmon from the Gulf of St. Lawrence area (Cape Gaspe to 

 Cape Breton) for the period 1 870-1954 (Elson and Kerswill, 44). 



not reduce the spawning population below what is necessary to provide all the young 

 that the streams, in their present condition, can support {_42). In other words, the 

 decline of the fisher}' has been due to the creation of unfavorable conditions in 

 streams rather than to overfishing (see also Maintenance and Restoration of the Fishery, 

 p. 488-490). 



Fluctuations in Abundance. It is reasonable to assume that the Atlantic Salmon 

 population has always fluctuated more or less in abundance, but it is only for recent 

 years that it has been possible to estimate with any degree of certainty from the catch 

 statistics the extent and nature of the fluctuations. Although catch cannot be regarded 

 as an accurate measure of actual population, it is the only available measure we have. 

 On the basis of such statistics it must be concluded that populations not only have 

 fluctuated widely from time to time but have declined seriously since 1930. However, 

 since 1955 there has been evidence of some improvement. 



The extent and nature of these fluctuations, illustrated in Fig. 123, show three 

 important features: (i) the great difference between neighboring highs and lows, for 

 instance between 1873 and 188 i and between 1924, 1928, and 1930; (2) the over-all 

 steady decline since 1930, with recent low catches persisting much longer than in earlier 

 years; and (3) the tendency of the peaks of production to occur about every 10 years. 

 This periodicity was noted almost simultaneously around 1930 by several investigators. 

 Griswold's discovery was based on a study of the records of the Cascapedia and Resti- 



