WHY DO SALMON ASCEND FROM THE SEA? 



Prof. Edward E. Prince, 



Dominion Commissioner of Fisheries, 

 Ottawa, Canada. 



Salmon problems are perennial and their solution, by the sports- 

 man, the fishery expert and the man in the street, appears to be 

 as distant as though not a word had been said, or a single 

 hypothesis offered. "Do salmon feed in fresh water?" "Do 

 salmon die after spawning?" "Do salmon spawn annually, 

 biennially, or when?" "Why do salmon ascend from the sea?" 

 These are amongst the multitude of perplexing questions which 

 seem to evade solution, and form the subjects of controversy as 

 keen today as in the days of Humphrey Davy and Izaac 

 Walton. 



I shall attempt to deal with the last question, because some 

 recent researches into the chemistry and physiography of the sea 

 appear to afford light which has long been sought in vain. 



Is Salinity a Cause? 



Professor Tory's well known views on the saltness of the sea 

 in past ages and at the present epoch, are of absorbing interest. 

 To most people their chief importance, perhaps, lies in the answer 

 they offer to the query, "How old is our earth?" But whether 

 the earth be ninety millions of years old, as Joly declares, or be 

 vastly older, the point of interest, so far as "salmon questions" 

 are concerned, lies in his very plausible contention that as the 

 sodium contents of the earth's rocky crust is decreasing, owing 

 to the continual wasting and wearing process, physical and chem- 

 ical, which are going on, the rivers of the world as a whole are 

 bringing down less sodium now than in past ages, and this decrease 

 in the amounts dissolved in the down-flowing streams, affords an 

 explanation of the salmon's migration.* If the salmon, living 



* Professor W. G. Bulman has pointed out that past and present marine 

 faunas show not a general increase in the sea's salinity, but a decrease, for 

 the Mollusks, Brachiopods, Cephalopods, Pteropods, and other exclusively- 

 marine Orders have diminished down to our own epoch. (Sci. Progress, 

 April, 1917). 



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