EDIBLE SPECIES 25 



rivers as early as the end of December. The same is 

 true of the sturgeon. The shoals of herring begin to 

 move before the spawning season. The herring, indeed, 

 often exhibits a double displacement, making one 

 journey before and one after spawning. Thus the winter 

 herring of the Boulogne fishery goes to spawn in the 

 neighbourhood of estuaries and shoals. The young are 

 already mingled with the gai or clean herring (fish whose 

 ovaries are empty) when the arrival of a microscopic 

 alga, the Phaeosphorus of Pouchet, is followed by 

 innumerable swarms of other clean herring, which in 

 their turn enter the estuaries. 



The term " migration " is used to denote the movement 

 at the time of spawning of a whole species in a particular 

 direction and at an almost constant date. 1 



Mr. Edward E. Prince, of Ottawa, has published some 

 excellent volumes dealing with the subject. Hardly has 

 it issued from the egg when the fish first migrates. It 

 travels from the west towards the deep bottoms or the 

 open sea, and its movements are as invariable as the 

 migrations of birds of passage. The ocean currents have 

 no effect on the fry of the cod, the whiting, and the 

 haddock ; after they have emerged from their first larval 

 stages they invariably make for the deeps, and only return 

 to the coast when their ovaries are filled. It is the same 

 with flat-fish. It will be seen that vertical displacements 

 are the rule ; 2 and the existence of local varieties indicates 



1 Sturgeon, salmon, sea-trout, Seine smelts, flounders, and shad run 

 up rivers to spawn. Eels, on the contrary, descend to the sea. 

 Dabs and plaice, and even soles, travel great distances up-river. 



3 The expression "vertical displacement" must not be taken 

 literally. It simply denotes a general tendency. Thus the pelagic 

 larvae born of the floating eggs of the sole make for the open sea. 

 After the lapse of a certain period they return to the coast, and 

 having become adult, resort to sandy bottoms at a depth of from 



