34 THE FISHING INDUSTRY 



The eggs of the cod, whiting, haddock, fluke, plaice, 

 etc., are relatively small, varying from % of an inch in 

 the case of a halibut, to ^ of an inch in a flounder. 

 The eggs are discharged into the water by the female. 

 This process takes place gradually, and generally 

 occupies many weeks. A few of the eggs come to 

 maturity at a time, and are extruded. They are 

 fertilized in the water by the spermatazoa of the male, 

 which are discharged into the water at the same time as 

 the eggs. The fish, both male and female, are closely 

 crowded together on the spawning grounds, so that the 

 fertilization of the eggs is fairly complete. With few 

 exceptions, the eggs of most species are buoyant and 

 float to the surface, where they drift in the warm surface 

 water until, happily, they hatch. Unhappily, however, 

 a very large proportion of them never reach maturity, 

 for, either as eggs, embryos or larvae, or post larval 

 young fishes, they soon fall a prey to marauding fish. 

 It is estimated that, of the thirty-two thousand eggs 

 laid annually by each female herring, not more than two 

 reach maturity. 



The spawning grounds of the herring are not definitely 

 known. Research is being carried out at present with 

 a view to solving this question. Haddock are to be 

 caught in various likely parts of the sea, marked with 

 the place of capture, and their interiors examined for 

 herring spawn. 



Certain demersal fish, notably shark, dogfish and skate, 

 deposit a few large, demersal eggs about a dozen in the 

 year in a carefully selected spot. The incubation period 

 of these eggs is unusually long, being from six months to 

 over a year, according to the species and the temperature 

 of the water 



Parental care is exhibited by very few fishes in this 

 part of the world, although many foreign fish build 



