284 A HISTORY OF FISHES 



ova for every pound of her weight, so that a fish of 20 lbs. will 

 have about 17,000 eggs. The breeding season of our own 

 Atlantic Salmon {Salmo salar) extends from September to 

 February, but these fishes approach the coasts and enter suitable 

 rivers in almost every month of the year. While in the estuaries 

 their ascent may be helped by the tide, but higher up they 

 have to make their way unassisted, and so great is the urge 

 for reproduction that they will display immense perseverance 

 in negotiating obstacles such as falls or weirs lying in their path. 

 Once in fresh water, active feeding is almost entirely given up, 

 and as a result there is a gradual decrease in the weight of the 

 fish after they leave the sea. When first entering the rivers 

 fresh from a lengthy stay in the sea, with its rich and abundant 

 food supply, the Salmon are in fine condition, and exhibit the 

 graceful form and familiar silvery coloration so characteristic 

 of the species, but with the approach of the spawning time they 

 undergo very marked changes, particularly in their external 

 appearance. The silver livery is replaced by one of a dull 

 reddish-brown tint, and in the males the front teeth become 

 enlarged, the snout and lower jaw are drawn out, and the 

 latter is turned upwards at the tip to form a prominent hook 

 (Fig. 104A). Further, the skin of the back becomes thick and 

 spongy, so that the scales are embedded in it, the body becomes 

 spotted and mottled with red and orange, and large black 

 spots edged with white are also developed. Such male breeding 

 Salmon are known as "Red-fish," and the ripe females, which 

 are darker in colour, as "Black-fish." Another important 

 change is in the character of the flesh. In a freshly run fish, 

 that is to say, in a Salmon which has just left the sea, the muscles 

 are firm and red, with a good store of fat in the tissues, but as 

 the time for spawning draws near this fat is used up in the 

 development of the organs of reproduction and the flesh itself 

 becomes pale and watery. The suggestion has been made that 

 this rapid transference of fatty substance from the flesh to the 

 sexual organs is the cause of the diflference between the sexes 

 in the breeding season, the process leading to the formation of 

 an excess of by-products which cannot all be excreted, and thus 

 give rise to the growths at the ends of the jaws or appear as 

 patches or spots of pigment in the skin. 



Gravelly shallows where the stream runs fairly rapidly are 

 selected as the spawning grounds, and on arrival the Salmon 

 more or less segregate into pairs, the female setting to work 

 to scoop out a shallow trough or trench by means of vigorous 



