196 BRITISH FRESH-WATER FISHES 



the female deposits such of her ova as are ripe for shedding, 

 beginning, it is said, at the lower end of the trough. The 

 male moves up and sheds his milt upon them, and, as the fish 

 work up stream, the action of their fins and tail bury the eggs 

 as fast as they are impregnated. This process is repeated daily 

 until all the ova are deposited. Generally there are a pair 

 of salmon, male and female, of about equal size on each 

 redd ; but in addition to these, smaller males hang about, 

 endeavouring to snatch an occasion for cutting in. The 

 result has been described by several observers as a series 

 of fierce tiltings between the rivals, many of whom lose 

 their lives in combat. 



The period of spawning varies slightly according to 

 latitude, fish in the extreme north of Scotland being from 

 a fortnight to a whole month in advance of those in rivers 

 further south. Thus in the autumn of 1899 the first 

 salmon were seen upon the redds of the Tay on November ist, 

 of the Forth on November 8th, of the Helmsdale on 

 October loth, and of the Findhorn on October lyth. The 

 months when the majority of salmon spawn in most rivers 

 are those of November and December. 



The spawn is exposed to many accidents after it has been 

 deposited in the redds in the manner described. Trout, 

 eels, and coarse fish eat the ova greedily ; in fact, salmon roe 

 is known to be such a deadly bait for trout that its use has 

 long been prohibited by law. Birds and water insects of 

 several species prey on this succulent fare ; pollution, especially 

 of a sedimentary nature, is very hurtful to the ova ; but 

 perhaps the greatest destruction of all is wrought by ice in 

 very hard winters. It is not that the eggs are destroyed by 

 cold ; they will stand exposure to a very low temperature ; 

 but the ground ice, which is formed in running water by 

 severe frost, rises when the fresh comes, carrying with it 

 masses of gravel and all that it contains. Nature, as usual, 

 has counterbalanced the risks of destruction by the fecundity of 



