SPAWNING 167 



him on his first spawning trip, and compel his return 

 to the sea. 



Salmon appear to be more irregular than grilse, 

 both as to the time of their return and also as to the 

 river they ascend ; but the ascent of both grilse and 

 salmon is affected by the state of the water in their 

 river. The early or late ascent peculiar to different 

 rivers by which they are known as early and late 

 waters is entirely due to the condition of such rivers, 

 and their natural temperature and local clinmte. 

 Each river may again vary as regards the average 

 date at which salmon run, being earlier or later than 

 the average date as the river varies in the volume of 

 its flow. The running of salmon will again vary, 

 being early or late in accordance with the annual 

 variation of the season in each river. Some few 

 salmon enter the rivers as fresh fish as early as 

 January, and continue to run up bill late in the 

 spawning season. 



SPAWNING 



At last our grilse has reached the gravelly beds of 

 the upper stream of his own river. Natural selection, 

 attended by combat, will decide his mate, and the 

 female salmon lying on her side, when her condition 

 is ripe, will with lateral movements of tail and fins, 

 sweep the sand and fine gravel away from her body, 

 and thus form a hollow trough, into which she proceeds 

 to deposit a proportion of her ova, the male fish 



