48 MARVELS OF FISH LIFE 
how environment and food supply have so greatly 
altered this fish in size, shape and markings as to make 
him appear in the guise of the migratory salmonoid, 
the Great Lake trout, the gillaroo and others. 
The brown trout is to be found in waters of very 
varied description. He may have to dart after every 
particle of food and passing fly in a barren Highland 
burn, or he may be able to pick and choose his food in 
a lake teeming with insect life. Whichever is the case, 
when the autumn arrives instinct tells him that there 
are other duties in life besides feeding, and so he gradu- 
ally makes his way to the spawning beds upon which the 
eggs are deposited. 
After the summer droughts the water is probably low, 
and the trout is prevented from getting to the gravelly 
bed he knows so well, and with many others is compelled 
to wait in the first deep pool for the autumn rain. Here 
he may meet a mate, and subsequently they may travel 
together to the spawning ground. More often than not 
he waits until he reaches his destination before selecting 
a bride. 
At last the rain descends, the river comes down in 
flood, and the pool which the day before held many 
waiting fish is now uninhabited. Trout racing through 
the rapids and resting for a time in the pools, gradually 
make their way to the very source of the stream, where 
the sparkling water gurgles over the gravelly beds. Here 
the male and female fish carefully select a suitable spot. 
The female then deposits her eggs, which are fertilised 
