WEEDS. 45 



the growth of the most suitable genera, and 

 no opportunity should be neglected of thinning 

 out or extirpating those which are too gross 

 of growth or in other ways unfavourable to the 

 development of the forms of animal life which 

 constitute in so great a degree the nutriment 

 of the Salmonidce. 



The presence of weeds is necessary for other Weeds a* 

 purposes besides the question of food supply. 

 In hot weather fish, like human beings, instinc- 

 tively seek shade during the long hours of 

 daylight, and except when feeding are usually 

 buried in the luxuriant growth, possibly indulging 

 in a siesta. Every time a trout or grayling is 

 scared, it seeks refuge in the nearest weed bed, 

 and the effect of mowing down wholesale all 

 vegetation in a stream is to increase their 

 shyness until at length they become quite 

 unapproachable. All these arguments point to 

 the desirability of having plenty of weeds in the 

 river. On the other hand, the greater the 

 quantity of weeds, the greater will be the number 

 of shrimps, snails, and caddis, and other larvae, 

 and although, of course, the flies constituting 

 the surface food come from the caddis and 

 other aquatic larvae, yet an excessive supply of 

 the shrimps, snails, &c, will infallibly induce the 

 fish to feed more at the bottom and in mid- 

 water and less on the surface. The presence 



