110 BRITISH SPORTING FISHES. 
crustacean can be found. But the economy of 
the otter ought not to be overlooked in connec- 
tion with our fish supply. Probably its increasing 
rarity has as much to do with disease as had 
the extermination of the nobler birds of prey 
with the grouse disease. A falcon always takes 
the easiest flight at its prey;* the otter, when 
fishing, captures the slowest fish. In each case 
they kill off the weakest, the most diseased, and 
thereby secure the survival of the fittest. Cor- 
porations are to blame in another particular. In 
seeking to prevent floods, all obstacles—natural 
boulders, rocks, and the trunks of trees—are 
removed from the river bed. This takes away 
the harbours of the fish without succeeding in its 
object ; for the old and disused weirs that exist on 
many trout-streams are important factors in pre- 
venting the rapid flow of water. Another thing 
to be considered is the nature of the dressings 
put on land in the shape of manure. The soluble 
parts, often poisonous, are carried by the rains 
into the stream ; and, nowadays, drainage is rapid 
—much more so than formerly, when streams 
took days to rise and fall. This brought food; 
but now surface-water is quickly directed into 
channels, and as quickly conveyed into the river. 
* This has been denied from an authoritative quarter, but I 
prefer to let the statement stand. 
