2 JUNE 1933, Page 14

Country Life

FRESH-WATER fish are divided into two main classes— coarse fish and fish of the salmon tribe. The latter, known technically as the sahnouidae, only thrive in fresh clear spring water ; but many kinds of "coarse fish" (a rather unfair designation) can thrive in water which is stagnant and somewhat polluted. Carp and tench are both partial to ponds muddy enough to kill a trout of suffocation ; and canals and rivers tinged with sewage matter are often full of roach, dace, and perch. So long as a river is not an open sewage drain and contains no pyrites or other strong chemical substance it is sure to harbour fishes of some kind.