The Movements and Population Densities of Roach (Rutilus rutilus (L.)) and Gudgeon (Gobio gobio (L.)) in the River Mole

Abstract

The move-ments of roach and gudgeon were investigated in the River Mole. Statistically, the river populations were divisible into mobile and static components; 61-70% of the roach and 66-69% of the gudgeon remained within home ranges, the remainders wandering more widely. Laboratory work showed that the majority of 2 gudgeon populations would accept parts of an artificial convoluted channel as a home range and suggested that the mobile component of the river population could be explained by the failure of some individuals, which are not otherwise distinguishable, to accept a home range. Using data from the field movement investigation, the population densities of roach and gudgeon were estimated as ranging between 0.4 and 4.2, and 0.3 and 2.8/m* r espectively.