The effect of density upon deposit-feeding populations: Movement, feeding and floating of Hydrobia ventrosa Montagu (Gastropoda: Prosobranchia).

Crawling rate, feeding rate and floating frequency were measured for laboratory populations of the deposit-feeding snail Hydrobia ventrosa at densities of 0.3-16 snails cm-2. Both movement and feeding were depressed with increasing density. However, floating increased with increasing density. Crowding effects are thus important in deposit-feeding populations and must be considered along with resource-renewal in considerations of population control. Floating may be an adaptation to escape crowded conditions.