Predator-prey interactions: effects of carp predation on Tubificid dynamics and carp production in experimental fishpond

Effects of predation by carp (Cyprinus carpio L) were analysed in an experimental fishpond where the main components of the benthic fauna were tubificids. Enclosures inaccessible to fishes were compared with the rest of the pond stocked with 30 young carps (1⁺). Fish predation reduced the density, biomass and production of prey; the production of Tubificidae inside the enclosures was 1.7 times higher than that of the part of the pond stocked with fishes. On the other hand tubificid turnover ratios (P/B) inside and outside enclosures were not significantly different (respectively 5.57 and 5.38), and the size distribution of tubificids was not significantly modified. The ratio of the energetic equivalent of net fish production to biomass of tubificids consumed was 5.59%.