Indices of trophic and competitive relationships in a planktonic meta-network of carp ponds.

The functioning of the trophic cascade in fishponds determines the ecosystem stability and breeding success. We investigated the trophic and competitive relationships in the meta-network of carp ponds. We hypothesised that small taxa of the zooplankton consumer level would play a dominant role in the community. The importance of taxa for biomass flux and the strength of interspecific relations were assessed using network graph modelling. Critical to the coherence of the meta-network were positive associations initiated by species that exploit different feeding niches and tolerate high cyanobacterial biomass, such as small cladocerans Bosmina longirostris and Chydorus sphaericus, and the rotifers Polyarthra longiremis. Negative associations, potentially reflecting predation and competitive exclusion, were less important. The observed characteristics of dominant species and their relationships made it possible to identify trophic pathways and their potential consequences for common carp culture. This study presents a new approach to understanding the functioning of the pond food web in aquaculture and may contribute to sustainable fisheries management.