original ecosystems, planktonic crustaceans are a common item in roach diet (García-Berthou 1999). In Joaquín Costa reservoir, this species has a high trophic overlap with carp, white bream and barbel, which all converge on the use of cladocerans, especially in spring and summer. The intensive consumption of cladocerans during both periods was related to their high availability (Palau, per. com.), when they are known to be abundant and hatch in large densities. With a superabundance of available food and consequently
a low search time, the fish could afford to specialise on this single food category (Mason & MacDonald 1982). Their consumption decreased towards winter as the density of cladocerans diminished, except for the roach. During winter, these species tend towards
a trophic segregation in their feeding niches, their dietary overlap being relatively low. This suggests that food resources were well partitioned among them
original ecosystems, planktonic crustaceans are a common item in roach diet (García-Berthou 1999). In Joaquín Costa reservoir, this species has a high trophic overlap with carp, white bream and barbel, which all converge on the use of cladocerans, especially in spring and summer. The intensive consumption of cladocerans during both periods was related to their high availability (Palau, per. com.), when they are known to be abundant and hatch in large densities. With a superabundance of available food and consequentlya low search time, the fish could afford to specialise on this single food category (Mason & MacDonald 1982). Their consumption decreased towards winter as the density of cladocerans diminished, except for the roach. During winter, these species tend towardsa trophic segregation in their feeding niches, their dietary overlap being relatively low. This suggests that food resources were well partitioned among them
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