Common carp ( <i>Cyprinus carpio</i> L.) alters its feeding niche in response to changing food resources: direct observations in simulated ponds

Abstract We used customized fish tanks as model fish ponds to observe grazing, swimming, and conspecific social behavior of common carp ( Cyprinus carpio ) under variable food‐resource conditions to assess alterations in feeding niche. Different food and feeding situations were created by using only pond water or pond water plus pond bottom sediment or pond water plus pond bottom sediment and artificial feeding. All tanks were fertilized twice, prior to stocking and 2 weeks later after starting the experiment to stimulate natural food production. Common carp preferred artificial feed over benthic macroinvertebrates, followed by zooplankton. Common carp did not prefer any group of phytoplankton in any treatment. Common carp was mainly benthic in habitat choice, feeding on benthic macroinvertebrates…