Natural diet of mirror and scaly carp (Cyprinus carpio) phenotypes in earth ponds

The natural diet of two different common carp (Cyprinus carpio) phenotypes (mirror and scaly) was studied in earth ponds
in the Czech Republic. The proportion of different items was assessed through analysis of gut contents in order to establish differences and similarities between the phenotypes. In addition, temporal changes through the growing season, the influence of fish weight on proportion of main items ingested and the relationship between gut content and natural food availability was also assessed. The results showed no difference in feeding behaviour between mirror and scaly carp, the two phenotypes displaying a diet overlap of around 0.8. A shift in food resources from benthic to planktonic organisms was observed between early and late summer, which was reflected in changes in electivity index for some taxa. Fish weight did not influence the proportion of organisms ingested. No correlation was found between natural food in the pond and that in the gut, any variation in diet probably reflecting the microhabitats in which individual carp choose to feed.