Qualitative and quantitative investigation of the Zooplankton in fish ponds

Abstract

Investigations on two Hungarian pond systems aimed to evaluate Zooplankton species as a utilizable feed source for common carp of different age-groups. Eight samples from six ponds were taken during the rearing season; number and biomass were determined per species and taxonomic group. Traditional quantitative analysis is based on taxonomic grouping. Zooplankton species were assigned to two size-groups of below and above 500 microns. Altogether 38 species were identified: 6 of above 75% incidence, 6 between 50 and 75% and 8 between 10 and 50%. For practical reasons relating to production biology only 7-8 species have a determinant role in carp feeding. The biomass data show that the incidence of Rotatoria-size plankton - according to taxonomic grouping and according to size - was lower than that of the other two groups. In our grouping - abundance - species smaller than 500 microns represented the larger part of Zooplankton throughout the entire rearing period. In the group above 500 microns Copepoda proved more important as natural feed for the different age- groups of carp than Cladocera (except carp-grass carp biculture). Grouping of Zooplankton according to size seems to be a much more informative method for evaluating available carp feed than taxonomic classification. The latter also has to be maintained as an important source of information on the biological water quality and the production biology status of fish ponds.