Dr. Éva Murai szerk.: Miscellanea Zoologica Hungarica 4. 1987 (Budapest, 1987)

Kiss, I.: Ecological studies on zooplankton species important for fish farms. II. Interspecific relations between zooplankton species

of progeny breeding ponds. One of the reasons is undoubtedly the competition for food due to the more intensive filtering activity. This phenomenon exists between the two Cladocera species, too. If, for some reason, the proliferation of the Cladocera spp. is hindered (e. g. in the case of the use of substances with trichlorfon as the agent), the stock of Rotifera, both filtering and predator species, may grow to significant size. Thus, with the above mentioned correlations taken into consideration, it can be understood why the progeny must be introduced into the ponds on the day following the flooding in technologies using selective plankton preparation. After the flooding, the Rotatoria spp. become predominant in the zooplanktonic stock of the pond, and they serve as the first food for the progeny. As an example for the prey-predator relationship, we showed the co-evolutionary relationship between Brachionus calyciflorus and Asplanchna spp. The Brachionus calyciflorus population is sensitive in its reaction to the presence of Asplanchna spp. , namely the proportions of the body construction of the new-born change, spine length increases, which serves as an effective means of protection against predators. The grown-up individuals are practically invulnerable, whereas some of the young can be ingested by the Asplanchna spp. ACKNOWLEDGEMENTS I would like to express my thanks to István TÖLG, László HORVÁTH and Gizella TAMÁS for providing the opportunity to carry out investigations in the Tempered Watered FishBreeding Farm of Százhalombatta, and for their invaluable professional assistance during the experiments. My special thanks are due to my colleague Gábor BAKONYI for his generous help and constant support during the evaluation of the results. REFERENCES DODSON, S.I. (1974): Zooplankton competition and prédation: an experimental test of the size efficiency hypothesis. - Ecology, j>5: 605-613. HALBACH, U. (1970): The factors determining temporal variation in Brachionus calyciflorus Pallas (Rotatoria). - Oecologia, 4: 262-318. HALBACH, U. (1971): Das Rädertier Asplanchna - ein ideales Untersuchungsobjekt. III. Ein Rauber liefert seine Beute die Abwehrwaffen. - Mikrokosmos, 60_: 360-365. HALBACH, U. (1979): Introductory remarks: Strategies in population research exemplified by rotifer population dynamics. - Fortschr. Zool., 25: 1-27. JACOBS, J. (1977): Coexistence of similar Zooplankton species by differential adaptation to reproduction and escape in environment with fluctuating food and enemy densities. - II. Field data analysis of Daphnia. - Oecologia, 30: 313-329. KERFOOT, W.C. and PETERSON, C. (1979): Ecological interaction and evolutionary arguments: investigations with predatory Copepods and Bosmina. - Fortschr. Zool., 25: 159-196. KISS, I. (1985): Ecological studies on Zooplankton species important for fish farms. I. Population biological investigations on Zooplankton breeds. - Miscnea zool. hung., 3: 91101. LANE, P.A. (1978): Zooplankton niches and the community structure controversy. - Science, 200

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