The crustacean Daphnia magna was cultivated, over two culture cycles, during the growing season of 1996. The cultures were kept under natural conditions of temperature and photoperiod, without any technical installations. The cladocerans were fed a fish processing plant wastewater in which an intense chlorophyte bloom was induced. The bloom was triggered in the raw wastewater by inoculating it with the chlorophytes Scenedesmus sp., Chlorella sp., or a mixture of the two. The D. magna population growth was controlled by harvesting it with different intensities. The highest yields (71.644 mg wet weight, i.e., 671.92 mg·dm-3 in summer and 180.694 mg, i.e., 1778.58 mg·dm-3 in autumn) were obtained from those populations subject to the most intensive exploitation. Productivity of a population was correlated with harvest intensity. Yields from the 51- and 70-d-long cycles were 2.2 and 2.7 times higher, respectively, than the yield from an on-exploited D. magna population. Compared to the latter, the harvested populations showed a higher reproductive rate.

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