Production dynamic and chan e of fatty acid and amino acid contents of the freshwater rotiferBrachionus calyciflorus Pallas f e l o n Dicryospbaerzum chlorelloides were investigated in batch and semicontinuous culture systems. The mean daily roduction was 57.4 and 34.2 mg of rotifers I-'&' (wet weight) respectively and were highly depen&nt o n initial algal cell density. The rotifer fed on algae contained high amounts of linoleic acid (18 : 2n-6) and amino acids such as arginine. The suitability of rotifers for gud eon Gobio gobzo L. and perch Percafluviatilis L. larvae during their early feeding stage was investigatei. After a 10-day experiment, larvae fed with rotifers grew significantly faster than those fed on micro-encapsulated dry food. The best food conversion and protein efficiency ratio were observed with the larvae fed with rotifers. Combining rotifers with micro-encapsulated dry food better improved growth rate and food utilization in perch than did the dry food alone. Zusammenfassung Nabwert des RadertiercbensBrachionus calyciflorus Pallas fur die Aufzucbt von Laruen von Supwasserfischen Die Produktionsdynamik und die Variation des Amino-und Fettsaure ehaltes von mit der Griinalge Dicryos{bae+m chlorelloides gefiitterten Sul3wasserridertierchen Brackonus calyciflorus Pallas wurden in ontinuierlichen und halbkontinuierlichen Kultursysternen untersucht. Die durchschnittliche Tagesproduktion lag bei 57.4 bzw. 34.2 mg Rotatorien I-'&' (Trockengewicht) und hing stark von der Ausgangsdichte der Algen ab. Mit Algen gefiitterte Radertierchen wiesen einen hohen Gehalt an Linoleinsauren (18 : 2n-6) und solchen Arninosauren wie z. B. Arginin auf. Den Nahrwert der Rotatorien wurde fur die Larven des friihen Entwicklungsstadiurns von Grundling Gobio obio L. und Barsch Percaflm&ztilis L. untersucht. Nach 10 Ta en zeigten jene mit Radertierchen gefutterten Larven eine signifikativ hohere Wachstumsrate als solcie die mit Trockenfutter ernahrt wurden. Die beste Nahrungskonversion und Proteinausbeute zeigten mit Rotatorien gefiitterte Larven. Irn Verhaltnis zur ausschliei3lichen Verfiitterung von Trockennahrung an Larven des Barschs brachte auch die Kombination von Trockennahrung und Radertierchen eine deutlich bessere Wachstumsrate und Nahrungsausbeute.

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The efficiency of the rotifer Brachionus calyciflorus Pallas as a nutritional soitrce for rearing larvae was studied in a coldwater cyprinid, the gudgeon Gobio gobio (L,), and in a percid, the perch Perca fluviatilis L., through their composition in fatty acids. Rotifer intake affected the fatty acid profiles of the larvae significantly, with an especially remarkable presence of the linoleic family. In gudgeon fed with rotifers, the polyunsaturated fatty acids (PUFA) reached 10,98% of the dry weight of the sample. This rate was highly influenced by the presence of the acids C18:2n-6 and C22:6n-3 which represented 66% of the total PUFA, In perch fed exclusively with rotifers, the PUFA represented 7,27% of the dry weight. In both cases, the ratio n-3/n-6 decreased by 75% and 73% after 10 days of feeding with B, calyciflorus. This variation was probably due to the exogenous supply in acids of the linoleic family through the rotifers and to the fact that these two species of fish seem to favour the mobilization of the n-3 PUFA such as C22:6n-3 for growth and survival. Moreover, with the utilization of rotifers, the reactions of elongation and desaturation from the C18;2n-6 and C18:ln-9 seemed to be much more important in the larvae. Lastly, the transition from a diet based on rotifers to one made up exclusively of frozen Artemia nauplii led to a significant reduction of fatty acids in fish. It reached 60,2% and 26,5% of the total fatty acids in the gudgeon and perch, respectively, and was observed especially at the level of the PUFA, On the other hand, a slight increase of the ratio n-3/n-6 was pointed out in the perch fed a mixed diet (co-feeding with rotifers and dry food), a phenomenon probably due to the reduction of C18:2n-6 in the larvae.

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