Background. Rearing larval fish under laboratory conditions requires the use of appropriate artificial diets that fully replace natural food. Up till now, no starter has been developed for cyprinid rheophilic fish larvae, and these fish are therefore fed diets developed for other fish species. The present study was undertaken to evaluate the effects of diets of different protein-, lipid-, and fatty acid compositions on growth, survival, and changes in the digestive system during larval development of sneep (nase), Chondrostoma nasus (L.), from hatching until the juvenile stage. Materials and methods. From day 4 until day 21 post-hatch, sneep larvae were fed, Artemia nauplii and three starters: Nutra AB 3.0 (NU), Perla plus (PP), and Perla larva proactive (PL). Each experimental treatment was run in triplicate. On day 21 of the experiment, samples of fish were taken for size measurement, histological and morphometrical examination, and fatty acid analyses. Results. The fish fed Artemia exhibited the highest growth rate and survival. Among the groups fed artificial diets, the highest survival and growth were observed in NU group, while PL group showed the worst results (P < 0.05). Comparison of the fatty acid composition in the diets and fish bodies revealed that the levels of n-3 PUFA were considerably higher in the bodies of fish fed starters than in the diets themselves, while concentrations of n-6 PUFA in the PP and PL groups were lower in fish than in diets. The NU diet showed the highest n-3 : n-6 ratio (5.54), while PP had the lowest. The highest MUFA : PUFA ratio occurred in Artemia nauplii and the lowest in the PP diet. Histological observations revealed the presence of supranuclear lipid vacuoles in the enterocytes of the middle intestine section of Artemia-fed larvae. No such vacuoles were found in fish fed artificial diets. Morphological changes in the livers of fish fed various diets involved hepatocyte size and cytoplasm area containing glycogen and lipids. Conclusion. Among the artificial diets, Nutra was the most appropriate for rearing sneep larvae. The results revealed that sneep larvae are capable of elongating and desaturating linolenic- and linoleic acids into longer-chain fatty acids.

fish, Chondrostoma nasus, sneep, nase, diets, fatty acids, histology, intestine, liver