AquaFlow Technical Leaflets
Production of cyprinids for re-stocking purposes - Part 3. Controlled larval rearing conditions
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In the last few years, great development in the rearing of fish larvae techniques has been observed. However, for many fish species, methods of juvenile production for re-stocking are still poorly defined. They require the study of many zootechnical aspects, including (in this project) larval density, optimal temperature and food regimes.
Embryos of wild cyprinids: asp (Aspius aspius), ide (Leuciscus idus), dace (Leuciscus leuciscus), chub (Leuciscus cephalus), nase (Chondrostoma nasus), vimba bream (Vimba vimba) and barbel (Barbus barbus) were kept at different temperatures for observation of yolk sac absorption, pigmentation and swim bladder inflation. Embryos were kept at four different temperatures: 10, 15, 20 and 25°C. Differences between temperatures, as well as between species, were observed in all of the noted characteristics. A similar difference was observed between embryos of asp, ide and dace and chub and is most probably due to their similar embryo size and similar yolk sac size. These differences were most apparent in nase (largest) and vimba bream (smallest) larvae.
The optimal density for rearing larvae under controlled conditions was between 40 to 100 larvae per liter. It was estimated at optimum temperature level, which was 25–28°C. The biggest differences were observed when feeding regimes were studied. Larvae of barbel and nase are fed initially with commercial dry feeds, as used for trout or carp. Other species need a period of feeding with live (i.e. Artemia nauplii) and mixed food. For asp, chub, dace and ide, 8 to 12 days of live food feeding is required. Vimba bream larvae need the longest period of feeding using live food. Shorter periods of live food feeding give rise to high levels of mortality, as well as some morphological abnormalities. Larvae of different species prefer different commercial dry food: i.e. larvae of asp grow better on trout feed; larvae of vimba bream on carp feeds. Larval survival was generally very high, especially in the case of barbel and nase. During three weeks of rearing, in all cases the survival rate was over 90%.
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