Essai d'élevage semi-intensif en bassin d'alevins de perche fluviatile (Perca fluviatilis) obtenus par reproduction artificielle

Mature perch were caught by electrofishing in the river Ourthe on April 20, 1983. Ova stripped from a female and fertilized by male milt were incubated in the laboratory. Hatching occurred after 11 days incubation at 13,4 °C (147 degree days) and the complete yolk sac resorption was observed on day 14 (179 degree days). The larvae (mean weight : 2 mg) were stocked at an initial density of 390/m2 (1040/m3) in a 4 m2-1,5 m3 fiber glass tank filled with aerated stagnant water (May 05- June 06) or supplied with water from a semi-closed recirculating system. The temperature was maintained within the range 17-27 °C around an optimum of 22 °C. The larvae and small fry were fed live preys (protozoa, rotifers, Daphnia spp.) which were progressively replaced by formulated trout fry feed. The 63 days old perch fry attain a mean weight of 533 mg (mean length : 35 mm) and their survival is 28 % (mortality rate : 1,15 %/day). From day 63 to day 95, they reach a mean weight of 1720 mg (mean length : 52 mm) but the mortality rate strongly increases (2,25 %/day) caused by the appearance of a cannibalistic behavior. The final survival from the stage of first feeding larvae to the 3 months-old fry is only 8 %. Despite this high mortality, the results presented here suggest that a semi-intensive rearing of 1,0 - 1,5 g perch fry could be carried out in tank within 70-80 days (at 18-24 °C) with an acceptable 10-20 % survival, achieved by a more efficient control of cannibalism and a more appropriate feeding strategy.