Intensive culture of juvenile and adult Eurasian perch (P. fluviatilis): effect of major biotic and abiotic factors on growth

Abstract

Recent developments in Eurasian perch (Perca fluviatilis) larval rearing and weaning techniques allow large-scale intensive rearing tests, both with juveniles and adults. This review presents the results of experiments conducted in a commercial scale production environment (0.5–1.6m3 flow-through tanks) and focuses on the most relevant factors influencing growth and production in intensive rearing systems. Combined effects of food ration and temperature showed that the maximum growth rates (0.06–1.80 g fish−1 day−1 for 1–300 g fish) were observed at 23°C. The thermal range for intensive rearing of perch extends at least down to 11°C (growth rate equivalent to 29% of that observed at 23°C). The maximum daily food ration (9–4.5% lipid; 57–44% crude protein) at 23°C resulted in feed conversion rates from 1.1 to 2.0 in fish ranging from 1 to 150g and was modelled as follows (R2= 0.89): Rmax (% day−1) = 7.60 w (weight, g)−0.31. Juvenile (1–15g) perch reared at 10000 fish m−3 showed a growth rate of 0.2 g fish−1 day−1, thus 67% higher than at 400 fish m−3. In the most intensive rearing trials (124kg m−3), the maximum production rate observed was 2.6 kg m−3 day−1. Growth heterogeneity constitutes a major constraint in perch culture. Size grading experiments resulted in the emergence of fast-growing fish in each sorted group. In addition, the sorting process caused the productivity to be slightly lower (5–6%) than in non-sorted populations of the same origin and body weight. Mass mortality may take place at any stage of perch rearing within the 1–200 g body weight range. In general, an overall 50% survival rate was recorded after 14 months. Parasites, bacteria and fungi were the most frequently encountered causes of mortality. The occurrence and impact of diseases were largely reduced in recirculating systems where the survival rate is 70% higher than the values observed in flow-through rearing systems. In intensive rearing systems at 23°C and at maximum stocking biomass of 50 kg m−3, 44-day- old weaned perch juveniles (ranging from 0.5 to 1 g initial body weight) reached an average body weight of 130–150 g after 1 year of rearing. Still, this marketable size was reached about 3 months earlier by fast growing individuals within the population. The intensive culture of perch at a constant 23°C water temperature allowed much higher growth rates than usually observed in conventional, extensive systems under natural thermal regimes. Constant temperatures also inhibited the sexual maturation in females. Further improvements in growth and productivity in intensive perch rearing will closely rely on techniques such as the selection of fast-growing strains, monosex female or sterile triploid fish production.