FIRST RESULTS OF EUROPEAN PERCH (PERCA-FL UVIATILIS) INTENSIVE REARING IN TANK - EFFECT OF TEMPERATURE AND SIZE GRADING ON GROWTH

Despite an important potential market in Europe few researches have ex amined the possibilities of intensive perch (Perca fluviatilis) cultur e in tanks or cages, This initial study investigated the effect of tem perature and size grading on the growth of perch reared intensively in tanks supplied with warm water from the cooling system of a nuclear p ower plant. The trials were conducted with weaned perch fingerlings (1 .9 g). Increasing the temperature from 22.9 degrees C to 26.5 degrees C resulted in a slight (+14.5 %) growth increase, although it was not significant (p > 0.05), probably because both temperatures were within the optimal thermal range of perch. At 26.5 degrees C, a high infesta tion (prevalence : 24.5 %) by the ciliate Heteropolaria sp. was record ed. Perch graded and divided into three size groups presented increasi ng growth polymorphism in each group and the body weight distributions overlapped between groups at the end of a 234-day experiment. Analysi s of covariance indicated there was no significant difference in growt h rate between the groups (F = 1.2). The potential for very variable g rowth, as shown in our trials, stresses the necessity of frequent grad ing of young perch for intensive rearing purposes.