Croissance, production et demande d'énergie d'une population de soles (Solea vulgaris) introduite dans une lagune aménagée (bassin d'Arcachon)

Population of 4000 soles received from an induced spawing (COB-BREST), with a mean weight o£ 54 mg were introduced into a man modified lagoon (1000 m2 ) at Certes (4 soles/m2 ). The experiment was continued until December 1977 and permitted an analysis of the demographic evolution of the population : structure number, biomass, growth, production. Simultaneously an estimate of the trophic support necessary for the population derived by correlating oxydative demands with rate of oxygen consumption, was determined experimentally with specimens obtained during the samplings for growth and production (19 VII, 14 IX, 24 XI, 20 XII 1977). 1°) The demographic evolution of the population shows a rapid growth and a strong spread in size. For the short duration of experiments, 5 months, the average weight rose from 54 mg to 9,9 g, with a maximum of 29,7 g, the gain is therefore appreciable. It would been better if the experiment had been started three months earlier. In spite of the unfavourable natural conditions which were volontary choosen, and which have resulted in high mortality ; the total gain in weight surpassed the numerical losses since; the production-budget is always posi­tive (max in july and September 4,43 g. m-2 month-1). 2°) Tljie total energy potentiel of consumed-food Ci, is calculated in KCal m-2 month-1 for each period, by the means of the estimation of the biomass variation (or in situ the production P) and with the total energy of the metabo­lism (equal to twice the rate of standard respiration M) for a fish population of mean age i and by surface unit - one assume with Winberg (1955) and Mann (1965) that Ci = 1,25 (P + 2 M) - From the calculation of Ci the augmentation of the summer temperature is associated to an augmentation of P and R (Ci = 20 KCal m-2 . month-1 from 19 VII to 14 IX) followed by a diminution of R and a stagnation of P (Ci = 14 KCal m-2 month-1 ) the production P is practically nil in autumn and winter (Ci = 1 KCal m-2 month-1 from 24 XI to 20 XII). A precise determination of the optimal charge per rearing area is given by the calculation of the total energy potential of the consumed food (Ci) accoun­ting for the diet and the ecophysiological capabilities of the population of soles.