Maximum yield approximation and size distribution patterns of stocker size largemouth bass, Micropterus salmoides reared in a semi-closed indoor system

摘要

The main objectives of this study were to approximate the maximum yield and evaluate size dispersion of stocker size largemouth bass, Micropterus salmoides reared in a semi-closed recirculating system for 60days. Fingerlings with an average body weight of 36.7g were utilized for the study. An experimental system consisting of 18 square plastic tanks (165L) equipped with a radial flow settler, a sump, a moving bed filter, a centrifugal pump, a rapid sand filter, a down-flow oxygen saturator and a UV sterilizer was utilized for the trial. The system was operated semi-closed, accounting for a daily exchange rate of 30-50 of total system water volume. Experimental stocking densities were 4.5, 9.1, 18.8, 36.5, 54.6 and 73kgm(-3) with three replicates per treatment. At the end of the experimental trial, largemouth bass showed acceptable feed conversion (1.00-1.48), specific growth rate (1.16-1.45 day(-1)) and survival rate (81.8-96.6) in all treatments, displaying the highest performance at an initial stocking density range of 18-36kgm(-3). Based on a piecewise regression model with breakpoint analysis, maximum yield of largemouth bass fingerlings should not exceed 70kgm(-3). As stocking densityincreased, relatively more underweight fingerlings were produced with a higher uniformity of fatness.