On the Assessment of Biomass Production of Intensively Raised Larval and Juvenile Ayu Plecoglossus altivelist

Abstract

The biomass production of intensively raised ayu Plecoglossus altivelis of larval and juvenile stages “shirasu stage” was investigated with regard to the individual differentiation of somatic growth in cohort. The estimates for increment of the variance in total length varied from 3.21×10^-2 to 5.24×10^-1mm²/ day. Although such a differentiation which often cause bias in biomass assessment had been long revealed, not much has been studied during fish nurturing process. Thereby, we employed the Population Balance Model which renders a linearly modeled biophysical process and is plausible to process the accretion of shirasu ayu. We recorded water temperature of the nurturing chambers over a time span of 77-181 days.
By using the Population Balance Model, the productivity measurements of [log_e(estimated weight gain/initial weight)/nurturing period] were 1.31-9.62×10^-2 1/day and the estimated value of the averaged yield was 9.04kg higher than the recorded value. All the parameters in this model were comparatively collated through classifying ingredients of each category in accordance with the matrilineal origins to which the cohort characterized. An analysis in the linear trends in water temperature of rearing chambers throughout the breeding round evinced that the productivity index positively correlated to the temperature when breeding started.