LENGTH-WEIGHT RELATIONSHIP OF PERCH (PERCA-FLUVIATILIS) LARVAE AND JUVENILES IN THE MOSTISTE RESERVOIR

Detailed regression analysis of the length-weight relationship in perch larvae and juveniles obtained from the Mostiste Reservoir in 1988-1989 was made using exponential predictive and functional regressions (y = a.x(b), y = u.x(v)). A high variability in the values of regression coefficients b and v was found during larval development and at the beginning of the juvenile period. The b coefficients varied from 0.35 to 5.36 (v coefficients from 3.7 to 7.43) in larvae and young juveniles, whereas later in the juvenile period, except, for April, the variability decreased considerably (b coefficient, from 3.02 to 3.19; v coefficient, 3.03 to 3.21). In April, the values of the two coefficientes were temporarily lower (2.23 and 2.34 resp.). The b coefficients were lower in fast growing than in slow growing individuals, and vice versa. The course of the length-weight relationships at different localities was most different at the beginning of the growing season and least so at the end. The observed great variability of values of regression coefficients in the relationship discussed is similar to that described in the carp, but the course of this variability is slightly different.