Mean and Standard Deviation in Fork Length Distribution of Red Sea Bream Pagrus major at Season and Age in the Waters off Shimane Prefecture

Abstract

In order to make the age-length key of red sea bream Pagrus major in the waters off Shimane Prefecture, mean and standard deviation of fork length distribution were estimated at season and age using the rings on scales of the fish caught by commercial and experimental fisheries. The rings on scales are formed once a year in the period from February to July around May. From estimates of fork length at age, the von Bertalanffy growth equation were estimated: L_t=582(1-e^{-0.174(t+0.146)}), where t is age in years and L_t fork length in mm at age t. The growth proportion of the month to annual growth was calculated by the ratio of the mean value of marginal growth index of scales in month to the slope of Ford Walford plot of radius of rings. This species was estimated to grow little in the period from January to March. The relationship between mean fork length and standard deviation was represented from the observed data as follows: s=-0.264+0.0787L, where s is standard deviation in mm and L is mean fork length in mm.