AGE AND GROWTH OF CHUM SALMON

Chum salmon belongs to anadromous fish and it dies after spawning. In order to determine age and growth simulation of chum salmon, 571 homing chum salmons were randomly collected in Ussuri River in autumn of 2010 and 2011. Biological parameters, such as fork length and body weight, were measured in the field, and scales were taken into the laboratory for age determination. The results showed that the scale of chum salmon, which was thin and small, belonged to round scale. The scale had clear annuli that was formed once a year, the annuli belong to loose-close type. Young annuli, formed when chum salmon enters into the ocean from river, was observed in some chum salmons. Young annuli could be distinguished from annuli easily, as the young annuli diameter was shorter than the fist annuli obviously. The chum salmon samples were divided into 2+, 3+ and 4+ age group, and the individual number of the 3+ group was the largest, male and female group had the same character. In order to select the optimal growth function, Special Von Bertalanffy (VBGF), Logistic, Gompertz and power exponential growth function were used to simulate chum salmon growth at the age of 1-4, respectively, and evaluate the effect of simulation. A maximum likelihood estimation procedure was used to fit the functions and calculate the function parameters. ARSS (Analysis of the residual sum of squares) was used to analyze the difference of growth, and the result suggested there were no significant differences in growth between male and female individuals among the four growth models (P0.05). Therefore, male and female chum salmons were pooled together to analyze their growth. VBGF model was considered as the most appropriate growth model based on the Akaikes Information Criterion (AIC), and Bayesian information criterion (BIC), because it had the smallest value. The function is as follow: Lt=90.041-e-0.3(ti+0.27). The relationship between AIC and BIC of other functions is as follow: Gompertz Logistic power exponential. Thus VBGF should be selected to simulate the growth of chum salmon when the scale was taken as the age determining material. With the increasing age of chum salmon, growth rate became lower, and the individuals whose maturation age was younger grow faster than the matured older ones. The study of the age and growth of chum salmon should be taken for ages, which can provide more basal data for enhancement and releasing of chum salmon for the fishery resource protection programs.