Using the back calculation to study of the age and growth of Caspian trout (Salmo Caspius)

The present study was aimed at studying the growth and age structure in the Caspian trout (Salmo Caspius). The back calculation and biometrical parameters including body length and weight, and age were, respectively determined in ۴۳ and ۱۰۱ individuals captured from Cheshmehkileh River, Tonekabon, Iran. The fish were with minimum and maximum age of ۴ and ۷ years, respectively, while the ۵ year-old fish were the most frequent. The mean length and weight of cathead individuals were measured to be ۶۹.۲±۶.۲ cm and ۳۳۲۳±۶۷۷ g, respectively. According to the back calculation method in ۲۰۱۴, the mean length of ۱-, ۲- and ۳-year-old fish were ۱۸.۹۸±۳.۵, ۳۰.۵±۷.۲۴ and ۴۱.۷±۹.۱ cm, respectively that were below maturity age, and thus did migrate to the coastal area for spawning. The males showed larger size, however greater prevalence and frequency were occurred in females. Growth parameters including growth coefficient (K) and L∞ were measured to be ۰.۱۸, ۱۰۴ cm, respectively, and growth performance index (Ø’) was calculated ۳.۲۸۹ indicating an allometric negative growth. Calculated L∞ and K were in an acceptable range. Here, we provide back-calculated size-at-age estimates based on otoliths from individuals belonging to native fish from the Cheshmekileh River while male possessed larger size however the greater prevalence and frequency occurred in female fish.

Keywords:

Back calculation , Caspian trout (Salmo caspius) , Caspian Sea , Growth , Age