An investigation of some biological features of Cyprinus carpio (Linneaus, 1758) in Gorgan Rud estuary

The total number of 460 specimens of Cyprinus carpio was collected from the product of fishery corporation companies located in Gorgan Rud estuary between December 1987 and June 1988. After doing the biometry processes, age of specimens was determined using scales and the fecundity of the fish is calculated by weighting and numerical methods. The mean length and weight of the fish were 466.7±79.92 mm, 1494.4±813.38 g and 430.04±85.26 mm, 1105.62±694.95 g for female and male ones, respectively. Also, the mean values of condition factor were 1.07±0.09 in females and 1.55±0.17 for males. In addition, the dominate age group was observed as 5 (33.48% of total numbers) and 6 (45.2% of total numbers) for females and males, respectively. Weight- length relationship showed a positive allometric growth (b=3.025) for females and a negative allometric growth (b=2.92) for males. The Von Bertalanffy growth equations were calculated as: Lt= 1054 (1-e-0.11(t.041)) and Lt = 901(1-e-0.12(t.402)) for females and males, respectively. Results also showed that growth performance index was equal to 5, mean gonadosomatic index in females was 16.98±2.46 and the maximum value was observed during the end of April to May and finally, average absolute fecundity for Cyprinus carpio was 185254±75778 eggs.