Biology of reproduction of sea carp (Cyprinus carpio Linnaeus 1758) in the southern shores of the Caspian Sea

Samples caught by beach seine nets in the fishing season of 2019-2021 in the southern costal zones of the Caspian Sea were used to study reproductive biology of Cyprinus carpio. Totally, 435 sea carp, including 237 female and 198 male were sampled, and their age and maturity stages were determined over sampling period. The results indicated that age range of the sampled C. carpio varied from 1 to 6 years in males, from 1 to 9 years in females, and from 1 to 9 years in combined sexes. The highest frequency of samples was in the age group of 1 for males (54.4%), 2 for females (34%), and 4 years for combined sexes (26.6%). Frequency of fish observed in the V and VI maturity stages was 45.14% and 27.17%, respectively. According to the frequency of different maturity stages and also the trend of changes in Gonado-somatic index (GSI), two spawning peaks were observed in C. carpio, including weak peak occurred in December-January and strong peak observed in March-April. The female mean length at sexual maturity (Lm50%) was 27.7 cm. Absolute and relative fecundity (mean ± SD) of C. carpio were 429310±233479 and 668±319 eggs, respectively. Since, there was an overlap between the spawning peak of C. carpio and beach seine fishing period for bony fish, it is proposed that fishing season to be banned at the beginning of April.