Long-term changes in the biological parameters of wild carp (Cyprinus carpio carpio) from the south-eastern Caspian Sea

Abstract

The populations of wild carp (Cyprinus carpio carpio), as a commercially valuable species in the southeast Iranian waters of the Caspian Sea, have been severely declined during last three decades, but there is no comprehensive research available on the biology of this species in this area. The age, growth and reproductive aspects of samples collected during 2009-2010 fishing season were measured and compared with data from previous studies to elucidate changes during the last five decades. The mean total length and weight of sampled carp ranged from 262- 726 mm and 314- 3733 g, respectively. The von Bertalanffy parameters of K and L∞ for both sexes were 0.24 year -1 and 68.13 cm, respectively. The Gonadosomatic index ranged from 6.61 to 20.12% and 1.2 to 7.11% in female and male samples, respectively. The mean fecundity of fish ranged from 33695 in 4 years carp to 1234567 in 12 years samples with mean of 273 thousand in all fish. The oocyte diameters ranged from 0.69 to 1.53 mm with mean of 1.32 mm. Egg size frequency distribution showed that wild carp has asynchronous ovarian development. Comparing the results from 5 decades ago showed that replacing the gill nets with beech seines has had evident impact on the growth and age-composition of wild carp and the observed asynchronous reproduction strategy should be considered for artificial reproduction programs.