A Study on the carp (cyprinus carpio L., 1758) population of the lake Nazik (Ahlat-Bitlis-Türkiye)

SUMMARY A STUDY ON THE CARP (Cyprinus carpio L., 1758) POPULATION OF THE LAKE NAZİK (AHLAT-BİTLİS-TÜRKİYE) The lake Nazik is located in Ahlat-Bitlis, East Anatolia. Its altitude is 1816 m surface 2 area is 46,6 km and has orginated by lava blockage. While native species of the lake are Capoeta capoeta and Chalcalburnus larichi, common carp and Crucian carp are being introduced species of the lake. In the study; structure, growth, reproduction, foods and some body ratios of the carp population; and some quality characteristics of the lake water were investigated between July 1997 and December 1999. During the study; water temperatures were obtained between 2 and 24,5 C, Secchi disc values between 125-284 cm, eufotic zone depth 480,4 cm, DO 1,0-13,2 mg/1, pH 8,06-8,87, conductivity 254,4- 340,6 umhos/cm, TDS 190-226 mg/1, and morphoedaphic index as 15,4-18,3 mg/l/m. Age of carps changed between 0 and XII and I. age group was found predominant. The male:female ratio was calculated as 1,68:1. 40,37% of the fishes was mirror carp, 59,17% of was scaly carp, and 0,46% of was line carp. FL and W of the fishes changed between 4,0-75,8 cm and 1,0-1 1698 g, respectively. Length-weight, age-length, and age- weight relationships were calculated as W=0,02239xL3'04, Lt= 100,00 x {\^fi^^^\ Wt=26918,701x(l-e"°'085(l+0'46))3'04, respectively. The index of growth performance (0) was estimated as 6,745 and the condition factor as 2,513. Sexual maturity were determined as IV. age, 29 cm FL, and 550-600 g W for males and as VI. age, 39 cm, and 1500-1550 g for females. Spawning was taken place between middle of the June to the end of the July. Individual fecundity was found as 3609-2488210 per female, and relative fecundity was estimated as 153169±10337 per kg female. Mean egg diameter was estimated as 0,919 mm. It was found that the feeding of population is being as good, they meanly fed with Chirinomid larvae and Tubifexes, and preferred zooplankton at younger ages. It was concluded that in order to utilize carp population more effectively, water of the lake used for irrigation should be regulated without damaging to feeding and spawning areas of the population. Fishing should be maintained under control, minimum catch size should not lower than 39 cm FL and 1500 g in W, close season for fishing should be adapted between 1 June-1 August, crucian carp population should be kept at low density to lessen competition with the carp.