A Study on the population structure and gonadal development of Anadara cornea (Reev, 1844) in the Eastern Black Sea, Turkey

A Study on the Population Structure and Gonadal Development of Anadara cornea (Reev, 1844) in the Eastern Black Sea, Turkey Population structure and seasonal (monthly) variations in growth rates, condition index, survival, biochemical composition of somatic tissues and gonadal developments of A. cornea inhabiting in Eastern Black Sea have been studied. Specimen of A. cornea were sampled form soft bottom of Çamburnu - Of coastline (Trabzon) using dredge and diving from March'98 until February'99. Relevant environmental variables, namely temperature, salinity and chlorophyll-a, were also followed. A. cornea population seemed to consist of individuals with size range of 5-85 mm and mean shell length live weight of 39.28±0.261 mm and 24.9±0.37 g. The relationship between shell length (L) and live weight (W) was estimated as: W=0.0002xL3058. Condition index values exhibited clear seasonal variations: reaching maximum values (Kf=11.3±0.67, Kn=10.4±0.59) in mid-spring (May), declining to minimum (Kr=4.7±0.24, Kn=4.3±0.22) in late summer (August) and recovering in early autumn. Growth parameters of the population were estimated after estimating the age composition by employing Bhattacharya's method. The population seemed to consist of 7 age groups (0-6). Calculated von Bertalanffy growth parameters for mean shell lengths corresponding these age groups were estimated as: L«,= 85.01 mm, K= 0.295, to=-0.081 and total mortality rate, Z=1.18. Biochemical composition values (dry meat or water, ash, crude protein and crude lipid) of the meat showed similar seasonal or monthly variation as condition index. Mean crude protein and lipid contents of A. cornea were 57.8% and 8.8%. Sex ration of the population was determined using the histological analyis and visual observation and it appeared around 1:1. Histological investigation showed that minimum size for first sexual maturity is around 20-24 mm and individuals with mature gonads could be encountered as early as May. Six main stages (namely immature, development, mature, spawning, spend and resting) were identified during gametogenesis or gonadal developments. Keyeords: A. cornea, Black Sea, population structure, growth parameters, condition index, mortality, biochemical composition, gonadal development, sex ration vn