Investigation of population dynamics of chub (Squalius cephalus (L., 1758)) and tench (Tinca tinca L., 1758) in Yenicaga Lake (Bolu)

This study growth and reproduction properties and mortality rates of chub (S. cephalus) and tench (T. tinca) were sampled from the lake of Yenicaga between March 2009 and July 2010 investigated, by the estimation of stock size, suitable fishing effort, product and biomass determined to utilize most efficient way. Moreover, some physical and chemical properties of lake water were investigated, suitability of lake water scrutinized in terms of fish life. Age of 729 chub which were sampled from Yenicaga Lake distributed between I-VIII, were determined as 74.9 % of female, 25.1% male, fork-length were determined between 12.8 cm and 34.6 cm, weigth varied between 31.8 g and 643.1 g. For all individuals von Bertalanffy growth parameters were determined as L?= 36.88 cm, W?= 713.01 g, k= 0.248, t0= -1.278 and b= 3.109. For all individuals average condition factor (CF) was calculated as 1.48± 0.01. First sexual maturity length of female and male chub were calculated as 19.2 cm and 15.3 cm respectively. Reproduction period was between the months April to July, egg diameter 1.29 mm and average egg yield were determined to be 25349 unit/ individual. Total mortality coefficient (Z) 0.68 year-1, natural mortality coefficient (M) 0.50 year-1, fishing mortality coefficient (F) 0.18 year-1, stock exploitation rate (E) 0.27 year-1, survival rate (S) were calculated as 50.14 %. During the survey period were calculated that 24209 unit (4800kg) chub fished from the Lake of Yenicaga and in one fishing season 108369 unit (16770 kg) chub were found in the lake. To benefit from chub stock in Yeniçağa Lake most efficently, by increasing the current fishing effort 87 % determined that 5709 kilos of product could be obtained. Age of 291 tench which were sampled from Yenicaga Lake distributed between I-IX, were determined as 60.5 % of female, 39.5 % of male. Fork-length and weight varied between 10.9 cm to 41.5 cm, 24.0 g and 1127.2 g respectively. For all individuals von Bertalanffy growth parameters were determined as L?= 44.19 cm, W?= 1304.46 g, k= 0.236, t0= -0342 ve b= 2.999. For all individuals average condition factor (CF) was calculated as 1.55± 0.01 First sexual maturity length of female and male tench were calculated as 21.4 cm and 19.8 cm respectively. Reproduction period was between June to July, egg diameter 0.85 mm and average egg yield were determined to be 198249 unit/ individual. Total mortality coefficient (Z) 0.55 year-1, natural mortality coefficient (M) 0.46 year-1, fishing mortality coefficient (F) 0.09 year-1, stock exploitation rate (E) 0.16 year-1, survival rate (S) were calculated as 57.86 %. During the research period 8344 (4350 kg) tenches which were caught from Lake of Yenicaga, was calculated that in one fishing season 130204 unit (43317 kg) tench were found in the lake. To benefit from this stock most efficiently, by increasing the current fishing effort 203 % were determined that 8793 kilos of product could be obtained.According to the result of the analyses which were obtained from the sampling points in Yenicaga Lake, despite some months ammonium, nitrite and phosphate values were found high, were determined that caused no danger in terms of fish living.