Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı 2

Growth, Feeding and Reproduction Biology of Squalius cephalus (Linnaeus, 1758) ın the Istranca Stream
In this study, growth, feeding and reproduction biology of chub [Squalius cephalus (Linnaeus, 1758)] living in Istranca Stream, which is one of the arms of Lake Terkos situated in the Thrace of Marmara region was studied.
Sampling was carried out in 6 stations from the stream monthly between March 2012 and June 2013 with the help of electrofishing. Length, weight, age, sex distribution and rates, age-lenght, age-weight, lenght-weight relationships, von Bertalanffy constants, condition factor, gonadosomatic index values, reproduction period, reproduction age and length, fecundity values and feeding characteristics of Squalius cephalus individuals were investigated.
Age distribution of the species was observed between 0. and VII. Total lenght values of all individuals were between 2,6-30,1 cm, weight values varied between 0,14-357,50 g. The female-male ratio was determined as 1:1,74. Lenght-weight relationship of all individuals was calculated as W=0,0078TL^3,1494. According to all individuals, von Bertalanffy growth constants L_∞, W_∞, K and t₀ were determined as 42,18 cm, 1023,97 g, 0,14 and – 0,58 respectively. Condition factor in all individuals was found the lowest value was 0,91 in February 2013, whereas highest value was 1,22 in June 2012. According to ages in all individuals average condition value was found the lowest value was 0,97 in 0. age group, and highest value was 1,34 in VII. age group.
For reproduction biology, gonads were examined as macroscopically and microscopically. According to GSI values reproductive period was between April and June. By lenght groups of S. cephalus sexual maturity at the lenght of % 50 was 12,02 cm for male individuals (II.-III. age), 13,63 cm for female individuals (II.-III. age). The lowest number of eggs as 1251 eggs/individual in IV. age group and the highest number of eggs as 10577 eggs/individual in VI. age group were found.
In order to determine feeding features digestive tract of caught fish samples were examined and food preferences was revealed. In the digestive tract in all seasons the most common food items were detritus, insecta and algae.
Previously conducted studies on the subject with the results are presented for comparison. In addition, this study is considered as important in terms of being first study on Istranca Stream performed with chub.