Researches on the population parameters of the crayfish (Astacus leptodactylus Eschscholtz, 1823) in the Yenicaga Lake (Bolu)

In this study, the population parameters, i.e. sex and lenght compositions, lenght-weight relationship, reproduction, morphometry and meat yield characteristics of Astacus leptodactylus in Yeniçağa Lake between May 2017 and April 2018 were investigated. Some physical and chemical properties of lake water have been recorded by field studies carried out at monthly at certain stations. As a result of the research, it was found that the sex ratio of 641 crayfish (female: male) was 0,62: 1,00 and the total lenght values were between 80 and168 mm, and the total weight values ranged from 15 to 133 g. According to the length and weight data obtained, it was found that there was a linear and very strong relationship between lenght and weight (r2 = 0,9936), and the population showed negative allometric growth. It has been determined that the breeding period of crayfish in Yeniçağa Lake is between February and May. The first female individual with eggs was encountered in February. The average number of eggs were 270 to 422, which is detected in female with eggs and the diameter of the eggs was 2,45 mm. As a result of morphometric measurements, it was determined that there was a statistically significant difference (p<0,05) between male and female individuals except total length and abdomen length parameters and male individuals were found to be larger than female individuals. Meat yield was evaluated on the basis of total meat yield, which is the sum of chelae meat yield and abdomen meat yield. In terms of meat yield, statistically significant difference was found only in chelae meat and It has been determined that males have higher values than females. It was detected that 14,35% of A. leptodactylus population in Yeniçağa Lake had crayfish disease. This ratio was found to be 15,10% in female subjects and 13.88% in male. As a result of this research, it was found that population parameters of A. leptodactylus population in Yeniçağa Lake are similar to other crayfish populations and they are suitable for the expected results.