Determination of Sizes at First Maturity and Reproductive Period of Freshwater Mussel Unio terminalis in Gölbaşı Lake (Hatay), Turkey

Abstract

In this study, reproductive characteristics of freshwater mussels (Unio terminalis) were determined according to months. Freshwater mussels, which are the research material of this study, were obtained from G & ouml;lba & scedil;& imath; Lake (Hatay). The mean length, width, height and weight of individuals sampled from the lake were 7.82 +/- 0.52 cm, 3.98 +/- 0.26 cm, 2.88 +/- 0.24 cm, and 42.28 g, respectively. When the gonad development of the species was examined on a monthly basis, it was determined that the gonads developed between December and February, and the release of glochidia occurred in January and February. During the breeding period, the length at first sexual maturity was investigated according to the determined length groups. 400 mussel samples of different sizes were collected randomly from the lake at a time, and the length, gill length and thickness were measured. The gonads of the mussels were visually and dimensionally examined. Length at first maturity is accepted as the size at which 50% of the mussels mature. In both sexes, there were no mature individuals in the 3.50-3.99 cm size group, but maturation started from 4.00-4.49 cm in males and 4.50-4.99 cm in female individuals. The size at which 50% of the individuals reached sexual maturity (Lm = 50%) for males and females were 6.10 cm and 6.00 cm, respectively, thus it was found that the female mussels reach sexual maturity at a slightly lower size. It was also determined that 100% of male and female individuals attain sexual maturity when they reach 7.50-7.99 cm in length.