Biological Characteristics of Siraz Fish, Capoeta kosswigi (Teleostei: Cyprinidae) and Host Relationship with Ectoparasitic Glochidia Larvae of Freshwater Mussel, Unio stevenianus (Bivalvia: Unionidae) in the Karasu River (Van, Türkiye)

Capoeta kosswigi (Karaman, 1969) and Unio stevenianus (Krynicki, 1837) are endemic species in the Karasu river, the Lake Van basin. This study was carried out to determine the biological characteristics of C. kosswigi and distribution and prevalence of U. stevenianus glochidia on this host fish. A total of 379 C. kosswigi were caught by electrofishing between March 2022 and February 2023. The maximum fork length and total weights of C. kosswigi were 29.2 cm and 421.8 g for females and 27.8 cm and 337.9 g for males. The length-weight relationships were calculated as W=0.017L2.881 (r2=0.986) for males (negative allometric growth) and W=0.016L3.001 (r2=0.953) for females (isometric growth). The Fulton condition factor was determined as 1.53±0.13 (1.23-1.99). The female:male ratio was calculated as 0.18:1.00. Additionally, a total of 12525 Unionid glochidia were detected on C. kosswigi samples in this study. Glochidia was more inclined to prefer male C. kosswigi as a host. The highest amount of glochidia was recorded in May, while the lowest in August. The amount of glochidia was statistically found the highest in the gill filaments (454.3±678.0) compared to all fins. Therefore, the native species, C. kosswigi is a suitable host for the freshwater mussel, U. stevenianus.