Determination of the reproductive characteristics of the European catfish (Silurus glanis) in Borçka Dam Lake

Abstract

This study was carried out to determine the reproductive characteristics (sex ratio, gonadosomatic index, hepatosomatic index, reproductive period, fecundity, egg size, gonadal maturity stages and length at first maturity) of the European catfish (Silurus glanis L., 1758) for the first time in Borcka Dam Lake. A total of 26 fishing operations were performed monthly between February 2016 and November 2017 and totally 156 European catfish specimens (99 female and 57 male) were sampled. Total lengths of all samples varied from 20.6 cm to 145.0 cm, (68.3 +/- 2.214 cm), and body weights ranged from 56.33 g to 21452 g (3090.18 +/- 307.505 g). the sex ratio (Male: Female) was calculated as 1.0: 1.74 and this ratio was statistically different from the expected value 1.00:1.00 (P<0.05). the length at first maturity was estimated as 85.0 cm for females and 79.9 cm for males. the length and age of the smallest matured individual was 81.3 cm and 4 years in females and 78.3 cm and 3 years in males. the minimum mean monthly egg diameters were measured in May as 1.097 +/- 0.0273 mm, while the maximum mean egg diameters were measured in August as 2.554 +/- 0.0221 mm. the total fecundity was estimated between 30379 and 301356 (179043 +/- 335.320) number eggs. There was a strong positive relationship between total fecundity-total length and total fecundity-body weight. the reproductive period of the European catfish in the Borcka Dam Lake was from July to September and the spawning ended completely in September. the results of this study could be useful to help sustainable fisheries management of inland fisheries resources and to provide a scientific data to further studies, also implementation of conservation and control measures in Borcka Dam Lake on the Coruh River.