Carotenoid content and colour of eggs in migratory broodstock kutum (Rutilus frisii kutum Kamensky, 1901) (Osteichthyes: Cyprinidae) in the Shirud and Tajan Rivers, south Caspian Sea

Abstract

Carotenoids have a proven and positive impact on fish reproduction success. It is believed that highly pigmented eggs reflect the level of carotenoid content and this, in turn, has an effect on the viability of the eggs. Kutum, Rutilus frisii kutum, a species endemic to the south Caspian Sea, display different egg colours (yellow, orange or green) during the spawning season. In this study, we investigated the percentage of adult female kutum with the different egg colours, analysing the carotenoid content for each egg colour and the fertilisation rate for each egg colour in female migratory kutum in the Shirud and Tajan Rivers within the province of Mazandaran, Iran. The average of egg-carotenoid content of kutum in the Shirud River (6.63 ± 0.28 µg.g−1) was less than those for fish in the Tajan River (7.91 ± 0.27 µg.g−1), indicating a spatial variation in egg-carotenoid content of the fish. The orange and yellow eggs had more carotenoid than green eggs. Additionally, larger fish had a higher concentration of carotenoid compared with their smaller counterparts. The fertilisation of orange and yellow eggs was somewhat associated with egg-carotenoid content.