Environmental determinism of sex-ratio in the bleak, Alburnus alburnus (Linnaeus, 1758) (Cyprinidae) in Keddara dam, Algeria

Abstract

The objective of the present study was to document the temporal variation in sex ratio and to determine the physiological and environmental variables influencing the temporal structure of the two sexes of Alburnus alburnus (Linnaeus, 1759), a Cyprinid fish newly introduced accidentally in Algeria. The study was conducted in Keddara dam, Algeria for a period of two years from May 2008 to April 2010. The temporal evolution of abundance is relatively irregular, with the species being abundant in spring and large numbers were recorded from March to June 2009. The sex ratio is in favour of females and the statistical comparison of means revealed that the rates of two sexes are significantly different. The principal components analysis showed a negative correlation between the rates of two sexes. This implies behavioural variability, which is strongly related with environmental factors where the males are strongly influenced by pH and conductivity and to a lesser degree by water temperature. However, the females are positively correlated with dissolved oxygen and conductivity. Peak feeding activity is during the end of autumn and beginning of winter for both the sexes and the reproduction period runs from February to May.