Background. In this study, we present the results concerning the growth, reproduction, and trophic activities of bleak, Alburnus alburnus (Linnaeus, 1758), a cyprinid fish recently introduced to Algeria. We need to show that this species is adapted to local conditions. We have also characterized the biological activity of the bleak and the impact of environmental parameters on this activity. Materials and methods. The fish sampling was carried out monthly from May 2008 through February 2012 in Keddara Dam Lake, from a single sampling station located in the proximity of the dam. We studied the biometric parameters of the fish, their length–weight relation, growth parameters, the reproductive and trophic activities, as well as the physical and chemical properties of the water.  The data collected were processed and interpreted using selected biological indices. The climatic data were obtained from the Algerian National Office of Meteorology. The statistical analysis was performed using the R program. Results. The length–weight relation of bleak represented positive allometry. The females grew less rapidly than males between 2–3 years of age. Beyond this age, females grew faster. The condition factor of females and males indicated that environmental conditions were unstable and varied between poor and good. The sex ratio was in favour of females. The reproduction activity was relatively spread over time. During the year there were many phases of sexual maturation and several spawning periods (3–4), which started from the end of January and lasted until the end of July. The last late spawning was between November and December. The sexual rest period was observed between August and September. The hepatosomatic index, in both sexes, showed no great differences. Also, the viscerosomatic index was stable. However, the repletion index was steadily increasing throughout the year. The RDA analysis  analysis allows characterizing the biological activity of the bleak and the impact of environmental parameters. Conclusion. We have characterized the biological and ecological variability of Alburnus alburnus in its new biotope and the relation of this species to the environmental parameters. This study brings new evidence for the adaptive potential of exotic species introduced in North Africa.

Mediterranean, North Africa, trophic index, alien species, non-indigenous fish, reproduction, growth, bleak