Influence of temperature and macrophytes development on the larval population dynamics of Epeorus sylvicola Pict (Ephemeroptera) in a torrential river of the «Haut-Atlas de Marrakech» (Morocco)

Abstract

Two successive generations of Epeorus sylvicola were studied in the Tifferguine, a torrential river in Morocco (2600 m altitude, water temperature 0-22°C, snow-cover : 1-2 months/year). The life cycle took one year and larval growth depended on temperature. Larvae fed on periphyton and lived mainly on stony substrates. In spring, macrophytes overgrew the bottom river and markedly reduced the amount of non-vegetated area ; combined with maximum and potentially lethal temperatures E. sylvicola larvae disappeared in May. Consequently, annual production depended on the development stage reached by the cohort when such unfavourable conditions occurred.