Seasonal diet of Salmo trutta macrostigma in a mountain stream (Ifrane Morocco)

Abstract

The diet of salmo trutta macrostigma in Sidi Rachid wadi was conducted on 94 individual ranging in weight from 3 to 575 g with a mean of 110.38 g and a standard deviation of 112.94. Crustaceans mainly characterize the annual food spectrum and insects constitute more than 98%. The study of the variations of the diet spectrum shows that the nature and the importance in number of the ingested items of prey change according to the seasons, with an important relative predominance of crustaceans during all the seasons except winter when insects are the more important food source. In addition, the different taxa can be classified into two categories, a first group of preys always present in the stomach contents during all seasons and whose relative abundance is generally high, and a second group whose presence in the stomach contents was limited to one or two seasons. The most commonly used taxa are amphipoda, Ephemeroptera, and Diptera, with these three taxa forming at least 77% in summer and 90% in winter.