A study of the diet of roach (Rutilus rutilus (L.)) in the lake of Pareloup (Massif Central, France)

The diet preferences of roach in the lake of Pareloup have been determined by analyses of their gut contents from January to July 1990. Changes in the food composition have been established by using a weight index that illustrates a hierarchy of prey in relation to the season. These analyses show that roach in the size range 10-21 cm have a diet of chiefly detritus and zooplankton whilst the oldest individuals are detritivores. There is a seasonal variation in the roach diet : detritus dominates in winter, it is replaced progressively by zooplankton (Cladocera) and, in lesser quantity, by macroinvertebrates (Chironomidae) from March. Phytoplankton (diatoms) are ingested in large quantities, but their contribution in terms of weight of food is always small. The roach of Pareloup fed actively throughout the study period and in a rather opportune way.