Spatial heterogeneity in roach (Rutilus rutilus) diet among contrasting basins within a lake
Archiv für Hydrobiologie Volume 146 Number 2 (1999), p. 239 - 256
published: Oct 11, 1999
ArtNo. ESP141014602005, Price: 29.00 €
Habitat and diet variation of roach (Rutilus rutilus) were studied in Lake Banyoles (Spain), an oligotrophic karstic lake with strong spatial heterogeneity in food resources. In addition to seasonal variation in diet, roach displayed an ontogenetic shift from zooplanktivory (dominated by the cladoceran prey Daphnia longispina) to benthivory (based on detritus, plant debris, amphipods, algae, and other invertebrates). Strong patterns of spatial heterogeneity in roach diet were detected for this lake. Firstly, there was a winter aggregation of smaller fish in the deepest basin, where benthos was scarce but a patch of copepods had been previously described. These fish displayed a high condition and fed on zooplankton, particularly those copepods. Secondly, meiobenthos, mainly ostracods and other microcrustaceans, was more important in the diet in the shallowest basin. The ontogenetic diet shift was also mediated by spatial heterogeneity, because in basins where benthos was scarce, larger roach continued to feed on zooplankton.