Feeding ecology of Cobitis paludica and Cobitis calderoni in Central Spain.

In total, 253 specimens of Cobitis paludica and 163 Cobitis calderoni were collected in the Lozoya River (Madrid, Spain) in April, May, July, September and December 1990. Both species showed high percentages of empty guts in all months. C. paludica fed mainly on detritus and invertebrates while Cobitis calderoni fed on invertebrates and unicellular algae. Preferred prey items were the larvae of Dipterans (Chironomidae, Simuliidae) and micro crustaceans, with Ephemeroptera (Caenis) in summer. Cobitis calderoni fed on the most abundant prey except in April and July, when it selected invertebrates. C. paludica selected invertebrates throughout all the months. Diet overlapping (Horn's Index) was complete except in September, when the abundance of invertebrates in both diets was similar. For the remaining months, food type (invertebrates, unicellular algae and detritus) abundance differed, minimizing the interspecific competition.