SPECIES INTERACTIONS AND SUBSTRATE PREFERENCES IN THREE SMALL BENTHIC FISHES

The interactions between bullhead (Cottus gobio), stone louch (Borbutulu bnrbatulu) and gudgeon (Gobio gobio) and subsequently their influence on the exclusion capacity of these species were examined in laboratory experiments. When a combination of gravel, sand and sand plus shelters substrate types were offered, the three species selected sheltered substrates. This preference was stronger when the three species wcre together rather than when in allopatry. None of the species showed any preference to coexist with another under sheltered positions. When only one specics occupied a sheltered position it was alone, without any other conspecific. Dispersal patterns differed bctween species but during this process there was no evidence of any species association. This study highlights a very limited interspecific interaction between bullhead, stone loach and gudgeon, and shows that intiaspccific exclusion in these species was much more important than the interspecific one