Mixed‐species brooding between two Baikal sculpins: field evidence for intra‐ and interspecific competition for reproductive resources

Abstract

In an examination of the distribution of nesting spaces of two Baikal sculpins, Paracottus kneri and Cottus kessleri, along two transects offshore at Bolshye Koty, a total of 43 P. kneri nests, 32 C. kessleri nests and one Batrachocottus baicalensis nest was found. Males of these species established breeding nests under overhanging stones in the same manner as most freshwater sculpins, but nests of each species were clearly partitioned in separate zones. Cottus kessleri nests were found where the lake floor was mostly covered with overhanging stones. Paracottus kneri nests, however, were found where the lake floor was moderately covered with overhanging stones. Two mixed‐species brooding nests with a C. kessleri guarding male were found in an area bounded by the two zones. Each of these nests comprised one P. kneri egg mass and several C. kessleri egg masses, guarded by a C. kessleri male. The nest distribution of these fishes appears to reflect intra‐ and interspecific competition for overhanging stones as a reproductive resource rather than interspecific difference of nest selection.