hybridization behaviour between two common European cyprinid fish species - silver bream Blicca bjoerkna and common bream Abramis brama - in a controlled environment

The egg release–mating comparison, heterospecific matings and mating success under two hybridization
conditions – (i) mixing one sex per species and (ii) mixing both sexes from each species – were investigated
to determine whether silver bream Blicca bjoerkna and common bream Abramis brama can hybridize in
nature.
The results revealed that non-matings in hybridization experiments of silver bream females × common
bream males can be explained by territorial and aggressiveness activities observed in common bream. In
common bream females × silver bream males, heterospecific matings were observed but their numbers
were signifi cantly lower than the spawning numbers, and in this experiment, a female mated with one to
four heterospecifi c males. In mixing both sexes from both species, similar spawning – mating numbers
were observed but heterospecific matings accounted for only 27% of the total matings, with 24% accounting
for heterospecifi c matings between common bream females and silver bream males, directly or by
opportunism. Mating success was characterized by the occurrence of fertilized eggs after matings.
Natural hybridization occurred preferentially between common bream females and silver bream males.