No reduction of hatching rates among F1 hybrids of naturally hybridizing three Far Eastern daces, genus Tribolodon (Cypriniformes, Cyprinidae)

Egg hatching rates of F1 hybrids among three fishes, Japanese dace Tribolodon hakonensis , Pacific redfin T. brandtii , and rosyface dace T. sachalinensis , were compared with pure crosses. They are highly divergent (diverged 10–20 million years ago) but naturally hybridizing. Although crosses involving female rosyface dace were not available, hatching success was high among all combinations of hybrids (76 ± 23%) and comparable to pure crosses (86 ± 8%), implying ecological or genetic isolation mechanisms maintaining each species in later life stages.