A note on the spawning and early life ecology of the pike gudgeon Pseudogobio esocinus (Cypriniformes, Cyprinidae)

Abstract

I surveyed the temporal appearance of adult individuals and the number of flowing eggs and larvae of the pike gudgeon Pseudogobio esocinus three times for 24 h in a spawning site in Nakagawa River, northern Kyushu Island, Japan. Sixty-four adult individuals were observed, but only at night-time; females appeared between 8:00 PM and 1:00 AM, and males appeared between 8:00 PM and 5:00 AM. A total of 11,293 flowing eggs were captured, and most of the eggs were found between 9:00 PM and 2:00 AM. Compared with the number of flowing eggs, the number of pelagic larvae was very small. Therefore, it was assumed that the spawning of P. esocinus occurs at night between approximately 8:00 PM and 1:00 AM, and that the spawned eggs floating downstream but the larvae do not.