Larval drift patterns of diadromous gobioids in the lower course of the Natori River, Northern Japan
1999
Tomiyama, T. (Tohoku Univ., Sendai (Japan)) | Honda, H. | Okata, A. | Omori, M.
Drifting larvae of one anadromous (Leucopsarion petersi) and three amphidromous (Chaenogobius annularis, Tridentiger brevispinis, and Rhinogobius sp. CB) gobioids (Gobiidae, Teleostei) were collected over 24 h into server nets in the tidal and non-tidal zones of the Natori River (northern Japan) to study the downstream migration of these species in the lower course of the river. The larval body sizes of all three amphidromous species declined from the beginning to the end of the 3-month spawning season, apparently due to decreases in the egg sizes. Drifting larvae, mostly at the yolk-sac stage, were caught mainly between dusk and dawn. Diel changes in the number of larvae collected showed one to three steep peaks of abundance. Analysis of the timing of the peaks in relation to the spatial distribution of the spawning grounds of each species indicated that there were two sources of larval gobioids caught in the tidal zone, larvae that had drifted downstream on the river current from nests above the collection station and larvae that were pushed upstream by tidal currents from sites below the station after they had entered the estuary
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