How do eggs and larvae come to nursery beyond front?

Abstract

Most pelagic fish spawns their eggs at offshore area but the larval nursery is usually formed at coastal area. We sometimes detected egg patches at frontal area as they were induced to stay. How do eggs and larvae come to nursery beyond front? It is a simple question that the success of recruitment of white bait fishery is decided by physical phenomena occurred at the front or hatched larval ability. I surveyed by using 4 methods, (1)abundance index of anchovy eggs at frontal area with some CPSs, (2)larval abundance index at nursery with fishery data, (3)drift card experiments to know the return ratio of nursery/offshore, and (4) satellite image and meteorological data analyses. The CPSs grid survey lines were arranged to cross the front and the drift cards were released at each continuous sampling station. Next, I collected anchovy larvae of white bait fishery each 7 days during 1 month after the egg distribution survey. The larvae were analyzed the otolith. These works carried out 9 times made possible to estimate relations between larval abundance index spawned at the egg distribution survey day, drift card return ratio of nursery/offshore, and physical data. The larval abundance index was not directly correlated to the egg abundance index. The drift card return ratio was more important to predict the larval abundance index. Then, I supposed the recruitment success was influenced by physical phenomenon, e.g. entrainment current and wind. © 2002, The Japanese Society of Fisheries Science. All rights reserved.