Diurnal and tidal vertical migration of presettlement King George whiting Sillaginodes punctata in relation to feeding and vertical distribution of prey in a temperate bay

Abstract

Vertically stratified sampling was undertaken for pre-settlement King George whiting Sillaginodes punctata at 1 site in 1995 and 4 sites in 1996, in Port Phillip Bay, Australia. In 1995, 3 depth strata were sampled: surface, 2.5-3.0 m, and 5.0-5.5 m, in a total water depth of 7 to 8 m. Sampling was conducted on 17 dates and encompassed all combinations of day and night, and ebb and flood tide. A total of 3, or in one case 4, replicate samples were taken at each depth. On 4 occasions a smaller zooplankton net was deployed at the same time as the ichthyoplankton net. Pre-settlement S. punctata showed 'reverse' diurnal vertical migration, with concentration near the surface during the day and d..