Vertical distribution of pilchard (Sardinops sagax) eggs and larvae off Southern Australia

Abstract

Plankton samples were obtained from four to six discrete depths at 33 stations in July 1994 by using the ‘EZ’ multiple opening and closing net during a cruise along the shelf region from Adelaide to Albany, southern Australia. At the 19 stations (88 tows) where pilchard eggs were common, recently spawned eggs were most abundant at depths of 40–60 m, or 60% of total bottom depth. Most older egg stages were found closer to, or at, the surface. During day-time, most pilchard larvae were caught at the surface. At night, pilchard larvae appeared to spread out, with lower overall rates of capture but a bigger proportion caught below the surface. The effects of these changes in relative depth with age are discussed in relation to the accurate estimation pilchard egg abundance for biomass calculations.