Vertical distribution of small pelagic fish eggs and larvae on the eastern Agulhas Bank, South Africa

Abstract

Vertical distributions of anchovy Engraulis encrasicolus and sardine Sardinops sagax eggs and larvae within the upper 50 m of the water column on the eastern Agulhas Bank, South Africa, were examined using discrete depth samples collected with a multiple, opening/closing plankton net. Eggs and larvae of sardine and anchovy had significantly different vertical distributions with eggs closer to the surface and larvae deeper for both species. Eggs of both anchovy and sardine were concentrated near the surface, but their vertical distribution patterns differed significantly with sardine eggs being generally closer to the surface than anchovy eggs. Early- and late-stage anchovy eggs were mainly near the surface, but had significantly different depth distributions, whereas most middle-stage eggs were at depth. This high, near-surface abundance of early-stage anchovy eggs on the eastern Agulhas Bank differs from observations made on the western Agulhas Bank, indicating that anchovy spawn at shallower depths on the eastern Bank. There were significant differences between the vertical distributions of small (< 7 mm standard length; SL) and large (≥7 mm SL) anchovy larvae, suggesting that the larger larvae exhibit vertical migratory behaviour.

Keywords: Agulhas Bank; anchovy; eggs and larvae; sardine; vertical distribution

African Journal of Marine Science 2010, 32(1): 115–125