Diatom diet of abalone post-larvae (Haliotis midae) and the effect of pre-grazing the diatom overstorey

Abstract

Gut content analyses of abalone post-larvae (H. midae) that settled on diatom-covered surfaces were conducted to determine selectivity in feeding. Diatoms were counted by the Utermohl method and scanning electron microscopy was used for their identification. Results indicated that abalone post-larvae preferred prostrate diatoms such as Cocconeis sublittoralis Hendey, Amphora proteoides Hustedt and Achnanthes brevipes Agasdh but would consume the more loosely packed, overstorey species such as Delphineis karstenii (Boden) Fryxell, Diploneis placida (Schmidt) Hustedt and Nitzschia palea (Kiitzing) Wm. Smith if their preferred food was not available. Pre-grazing of settlement surfaces by juvenile abalone before the introduction of larvae removed most of the overstorey diatoms but left the preferred species virtually intact.