Grazing Selectivity of Red Abalone Haliotis rufescens Postlarvae on Benthic Diatom Films under Culture Conditions

The gut contents of Haliotis rufescens postlarvae that had grazed on a diatom film grown in PVC buckets were analyzed to determine selectivity in feeding. Species composition and abundances were compared to that of the surrounding film. Diatom samples were oxydized and mounted permanently, or observed directly by the squash technique under phase contrast microscopy. The surrounding flora yielded 111 taxa, while 64 species appeared in the gut contents. A high proportion of Pinnularia biceps v. minor and Navicula incerta (and others) in the gut contents, which were rare or absent from the samples of the surrounding flora, indicated grazing selectivity by the postlarvae. An analysis of similarity confirmed that samples from the gut contents could be grouped together and that they were clearly different from the surrounding flora.