Feeding Preferences of the Abalone Haliotis Iris in relation to macroalgal species, attachment, accessibility and water movement

Haliotis iris is a species of abalone common on rocky reefs in southern and central New Zealand. This study examined the poorly understood feeding habits and preferences of H. iris in a series of laboratory experiments. Generally, H. iris consumed the blades of brown algae over red and green algae. However, when upright whole plants were given to H. iris, the highly preferred kelp Lessonia variegata was consumed in lower proportions than the less preferred but more accessible red alga Gigartina circumcincta. H. iris were less capable of reaching the blades or consuming the stipe of L. variegata, which has a stipe of ;100–350mmhigh. H. iris consumed greater amounts of drift over benthic L. vareigata. Water movement appeared to inhibit the active grazing of H. iris, but not the drift-trapping behavior, resulting in lower overall feeding rates for abalone under conditions of higher water movement. Abalone consumed fresh and aged algae equally.We conclude that H. iris feeds primarily on drift algae because preferred food sources are more accessible as drift than as attached macroalgae, and because this may be a more successful foraging strategy in the high flow environment this species commonly inhabits.