DENSITY-INDEPENDENT GROWTH OF HALIOTIS-IRIS MARTYN (MOLLUSCA, GASTROPODA)

The growth rate and nutritional status of abalone (Haliotis iris) expo sed to low (similar to 0.3 m(-2)) and high densities of conspecifics ( similar to 15 m(-2)) was measured in 5 x 5 m experimental enclosures. Over the duration of the experiment (15 months), estimates of the perc ent cover of macroalgae revealed no significant difference attributabl e to density except for crustose coralline algae which had significant ly greater cover in high density enclosures. Drift seaweed, the prefer red food of Haliotis iris was always present in low abundance (<5% cov er). There was no significant effect of density on the relative gut fu llness or growth of H. iris, but significant variation in the dry weig ht of pedal muscle was due to density. Measurements of the dry weight of gonad and the ash-free dry weight of pedal muscle or gonad were oth erwise similar between low and high density treatments for H. iris. Sh ell growth was similar among high density and low density treatments b ut high in relation to other populations of H. iris. Density independe nt growth is consistent with the feeding biology of H. iris and may ap ply to other species of abalone.