ASFB Home > The effects of spatial and temporal factors on the abundance of seven key finfish species along south-western Australia.

Effect of density on settlement, early growth and survival of Haliotis rubra

Sylvain Huchette and Sabine Daume

The University Of Melbourne, PARKVILLE, AUSTRALIA

THEME: ASFB

Two types of substrate were evaluated for settlement comparing plates covered with Ulvella. lens and associated natural biofilm grown over 4 or 18 days. Larvae were released at several densities to investigate if larval density influences overall settlement rates and later performances. Additional food was provided to half of the tanks inoculating cultured diatom Navicula sp. to determine the effect of food on early growth and survival. Settlement rates varied averaging 62% were amongst the highest recorded in commercial nurseries. Settlement was highly variable, however higher larval concentration tended to reduce overall settlement rate. There was a marked preference of the larvae to settle on substrates where U. lens cover was lower and the diatom biofilm had been grown for a longer period of time. Density had a strong effect on growth at all time. Considering that growth of abalone is notoriously variable, our experiment design failed to explain a large part of the variability, but allowed to confirm the great impact of density and light as a function of food availability. Recruitment showed a strong density-dependence after 64 days when the food started to be limiting. Despite a similar rate of recruitment at this stage, we observed an over compensation for density and final biomasses on the plates were lower when the initial density was high.