Investigation into the ecology of the ormer (Haliotis tuberculata L.), factors influencing spatial distribution

The factors affecting spatial distribution of the ormer (Haliotis tuberculata L.) in the vicinity of Saint-Malo (northern Brittany, France) are analyzed using a multivariate approach. A correspondence analysis is applied to a contingency table based on 200 samples. Ormers are always absent from smooth rocky substrata, exposed to a strong current or deeper than 8 m below low chart datum. Abundance and biomass of H. tuberculata are distributed along a gradient correlated with an increasing complexity of habitat and a reduction of current. Otherwise, no correlation has been found between characteristics of ormer distribution and surge, depth or large and turf algae.