Distribution of Phorcus turbinatus along the littoral zones of Al-Haneah and Susah, eastern Libya’s Mediterranean Sea, at day, at low tide, was studied using belt transects with quadrates. P. turbinatus in both sites inhabited only the lower rocky littoral, many times in aggregates in tidal pools. P. turbinatus was absent in the mid and the upper rocky littoral, all the sandy shores, and the sublittoral. The abundance was maximum just above the shoreline (209 and 207 individuals/m2 in both sites), and decreased on moving up the littoral. Factors controlling the distribution were discussed. P. turbinatus showed no size gradient on moving upwards from the shoreline to the upper littoral. Frequency distribution of “height of shell from base to the apex” (HBA) indicated that P. turbinatus populations of both study sites exist in three age cohorts. Mean HBA of cohort 1 and 2 in Al-Haneah was 7 and 15mm, mean HBA of cohort 3 could not be determined; in Susah, HBA of cohorts 1 and 2 were 6 and 11.8mm.
Keywords: Abundance, Distribution, Monodonta turbinata, Phorcus turbinatus, age cohort.
