Population dynamics of the intertidal limpet, Siphonaria diemenensis at Griffith Point, Victoria.

A combination of surveys and experiments were used to determine the size distribution, recruitment, mortality and growth rates of Siphonaria diemenensis in 2 zones on the rocky shore at Griffith Point, San Remo, Victoria. One zone was in the high intertidal (Zone 2) and one was in the low intertidal area on the shore. There were 3 sites in Zone 1 and 2 sites in Zone 2 (see parent record for more details).

A size frequency distribution was constructed for each site from surveys that recorded the size of all individuals every 2 months from October 1979 to December 1981. In addition to the sites in Zone 1 there were 12 permanent quadrats (50 x 50cm) which were surveyed in the same manner from December 1980 to December 1981. The sizes of recruits were similar in both Zones but the sizes of adults were significantly greater in Zone 2. In both years, the maximum density of recruits in Zone 1 was greater than in Zone 2. The mortality rate of adult limpets in Zone 2 was lower compared to limpets in Zone 1.

The growth rates (mm per month) of marked individuals were calculated for 3 time intervals; January-March, March-May and May-late July (Zone 2) and Mary-early August (Zone 1) in 1981. Limpets in Zone 2 grew faster (average 0.63 mm per month) than the limpets in Zone 1 (average 0.11mm per month).

In addition, an experiment was conducted in Zone 1 from May to July in 1981 to determine the effects of adult density and macroalgal cover on limpet recruitment. It was found that there was no effect of adult density but a significant interactive effect of algal cover and sampling date on the number of limpet recruits.