ROCKPOOLING WITH JOHN HAYES AT OSMINGTON MILLS, DORSET
by John Hayes
(Dorset Heritage Coast Warden)




The shore at Osmington Mills faces south-west and is somewhat sheltered, being leeward of Portland Bill. A series of intertidal ridges are formed by the Weymouth anticline. Large 'doggers' eroded out of the adjacent cliffs are cut in the intertidal zone. A fresh water stream enters the sea at the east of the site.

Dominant Fauna

Animal fauna that dominates the rocky shore boulders are the expected acorn barnacles, limpets, grey topshells  and periwinkles. These are preyed on by dogwhelks. The Purple Topshell, Gibbula umbilicalis, occurs in large numbers.

Features

The channels and ridges of the intertidal geology result in a confused zonation. A preponderance of small boulders high up the shore provide a good habitat for crabs and sea anemones. Large clumps of the Japweed, Sargassum muticum, inhabit some of the deep water pools. Two small areas of this alien weed are present just south of the slipway.

Mobile Fauna

Anemones are represented by the Beadlet, both red and green specimens, and also the 'strawberry' variety, and the Snakelocks Anemone. Crabs are represented by the Shore Crab, Edible Crabs and Hermit Crabs in a variety of shells. The Spiny Spider Crab, Maja squinado, has been recorded on this shore. Prawns, Palaemon sp., are found in the pools.

   Corkwing Wrasse
 

Rock pool fish in July (1994) include the inevitable Common Blenny, Lipophrys pholis, and young Corkwing Wrasse, Crenilabrus  melops,  with other species of wrasse found but not positively identified. Mackerel shoal close inshore.
 


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