Unchecked, vast areas of green seaweeds are likely to become established in a few weeks, followed by the fucoid wracks which may become the dominant fauna on all but the most exposed shores. Limpets reproduce by discharging sperm and eggs into the sea, followed by a planktonic larval stage. The young limpet then settles on the shore and in two years will be 5 cm diameter and graze an area of about 150 sq. In areas where periwinkle over-collection has caused the same seaweed explosion, the shore shows very little evidence of returning to normal even after 10 years. It seems probable that the limpet kills will not be high enough to cause any faunal alterations that are greater than natural fluctuations on most of the oiled shores.
Periwinkles also reproduce by sexual discharge into the oceans.
Other Rocky Shore Animals Acorn barnacles are a fouling organism on piers and boats, and ever since people found that they had a planktonic stage have been trying to find a safe method to discourage them from settling on suitable surfaces. To a certain extent they are discouraged from settling on tar, especially if it is still sticky. Their high productivity will mean that by the following year they will be settling again in their former numbers. I would anticipate the complete recovery of the populations of all the common crustacean species by the following year. Beadlet Anemones , Dogwhelks , Rough and Flat Winkles , are abundant and permanent shore residents that do not have a planktonic stage.