Assessments have been made of the increasing populations of Osilinus lineatus near its eastern English Channel limit of distribution for the year 2008. The first record of a breeding population of Osilinus east of the Isle of Portland at Western Ledges in Portland Harbour was made during a survey in 2004. The 2008 study provides evidence that the breeding range in East Dorset has since extended to Redcliff Point and Osmington Mills, east of Weymouth Bay. Surveyed sites from Portland Harbour to White Nothe have shown large increases in numbers since 2004. The small size of populations to the east of White Nothe indicates that recruitment to sites further east still depended on small numbers of larvae that drifted around Portland Bill from Lyme Bay without supplementation from the Portland Harbour to Osmington Mills sites.
