Survey of imposex in dogwhelks (Nucella lapillos) from north sea coasts

Following a North Sea Task Force (NSTF) initiative in 1991, and funding fro m the Department of Environment (DOE), The Scottish Office Agriculture, Env ironment and Fisheries Department Marine Laboratory (SOAEFD), Aberdeen, was awarded a contract to assess the impact of tributyltin compounds in dogwhe lks in all North Sea coastal waters. These waters were surveyed in 1991 and 1992 to evaluate the distribution and effects of tributylin (TBT) compound s on the common dogwhelk, Nucella lapillus. Wild and, where necessary, tran splanted dogwhelks were analysed for imposer. Historical records indicate that Nucella lapillus was once present, on suit able substrates, around the whole of the North Sea coastline. Wild dogwhelk s could be collected in all countries except Belgium and Germany, where the species is present only on Helgoland (in numbers too small to be sampled). All wild populations of dogwhelks showed imposer. Near sites of intense boa ting activity, all populations examined contained some sterile females. At all sites where transplants were recovered, the dogwhelks were affected by TBT. Prolonged survival of dogwhelks at any of these sites would not be exp ected, except perhaps at Torsminde in Denmark. All sites studied were categ orized with reference to their potential for the maintenance of self-sustai ning Nucella populations. All sites in the southern part of the North Sea (i.e. the coastlines of Bel gium, The Netherlands, Germany and southern Denmark) were placed in Categor y C (reduced egg capsule production) or D (adult females expected to be ste rile). In Norway, sites near large harbours had only sterile females in the popula tion (Category D), whilst those further from harbours probably had reduced egg capsule production (Category C). In Sweden, all wild sites were affecte d but probably had no reduction in egg capsule production (Category B). In France and the UK, sites near large harbours or areas of small-boat acti vity probably had reduced egg capsule production (Category C). Sites furthe r from sources of TBT contamination probably do not have reduced egg capsul e production (Category B), One site on the north east coast of Scotland sho ws effects consistent with an area distant from a source of TBT pollution ( Category A). Copyright (C) 1999 John Wiley & Sons, Ltd.