DISPERSAL OF TBT FROM A FISHING PORT DETERMINED USING THE DOGWHELK NUCELLA-LAPILLUS AS AN INDICATOR

Ireland was the first country to introduce a legislative ban in April 1987 on the usage of organotin antifouling paints, this included tri-b utyl-tin (TBT). Vessels under 25 metres were not permitted to use thes e substances because of harmful effects to shallow water sea inlets. T he ban prevented use of organotins on most fishing vessels and pleasur e craft. TBT causes a condition, imposer, resulting in sexual impairme nt in neogastropods. This condition was examined in the dogwhelk Nucel la lapillus at 66 stations in Bantry Bay, SW Ireland, to determine dis persal from source from the main input areas. Highest imposer levels w ere recorded in the harbour of the fishing port Castletownbearhaven. H igh levels of TBT in sediments and use of TBT antifouling paints by th e fishing fleet have resulted in reductions of dogwhelk abundance at t he harbour entrance. Nearby, dogwhelks had high levels of imposer, whi ch declined with distance from source. The lower frequency of imposer observed elsewhere within Bantry Bay may be due to residual flow of wa ter through the Bay and periodic exchanges with shelf water from an ar ea of upwelling off the bay entrance. A gradual recovery of the area w ould be expected if the ban on TBT usage were applied to vessels of le ss than 50m.