ASSESSMENT OF IMPOSEX IN THE DOGWHELK NUCELLA-LAPILLUS (L) AND TRIBUTYLTIN ALONG THE NORTHEAST COAST OF ENGLAND

Concentrations of tributyltin (TBT) less than 5 ng/l were recorded in most coastal water samples taken from a series of sites in north-east England during autumn 1991. Levels in the industrialized Tyne estuary still exceeded the Environmental Quality Standard (EQS) in 1991 but ha d fallen from values recorded in 1989-90. Coastal dogwhelk Nucella lap illus (L.) samples taken in 1991 had low concentrations of < 0.01-0.03 mug TBT/g wet tissue. Dogwhelk populations were suffering from severe imposex when they were sampled in 1986, but there was clear evidence of recovery by 1991/92. Relative Penis Size Index scores declined betw een 1986 and 1991/92; two populations which were not breeding in 1986 (as evidenced by lack of juvenile recruitment) reproduced successfully in the years preceding 1991; and dogwhelk abundance on the shore incr eased over the study period.