Sympatric Populations Ofthe Hermaphroditic Scallop, Pecten Fumatus Reeve, And Ofthe Dioecious Scallop, Chlamys (Mimachlamys) Asperrima (Lamarck), From Jervis Bay, New South Wales, Australia, Were Sampled Between October 1991 And December 1994. Over The First 2 Years, 5-1% Of Adult P. Fumatus And 4-5% Of Adult C Asperrima Were Infected With A Trematode, Bucephalus Sp., That Causes Parasitic Castration. A Significant Increase In The Numbers Of Infected Scallops Occurred In Spring 1993, Teaching 63% In P. Fumatus And 24% In C. Asperrima In May And March 1994, Respectively. The Prevalence Of Infection Increased With Scallop Size, Reaching (YdˇM In P. Fumatus Greater Than 80 Mm In Shell Height And 40% In C. Asperrima Greater Than 75 Mm In 1994. Seasonal And Interannual Variations In Parasitism For The P. Fumatus Recorded Over A Continuous Period Of 5 Years In Jervis Bay Are Discussed, As Are Interspecies Differences And The Potential Impacr Of The Parasitic Castration On Reproductive Potential And Marketability Oˇ P. Fumatus Dind C. Asperrima. [ABSTRACT FROM AUTHOR]