Infestation of european flat oyster (Ostrea edulis) by polychaete (Polydora hoplura) in the northern Adriatic Sea

Abstract

       The intensity of infestation of commercial oysters Ostrea edulis Linnaeus by the polychaete Polydora hoplura Claparède, was studied in two commercial farms located in Limski kanal and Raša Bay (northern Adriatic Sea) in 1985. The percentage of oysters invaded by this polychaete ran­ged from 0.0 to 88.8% per sample. Despite the high infesta­tion of some samples, the number of the observed live polychaetes per oyster was low with mean values ranging from 1-3 specimens. The highest registered number in one oyster was 5 polychaetes. No relationship exists between the mean number of polychaetes and index of condition of commer­cial oysters, probably due to the low number of polychaetes per investigated oyster. Negligible differences in the index of condition of oysters among the investigated localities oculd be the result of either of differences in environmental conditions or in the stages of gonad development of oysters in various months.