No abstract

Abstract. Some 30,000 specimens of the Mediterranean clam Tapes decussatus were suspended in nylon bags of two different mesh sizes and pre-grown in the Calich lagoon (Sardinia, Italy) from March to June 2001. The samples differed in size at the end of the pre-growth stage. They were then sown at a density of 650 specimens m )2 in two stations of the lagoon. The growth rates in the stations were different according to the Von Bertalanffy model. Primary and secondary plankton production was calculated by field measurements as well as by modelling. The results indicate that the Calich lagoon could produce a maximum of 753.25 g m )2 yr )1 WW, with shell, for Tapes decussatus. Our culture experiments lasted 15 months with an estimated mortality of 50% and the yield of T. decussatus was 4.3 times greater than the calculated natural production.

Marketable mussels Mytilus qalloprovlncla0's traded with commercial certification from production sltes in Italy and abroad (France, Spain) were exarnlned for the presence of A4ytrllcola intestinalls (Copepoda. Mytllicolidae) and Urastoma cyprlnae (Turbellana Hypotrichlnidae) from October 1994 to February 1996. The prevalence of M. intestlnahs was 4 1 % and 4.7% respectively In mussels from Lerici (La S p e z~a ) and S Pietro in Volta (Venice), whereas ~t rose to 57.9% in the samples from Spain. A4. intestinalis was absent In mussels from C h i o g g~a (Venlce). Ganzlrn (Messina), Taranto, Tneste and France. The prevalence of U cyprinae vaned considerably, ranging from 0 . 3 Y in mussels from Trani (Bari) to 33 2 % and 86.3% respectively in those from Chioggia and Tr~este. It was 85 7 "h in samples from France and 63.7 ";P in those from Spain KEY WORDS-Mytilus galloprovinclaljs . Mytlllcola ~ntestinalis . UI-astoma cyprinae . Paras~tology Epidemiology