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Abstract. The vertical zonation of the hydroid fauna associated with Posidonia oceanica leaves in three different localities of the central Mediterranean reveals the presence of two distinct communities. This depth‐related zonation shows patterns that are independent on the geographic area.

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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.

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