Bioindicators for siting the carpet clam Tapes decussatus L. farming in Mediterranean lagoons

With a worldwide increase in shellfish aquaculture and awareness towards sustainable practices, this paper provides a method based on bioindicators for identifying a suitable site for rearing the carpet clam Tapes decussatus in a lagoon of the South Adriatic coast of Italy (Varano lagoon). Although the species is naturally widespread in Italian coastal lagoons, it was in fact absent from Varano lagoon. However, we would like to judge whether Varano lagoon offered a suitable habitat for farming this clam when no local wild population could give us a clue. We applied the indirect method of investigating the indicator species for this purpose. We sampled the benthic macrofauna of Varano lagoon for the presence of species known to be sympatric with the carpet clam, based on our judgement on the bionomic classification of Frisoni et al. (1984). The data analysis on the presence/absence of benthic indicators shows that Varano lagoon is divided into three Zones from among those described by Frisoni. The existence of two areas with the characteristics of a Zone III fulfilled the first prerequisite of our working hypothesis. In October 2002, N° 50,000 seed clams were placed in the park in Zone III. The clams grew from 16 to 35 mm in 21 months with growth concentrated in summer with lost of 20%.