Effects of management and fishing systems on Tapes philippinarum resource in Venice lagoon.
This study focused on evaluating the exploitation of T. philippinarum in Venice lagoon, in terms of biological and management aspects. Two different approaches viz. free fishing and aquaculture in authorized waters were compared in relation to their relative sustainable yield and to the biological characteristics of the differently managed populations, as determined by a number of biomarkers; these include condition index, reburrowing behaviour and survival in air. Moreover, a similar biomarker approach was used to show, if present, acute effects on the target species due to the different fishing systems practiced in the lagoon. The overall results indicate better conditions for cultured than natural populations. In particular, with regard to the 'well being' of differently managed populations, results indicate that condition index and reburrowing behaviour rates are higher in samples from aquaculture areas. Moreover, free fishing was found to be responsible for the progressive decrease in clam resource and for the other negative effects on recruitment, due to environmental changes caused by the fishing action on sediments. The use of highly mechanized fishing systems caused a reduction in the reburrowing rates of commercial-sized clams.