This issue presents some articles concerning different features (feeding, reproduction, welfare and immune defence) which have been addressed during several research programs aimed at assessing the suitability of some fish species indicated as potential candidates for Mediterranean aquaculture diversification. Over the last decade, finfish aquaculture production has been experiencing a worldwide expansion and is projected to become an increasingly significant source of animal proteins; it is estimated that, by 2015, about 39% of world fish production will come from aquaculture. The current trend in European fish farming is to increase the production of marine species; however, the massive production of seabass (Dicentrarchus labrax) and gilthead seabream (Sparus aurata) in the Mediterranean area has resulted in the decline of economic profits, leading to the collapse of several fish farming operators. Therefore, Mediterranean aquaculture development is now at croassroads and new markets have to be found to ensure growth and viability to seafood industry. In this context, species diversification in aquaculture has been considered the most attractive strategy to expand actual market constraints and to open interesting perspectives of development in aquaculture productions...