Effects on fish community induced by installation of two gas platforms in the Adriatic Sea

The Regina (R-p) and Annalisa (A(p)) gas platforms, placed in the northern Adriatic Sea at different depths and distances from the coast, were monitored for 3 yr to evaluate changes induced by their construction on natural-habitat fish assemblages. Fishes were sampled monthly with a trammel net both at the rigs and at 2 open-sea control sites. From a qualitative point of view, both platforms showed their influence within the first year after their installation, inducing higher species richness and greater diversity of fish assemblages due to the appearance and constant occurrence of reef-dwelling or partially reef-dwelling species, which are rare in the natural habitat. In terms of biomass, the platform further offshore and in deeper water (A(p)) had higher fish abundances than that closer to shore in shallower waters, revealing a greater and faster aggregation effect. This difference was mainly due to an increase in pelagic and nekto-benthic fishes, which are partially attracted by hard substrates. A few voracious predators were also recorded at this site, probably in response to the increase in prey biomass.