Impacts of hydraulic dredging on a macrobenthic community of the Adriatic Sea, Italy

Hydraulic dredging that targets the bivalve Chamelea gallina in the northern and central Adriatic Sea (Italy) has been taking place for over 30 years. Seventy-three commercial dredgers harvest the resource within the sandy coastal area of the Ancona Maritime District (central Adriatic Sea). Despite this chronic disturbance, studies aimed at investigating the impacts of the fishery on the macrobenthic community of the area have never been carried out. To remedy this, sampling was accomplished within an area of the District from which hydraulic dredging was banned, within the framework of a balanced beyond-BACI (before/after, control/impact) experimental design. Data regarding seven groups of species were analysed separately by means of permutational multivariate analysis of variance. No impacts attributable to hydraulic dredging were found upon consideration of the entire sampled macrobenthic community, the Polychaeta, the Crustacea, detritivores, and suspensivores. In contrast, a sustained press impact of fishing was revealed for the Mollusca, and the bivalve Abra alba was found to be particularly susceptible. Abra alba was suggested as a possible impact indicator. A short-lived pulse impact on the predator and scavenger trophic guild was observed and was limited to the 1st sampling day after experimental hydraulic dredging.