Sewage pollution impact on Mediterranean rocky-reef fish assemblages

Ernesto Azzurro , Marco Matiddi , Emanuela Fanelli , Paolo Guidetti , Gabriele La Mesa , Alfonso Scarpato , Victor Axiak (1)

1 Department of Biology

The effects of sewage outfalls on subtidal fish assemblages were studied along the NW coasts of Malta (Sicily channel, Mediterranean Sea) by means of underwater visual census. The presence of two spatially distinct outfalls discharging untreated wastewaters allowed to use a balanced symmetrical ACI (After Control/Impact) design that consisted of two putatively impacted locations and two controls, with four sites nested in each location. Surveys were performed in 2006 at two random dates. The study highlighted significant changes at both assemblage and individual species levels. Fish assemblages structures were different between controls and sewages, where total abundance of fish were higher. The responses of individual species to sewage pollution were mostly related to an anomalous increase of two small opportunistic species i.e. and and to a decrease of species of the genus , particularly and Moreover in correspondence of the outfalls, significant changes of the fish size distribution were detected for several species. These results support the use of fish assemblages as biological indicators for marine coastal waters and demonstrated the possibility to obtain sharp signals of environmental impact from some individual fish species.

Mots clés: Sewage impact; fish assemblages; opportunistic species; sensitive species; visual census

Ernesto Azzurro, Marco Matiddi, Emanuela Fanelli, Paolo Guidetti, Gabriele La Mesa, et al.. Sewage pollution impact on Mediterranean rocky-reef fish assemblages. Marine Environmental Research, 2010, 69 (5), pp.390. ⟨10.1016/j.marenvres.2010.01.006⟩. ⟨hal-00591227⟩