Changes in Mediterranean rocky-reef fish assemblages exposed to sewage pollution

Abstract

The fish fauna associated with shallow subtidal rocky-reefs in southern Apulia (SE Italy, Mediterranean Sea) was investigated to assess whether fish assemblage structure, and temporal trends in species richness and abundance of fishes were affected by sewage pollution. Fish assemblages were evaluated by visual census at 3 locations (3 to 4 km apart), 1 putatively impacted by a sewage outfall (discharge rate from 200 to 600 m 3 h -1) and 2 controls; within each location, 3 sites (100 to 300 m apart) were surveyed 4 times over the study year. In general, dissimilarities in assemblage structures between the 2 controls were always lower than between each control and the outfall location. During winter, however, the dissimilarities between controls were very low and similar to those between each control and the outfall location, suggesting that in this period, fish assemblages from the outfall did not greatly differ from those in the controls. Planktivorous and detritivorous fishes were more abundant at the impacted location and contributed most to dissimilarities in assemblage structures between the outfall and controls. Furthermore, the outfall significantly affected total fish abundance (which was consistently about 5-fold greater at the outfall than at the controls), and temporal trends in the average density of sparids and small serranids at the scale of locations, while small benthic fishes were influenced at the scale of sites (within locations). Particulate feeders and planktivorous fishes showed different temporal trends in average densities between outfall and controls at both spatial scales examined. Species richness and density of herbivorous fishes did not show significant differences attributable to the outfall. The data thus show that nearshore sewage discharges have the potential to alter spatio-temporal patterns in littoral fish assemblages.

Assessing the suitability of a remotely operated vehicle (ROV) to study the fish community associated with offshore gas platforms in the Ionian Sea: a comparative analysis with underwater visual censuses (UVCs)

“…This recording system leads to a similar degree of error over a wide range of abundances, ensuring homogeneity of variance after log-transformation of the data (Frontier 1986;Guidetti et al 2003). ROV trials were recorded on video tapes and four different researchers contributed to both underwater and video data recordings thus reducing any systematic error between methods.…”

Simulation of the combined effects of artisanal and recreational fisheries on a Mediterranean MPA ecosystem using a trophic model

“…The underwater visual census (UVC) method is commonly employed for fish counts in Mediterranean marine environments (Guidetti et al 2003, Claudet et al 2006, Harmelin-Vivien et al 2008.…”

Taxonomic structure and the effectiveness of surrogates in environmental monitoring: a lesson from polychaetes

“…For the analyses, we followed the logic of beyond-BACI (before, after, control, impact) designs (Underwood 1991(Underwood , 1994 and their modifications to deal with cases in which no data have been collected before the purported impact (Glasby 1997, Terlizzi et al 2005a. We focused on a sewage outfall as an example of human disturbance, extending the information already available in the literature about the impact of the same source of disturbance on other components of the biota such as sessile macrobenthos, some meiofaunal components, fish and mollusc assemblages (Terlizzi et al 2002, 2005b, Guidetti et al 2003, Fraschetti et al 2006. Specifically, the present study aimed to (1) establish whether and how the taxonomic structure of the assemblage may influence the results of TS-based analyses, and (2) verify the descriptive efficiency of the species belonging to the most representative taxonomic subsets of Polychaeta in the analysed assemblage.…”