Trophodynamic effects of trawling on the feeding ecology of pandora, Pagellus erythrinus, off the northern Sicily coast (Mediterranean Sea) E. Fanelli A,B,C , F. Badalamenti B , G. D’Anna B , C. Pipitone B and C. Romano B A Institut de Ciencies del Mar – Consejo Superior de Investigaciones Cientificas (CSIC), Passeig Maritim de la Barceloneta 37–49, 08003 Barcelona, Spain. B CNR–IAMC, Via Giovanni da Verazzano 17, 91014, Castellammare del Golfo (TP), Italy. C Corresponding author. Email: efanelli@icm.csic.es Abstract. Because trawling disturbs benthic organisms, it could affect the diet of benthic-feeding fish with implications for food-web dynamics. The present study assessed the effects of commercial trawling on the trophodynamics and diet of pandora, Pagellus erythrinus, by comparing its stomach contents and stable-isotope (d 15 N and d 13 C) composition in two trawled and two untrawled gulfs in northern Sicily (central Mediterranean). Fish were collected on muddy bottoms at 50– 100-m depth. Higher abundance and biomass and a slightly larger mean body length were found in the untrawled gulfs. The feeding habits were similar although more selective in the untrawled gulfs. The diet was mainly composed of decapod crustaceans (especially the brachyuran crab Goneplax rhomboides) and of polychaetes. The trophic level of pandora, estimated by its d 15 N values, was higher in the untrawled gulfs. No clear trend between trawled and untrawled gulfs was found for the source of carbon in the diet (d 13 C). The diet of a benthic feeder such as pandora may be used as an indirect indicator of trawling disturbance, as long as stomach contents and stable-isotope analysis are used jointly to assess the diet and trophodynamics of a species. Additional keywords: benthic communities, diet, fishing effect, Pagellus erythrinus, stable isotopes, trophodynamics. Introduction Bottom trawling is known to affect directly and indirectly the structure and functions of benthic ecosystems (Jennings and Kaiser 1998; Hall 1999; Kaiser et al. 2002). Direct effects include the removal of benthic and benthopelagic species, whereas indirect effects include a wide range of impacts on the seabed and resident species. The physical impact of trawling on the bottom may cause modifications to deposition rates, composition and structure of the sediment, affecting the relative abundance of filter feeders and deposit feeders and causing an increase in opportu- nistic species adapted to unstable environments (Lindeboom and de Groot 1998; Kaiser et al. 2000; Hinz et al. 2009). Trawling can also lead to a decline in the density and size of individuals (Duplisea et al. 2002) and also reduce diversity (Thrush and Dayton 2002). Functional changes to benthic communities fol- lowing trawling disturbance have also been reported (e.g. De Juan et al. 2007a). It is likely that an impoverished benthic community leads to a reduction in food-web connectivity, with a consequent decrease in the trophic level of predatory fish (Jennings and Kaiser 1998). However, Jennings et al. (2001) did not find effects on the mean trophic level of the benthic community by using a stable-isotope approach. Because of the importance of benthic organisms as a food supply in marine food webs, changes in benthic communities may affect the diet (i.e. food preferences and feeding habits), the trophodynamics (i.e. trophic level in the food chain) and the spatial distribution of benthic-feeding fish (Thrush and Dayton 2002). However, fish are able to adapt to changes in the food supply according to the degree of selectivity in their diet (Serrano et al. 2003; Hinz et al. 2005); thus, species with a generalist diet are expected to be less affected by changes in food availability. Such changes in the benthic food web may be investigated in the muddy areas of the continental shelf, a productive and economically important region worldwide that has been intensively fished over the past century, often resulting in the overexploitation of commercial species and the impoverish- ment of benthic communities (Dayton et al. 1995; Pauly et al. 1998). The pandora, Pagellus erythrinus (Linnaeus, 1758), a com- mercially important fish for Mediterranean shelf fisheries (Fiorentini et al. 1997), seems a good candidate to investigate the effects of fishing on the food web of a benthic consumer. Pandora is a surface and infaunal predator (Rosecchi 1983; Caragitsou and Papaconstantinou 1988; Benli and Kaya 2001) that has shown strong potential for recovery in trawl exclusion areas (Pipitone et al. 2000). The main objective of the present study was to assess whether bottom trawl fishing affects the trophic ecology of pandora. The CSIRO PUBLISHING Marine and Freshwater Research, 2010, 61, 408–417 www.publish.csiro.au/journals/mfr Ó CSIRO 2010 10.1071/MF09049 1323-1650/10/040408