An ecological model of the Northern and Central Adriatic Sea: Analysis of ecosystem structure and fishing impacts Marta Coll a, ⁎ , Alberto Santojanni b , Isabel Palomera a , Sergi Tudela c , Enrico Arneri b a Institut de Ciències del Mar (ICM–CSIC), Passeig Marítim de la Barceloneta, 37-49-08003 Barcelona, Spain b Istituto di Scienze Marine (CNR), Sede di Ancona, Largo Fiera della pesca, 2-60125 Ancona, Italy c WWF Mediterranean Programme Office, Canuda, 37, 08002, Barcelona, Spain Received 14 June 2006; received in revised form 25 September 2006; accepted 4 October 2006 Available online 20 November 2006 Abstract A trophic mass-balance model was developed to characterise the food web structure and functioning of the Northern and Central Adriatic Sea and to quantify the ecosystem impacts of fishing during the 1990s. Forty functional groups were described, including target and non-target fish and invertebrate groups, and three detritus groups (natural detritus, discards and by-catch of cetaceans and marine turtles). Results highlighted that there was an important coupling between pelagic–benthic production of plankton, benthic invertebrates and detritus. Organisms located at low and medium trophic levels, (i.e. benthic invertebrates, zooplankton and anchovy), as well as dolphins, were identified as keystone groups of the ecosystem. Jellyfish were an important element in terms of consumption and production of trophic flows within the ecosystem. The analysis of trophic flows of zooplankton and detritus groups indirectly underlined the importance of the microbial food web in the Adriatic Sea. Fishing activities inflicted notable impacts on the ecosystem during the 1990s, with a high gross efficiency of the fishery, a high consumption of fishable production, high exploitation rates for various target and non target species, a low trophic level of the catch and medium values of primary production required to sustain the fishery. Moreover, the analysis of Odum's ecological indicators highlighted that the ecosystem was in a low-medium developmental stage. Bottom trawling (Strascico), mid-water trawling (Volante) and beam trawling (Rapido) fleets had the highest impacts on both target and non target ecological groups. On the contrary, purse seining (Lampara) showed medium to low impacts on the ecosystem; cetaceans, marine turtles and sea birds were not significantly involved in competition with fishing activity. © 2006 Elsevier B.V. All rights reserved. Keywords: Adriatic Sea; Food web model; Ecopath; Network analysis; Keystone species; Fishing impact 1. Introduction Fishing activities inflict direct and indirect impacts on the ecosystem, where target and non-target species interact establishing complex relationships (e.g. Jen- nings and Kaiser, 1998; Jackson et al., 2001). The need for the adoption of integrative approaches to understand how fishing activities impact complex food webs is thus evident under an ecosystem approach to fisheries (FAO, 2003; Walters et al., 2005). At present, ecological modelling, in part due to the application of the Ecopath with Ecosim approach (EwE, Christensen and Walters, 2004), is a worldwide used tool that can be applied for the description of ecosystem structure and functioning. Journal of Marine Systems 67 (2007) 119 – 154 www.elsevier.com/locate/jmarsys ⁎ Corresponding author. E-mail addresses: mcoll@icm.csic.es (M. Coll), a.santojanni@ismar.cnr.it (A. Santojanni), isabel@icm.csic.es (I. Palomera), studela@atw-wwf.org (S. Tudela), e.arneri@ismar.cnr.it (E. Arneri). 0924-7963/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmarsys.2006.10.002