Application of a complex ecosystem model to evaluate effects of finfish culture in Pagasitikos Gulf, Greece G. Petihakis a, ⁎, K. Tsiaras a , G. Triantafyllou a , G. Korres a , T.M. Tsagaraki a, b , M. Tsapakis a , P. Vavillis a , A. Pollani a , C. Frangoulis a a Hellenic Centre for Marine Research, P.O. Box 2214, Iraklio, 71003 Crete, Greece b Biology Department, University of Crete, PO Box 2208, GR-71409, Heraklion, Crete, Greece abstract article info Available online 11 November 2011 Keywords: Greece Pagasitikos gulf Hydrodynamic modeling Ecosystem modeling Aquaculture In order to support management decisions for aquaculture, a modeling tool capable of simulating the ecosys- tem response was developed and is presented here. The impact on the Pagasitikos gulf ecosystem from two marine fish farms, one in a well protected cove and one in a more exposed area of the gulf, is explored and analyzed in the framework of the INSEA EU project. Model results show little effects of nutrient inputs near the exposed site. It appears that effluents from the exposed site may affect more distant areas due to hydrodynamic transport, while effects in the well protected site are more localized and intense (hot spot). Additionally, as the system dynamics are driven to large extent by the seasonal physical variability, the effect depends not only on the location of the farm but also on the season. Planning decisions for coastal areas require integrated management policies based on holistic approaches that include as many system compo- nents as possible. The tool capabilities illustrated by the simulation results demonstrate its role in supporting management decisions. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Capture fisheries and aquaculture supplied the world with about 106 million tons of food fish in 2004. Aquaculture continues to grow more rapidly than all other animal food-producing sectors, with an average global annual growth rate of 9% since 1970, compared with only 1% for capture fisheries and 3% for terrestrial farmed meat pro- duction systems. Today more than 30% of the global fish production comes from aquaculture although there are signs that growth of global aquaculture has peaked, high rates may persist for some regions and species (FAO, 2007). More specifically, in the Mediterranean, fish farming has grown exponentially during the last 20 years. Greece is the largest producer of seabass and seabram in the region. The European seabass and the gilthead seabream are currently the most widely caged fish species in the Mediterranean with an average annual growth rate of 17%. In 2004, the cage production of these two species accounted for approx- imately 85% of the total production (Cardia and Lovatelli, 2007). As is the case in most food production systems, aquaculture has, or can have, negative impacts which must be kept within socially ac- ceptable limits. Letting aquaculture development and management proceed irresponsibly increases the risk of negative impacts such as drop of expected production and increased mortality, counteracting aquaculture benefits. In the long term, aquaculture may fail to pro- vide the additional fish supplies needed to meet the demands of a growing world population. In the Mediterranean, aquaculture effects on the ecosystem have been widely reported regarding the degradation of sediments sur- rounding fish farms (Kalantzi and Karakassis, 2006; Karakassis et al., 2000), detrimental effects on seagrass meadows (Holmer et al., 2008) with which many aquacultures share grounds and wild fish biomass and abundance changes at mesoscale distances (Machias et al., 2004). Concerns have also been expressed about the underlying effects of dissolved nutrients released which appear to have no im- mediate large scale effects (Karakassis et al., 2005; La Rosa et al., 2002; Pitta et al., 1999) but could trigger deviations in ecological pro- cesses and have effects in biodiversity levels of water bodies even at large distances from the farm (Sara, 2007). Lastly, one of the most far reaching effects of aquaculture is the farming of carnivorous spe- cies, whose demands on fish feed is exerting a pressure on wild stocks which counterbalances the contribution of farmed species to fish stock supplies (Naylor et al., 2000). With the above in mind, planning authorities not only have to decide if permission should be given to a new farm but also if an existing license should be renewed or extended. Crucial issues on the location and size of the farm are often explored based on subjec- tive criteria and incomplete data. Journal of Marine Systems 94 (2012) S65–S77 ⁎ Corresponding author. Tel.: + 30 2810 337755. E-mail address: gpetihakis@hcmr.gr (G. Petihakis). 0924-7963/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jmarsys.2011.11.002 Contents lists available at SciVerse ScienceDirect Journal of Marine Systems journal homepage: www.elsevier.com/locate/jmarsys