The European policies regarding biological conservation (mainly the Habitats and Birds Directives and, more recently, the Marine Strategy Framework Directive) strongly encourage the development of marine protected areas (MPAs) (IEEP and NRDC 2008). MPAs have been envisaged as a potential tool for conservation and safeguarding of the structure and function of marine systems against most anthropogenic activities that contribute to the decline of living resources (Colloca et al. 2004, Griffiths et al. 2007, Guidetti et al. 2010). Further management of MPAs must reconcile the human pressure on these sites with their functional integrity.

Fisheries constitute one of the most important uses of the seas. Two of the most important ecosystem services observed in the marine environment (food production and maintenance of biological condition) are affected by fisheries. Fishing activities play a role in habitat destruction and accidental mortality of non-target species, changing ecosystem functioning and evolutionary shifts in demography of populations (Pikitch 2004). Benthic habitats are mostly pressured by benthic fishing that involves mobile gears producing physical impacts on the seabed and on its biota (Tillin et al. 2006, De Juan et al. 2007, Hinz et al. 2009).

The EU Mediterranean fleet includes a large fraction (80%) of artisanal fisheries (COM 2002). They are generally defined as traditional fisheries involving fishing households, using a relatively small amount of capital and energy and relatively small fishing vessels, making short fishing trips close to shore, and mainly supplying local consumption (FAO 2005-2012). In the Mediterranean, fishermen’s local knowledge determines the seasonal effort according to species behaviour and abundance throughout the year (Stelzenmüller et al. 2007), segregating the impacts of habitats in a patchy distribution and delimiting the fishing footprint. Fishing footprint can be estimated by the use of vessel monitoring system (VMS) data and information on landings. The use of the VMS can facilitate conservational aspects in management by georeferencing fishing grounds, determining fishing pressures and relating local knowledge to practice. However, in artisanal fisheries, implementing VMS is especially difficult because artisanal boats usually do not exceed 15 m length, so they are not obliged to use this system. Consequently, the precise location of their fishing activities is neither recorded nor monitored, resulting in a lack of reliable data on the spatial coverage of their activities. An alternative approach to provide reliable figures of fishing grounds is through direct interviews with fishermen (e.g. questionnaire-based surveys) gathering all the relevant information (Stelzenmüller et al. 2007, De Freitas and Tagliani 2009, Forcada et al. 2010).

The Mediterranean, like other regions of Europe, faces a problem of habitat conservation (Stergiou et al. 1996, Guidetti et al. 2010). Under this scenario, the European Comission (EC) Natura 2000 network intends to ameliorate the loss of biodiversity caused by human activities and to restrain certain activities to safeguard the integrity of Sites of Community Interest (SCI). The Cap de Creus offshore area, a SCI since 2006 (Gili et al. 2011, www.indemares.com), is in the process of becoming a new Natura 2000 offshore MPA, thus increasing the protected area of European marine ecoregions. The Cap de Creus hosts an outstanding diversity of marine benthic habitats in which valuable key vulnerable ecosystem components (KVECs) have been identified (Gili et al. 2011). Recent research in Mediterranean submarine canyons close to the Cap de Creus coast revealed rich habitats with a high degree of endemism (Orejas et al. 2009, Gili et al. 2011), indicating that these hotspots of biodiversity might play an important role in providing portions of migration routes and nurseries. During the last few decades, fishing pressure has increased in this area (Gómez et al. 2006) but little information is available on the spatial assessment of its potential impact. During the evaluation phase of the Cap de Creus region to assess its potential interest for conservation, recorded images from remotely operated vehicles (ROVs) and manned submersibles were used. High abundance of cables and abandoned fishing gears was observed in the videos, demonstrating a high impact of these fishing activities on the littoral zone, continental shelf and slope (Gili et al. 2011, Sardá et al. 2012).

The future management of this MPA area is thought to be based on the ICES 2005 ecosystem approach to management, following modern management tendencies developed in ICES 2013 and 2014. One of its main management principles is to use scientific knowledge, so we started a rigorous analysis to determine the state of the Cap de Creus benthic habitats (Gómez et al. 2006, Orejas and Gili 2009, Gili et al. 2011, Sardá et al. 2012), including fishing gear pressure on them, in the best possible way. A spatial fisheries data map was needed to gain a comprehensive view on the usage and distribution of the artisanal fishing effort on this future Natura 2000 MPA area. To develop it and to estimate different potential cumulative impacts of artisanal fishing gears on KVECs, we used the Cap de Creus’ benthic assessment and questionnaire-based surveys from fishermen as the best available information to date. The main objective of the present study is to identify and quantify the potential cumulative impact value of artisanal fishing gears on the benthic environment, to determine the habitat distribution of KVECs, and to provide a geographical representation of the potential spatial distribution of fishing gears with a view to informing further decision making within a future ecosystem approach to management implementation for the region.

The four fishing gears analysed in the present study are the most common artisanal fishing gear types used in the western-central Mediterranean (Coppola 2003, Tzanatos et al. 2006, Cadiou et al. 2009). We estimated the potential impact of these artisanal fisheries on the seabed. Our 11 criteria allowed us to determine the heterogeneous distribution of the combined pressure of these gears over time and space where different metiers overlap. The areas subjected to higher pressure corresponded to both the coastal fringe and those relatively undisturbed by natural processes (i.e. muddy areas) in contrast to areas in the channel between the canyon and the coast, which mostly had coarser sediments, suffering a higher natural disturbance due to currents (Tudela 2000, Gili et al. 2011). The spatial exclusion of each fishing gear type (i.e. trammel nets and surface longlines rarely coincide in space) is possibly due to the incompatibility of the associated fishing methods and the likely consequent spatial exclusion (Aldebert et al. 1993). Bottom longlines appeared to be only present off the coast (in areas at depths greater than about 50 m), although in some areas there was an overlap with trammel nets and gillnets.

All habitats and/or communities can contain smaller and more homogeneous units which can be considered vulnerable components. In some cases, the entire community can also be considered a vulnerable component (such as coralligenous communities). Normally, in our case study, these communities occurred in small patches in a landscape mosaic and scattered amongst larger habitats with which they were associated. The KVECs selected in the present study play important functional roles in the ecosystem. On the continental shelf and the canyon head, the emerging sessile organisms, such as cold-water corals, Pennatulacea, Ceriantharia, gorgonians, sponge gardens and calcareous algae are among the most sensitive species to fishing gear impacts since they all function as key benthic engineer organisms (Cocito 2004). Under this definition, large, erect well-skeletonised mound or branching organisms are considered to host abundant epifauna, providing a fundamental structural framework for the ecosystem (Kaiser et al. 2002, Cocito 2004). To maintain the functional role of bioengineers, it is necessary to conserve dense assemblages (Thrush et al. 1998, Kaiser et al. 2002). At the Cap de Creus, cold-water coral species Madrepora oculata and Lophelia pertusa were found to be highly abundant at the margins of the continental shelf between depths of 150 and 400 m, where the steepness of the canyon walls provides natural protection for their development and suitable oceanographic conditions for growth (Orejas et al. 2009). The assessment of the current state of these communities revealed that longline fishing activities might represent a serious threat to their survival, especially on the canyon margins (Fig. 6), where these species become accidental catch (Gili et al. 2011), as occurs worldwide (Turner et al. 1999, Tudela 2000, De Juan et al. 2007). On the other hand, in littoral shallow environments, Posidonia beds are spatially complex and biologically productive ecosystems that provide habitat, food and nursery areas essential for a wide range of fish fauna (e.g. Sparidae, Labridae) (Thayer et al. 1975) and they are defined as special conservation areas according to the EC Habitats Directive. In the present study they showed a relatively low percentage of coverage. Furthermore, in the regions where Posidonia beds were present, no cells free of impact were found, suggesting that they are subject to strong fishing pressure. It is predictable that the local megabenthos assemblages will drastically change due to a potential decline in Posidonia beds that will affect the entire ecosystem structure, as previously found in other Mediterranean settings (Tudela 2000, Boudouresque et al. 2009).

The information from the fishermen questionnaires allowed us to represent a spatial map of the artisanal fishing activities in the area showing the overlap of several fishing gears. Obtaining data on artisanal fisheries is not an easy task and the available information is scarce because the fishermen community is not forced to use VMS and they are reluctant to reveal their fishing grounds and activity pattern. The pressure of artisanal fisheries on KVECs over time is assumed to be constant, producing a permanently altered state (Collie et al. 2001). Thus, an entire annual dataset (2000-2001) is of high analytical value and provides the best information possible. However, fishing practices can alter and weaken the complex structure and dynamics of benthic ecosystems and associated fish species (Tudela 2000) and if the area is going to be managed under an MPA figure, impacts should be alleviated as much as possible.

Cumulative impact indexes based on the best scientific information possible have been developed to support maritime spatial planning and ecosystem-based management (Halpern 2008). Science should improve its capacity to characterize, if not quantify, uncertainty in assessments and predictions and to effectively communicate this uncertainty to managers and the public (Boesch 2006). In the absence of a planned scientific methodology, compiling available information and translating it into advantageous knowledge is the best procedure. For the Cap de Creus region, in the absence of more sophisticated data that allow us to calculate fishing intensity per cell, we combined the potential cumulative impact value with the KVEC distribution in a cartographical way.

The potential impact affected especially Posidonia and maërl beds, covering 13% of the areas with KVECs; on the other hand, low potential cumulative impact values were associated with the majority (nearly two-thirds) of the study area, where Pennatulacea, gorgonians and sponges and cold-water corals were found. Therefore, a relationship between a higher number of KVECs and a low to medium fishing pressure is clear. This relation supports the fact that the knowledge of benthic characteristics and the current state of these species and communities is essential to ensure the implementation of appropriate preventive measures for the upcoming management, i.e. to enforce protection of KVECs. It is important to note that though maërl obtained the highest median impact score (0.71), the consecutive KVECs in decreasing order were considerably affected, with 0.46 as the median score. Whereas coralligenous communities were the KVEC with the broadest distribution, implying an exposure to the entire impact gradient, Posidonia beds and gorgonians and sponges were narrowly distributed and obtained no 0-impacted cells, thus corroborating the higher pressure exerted on these habitats.

Partitioning of fishing activities arises as an effective approach for habitat conservation. Both areas where one type of fishing gear is used (i.e. parcelling) and areas shared seasonally by two or more (i.e. considering the target species’ behaviour) have been seen to be useful to preserve the ecosystem and to avoid possible conflicts among fishing sectors (Kaiser et al. 2002, Morgan and Chuenpagdee 2003, Grau 2008). Fishermen rotate among their best fishing grounds to prevent crowding, implying that they self-regulate for their own benefit and for the prevention of possible arguments among colleagues (Aldebert et al. 1993, Scott 1993, Bonzon 2000). Agreements for sharing access to resources over space and time are common (Bonzon 2000, Morgan and Chuenpagdee 2003). Significant contributions of this benefit in the Mediterranean have been demonstrated (Scott 1993, Lleonart et al. 1998, Turner et al. 1999, Gómez et al. 2006), as has also been reported in the Chilean scenario, considering fishermen’s behaviour, traditional knowledge, property rights and the equitable use of marine resources (Castilla 2000, Fernández and Castilla 2005). To facilitate fishermen’s participation (e.g. through questionnaires, which have proved to be scientifically meaningful) in the local management of the area and provide them with a sense of ownership, communities should be responsible for managing a delimited area, known as territorial use rights in fisheries (Castilla 2000). Additionally, as seen in other fishing communities in Greece, Italy and France, alternative income solutions, such as eco-tourism or involvement in the design of existing or future MPAs, have also proved to be successful (Collet 2006).

Environmental (e.g. currents), socioeconomic (i.e. fishing gear types) and geophysical (e.g. the narrowness of the shelf) components in the study area favour artisanal fisheries as the prevailing activity. The combination of this set of factors has ended in the actual state of KVECs. However, we cannot track past interactions among them or determine the degree to which each of them has affected the seabed components; thus, we cannot distinguish areas where, e.g., environmental factors have had a greater influence on the absence/presence of KVECs than fisheries pressure. This limitation does not prevent the present analysis from providing an approach to be used for artisanal fisheries to identify areas which are prone to conflict, are subject to greater fishing pressure or host relatively well preserved benthic communities. The possible use of the developed maps for the involvement of fishermen and other stakeholders in workshops could be of real application, helping to diminish possible conflicts and illustrating the importance of spatial data at relevant scales for decision making.

Artisanal fisheries are the best alternative for achieving a sustainable use of coastal marine resources (Pauly 2006) and in the case of Cap de Creus they also represent part of the cultural heritage. Nevertheless, it is important to consider that ecological impacts do not depend entirely on the size of fishing vessels but are more strongly related to the fishing gear type and habitat features, as observed in studies addressing a small-scale fishery in Baja California (Shester and Micheli 2011).

An integrative map showing the potential cumulative impact values of the four most common fishing gears in the Cap de Creus region was developed based on fishermen information and permitted the estimation of fishing pressure on the selected KVECs from the local benthic communities. The method developed was used to identify the fishing gears exerting the pressures and the KVECs suffering the greatest pressure. Mapping the fishing pressure is a useful approach to identify the potentially most impacted KVECs and areas, as well as areas of conflict among fishermen. The approach presented here could be greatly improved by fishing activity records (VMS) or by a direct contribution from fishermen through questionnaire-based interviews.