Integrating benthic ecological status and spatial planning to guide sustainable bottom-contacting fisheries in the Eastern Mediterranean

Abstract

To inform ecosystem-based fisheries management in line with the EU legislation objectives for marine fisheries, we evaluated the ecological outcomes of alternative spatial management scenarios to fisheries that consider the ecological impact of bottom trawling on the benthic ecosystem in the Eastern Ionian Sea. Trawling intensity in terms of swept area ratio (SAR) and benthic community sensitivity were combined to estimate the relative benthic status (RBS). Then, five management scenarios were tested. The scenarios include four static closure scenarios (below 800 m, below 600 m, the least-trawled 10% of fishing grounds, and areas shallower than 150 m), where trawling is completely excluded without fishing effort redistribution, and one with a trawl ban in all marine protected areas, where fishing effort displacement is modelled dynamically. Baseline RBS was high (>0.9 on a scale of 0 to 1 where 1 is unaffected benthic community) in all habitats, reflecting relatively low benthic degradation due to bottom trawling. Excluding bottom trawling from areas shallower than 150 m in depth produced the greatest improvements, while thresholds at 600 or 800 m depth, and the closure of the 10% least-trawled grounds, had no significant effects on benthic ecological status. Closure of trawling in the marine protected areas produced mixed outcomes, with improvements in some habitats but localized declines due to displaced effort in others. Our study demonstrates the value of including benthic indicators in spatial management strategies to guide adaptive, evidence-based fisheries governance, balancing conservation objectives with socio-economic sustainability.

1 Introduction

The Mediterranean Sea is one of the most heavily exploited marine areas in the world. Due to its semi-enclosed nature and the long history of human use, ecological pressures and socio-economic demands are tightly interlinked (Rick et al., 2020). Fishing is an important activity throughout the sea, supporting local economies and culture, yet it causes significant pressures on marine ecosystems (Fiorentino and Vitale, 2021; FAO, 2023). In the Mediterranean, the activity takes place throughout the region from depths ranging 50–1000 m and in 2016 to 2018, it was responsible for 27.0% of Mediterranean landings through just 7.9% of the vessel segment (FAO, 2020). The 1000 m depth trawling limit was set by the General Fisheries Commission for the Mediterranean and Black Sea (GFCM) and intended to protect deep-sea ecosystems, which are particularly vulnerable to fishing pressure and slow to recover (EC, 2006). Among fishing methods, bottom trawling is the most pervasive and destructive activity for the seabed due to its direct contact with the benthic environment (Kaiser, 1998; Foden et al., 2011). As well as direct removal of benthic and demersal species, bottom trawl gear reshapes benthic community structure, reduces habitat integrity, and affects the biodiversity and overall resilience of marine ecosystems (Eigaard et al., 2016; Tiano et al., 2019; Bradshaw et al., 2024; Agnetta et al., 2025). In Europe it is the most widespread marine activity with varying levels of intensity and impact across almost all shelf areas (Hiddink et al., 2026).

Until recently, scientific and policy debates about Mediterranean fisheries focused on whether fish stocks were overexploited and if so how to best reduce this pressure, neglecting the ecological impacts of fishing on benthic habitats (Bahamon et al., 2024; Bastardie et al., 2025). For example, the GFCM 2030 Strategy proposes to establish effective area-based conservation measures based on the mapping of essential fish habitats and vulnerable marine ecosystems (VMEs) (FAO, 2021). However, it pays little or no attention to other benthic habitats that cover most of the seafloor and offer invaluable services to humans, such as carbon sequestration (Porz et al., 2022). Yet, growing evidence highlights that all benthic ecosystems are highly sensitive to bottom-contacting fishing (Tiano et al., 2019; Pitcher et al., 2022). In addition, recent policy and legislation in the European Union has incorporated not only biodiversity but also seafloor integrity as key descriptors of good environmental status (GES in EU, 2008 – Marine Strategy Framework Directive, MSFD), placing benthic habitats at the heart of marine sustainability objectives. More recently and in accordance with the MSFD, the Nature Restoration regulation (EU, 2024) sets specific restoration targets for degraded benthic habitats. In this context, policy around fisheries should also consider seafloor ecological status. To achieve this, mapping the spatial footprint, i.e. the extent and intensity of seafloor disturbance caused by bottom trawls and also assessing benthic status are essential steps for identifying sensitive areas and areas of high pressure, guiding more effective, spatially explicit management strategies (Bona et al., 2025).

The Eastern Ionian Sea offers a valuable case study for examining the dynamics and trade-offs between bottom trawling and benthic ecological impacts. This region hosts a mosaic of habitats—ranging across multiple MSFD broad habitat types from infralittoral to deep bathyal zones, each supporting distinct benthic assemblages with varying sensitivity to disturbance (Smith et al., 2023). This area includes Patraikos Gulf, one of Greece’s main fishing grounds. The Gulf is also adjacent to a marine protected area (MPA), Zakynthos national park, and therefore this area illustrates the tension between ecological protection and extractive fishing industries. Few studies have tested the impact of different spatial management scenarios on reducing the environmental footprint of bottom trawling, mainly focusing on the fisheries themselves, i.e. bycatch, fish stock assessment, nursery-ground protection, and on the economic outcomes (Bastardie et al., 2017, Bastardie et al., 2025; Sbrana et al., 2025), with even less providing evidence on how benthic status is influenced (Bastardie et al., 2020; Zupa et al., 2025).

In this context, our study aims to evaluate the ecological outcomes of various management measures and fishing restrictions on the benthic ecosystem and to explore the implications of these findings for regional fisheries governance. This is in accordance with the objectives of the EU Biodiversity Strategy to achieve GES in at least 30% of the habitats in the EU marine waters by 2030 (EC, 2021) and aligns with the recent goals of the GFCM, which among others promotes sustainable fisheries through the protection of vulnerable marine ecosystems (FAO, 2021). By integrating ecological assessments with management scenarios, this research contributes to the advancement of ecosystem-based fisheries management in the Mediterranean. It provides insights into the trade-offs and co-benefits between marine habitat conservation and resource exploitation, offering evidence-based guidance for environmental and fisheries policymakers seeking to align marine ecosystem health with socio-economic sustainability. This approach has been to anticipate the impacts of different protective management strategies by modelling scenarios of alternative spatial allocations of bottom trawling effort on seabed ecological status.

2 Materials and methods

2.1 Study area

The study area is in the Eastern Ionian Sea in the GFCM geographical sub-area 20 (GSA20) (Figure 1). The area was divided into grid cells of 0.05x0.05 decimal degrees (dd) using the C-square grid approach (Rees, 2003). The EMODnet seabed habitat data portal (Vasquez et al., 2023) was used to extract the distribution of MSFD broad habitat types within the study area. In order to link habitat information to fishing intensity, habitat types were transferred into the midpoints of the C-square grid cells. The MSFD broad habitat type that overlapped the central point of the C-square was assigned to the whole C-square. Due to the centroid based assignment as well as the grid resolution, minor spatial resolution artifacts may occur where a single cell spans across bathymetric contours.

Figure 1

2.2 Baseline benthic ecological status assessment

To assess the baseline conditions of the benthic ecosystem in the study area, we used the Relative Benthic Status (RBS) indicator proposed by Pitcher et al. (2017). The calculation of RBS requires a benthic community sensitivity spatial layer, distribution of fishing intensity layer per type of fishing activity (here bottom trawling), depletion rates of benthic animals affected by specific fishing activity (i.e. métier) and recovery rates of the benthic community associated with the habitat types (see details in Hiddink et al., 2017; Pitcher et al., 2017). RBS takes values from zero to one with higher values indicating better benthic status.

2.2.1 Benthic community sensitivity assessment

RBS assumes that the sensitivity of the benthic community to bottom trawling is related to the median expected longevity of the community. A community longevity is defined as the combination of the theoretical life expectancy of all the species that make up this community (Rijnsdorp et al., 2020). The median longevity of the community is the longevity defined at the 50^th percentile of the cumulative biomass of this community. Benthic community sensitivity was quantified using species longevity traits, a widely applied ecological proxy for vulnerability to bottom trawling disturbance. Briefly, the method required firstly that the macrofauna species from undisturbed stations are assigned to one of four longevity classes (<1 year, 1–3 years, 3–10 years, >10 years) using a fuzzy-coding approach. Then, the relationship between cumulative biomass and longevity was estimated using generalized linear mixed models (GLMMs) with a binomial distribution. Environmental predictors included bathymetry (log-transformed) and MSFD broad habitat type as fixed effects, while sampling site was included as a random effect. All model combinations were compared using the Akaike Information Criterion (AIC). Benthic sensitivity of the study area was extracted from Smith et al. (2023). Sensitivity was available only for specific MSFD broad habitat types, including infralittoral sand, infralittoral mud, circalittoral sand, circalittoral mud, offshore circalittoral mud and upper bathyal sediment. Median longevity was extracted as the indicator of benthic sensitivity for each habitat type in the GSA20.

2.2.2 Depletion and recovery rates

Demersal otter trawls are the only métier that operates in the study area. The depletion rate for otter trawls was obtained from the global meta-analysis conducted by Hiddink et al. (2017) and was set at 0.06. Similarly, the recovery rate (r) was based on a meta-analysis, calculated as r = 5.31/longevity (Hiddink et al., 2019).

2.2.3 Fishing intensity assessment

Fishing intensity was quantified using the swept area ratio (SAR), an indicator used widely and defined as the area swept by trawl gear relative to the surface area of a grid cell (Amoroso et al., 2018). Vessel Monitoring System (VMS) data from 2018–2020 were used to estimate SAR for demersal otter trawls. Annual SAR values were averaged over 2018–2020 to produce a baseline measure of trawling intensity in GSA20. Grid cells were categorized by trawling frequency, and their overlap with habitat types was mapped. Raw VMS data for the years 2018–2020 were provided by the Hellenic Ministry of Mercantile Marine and Island Policy and were analyzed based on the methods and specifications further described in Maina et al. (2021).

2.3 Fisheries management scenarios

The RBS was calculated for GSA20 by combining the trawling intensity (SAR) with benthic sensitivity (Pitcher et al., 2017). Since the benthic sensitivity layer was available only for specific habitat types (Smith et al., 2023), RBS was not calculated for infralittoral biogenic habitats, bathyal and abyssal zone. Five spatial management scenarios were tested to predict their effect on benthic ecological status (i.e. RBS). Scenarios were run by changing SAR according to different rules and recalculating RBS over the area. Scenarios were chosen from a range of possibilities from strict conservation actions to more gentle actions that reflect closing areas of minimal fishing use.

Four of the management scenarios that were tested were based on a reduction of fishing (static approach), i.e. with fishing effort totally cut from closed areas, assuming effort is removed completely. The fifth scenario was dynamic including re-allocation of fishing effort (see section: Specifications for SAR inputs per scenario). The dynamic scenario is expected to provide a more realistic representation of fleet responses, since fishing effort is unlikely to be removed entirely unless authorities specifically reduce effort through spatial management measures. Moreover, given that the focus of this work was to investigate potential changes in RBS, the effects of such management options on alternative resources and on the fisheries economy require further investigation. The following spatial management scenarios were tested:

• Scenario 1 (static): Restricting bottom trawling below 800 m, reducing depth of the current Mediterranean-wide 1000 m depth limit of trawling, with no effort displacement. This scenario was inspired by GFCM recommendations for the protection of VMEs.

• Scenario 2 (static): Restricting bottom trawling below 600 m depth, with no effort displacement. This is a stricter version of scenario 1 that was inspired by GFCM recommendations for the protection of VMEs and sensitive habitats.

• Scenario 3 (static): Closure of the least-trawled 10% of core fishing grounds (Figure 2B), retaining the core fishing areas to attain the least socio-economic consequences. This scenario was inspired by the International Council for the Exploration of the Sea (ICES) as the one with the smallest economic impacts on fisheries.

• Scenario 4 (static): Restricting bottom trawling down to 150 m depth, based on an Oceana proposal¹. This scenario, although might be perceived as unrealistic due to its potential economic consequences, will effectively exclude from bottom trawling, shallow sensitive habitats such as seagrass meadows, coralligenous reefs, and maerl beds by creating broad-scale trawl-free areas in the coastal zone.

• Scenario 5 (dynamic): Restricting bottom trawling in all Eastern Ionian Sea designated MPAs (Figure 2A), including National Parks and Reserves, RAMSAR Sites and other Special Sites/Areas and Refuges, with effort redistributed. This scenario was inspired by the EU Action Plan for protecting and restoring marine ecosystems to achieve sustainable and resilient fisheries (European Commission, 2023). EU Member States are called on, among other things “to adopt national measures and, where relevant, submit joint recommendations to the Commission to ensure that mobile bottom fishing is phased out, in all MPAs by 2030”.

Figure 2

2.4 Specifications for SAR inputs per scenario

For Scenarios 1–4 (static scenarios), SAR within closed areas was set to zero (SAR = 0 in all C-squares inside banned zones) assuming trawling effort is removed completely from the area. In all other C-squares, SAR was based on mean values for 2018–2020.

For Scenario 5 (dynamic scenario), SAR values were obtained from simulations using the DISPLACE spatially explicit bioeconomic model (Bastardie et al., 2014; www.displace-project.org). The DISPLACE framework simulates the behavior of individual fishing vessels by integrating fleet dynamics, resource availability, and fisheries management options. It enables the evaluation of biological, ecosystem, economic, and energy efficiency effects resulting from the redistribution of fishing effort to alternative grounds. The Eastern Ionian Sea application was parameterized with data on fishing effort distribution, fish stock traits, species abundance, selectivity, and economic indicators (see details in Maina et al., 2021; Bastardie et al., 2025). Fishing effort redistribution was assumed to occur within GSA 20, reflecting the typical behavior of the local fleet. The model can also incorporate benthic community dynamics by coupling gear-specific depletion rates with habitat-specific, trait-based recovery rates (Bastardie et al., 2020). However, this benthic component is still under development for the Eastern Ionian Sea application. Simulations performed for the period 2020–2027 aimed at evaluating the effects of effort displacement from all MPAs, to alternative fishing grounds. The simulated SAR was derived from 50 Monte Carlo replicates, allowing estimation of uncertainty around the mean SAR. The simulated SAR values (at C-square resolution) were used for Scenario 1 purposes and correspond to the final simulated year (2027). The resulting SAR was then combined with benthic sensitivity data to estimate Relative Benthic Status (RBS).

2.5 Estimation of RBS

RBS was calculated for all management scenarios and compared with the baseline (status quo) conditions, i.e., the mean RBS for the period 2018–2022. A threshold of RBS > 0.8 was used as a candidate benchmark for Good Environmental Status (Smith et al., 2023). The non-parametric Wilcoxon signed-rank test was selected to compare RBS between baseline conditions and the different management scenarios per habitat type (Haynes, 2013), since the normality and homogeneity of variance assumptions were violated. Statistical significance was determined at a threshold of p-value < 0.05.

RBS estimations were carried out in the R software (R Core Team, 2024). Scripts were developed by adapting the code from van Denderen et al. (2020).

3 Results

3.1 Baseline conditions

Baseline fishing pressure exceeded SAR values of 1 only in 17% of the trawled cells in the grid (Figure 3a). Maximum SAR value recorded in the area was approximately 2.8. This value was recorded in only one grid cell emphasizing that trawling pressure did not exceed SAR = 3 even in areas of concentrated trawling. The baseline RBS reflected the annual average trawling pressure distribution in GSA20 from 2018-2020. RBS was higher than the 0.8 threshold, that defines GES, in the entire study area, indicating minimal impact from bottom trawling. The lowest RBS values (still >0.8) were recorded in the centre of the study area (outer Patraikos Gulf) where the main fishing grounds are found – with highest SAR intensities (Figure 3b). When aggregated by MSFD broad habitat type, RBS values exceeded 0.9 in all cases indicating low average impacts across the assessed habitats (Table 1). The most impacted habitat for the period 2018–2020 was offshore circalittoral mud where more than 85% of the area that this habitat occupies was bottom trawled. Circalittoral sand exhibited the highest average SAR values (0.76), followed by offshore circalittoral mud (0.60) (Table 1). In contrast, infralittoral and bathyal sediments showed SAR values close to zero due to European and national legislation that prohibit trawling in shallow (i.e. within 3 nm distance from the coast or less than 50 m depth) and deeper depths (i.e. below 1000 m depth) as well as in certain areas/gulfs (see Maina et al., 2021).

Figure 3

3.2 Scenario 1: restricting bottom trawling below 800 m depth (static)

This scenario excluded 7% of the baseline trawled area and produced no significant changes from the baseline conditions (Tables 1, 2). RBS values across most habitats remained identical to baseline estimates, as trawling activity below 1000 m depth was already prohibited (Figure 4a). The proportion of trawled cells decreased slightly for lower bathyal sediments, with no measurable change at 4 decimal precision points in the RBS.

Figure 4

3.3 Scenario 2: restricting bottom trawling below 600 m depth (static)

Similar to the 800 m scenario, the 600 m depth restriction excluded 16% of the trawled area but produced no substantial improvements in RBS values per habitat type (Figure 4b; Tables 1, 2). The reduction in the proportion of trawled cells was slightly greater than under Scenario 2, but overall differences compared to the baseline remained minimal. In all habitat types, RBS values were above 0.97, with upper bathyal sediments showing no significant increase in benthic status (Table 2).

3.4 Scenario 3: closure of the least-trawled 10% of core fishing grounds (static)

Closing the least-trawled 10% of core fishing grounds although excluded 22% of the baseline trawled area, had a minor effect on the benthic status (Figure 4c). SAR and RBS remained nearly unchanged across all habitats compared to the baseline conditions although in the upper bathyal sediment the increase in RBS was statistically highly significant (Table 2).

3.5 Scenario 4: restricting bottom trawling down to 150 m (static)

The most substantial changes were observed under Scenario 4, which prohibited trawling down to 150 m depth, excluding 41% of the baseline trawled area (Figure 4d; Table 1). RBS in all habitat types, except for the infralittoral zone, significantly increased (Table 2). SAR values for these habitats dropped to zero, and the proportion of trawled cells was reduced correspondingly.

3.6 Scenario 5: restricting bottom trawling in all MPAs (dynamic)

Among the spatial management scenarios, dynamic Scenario 5 restricted trawling in all protected areas (Figure 2A), excluding 36% of the baseline trawled area. This resulted in statistically significant increase (improvement) in RBS values for some habitat types, such as in the circalittoral sand and the upper bathyal sediments (Tables 1, 2). However, redistribution of fishing effort to other nearby grounds led to localized decreases in RBS, most notably in Patraikos Gulf, where fishing effort was concentrated (Figure 5). Although a decrease in average RBS was recorded in the offshore circalittoral mud, it was not statistically significant. It is also worth noting that although the average benthic status in all habitat types was above 0.8, there is a certain area in the inner Patraikos Gulf where the RBS was below this threshold (Figure 5).

Figure 5

4 Discussion

Mapping regional trawling activity and benthic ecological status are valuable policy tools, enabling effective spatial management by identifying sensitive or marine areas at high risk to disturbance (Bona et al., 2025). Insufficient knowledge of fisheries distribution and sensitive areas can lead to incorrectly placed closures that will not only result in a reduction of economic profit but may also fail to provide benefits to maintain or improve the benthic ecological status (Vaughan, 2017; Sbrana et al., 2025). Based on the benthic status (RBS) estimated with recent trawling effort in the area by Pitcher et al. (2022) and Smith et al. (2023), this study explores how different fisheries spatial management scenarios would change RBS. Trawling intensity and benthic sensitivity are linked across different habitat types and alternative management measures. Our findings suggest that the selection of specific management measures is critical, since different measures have yielded different outcomes. While bottom trawling closures in shallow waters (<150m) offered the most substantial improvement in RBS, deeper bathymetric closures and the displacement of effort from protected areas resulted in negligible or mixed effects.

Techniques for reconciling fisheries’ economic performance and minimization of their impacts on the seafloor are of growing interest to policymakers now that environmental targets are pursued (within the GFCM, the MSFD, and the Nature Restoration Regulation). In this context, this study aimed to evaluate the performance of different management scenarios to reduce the ecological impact of bottom trawling on the seafloor. This study prioritized seafloor integrity in the management scenarios tested, with the expectation that preserving benthic habitats will, in turn, promote the long-term sustainability of the fisheries sector. Among the scenarios examined, four of them were based on a bathymetric ban of trawling where fishing pressure is removed from the system entirely. The outcomes of these scenarios indicated that reducing trawling effort does not always improve benthic status. Specifically, restricting trawling down to 150 m depth yielded the strongest improvements, while closures of trawling in areas deeper than 600 or 800 m had negligible changes in the benthic status. The latter has been suggested as a sustainable measure that would allow the protection of the deep-sea including several deep-water coral species and vulnerable marine ecosystems, with relatively little economic impact (Sbrana et al., 2025). Nevertheless, the negligible difference in RBS between the 800 m and 600 m scenarios suggests that for the Eastern Ionian Sea, the ‘ecological gain’ is relatively small, indicating that targeted, habitat-specific interventions rather than broad bathymetric shifts may be more beneficial. In contrast, the implementation of a drastic management plan that would offer protection to the shallower habitats (to 150 m depth) delivered significant ecological benefits in the model, first explained as these habitats host the core fishing grounds in the area and also host the most sensitive benthic communities (Smith et al., 2023). However, as maximum trawling intensity is generally observed at 50–200 m depth, this scenario may have significant economic costs to fishers, particularly if no “reserve effect” is to be expected. For example, if this ban leads to increased productivity or redistribution of species that could benefit fisheries outside the closed area, this can offset some short-term economic losses. Thus, reducing trawling entirely in a core fishing ground may not be realistic, and anticipating effects without accounting for likely effort displacement may overestimate ecological improvements (Bastardie et al., 2014; Vaughan, 2017).

Spatial closures of trawling may be insufficient if effort is redistributed rather than reduced (Bastardie et al., 2025; Binch et al., 2025). Hence, a dynamic scenario was implemented to predict the effects of closing all MPAs in the study area and the consequent redistribution of trawling effort. This scenario is policy relevant as the Greek government is currently in the process of implementing a trawling ban in all MPAs². This scenario yielded minimal benthic ecosystem benefits. This is because many of the MPAs in the study area were established to meet Natura 2000 conservation objectives, i.e., the protection of habitats and species included in Natura 2000’s annexes, rather than as fisheries management tools designed to maintain or restore seafloor integrity. Our results show that the Greek government’s policy, while well-intentioned, may produce unintended ecological consequences if implemented without complementary management measures. Specifically, we found that MPA closures resulted in localized RBS declines in already heavily fished areas, particularly in Patraikos Gulf. In certain grid cells within this area, our model predicted RBS values falling below 0.8 - the proposed threshold for GES - as displaced fishing effort concentrated in the remaining accessible grounds. This result is concerning given that Patraikos Gulf represents one of the most economically important fishing grounds in the region, where increased effort intensity could simultaneously compromise both ecological status and long-term fishery sustainability. The displacement effect we observed complements the findings by Bastardie et al. (2025), who showed through bioeconomic simulations that spatial restrictions can have unexpected negative outcomes when effort is reallocated to adjacent areas. Similarly, Binch et al. (2025) concluded that trawling effort displacement can transfer ecological impacts beyond protected areas and influence whole food webs in the North Sea. Despite the ecological risk, spatial restrictions and fishing effort redistribution also impose significant economic trade-offs. For example, Sbrana et al. (2025) noted from a modelling scenario, restricting fishing in shallow coastal areas (<6 nm) in Italian waters, significantly affects fleet profitability by reallocating effort to other fishing grounds.

Overall, most habitat types in the GSA20 are currently in good condition (with RBS values higher than 0.9 in every habitat), even though some areas, particularly in circalittoral and offshore circalittoral mud habitats, exhibit higher impact from bottom trawling pressure. This is due to two reasons, firstly the Eastern Mediterranean, with the exception of some localized trawling hotspots, is not under intensive trawling pressure compared to other regions of Europe; maximum SAR in Northern European waters and the Adriatic Sea can reach values of more than 10 or 40, respectively (van Denderen et al., 2020; Zupa et al., 2025). Secondly, our benthic assessment was based on the macroinvertebrate community that tend to have lower longevity (and therefore less sensitive) than the larger sized epifaunal species that are used in other Mediterranean assessments (Zupa et al., 2025). The use of infauna-based sensitivity may be a source of underestimation of trawling impact. However, highly mobile larger epifaunal species are usually not effectively sampled by the grab devices, while trawl caught epifauna used for sensitivity estimation in other European assessments may not represent near pristine communities required for the analysis. Additionally, the spatial resolution of our study, which had C-squares of around 25 km² (resolution), may make it difficult to capture the very localized effects of bottom trawling, requiring higher resolution in habitat, sensitivity and trawling pressure maps. While this assessment is effective at characterizing impacts across broad spatial scales, they are less effective at detecting impacts on VMEs that are highly localized.

Together, these comparisons between the scenarios raise the question of whether large-scale spatial restrictions are necessary for seafloor integrity in areas where the baseline benthic status is already high, such as in the case of Eastern Ionian Sea. Instead, more targeted measures may be more effective, such as protection of the most sensitive habitats (e.g., maerl beds, Posidonia meadows, VMEs), reduction in overall fishing effort (which is also important for fish stocks management), gear improvements to reduce physical impact, and the use of management frameworks that minimize harmful effort displacement. These alternatives may better support the EU’s 30 by 30 targets and Restoration Regulation objectives by focusing on ecologically valuable or vulnerable habitats.

Our study provides useful insights for fisheries governance in the Eastern Ionian Sea. Integrating benthic quality indicators such as RBS into spatial planning can improve alignment with EU legislation objectives, while coupling ecological assessment with socioeconomic analyses will provide a more comprehensive basis for decision-making. In this context, future research should combine RBS modeling with fleet economics, fuel consumption, carbon emissions, and target species distribution modeling at high resolution to more accurately quantify trade-offs and co-benefits, supporting sustainable fisheries management in the entire Mediterranean Sea.

5 Conclusions

Our study indicated that spatial management can meaningfully improve benthic status in the Eastern Ionian Sea, but the effectiveness of closures depends on the area characteristics and habitat sensitivity. Closures down to 150 m depth produced the largest improvements in benthic status, particularly in infralittoral and circalittoral habitats that host sensitive communities, but the economic costs of this type of closure might be significant since this zone has the highest concentration of bottom trawling activity (from 50 to 200 m depth). Moving the already established boundary of 1000 m maximum fishing depth to 800 or 600 m depth had negligible effects on the benthic state given there are no targeted bottom trawling activities in that zone compared to other areas in the Mediterranean Sea. In contrast, when the effort displacement triggered localized declines in the benthic status in heavily fished areas, spatial protection alone may be insufficient without complementary measures to control effort.

These comparisons highlighted that in regions like the Eastern Ionian Sea, where a high proportion of benthic habitats are in good status, additional ecological gains require measures that either target the most sensitive habitats (e.g. infralittoral sand, maerl beds, Posidonia meadows or vulnerable marine ecosystems) or reduce overall fishing effort. Closures at intermediate depth or minimal area restrictions are unlikely to produce measurable improvements. In addition, failure to predict displacement risks may compromise MSFD objectives and its socioeconomic benefits. Thus, future work should compare optimized management scenarios that integrate: (1) targeted protection of the most sensitive habitats or species, (2) graduated effort reduction targets coupled with spatial closures, and (3) socio-economic impact assessments to identify solutions that maximize benthic status while minimizing economic loss of fisheries.

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