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Article

Ecological Assessment and SWOT–AHP Integration for Sustainable Management of a Mediterranean Freshwater Lake

by
Olga Petriki
* and
Dimitra C. Bobori
Laboratory of Ichthyology, Department of Zoology, School of Biology, Aristotle University of Thessaloniki, Box 134, GR54124 Thessaloniki, Greece
*
Author to whom correspondence should be addressed.
Sustainability 2025, 17(11), 4950; https://doi.org/10.3390/su17114950
Submission received: 7 April 2025 / Revised: 24 May 2025 / Accepted: 27 May 2025 / Published: 28 May 2025
(This article belongs to the Special Issue Tools for Ecological Assessment and Supporting Decision-Making in Sustainable Freshwater Ecosystem Management)
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Abstract

:
The Mediterranean region is highly vulnerable to environmental and anthropogenic pressures, including climate change, which significantly affect its aquatic ecosystems, especially shallow lakes. This study examines the fish community and ecological quality of Lake Paralimni, a shallow mesotrophic lake in Central Greece that experienced complete desiccation between 1991 and 1996. Using field surveys, fish species composition, abundance, and biomass were assessed, and the lake’s ecological quality was evaluated through the Greek Lake Fish Index (GLFI) alongside an integrated SWOT (strengths, weaknesses, opportunities, threats) and AHP (Analytic Hierarchy Process) analysis. Six fish species from three families were recorded, predominantly native and endemic, with introduced species representing a minor fraction. While GLFI rated the lake’s quality as “Good,” other multi-metric indicators downgraded it to “Moderate”, highlighting the importance of comprehensive assessments. SWOT analysis revealed strengths such as high native biodiversity and legal protection under Natura 2000, but also weaknesses like fluctuating water levels and limited monitoring. Opportunities include sustainable fisheries and conservation efforts, while threats involve climate change, eutrophication, and illegal species introductions. AHP emphasized threats and weaknesses as top priorities. The study recommends hydrological regulation, invasive species control, and long-term monitoring for sustainable lake management and biodiversity conservation.

1. Introduction

The Mediterranean region is among the most vulnerable areas to environmental changes [1]. These changes, driven primarily by climate change and anthropogenic pressures, may significantly alter the hydrology of aquatic ecosystems in the region [2]. Shallow lakes and their associated fish communities, which are vital components of freshwater ecosystems, are particularly vulnerable to these impacts. Fish play a crucial role in maintaining biodiversity and supporting ecological balance. In addition, freshwater fish communities contribute to ecosystem services such as recreational fishing, food provision, and cultural value [3,4,5]. However, freshwater ecosystems face growing threats from multiple environmental pressures, including habitat degradation, climate change, invasive species introductions, and pollution [6,7,8]. Biodiversity loss presents a significant challenge to lake fish populations, which are particularly sensitive to environmental changes and habitat disturbances [9]. Declines in water quality, alterations in hydrological regimes, and competition from invasive species further exacerbate the risks to native fish communities [10]. Climate change intensifies these threats by altering temperature and oxygen levels, potentially leading to shifts in species distribution or even local extinctions [8,11,12]. Given the ecological importance of freshwater fish for ecosystem stability and the delivery of key ecosystem services [13], effective conservation strategies are urgently needed. Moreover, robust risk assessment and management frameworks are essential to safeguard the ecological integrity and sustainable use of these aquatic systems [14]. Sustainable lake management in complex socio-ecological contexts requires an integrated understanding of ecological conditions and structured tools for action prioritization [15]. Yet, few studies have systematically combined ecological assessments with strategic planning tools, such as SWOT (Strengths, Weaknesses, Opportunities, Threats) and the Analytic Hierarchy Process (AHP) [16,17,18]. This study addresses this gap by integrating fish-based ecological quality assessment with SWOT–AHP analysis to develop a risk-informed and management-oriented approach for Mediterranean lakes. SWOT enables qualitative identification of internal and external factors affecting lake ecosystems, while AHP adds quantitative prioritization, enabling objective, transparent decision-making. Together, these tools form a hybrid framework capable of linking biological conditions with management priorities, in line with EU policies like the Water Framework Directive (WFD, 2000/60/EC), which aims for good ecological and chemical status of all water bodies [19]. Maintaining a good ecological status is essential not only for biodiversity protection but also for ensuring long-term ecosystem services such as water purification, fisheries, and recreation [3,20], contributing directly to the Sustainable Development Goals (SDGs) [21]. Incorporating SWOT–AHP into lake management can help identify system-level strengths and weaknesses, align actions with WFD objectives, and support evidence-based policy formulation by ranking strategies based on environmental, economic, and social criteria.
This study uses Lake Paralimni as a case study to demonstrate the application of the SWOT–AHP method for assessing ecological risk and prioritizing lake management strategies. Specifically, it assesses the fish community structure, evaluates ecological quality using the Greek Lake Fish Index (GLFI), and identifies management priorities using the integrated framework. The findings emphasize the value of strategic planning in protecting freshwater biodiversity and promoting sustainable ecosystem governance, especially for small lakes in water-stressed regions.

2. Materials and Methods

2.1. Study Area

Lake Paralimni (Figure 1) is in Central Greece (Eastern Mediterranean), specifically in the Boeotian Kifissos River basin. Its geographic coordinates are approximately 38.45° N latitude and 23.22° E longitude. Together with Lake Yliki, it forms part of a hydrological network that historically encompassed the Kopaida basin [22], situated in a typical Mediterranean climate zone characterized by hot, dry summers and mild, wet winters. The two lakes are hydrologically connected via a 2.5 km canal located southwest of Lake Paralimni, enabling water exchange and contributing to the lake’s fluctuating water levels. Historically, Lake Paralimni was significantly larger, with a stable surface area of 14.7 km2 in the 1940s. However, extensive water withdrawals for irrigation and groundwater pumping led to the complete desiccation of the lake between 1991 and 1996. Additionally, it has periodically been used to supply drinking water to the Municipality of Chalkida [23].
In recent years, direct water extraction for drinking purposes has been halted to prevent further water loss. Despite this, the lake has shrunk to an area of about 4 km2 and has an average depth of 5 m, classifying it as a shallow lake. It discharges periodically into the North Euboean Gulf through a seasonal stream. The lake is considered mesotrophic but shows tendencies toward eutrophication, indicating moderate nutrient levels with potential risks of algal blooms [24].
Lake Paralimni is part of the Natura 2000 network (Lakes Yliki and Paralimni—Boeotian Kifissos System, GR2410001), underlining its ecological significance. Additionally, it is subject to a Public Health Decree (Ministerial Decision A5/2280/A.F. 720, 13 December 1983) aimed at protecting the drinking water sources of the city of Athens.
The fish community of Lake Paralimni includes 11 recorded species from five families, with a high proportion of endemic species [25,26] (Table 1). Notable endemics include Luciobarbus graecus, Leucos ylikiensis, and Scardinius graecus, highlighting the lake’s value as a conservation hotspot. However, species introductions pose ecological risks. Alien species, such as Ctenopharyngodon idella, Hypophthalmichthys molitrix, and Hypophthalmichthys nobilis, were introduced to improve fisheries productivity and control macrophyte overgrowth. Additionally, Silurus aristotelis, originally native to the Acheloos River basin in Western Greece, was translocated and may impact native fish populations [25].
Fishing intensity in Lake Paralimni remains low, with fewer than 10 professional fishermen operating in the area. However, recreational and competitive carp fishing has increased in recent years. While overall fishing pressure is currently limited, the absence of systematic long-term monitoring raises concerns about undetected ecological changes, shifts in fish populations, and the long-term effects of non-native species.

2.2. Data Sources

Primary data used in the SWOT analysis were obtained from fish samplings conducted at Lake Paralimni in October 2022. Sampling was conducted during a period when surface water temperature exceeded 15 °C, following the guidelines of the international standard ISO EN 14757 CEN [28]. Benthic Nordic multi-mesh gillnets (consisting of 10 different mesh panels (30 m × 1.5 m, length × height) with mesh sizes ranging from 8 to 70 mm knot to knot, i.e., 8, 14, 16, 20, 24, 30, 36, 45, 55, 70 mm) were deployed at 20 locations throughout the lake (Figure 1). The total fishing effort was determined based on (a) the surface area and maximum depth of the lake, (b) general guidelines provided by [28] regarding fishing effort estimation and its distribution across depth zones, (c) recommendations by [29] to reduce the [28] recommended effort, aiming to lower monitoring costs and protect species. The fishing effort was distributed across three depth zones. The gillnets were deployed in the evening (e.g., 18:00–20:00) and retrieved the following morning (e.g., 06:00–08:00), ensuring a soaking time of approximately 12 h. Fish were identified to the species level, and each individual was measured for Total length (TL, mm) and Body weight (W, g). Finally, the abundance and biomass of each species were estimated based on the total number of individuals and total weight.
Simultaneously, an oxygen and temperature profile was recorded by conducting on-site measurements at 1-m depth intervals at the deepest point of the lake using a portable multiparameter instrument.
Additional (secondary) data used for SWOT analysis were derived from existing literature (e.g., prior ecological assessments [30,31,32], water quality data, habitat condition [33,34] national and regional environmental databases, expert consultations with fisheries biologists and regional water authorities), and focused-group discussions with stakeholders (e.g., fishers, planners, ecologists). Land-use metrics (e.g., percentage of non-natural land cover) were extracted from official GIS land-use datasets [35].

2.3. Ecological Quality Assessment

The ecological quality of Lake Paralimni was assessed based on the fish catch data using the Greek Lake Fish Index (GLFI) [36]. This index incorporates two fish-based metrics: (a) the relative numerical abundance of introduced species (including both alien and translocated) and (b) the relative biomass of omnivorous species. Both metrics respond to overall lake degradation and eutrophication [36]. In addition to biological metrics, the index incorporates several environmental descriptors that define lake typology, such as altitude, maximum depth, and alkalinity, the latter serving as an indicator of the geological influence on water chemistry. The GLFI also integrates pressure indicators, including the percentage of non-natural land cover (NNLC) in the drainage basin, the Lake Habitat Modification Score (LHMS), reflecting the extent of overall degradation [37], and the Total phosphorus (TP) concentrations (µg/L) in water, as a proxy for nutrient enrichment and eutrophication. The GLFI produces a score ranging from 0 (highly degraded conditions) to 1 (undisturbed conditions) [36]. Additionally, the lake’s ecological quality, as evaluated by various Greek biological indices—including the phytoplankton index (HeLPhy) [30], the benthic macroinvertebrate index (GLBiI) [31], and the macrophyte index (HeLM) [32]—was obtained from the available literature. Finally, the “one-out, all-out” approach was applied to determine the lake’s ecological status. According to this approach, the overall status of a water body is assigned based on the lowest classification among the assessed biological quality elements [38].

2.4. The SWOT–AHP Method

SWOT analysis is a structured decision-support tool used to qualitatively identify and evaluate the internal and external factors influencing ecosystem management. It helps identify the strengths, weaknesses, opportunities, and threats affecting a lake’s ecological integrity [39,40,41,42].
In lake ecosystems, typical strengths include biodiversity, legal protection (e.g., Natura 2000), and low anthropogenic disturbance. Weaknesses may involve insufficient long-term monitoring, invasive species, or hydrological instability. Opportunities can arise from conservation funding, policy support, or local engagement. Threats include climate-induced droughts, nutrient loading, illegal species introductions, or land-use change. Combined with ecological assessment, SWOT provides a framework for identifying conservation needs and informing policy-aligned management strategies [43].
To transform qualitative SWOT results into measurable decision criteria, the Analytic Hierarchy Process (AHP) can be employed [17,44]. AHP is a multi-criteria decision-making (MCDM) technique that allows pairwise comparison of alternatives and criteria to assign relative importance values [45,46].
The SWOT–AHP process used in this study included three main levels:
  • Goal level—Prioritizing effective, sustainable management strategies for Lake Paralimni.
  • Criteria level—SWOT categories (strengths, weaknesses, opportunities, threats).
  • Alternative level—Proposed strategies for conservation and lake management.
Key SWOT elements were identified through a combination of field-based ecological quality assessment, literature reviews, focused-group discussions with stakeholders (fishermen, ecologists, planners), and expert consultation with fisheries biologists and regional water authorities.
Each identified factor was inserted into a pairwise comparison matrix using Saaty’s 1–9 scale (Table 2), where 1 indicates equal importance, and 9 represents extreme importance of one element over another as determined through expert judgment.
The priority weight vector for each matrix was calculated by normalizing each column (i.e., dividing each element by its column sum) and then averaging the rows. This process yields the relative weight of each element within its matrix. To ensure that the comparisons were logically consistent, a consistency test was performed. Initially, the Weighted Sum Vector (WSV) was calculated by multiplying the comparison matrix A by the priority weights vector w (i.e., WSV = A × w). Subsequently, each row of the WSV was divided by its corresponding priority weight to yield the consistency vector λ i = W S V i w i and then the principal eigenvalue λ m a x = Σ λ i n was estimated. The above was used to estimate the Consistency Index ( C I = λ m a x − n n − 1 ) with n the number of rows and finally the Consistency Ratio ( C R = C I R I ). RI is a Random Index (depends on the matrix sizes, e.g., for n = 4, RI = 0.90, and for n = 5, RI = 1.12 [47]). This ratio is computed to measure the consistency of pairwise comparisons. A CR below an acceptable threshold (typically 0.1) confirms that the comparisons are logically consistent and reliable for decision-making [18,44,47,48].
The SWOT–AHP approach was applied to Lake Paralimni to guide management priorities for fish community sustainability. Based on the combined ecological and stakeholder inputs:
  • SWOT categories were ranked by importance (e.g., threats > weaknesses > strengths > opportunities),
  • Factors within each SWOT group were weighted (e.g., Water Level Fluctuations, Climate-induced Droughts),
  • Management strategies were evaluated and prioritized across three AHP criteria: environmental impact, feasibility, and urgency.
The weighted results were integrated into a final decision matrix to guide management action planning. A visual representation of this framework is presented in Figure 2.

3. Results

3.1. Field Survey

The vertical profile of temperature (T, °C) and dissolved oxygen (DO, mg/L) recorded in the water column during the field survey is depicted in Figure 2. Dissolved oxygen (DO) concentrations exhibited a gradual decline below a depth of 6 m. Near the surface, DO levels exceeded 10 mg/L, decreasing steadily to approximately 6 mg/L at a depth of 11 m (Figure 2). In contrast, temperature remained relatively stable throughout the water column, ranging from 18.4 °C to 19.2 °C, with only a slight decline observed in the bottom layers (Figure 3).
As for the fish, a total of 3635 fish, with a combined weight of approximately 81 kg, were caught during the survey, representing six species from three families (Table 3). The most abundant species in terms of the number of individuals was Luciobarbus graecus, followed closely by Leucos ylikiensis (Table 3). In terms of biomass, Leucos ylikiensis was the dominant species, followed by Luciobarbus graecus. The presence of the alien Carassius gibelio was also confirmed in the lake. Overall, the fish community of Lake Paralimni was dominated by native and endemic species, while the introduced species (Carassius gibelio and Silurus aristotelis) accounted for only a small proportion of the total catch.
The highest fish abundance and biomass were recorded in the shallow zone (0–2.9 m depth), whereas the deepest zone (>6 m depth) exhibited the lowest abundance and biomass (Figure 4). However, zero catches were not observed at any depth (Figure 5).

3.2. Ecological Quality

Omnivorous species accounted for 47.04% of the total biomass in the benthic gillnet catch, while introduced species represented 2.59% of the total number of individuals. The Ecological Quality Ratio (EQR) for omnivorous species biomass (EQR-OMNIb) was 0.752, and for introduced species abundance (EQR-Introduceda) it was 0.613. These values yielded a final GLFI score of 0.68, corresponding to a “Good” ecological quality classification for Lake Paralimni.
The lake’s ecological quality assessment, incorporating different biological quality elements and multi-metric indices, yielded the following results: GLFI indicated a “Good” status, HeLPhy and HeLM both indicated a “High” status [30,32], while GLBiI assessed a “Moderate” status [31]. Thus, based on the “one-out, all-out” principle, the overall ecological status of the lake was classified as “Moderate”.

3.3. SWOT–AHP Analysis

The aggregation of primary and secondary data available for Lake Paralimni resulted in the list of SWOT factors presented in Table 4.
The AHP analysis showed that threats (53.93%) were the most critical factor for Lake Paralimni’s management, followed by weaknesses (29.50%), while strengths (11.01%) and opportunities (5.56%) were assigned lower priority (Table 5). The CI was 0.0782, and the CR was 0.0869 (i.e., <0.1), confirming acceptable consistency and reliability of the comparisons.
Within strengths, the low abundance of invasive species was the most significant factor (38.4%), followed by biodiversity (30.0%) and Natura 2000 protection (19.1%) (Table 6). Among weaknesses, water level fluctuations were identified as the most critical issue (55.8%), reflecting the lake’s hydrological instability, followed by connectivity risks (26.3%), which increase the potential for species introductions (Table 6). Conservation and restoration initiatives (55.8%) ranked as the most valuable opportunity, whereas climate change and droughts (49.3%) emerged as the most severe threat, emphasizing the risk of declining water levels (Table 6).
The AHP analysis used to prioritize management measures for Lake Paralimni was structured to ensure consistency between environmental impact and urgency (Table 7), reflecting the assumption that the ecological significance of each measure is inherently tied to its immediacy of implementation. Under this framework, Hydrological regulation and water level management emerged as the top priority, combining the highest feasibility (50.28%) with substantial environmental impact and urgency (42.45% each) (Table 7). Climate adaptation and drought mitigation ranked as a high-priority action, with scores exceeding 26% across all criteria. Illegal species monitoring and prevention was classified as a moderate priority (17.7% for both impact and urgency; 13.4% feasibility). Agricultural runoff control was ranked lower due to feasibility constraints (6.8%) despite moderate ecological importance (8.4%). Lastly, Conservation and habitat restoration was identified as a long-term action, with the lowest scores across all dimensions (4.2% impact and urgency; 3.5% feasibility).
These strategic priorities are visualized in Figure 6, which presents the average relative weights of the five key management strategies across the three AHP evaluation criteria.

4. Discussion

4.1. Fish Fauna Composition and Ecological Insights

The results of the fish monitoring survey in Lake Paralimni reveal valuable insights into the structure and distribution of its fish community, offering guidance for future ecosystem management strategies. The fish assemblage in Lake Paralimni is characterized by a predominance of native and endemic species, although introduced species such as Carassius gibelio and Silurus aristotelis were also recorded.
It is worth mentioning here that this is the first documentation of Carassius gibelio in Lake Paralimni. According to local fishermen, this species was absent prior to the early 2000s. Its introduction was likely facilitated either through hydrological connectivity with Lake Yliki or via informal stocking by local anglers/fishermen. The introduction of non-native fish species, whether deliberate or accidental, is a common phenomenon worldwide with potentially significant ecological implications. While the full extent of these impacts often remains uncertain [49,50], non-native species introductions generally contribute to the homogenization of aquatic ecosystems, posing risks to native biodiversity and altering ecosystem functioning [51,52,53]. The absence of Pelasgus marathonicus and Telestes beoticus in this survey is also noteworthy. These species, typically associated with riverine environments, may have historically been present but have declined due to past hydrological alterations and habitat fragmentation.
Similarly, the absence of Anguilla anguilla in the catch may be attributed to a combination of factors. These include the known limitations of gillnet sampling and the broader population decline observed across Europe—caused by overfishing, habitat degradation, and migration barriers [54,55]. Moreover, the recruitment of the species in Lake Paralimni may be further impeded by the disrupted connectivity with the sea, as overflow events toward the Euboean Gulf have become increasingly rare in recent years, thereby hindering the upstream migration and recolonization of Anguilla anguilla.
The relatively low abundance of non-native species in Lake Paralimni represents a positive ecological indicator. Introduced species are known to impact native fish populations through competition, predation, hybridization, habitat degradation, and disease transmission [56,57]. Even at low densities, introduced species can initiate long-term ecosystem shifts, as their ecological effects often unfold gradually over time [50], particularly in ecosystems with high endemic biodiversity like Lake Paralimni. The persistence of native and endemic species in the lake suggests that, thus far, non-native introductions have not caused major ecological imbalances, further indicating a relatively stable trophic web. However, without continuous monitoring, it remains uncertain whether their presence will eventually disrupt trophic interactions or induce shifts in community structure. Additionally, the ecological role of Silurus aristotelis, translocated from Western Greece, warrants further investigation, as predatory species can significantly influence prey abundance and trophic dynamics [58,59].
Fish abundance and biomass were highest in the shallow zones (0–2.9 m), reflecting the ecological preferences of many species for warmer, more productive areas with abundant food resources and a heterogeneous microhabitat structure [60]. These conditions are likely optimal for growth and reproduction [61]. In contrast, the lowest values were recorded in deeper zones (>6 m), likely due to reduced resource availability and lower temperatures [62]. However, the absence of zero catches in these deeper areas suggests that fish were distributed throughout the water column, likely supported by dissolved oxygen concentrations remaining above 5 mg/L. The lake’s temperature and oxygen profiles indicated well-mixed thermal conditions, with moderate oxygen depletion at depth—possibly driven by limited light penetration and reduced biological activity. Notably, hypoxic conditions commonly observed in eutrophic Mediterranean lakes [63,64] were not detected in this study.

4.2. Ecological Quality

The Greek Lake Fish Index (GLFI) developed using functional groups rather than individual species identities [29], provides a robust ecological assessment framework for Greek lakes with high endemic fish diversity. The classification of Lake Paralimni as having “Good” ecological quality under the GLFI indicates a moderate level of ecological integrity despite its history of hydrological disturbances. This suggests that the lake has maintained functional ecological processes and has not suffered severe degradation from eutrophication, pollution, or excessive anthropogenic pressures. However, this classification was somewhat unexpected, considering the lake’s history of hydrological instability, including its complete desiccation from 1991 to 1996. The recovery of the fish community likely reflects the positive influence of hydrological connectivity with Lake Yliki, which facilitated recolonization, along with limited fishing pressure that allowed populations to rebound (personal communication with professional fishermen).
Despite the GLFI classification, the overall ecological status of Lake Paralimni was downgraded to “Moderate” due to the integration of multiple biological indices using the “one-out, all-out” approach. Specifically, the Greek Lake Benthic Invertebrate Index (GLBiI) assessed the lake as “Moderate” [31]. These discrepancies between indices reflect differences in biological responses to environmental stressors, as fish, phytoplankton, macrophytes, and benthic macroinvertebrates respond uniquely to variations in water quality, hydrology, and habitat conditions. Discrepancies may also arise from differences in sampling periods and indicator sensitivities. These findings underscore the importance of a multidimensional assessment approach, as emphasized by [19]. By integrating multiple biological indices, a more comprehensive evaluation of ecological conditions can be achieved, ensuring that potential stressors affecting different biological communities are effectively captured.

4.3. The SWOT–AHP Analysis in Fish and Water Resources Management

SWOT and AHP analyses have been widely utilized in water resource and aquatic ecosystem management, highlighting their role in sustainable conservation strategies [16,18,65]. These frameworks provide a structured approach for assessing ecological, economic, and social factors that influence decision-making [16,18,65,66]. Their application spans diverse aquatic environments, including freshwater lentic and lotic systems, as well as coastal and marine ecosystems [16,18,65,66,67,68]. Although the outcomes of these analyses may be influenced by author subjectivity [69], they continue to offer valuable insights for ecosystem management.
In this study, the combined use of SWOT and AHP analyses was employed to identify key conservation and management priorities for a Mediterranean lake, with a focus on sustaining its fish fauna. The approach revealed notable strengths, such as the dominance of native fish species, alongside key weaknesses like water level fluctuations. Identified opportunities included the promotion of sustainable fisheries practices, while primary threats encompassed the impacts of climate change and species introductions—factors known to influence lake ecosystems [8,70]. Similar methodologies have been applied in fisheries conservation globally. For instance, [71] used a SWOT framework to evaluate sturgeon stock restoration in the Iranian waters of the Caspian Sea, identifying major threats such as ineffective management, unsustainable fishing, habitat degradation, and socio-economic pressures. Likewise, [67] implemented a combined SWOT–AHP approach to design a sustainable fisheries strategy in a marine protected area in Indonesia, highlighting the value of structured decision-making in balancing conservation goals with economic needs. These examples further underscore the utility of SWOT and AHP analyses in supporting sustainable resource management across aquatic systems.

4.4. Management Priorities and Conservation Strategies

Our study highlighted the key ecological dynamics and conservation challenges in Lake Paralimni, underscoring the necessity for targeted management interventions. Based on the SWOT–AHP analysis, the most pressing concerns for the lake’s fish community revolve around hydrological instability, climate-induced drought risks, and the potential ecological impacts of introduced species. To address these challenges, a multi-faceted, science-based management strategy is required, aligning with the principles of ecosystem-based management and the objectives of the WFD.
Hydrological regulation and water level management should be prioritized to prevent excessive water withdrawals, particularly during dry seasons. Implementing adaptive water management strategies, such as controlled water transfers from Lake Yliki, could mitigate extreme fluctuations. A hydrological monitoring network would provide real-time data on water levels, rainfall, and inflows, allowing timely interventions [70]. Establishing drought contingency plans, informed by climate modeling and hydrological assessments, would improve preparedness for extreme weather events.
Eutrophication prevention is another critical issue, as agricultural runoff remains a potential threat [72], emphasizing the need for adaptive nutrient management strategies. Enforcing stricter agricultural runoff regulations, including controlled fertilizer application, could minimize the risk of eutrophication. Introducing buffer zones and restoring riparian vegetation would help filter nutrients and sediments before they reach the lake [73], and also, along with the restoration of wetland habitats, will enhance water retention and reduce the impacts of seasonal droughts. A long-term water quality monitoring program should be maintained to track nutrient concentrations and detect early signs of degradation.
Species introductions continue to pose a significant concern, underscoring the need for stricter regulations to prevent unauthorized fish stocking. This is particularly important as rising temperatures may increasingly favor invasive species over native ones, potentially disrupting trophic interactions and further stressing native fish populations [72,74]. To address this, public outreach programs targeting local fishermen and recreational anglers should highlight the ecological risks associated with illegal introductions. In parallel, a systematic monitoring program should be implemented to track both the abundance and ecological impact of non-native species.
Sustainable fisheries management offers an opportunity for conservation and economic benefits. Establishing a regulated recreational fishing framework and incorporating catch-and-release policies for vulnerable native species could support conservation efforts while fostering ecotourism. The introduction of a permit system for recreational anglers, currently absent in Greece [75], could generate revenue that could be reinvested in conservation and monitoring programs.
Scientific data should play a central role in policy-making and management strategies. Ecological indices like the GLFI provide valuable insights into the lake’s ecological status, and decision-makers should incorporate these assessments into water management policies. Strengthening collaborations between researchers, policymakers, and local stakeholders would enhance adaptive management efforts, ensuring that conservation strategies evolve in response to emerging threats and ecological changes.
Public engagement is essential for long-term conservation success. Raising awareness about the lake’s ecological significance, biodiversity value, and conservation challenges through education programs and outreach initiatives can foster a sense of stewardship among local communities. Organizing stakeholder workshops, citizen science programs, and educational campaigns focused on the risks of invasive species, sustainable fishing practices, and climate resilience can improve compliance with conservation regulations.
Overall, Lake Paralimni serves as an important case study highlighting the value of integrating ecological assessments with structured decision-making tools like SWOT and AHP. This approach not only identifies key conservation priorities but also provides a framework for sustainable lake management that can be applied to similar freshwater ecosystems. We acknowledge that future work could incorporate more rigorous methodologies, including long-term ecological monitoring, advanced modeling, and participatory stakeholder engagement.

5. Conclusions

This study demonstrates that the ecological sustainability of shallow Mediterranean lakes such as Lake Paralimni depends on the implementation of a scientifically informed, ecosystem-based management approach. Through the integration of a biological quality index, the SWOT–AHP analysis identified critical stressors, including hydrological instability and nutrient enrichment, underscoring the need for targeted remediation efforts. Key management priorities include enhancing hydrological regulation, mitigating eutrophication through nutrient load reductions, controlling non-native species, and reinforcing catchment-level land-use planning. Given the vulnerability of Mediterranean lakes to seasonal fluctuations, eutrophication, and anthropogenic pressures, these priorities should be pursued within the framework of adaptive management strategies that are responsive to climatic variability and anthropogenic drivers. Furthermore, aligning these actions with the objectives of the EU Water Framework Directive and leveraging structured decision-support tools—such as the integrated SWOT–AHP framework presented in this study—can facilitate more transparent and evidence-based policy formulation. The methodological approach employed here provides a transferable model for assessing and managing similar lentic ecosystems facing multifactorial pressures across the Mediterranean basin, particularly under similar socio-economic and ecological conditions, including EU water policy frameworks.

Author Contributions

Conceptualization: O.P.; Developing methods: O.P.; Conducting the research: O.P. and D.C.B.; Data analysis: O.P. and D.C.B.; Data interpretation and Preparation of figures and tables: O.P.; Writing: O.P. and D.C.B. All authors have read and agreed to the published version of the manuscript.

Funding

This research was financed by the Goulandris Natural History Museum Greek Biotope/Wetland Centre in the framework of the research project “Fish sampling in Greek lakes”.

Institutional Review Board Statement

The research received approval from the relevant committee in Greece for the conducted fish samplings.

Data Availability Statement

The data supporting the findings of this study are available within the paper. For additional information, please contact the corresponding author.

Acknowledgments

The authors would like to thank the four anonymous reviewers for their valuable comments and suggestions, which helped improve the clarity and quality of this manuscript. During the preparation of this manuscript, the authors used ChatGPT (OpenAI, GPT-4) for the purposes of language editing and refinement. The authors have reviewed and edited the output and take full responsibility for the content of this publication.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Location map of Lake Paralimni and the Boeotian Kifissos River basin. The sampling stations where benthic gillnets were deployed for fish monitoring in October 2022 are also indicated (S1, S2, …S20).
Figure 1. Location map of Lake Paralimni and the Boeotian Kifissos River basin. The sampling stations where benthic gillnets were deployed for fish monitoring in October 2022 are also indicated (S1, S2, …S20).
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Figure 2. Hierarchical flowchart of the methodology followed, combining biological assessment and SWOT–AHP analysis.
Figure 2. Hierarchical flowchart of the methodology followed, combining biological assessment and SWOT–AHP analysis.
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Figure 3. Vertical profiles of temperature (T, °C) and dissolved oxygen (DO, mg/L) in the water column of Lake Paralimni, recorded in October 2022. Temperature is shown in black and DO in grey.
Figure 3. Vertical profiles of temperature (T, °C) and dissolved oxygen (DO, mg/L) in the water column of Lake Paralimni, recorded in October 2022. Temperature is shown in black and DO in grey.
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Figure 4. Fish abundance Ν (number of individuals) and biomass (kg) per depth zone (m) in Lake Paralimni, October 2022. The numbers above each column represent the number of gillnets deployed in each depth zone.
Figure 4. Fish abundance Ν (number of individuals) and biomass (kg) per depth zone (m) in Lake Paralimni, October 2022. The numbers above each column represent the number of gillnets deployed in each depth zone.
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Figure 5. Box-and-whisker plots of fish catches per sampling station, based on the number of individuals (NPUE, n/gillnet) and biomass (BPUE, kg/gillnet) in Lake Paralimni, October 2022. The horizontal line within the box represents the median value, while the “x” marker denotes the mean. The box represents the interquartile range (IQR), encompassing 50% of the data between the first (Q1) and third quartile (Q3). The vertical whiskers extend to the minimum and maximum values within the data range, excluding outliers, which are represented as circles.
Figure 5. Box-and-whisker plots of fish catches per sampling station, based on the number of individuals (NPUE, n/gillnet) and biomass (BPUE, kg/gillnet) in Lake Paralimni, October 2022. The horizontal line within the box represents the median value, while the “x” marker denotes the mean. The box represents the interquartile range (IQR), encompassing 50% of the data between the first (Q1) and third quartile (Q3). The vertical whiskers extend to the minimum and maximum values within the data range, excluding outliers, which are represented as circles.
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Figure 6. Strategic polygon illustrating the prioritization of management strategies—hydrological regulation, climate adaptation, illegal species prevention, agricultural runoff control, and habitat restoration—based on AHP-derived weights for Environmental impact, Feasibility, and Urgency in Lake Paralimni.
Figure 6. Strategic polygon illustrating the prioritization of management strategies—hydrological regulation, climate adaptation, illegal species prevention, agricultural runoff control, and habitat restoration—based on AHP-derived weights for Environmental impact, Feasibility, and Urgency in Lake Paralimni.
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Table 1. Fish species reported in Lake Paralimni [25,26].
Table 1. Fish species reported in Lake Paralimni [25,26].
FamilySpeciesOriginIUCN
Status
AnguillidaeAnguilla anguilla (Linnaeus, 1758)NCR
CyprinidaeCyprinus carpio Linnaeus, 1758NLC
Luciobarbus graecus (Steindachner, 1895)NLC
LeuciscidaePelasgus marathonicus (Vinciguerra, 1921)NNT
Leucos ylikiensis (Economidis, 1991)NEN
Scardinius graecus Stephanidis, 1937NEN
Telestes beoticus (Stephanidis, 1939)NEN
SiluridaeSilurus aristotelis Garman, 1890TEN
XenocyprididaeCtenopharyngodon idella (Valenciennes, 1844) ALC
Hypophthalmichthys molitrix (Valenciennes, 1844)ANT
Hypophthalmichthys nobilis (Richardson, 1845)ADD
Total species number 11
N: Native, A: Alien, T: Translocated. The nomenclature and classification of species into families follow the latest taxonomic updates [27]. The conservation status categories are as follows: CR: Critically Endangered, EN: Endangered, NT: Near Threatened, LC: Least Concern, DD: Data Deficient.
Table 2. Scale of comparative importance in pairwise comparisons between SWOT factors, using Saaty’s 1–9 scale [47].
Table 2. Scale of comparative importance in pairwise comparisons between SWOT factors, using Saaty’s 1–9 scale [47].
Intensity of ImportanceDefinition Explanation
1Equal importance Two activities contribute equally to the objective.
3Moderate importance Experience and judgment slightly favor one activity over another.
5Strong importance Experience and judgment strongly favor one activity over another.
7Very strong importanceAn activity is favored very strongly over another; its dominance is demonstrated in practice.
9Extreme importanceThe evidence favoring one activity over another is of the highest possible order of affirmation.
2, 4, 6, 8Intermediate values Intermediate values for compromise between the above judgments.
1/3, 1/5, 1/7, 1/9Values for inverse comparison
Table 3. List of fish species recorded in Lake Paralimni during the fish monitoring survey (October 2022). The total number of individuals (N) and total biomass (W, kg) per species are provided. The species classification into feeding groups according to their diet is also provided.
Table 3. List of fish species recorded in Lake Paralimni during the fish monitoring survey (October 2022). The total number of individuals (N) and total biomass (W, kg) per species are provided. The species classification into feeding groups according to their diet is also provided.
FamilySpeciesΝ (Number of Individuals)W (kg)Feeding Group
CyprinidaeCarassius gibelio292.36OMNI
Cyprinus carpio26311.44OMNI
Luciobarbus graecus165824.47OMNI
LeusiscidaeLeucos ylikiensis157930.14INV
Scardinius graecus411.19HERB
SiluridaeSilurus aristotelis6511.76PISC
Total 363581.36
Omnivores (OMNI), Benthivores (INV), Herbivores (HERB), Piscivores (PISC).
Table 4. Strengths, Weaknesses, Opportunities, and Threats (SWOT) analysis for the fish fauna of Lake Paralimni.
Table 4. Strengths, Weaknesses, Opportunities, and Threats (SWOT) analysis for the fish fauna of Lake Paralimni.
StrengthsWeaknesses
  • Rich native biodiversity: The lake hosts several endemic and native fish species, indicating a relatively healthy ecosystem.
  • Low abundance of invasive species: The presence of introduced (including translocated species) is limited, which is a positive indicator of ecosystem integrity.
  • Natura 2000 protection: The lake benefits from legal protection, which may help mitigate future threats.
  • Limited fishing pressure: Low commercial and recreational fishing activity does not put stress on fish populations.
  • Water level fluctuations: The historical desiccation (1991–1996) highlights hydrological instability and vulnerability to water withdrawals.
  • Connectivity with Lake Yliki: While connectivity helps recolonization, it also increases the risk of species introductions.
  • Limited long-term monitoring: Fish population assessments are not regularly conducted, making it difficult to track ecological trends.
  • Commercial and recreational fishing: Even though commercial and recreational fishing activity is currently limited, it has the potential to increase pressure on certain fish populations.
OpportunitiesThreats
  • Conservation and restoration initiatives: Potential for improving water management and implementing conservation actions.
  • Public awareness and education: Developing programs for local fishermen and communities could help prevent unauthorized fish introductions.
  • Sustainable fishing practices: Game fishing within the framework of catch-and-release competitions could serve as an alternative form of tourism, while the requirement for a paid recreational fishing license would generate revenue for the Greek state.
  • Use of scientific data for policy-making: Findings from this study could be used to inform environmental policies and water management regulations.
  • Illegal species introductions: Unauthorized fish stocking by local fishermen could disrupt the ecosystem and outcompete native species.
  • Climate change and droughts: Increased drought risk could further reduce water levels and impact fish habitats.
  • Eutrophication: Agricultural runoff and nutrient pollution could increase the risk of eutrophication, leading to oxygen depletion and fish mortality.
  • Urban expansion and land-use changes: Increasing non-natural land cover in the watershed could degrade water quality and disrupt habitats.
Table 5. Pairwise Comparison using Saaty’s 1–9 scale and Priority Weights of SWOT Factors in the AHP Analysis for Lake Paralimni.
Table 5. Pairwise Comparison using Saaty’s 1–9 scale and Priority Weights of SWOT Factors in the AHP Analysis for Lake Paralimni.
CriteriaStrengthsWeaknesses Opportunities Threats Priority Weights
Strengths11/531/50.110
Weaknesses5151/30.295
Opportunities 1/31/511/70.056
Threats53710.539
λ_max ≈ 4.235, RI = 0.90 (Random Index for n = 4), CI (Consistency Index) = 0.0782, CR (Consistency Ratio) = 0.0869.
Table 6. Pairwise comparisons of factors within each SWOT category (Strengths, Weaknesses, Opportunities, and Threats) using Saaty’s 1–9 scale for Lake Paralimni.
Table 6. Pairwise comparisons of factors within each SWOT category (Strengths, Weaknesses, Opportunities, and Threats) using Saaty’s 1–9 scale for Lake Paralimni.
StrengthsBiodiversityInvasive SpeciesNatura 2000Low Fishing PressurePW
Biodiversity11/5230.300
Invasive species21220.384
Natura 20001/21/2120.191
Low fishing pressure1/31/21/210.126
WeaknessesWater level fluctuationsConnectivity risksLimited monitoringCommercial/
recreational fishing		PW
Water level fluctuations13570.558
Connectivity risks1/31350.263
Limited monitoring1/51/3130.122
Commercial/recreational fishing1/71/51/310.057
OpportunitiesConservation and restoration initiativesPublic awareness/educationSustainable fisheriesUse of scientific data for policy-makingPW
Conservation and restoration initiatives13570.558
Public awareness/education1/31350.263
Sustainable fisheries1/51/3130.122
Use of scientific data for policy-making1/70.21/310.057
ThreatsIllegal species introductionsClimate change-droughtsEutrophicationUrban expansion and land-use changesPW
Illegal species introductions11/2570.350
Climate change—droughts21570.493
Eutrophication1/51/5130.106
Urban expansion and land-use changes1/71/71/310.051
PW: Priority weights. In all cases, CR < 0.1.
Table 7. Pairwise comparisons of five key management strategies for Lake Paralimni evaluated based on three criteria: Environmental impact, Feasibility, and Urgency. The comparisons were conducted using Saaty’s 1–9 scale.
Table 7. Pairwise comparisons of five key management strategies for Lake Paralimni evaluated based on three criteria: Environmental impact, Feasibility, and Urgency. The comparisons were conducted using Saaty’s 1–9 scale.
Environmental ImpactHydrological Regulation/Water Level ManagementClimate Adaptation/Drought MitigationIllegal Species Monitoring/PreventionAgricultural Runoff ControlConservation/Habitat RestorationPW
Hydrological regulation/Water level management123570.425
Climate adaptation/Drought mitigation1/212460.273
Illegal species monitoring/prevention1/31/21350.177
Agricultural runoff control 1/51/41/3130.084
Conservation/Habitat restoration1/71/61/51/310.042
Feasibility
Hydrological regulation/Water level management135790.503
Climate adaptation/Drought mitigation1/313570.260
Illegal species monitoring/Prevention1/51/31350.134
Agricultural runoff control 1/71/51/3130.068
Conservation/Habitat restoration1/91/71/51/310.035
Urgency
Hydrological regulation/Water level management123570.425
Climate adaptation/Drought mitigation1/212460.273
Illegal species monitoring/Prevention1/31/21350.177
Agricultural runoff control 1/51/41/3130.084
Conservation/Habitat restoration1/71/61/51/310.042
PW: Priority weights. In all cases, CR < 0.1.
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Petriki, O.; Bobori, D.C. Ecological Assessment and SWOT–AHP Integration for Sustainable Management of a Mediterranean Freshwater Lake. Sustainability 2025, 17, 4950. https://doi.org/10.3390/su17114950

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Petriki O, Bobori DC. Ecological Assessment and SWOT–AHP Integration for Sustainable Management of a Mediterranean Freshwater Lake. Sustainability. 2025; 17(11):4950. https://doi.org/10.3390/su17114950

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Petriki, Olga, and Dimitra C. Bobori. 2025. "Ecological Assessment and SWOT–AHP Integration for Sustainable Management of a Mediterranean Freshwater Lake" Sustainability 17, no. 11: 4950. https://doi.org/10.3390/su17114950

APA Style

Petriki, O., & Bobori, D. C. (2025). Ecological Assessment and SWOT–AHP Integration for Sustainable Management of a Mediterranean Freshwater Lake. Sustainability, 17(11), 4950. https://doi.org/10.3390/su17114950

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