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Article

Climate Warming and Mismanagement Drive the Shift of Fish Communities in the Wadi El-Rayan Arid Lakes

by
Ahmed A. Abdelhady
1,
Mohamed Samy-Kamal
2,
Esam Ismail
1,
Ali M. Hussain
1,
Dimitra E. Gamvroula
3,*,
Ahmed Ali
1,
Mohamed S. Ahmed
4,
Khalaf H. M. Abdel-Raheem
1,5,6,
Hakim Saibi
7,
Mabrouk Sami
7,*,
Dimitrios E. Alexakis
3 and
Mahmoud M. Khalil
1
1
Geology Department, Faculty of Science, Minia University, El-Minia 61519, Egypt
2
Departamento de Ciencias del Mar y Biología Aplicada, Universidad de Alicante, Edificio Ciencias V, Campus de San Vicente del Raspeig, P.O. Box 99, 03080 Alicante, Spain
3
Laboratory of Geoenvironmental Science and Environmental Quality Assurance, Department of Civil Engineering, School of Engineering, University of West Attica, 250 Thivon & P. Ralli Str., GR 12241 Athens, Greece
4
Geology and Geophysics Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
5
State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
6
University of Chinese Academy of Sciences, Beijing 100049, China
7
Geosciences Department, College of Science, United Arab Emirates University, Al Ain 15551, United Arab Emirates
*
Authors to whom correspondence should be addressed.
Water 2024, 16(18), 2685; https://doi.org/10.3390/w16182685
Submission received: 21 August 2024 / Revised: 14 September 2024 / Accepted: 18 September 2024 / Published: 21 September 2024
(This article belongs to the Section Biodiversity and Functionality of Aquatic Ecosystems)
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Abstract

:
The Wadi El-Rayan lakes are important aquatic environments located at the border of the great North African Sahara. Quantifying the temporal changes in these lakes due to natural and/or anthropogenic stressors is critical when assessing potential impacts on aquatic ecosystem health and the sustainability of fisheries. To detect the changes in fish communities and their drivers, the landing composition of the Wadi El-Rayan lakes over the past 30 years was quantitatively analyzed. The areas of the lakes dramatically decreased from 110 km2 in 1991 to 73 km2 in 2019. The loss of the lake area was attributed to climate warming, where the evaporation rate exceeded the volume of recharge and the recharge decreased due to an increase in agriculture and aquaculture. The total landing significantly increased in the past three decades due to an increase in the fishing effort (number of licensed boats). Nile tilapia, mullet, and grass carp dominated the landings. The pelagic-to-demersal ratio indicated a shift in the fish community composition towards demersal species. This shift was attributed to an increase in the eutrophication level. The fish communities of the landing data were clustered into four distinct groups. These clusters were significantly differentiated (p < 0.001) in both a PERMANOVA test and a PCA plot. There was a gradual replacement of the dominant species among these clusters. The most recent cluster (2018–2019) was characterized by rare species dominating the community. This shift in species composition suggests that target taxa may have been overexploited. The total landing also decreased, which may have been a result of climate warming. Furthermore, the presence of alien and warm-water species significantly increased. The fish community structure and composition shift could be attributed to anthropogenic (mismanagement) and natural climatic changes (warming).

1. Introduction

Lake temperatures are rising globally, impacting aquatic ecosystems. As documented in [1,2,3], seasonal temperatures now include extreme heatwaves. Understanding the potential impact on fish communities is crucial for the maintenance of healthy aquatic ecosystems and the promotion of sustainable development.
Climate warming may directly and indirectly influence fish communities [4]. Many fish are ectotherms, so minor changes can crucially impact their physiology [5,6,7,8]. Usually, warming is associated with a decrease in water levels, an increase in eutrophication, and an increase in salinity. These changes significantly affect fish metabolism, shifting diversity, abundance, and geographic ranges. In addition, lake temperatures impact the body size of fish [9]. Furthermore, the community structure of fish changes (e.g., warm- vs. cold-water species, freshwater vs. brackish or marine species, and demersal vs. pelagic species).
Fish are one of the dominant animal groups in aquatic ecosystems but anthropogenic activities significantly threaten them. Both natural climatic changes and anthropogenic influences exert high pressure on the temporal dynamics of fish communities. Moreover, the documentation of biotic and abiotic interactions in fish ecosystems remains incomplete and unclear [10,11,12]. Our study aimed to interpret the effects of climate warming on the fish communities of the Wadi El-Rayan lakes.
In arid zones, frequent droughts, eutrophication, and low-water-level-induced hypoxia can threaten many species, especially stenothermal species that cannot adapt to thermal changes. Consequently, their geographic ranges may shrink, and extinction becomes a possibility. In contrast, the ranges of eurythermal species that can adapt to new thermal conditions experience expanded geographic ranges [13,14]. The Wadi El-Rayan lakes in Egypt are a typical example of inland lakes that face the challenge of climate warming. According to [15], the Wadi El-Rayan lakes are highly vulnerable due to the mismanagement of their water resources, which could lead to resource depletion and ecosystem deterioration. Despite their diverse fisheries, the relative significance of the Wadi El-Rayan lakes in Egypt’s fish production remains limited (0.24% [16]). Therefore, understanding how these ecosystems respond to climate warming is crucial to set realistic targets to mitigate climate-change impacts.
Herein, we analyzed lake fish-landing data to assess temporal variations and their potential drivers. The composition of fishery landings is a valuable indicator of fishery health, where changes over time can be linked to various factors [12,17]. It is widely recognized that fishing yield correlates with fish diversity [18]. Additionally, landing data provide insights into the overall health and stability of an ecosystem [19]. Furthermore, data obtained from trawl surveys were correlated with landing data [20,21,22].

2. Materials and Methods

2.1. Study Area

Wadi El-Rayan is a natural depression, with a total area of 1759 km2 and a depth of 42 m below sea level. It is a part of the Faiyum Oasis to the west of the Nile River, 140 km southwest of Cairo (Figure 1). Faiyum Oasis is located on the eastern margin of the North African desert region that extends from Egypt in the east to Morocco in the west. Ten million years ago, the old delta of the Nile was the Faiyum depression. Ten thousand years ago, fine-grained sediments (silt and clay) of the Nile Valley accumulated when the Nile flooded and overflowed into the Faiyum depression via the Hawara Channel, forming ancient Lake Moeris. This lake was solely fed by the Nile floods. More than five thousand years ago, ancient Egyptians inhabited the shoreline of Lake Moeris. Wadi El-Rayan is now a protected area on the margin of the great Sahara and includes two lakes artificially created between 1970 and 1980 by a governmental drainage project. The two lakes have different elevations and are connected by a narrow channel that features Egypt’s only waterfall (Figure 1). The lakes have a remarkable biodiversity, including many wild plants, zooplankton, phytoplankton, macrobenthos, birds, reptiles, and mammals. Therefore, the area was designated as a Protected Area in 1989. Agricultural land reclamation, fish farming, petroleum exploration, and tourist activities have negatively affected the water quality.
Wadi El-Rayan is characterized by a hot and dry climate, with rare rain in the winter (i.e., typical Saharan). Wadi El-Rayan has been classified as a hyperarid region, with mild winters and hot summers [23]. The average evaporation rate is 3.2 in winter and up to 25.7 in summer. The water temperature varies between 14 °C in December and 29 °C in August. The pH is alkaline all year, with slight spatial differences and no significant seasonal variations (8.0–8.5 [24]). The electric conductivity (EC) varies between 6.50 and 17.6 mS cm−1 in the lower lake and 2.20 and 3.04 mS cm−1 in the upper lake [25]. A marked increase in the salinity of the lower lake was observed in 2010, whereas no significant change has been recorded in the upper lake [26,27]. The upper lake was classified as mesotrophic to eutrophic, while the second lake ranged from oligotrophic to eutrophic. Unfortunately, no temporal data are available for the nutrient levels. The dissolved oxygen value varies between 4.4 and 13.4 mg O2 L−1; the minimum values were recorded in the deepest parts of both lakes [24,25].
The El-Wadi Drain is the source of the inflow to the lakes, while evaporation from the lakes’ surfaces is the only outflow available. The total inflow to the upper lake is 221,106 m3 y−1, from which only 127,106 m3 y−1 is discharged to the lower lake [25]. The net water budgets are 13,106 m3 y−1 for the upper lake and 39,106 m3 y−1 for the lower one. These values have significantly reduced in the past few years [25,26,27,28,29]. Fish farms are situated along both sides of the canal connecting the two lakes; these were established in 2005 [29]. The escape of farmed fish into the lakes could change the fish community composition in the lakes; however, fish farms usually contain the same species as the natural water bodies. Therefore, this factor was limited in the study area. There were 68 licensed fish farms in the extensive section but only 12 were in operation. The different fishing methods used in the Wadi El-Rayan lakes include drifting, bottom-set, trammel, and Seine nets, according to the target species (demersal or pelagic fish). No marked changes occurred because human activities that could change the natural biological, geological, and cultural resources of this Protected Area had a high level of control.

2.2. Data Analysis

The data for the annual fishing yield (ton year−1) of the Wadi El-Rayan lakes from 1991 to 2019 were obtained from the General Authority for Fisheries Resources and Development (GAFRD) (Supplementary Material). The fishing effort (the number of licensed fishing vessels) was also obtained and included in the analysis. Species bioecological data were compiled using Fish Base ([30]; http://www.fishbase.org) or existing literature. The data were used to extract the habitat preferences of each species from the GAFRD database. The ecological preferences included the feeding mode, life habits, diet, climate zone, and salinity (Table 1). Nile tilapia included three species (Oreochromis niloticus, Oreochromis aureus, and Tilapia zilli), which were not separated in the landing data (Table 1).
The fish species were categorized according to their ecological preferences (e.g., demersal vs. pelagic, introduced vs. native, euryhaline vs. stenohaline, and equilibrium vs. opportunistic). Furthermore, the mid-point of the optimal temperature range was used to calculate changes in the temperature of the catch. We used the annual landing biomass (tons year−1) to assess the temporal changes in the fish communities. The annual precipitation (mm) and annual mean temperature (°C) in Faiyum City from 1991 to 2019 were downloaded from NOAA Climate Data Online (CDO) and used to assess their relationship to the fish landings. Historical changes in the lakes’ areas were obtained from [26] and compared with those extracted from satellite data [29]. As there were missing values in the latter, the weighted moving average method was used to interpolate these values. A neural network (Neuro Xl) was used to calculate the linear interpolation (http://neuroxl.com/).
We used the landing patterns and ecological aspects of the fish species to analyze the changes in the fish communities. The total landing data were transformed into the annual relative abundance of each species within a data matrix. This matrix underwent clustering via a method based on Bray–Curtis dissimilarity measures to detect the structural shifts in the fish communities across the lakes from 1991 to 2019. The CONISS method, which incorporates chronological constraints, was applied to the clustering. The canonical correlation coefficient (CCC) was used to assess the fit quality [31]. To test for significant differences in fish-species compositions among clusters, a permutational multivariate analysis of variance (PERMANOVA) was used. We conducted principal component ordination to reduce the dimensionality of the multivariate fish community composition and identify the main species contributing to the clusters [32]. The reduced major axis (RMA) linear regression model was used to assess the relationships using a one tailed t-test and a sequential Bonferroni p-value (<0.001). All analyses were carried out using PAST V. 2.17 [33].

3. Results

3.1. Total Fish Landing

A total of 70,439.99 tons were landed from the Wadi El-Rayan lakes in the past three decades (annual mean = 2429 tons), with a steady increase and peak production in 2017 (Figure 2A). A total of fourteen species were included in the GAFRD database in addition to rare species (Table 1; Figure 2B). The ‘rare species’ in the GAFRD database (Figure 2B; Supplementary Material) included a mix of species with a very low percentage. The landing data indicated a clear distinction pattern among the sixteen recorded species, where tilapia, mullet, and grass carp represent the highest production (Figure 2B). The dominant species of the landings was Nile tilapia (Tilapia zilli, Oreochromis aureus, and Oreochromis niloticus; Table 1), collectively representing 33.25% of the total landing in the interval from 1991 to 2019 (23,422 tons). This was followed by mullet, which represented 20% (14,267 tons), then grass carp (Ctenopharyngodon idella), which represented 15.25% (10,746 tons).

3.2. Fish Community Composition

There was a general increasing trend for two main fish groups. The first was the alien species, which included grass carp (C. idella) and silver carp (Hypophthalmichthys molitrix) (R2 = 0.67; Figure 3A). In addition, warm-water species (Table 1) also significantly increased (R2 = 0.65; Figure 3B). Euryhaline and freshwater species slightly decreased from 2004 to 2006, while brackish ones slightly increased during this interval and remained relatively stable from 2006 onward (Figure 4A). A clear increase in demersal species and a decrease in pelagic species were observed (Figure 4B). This resulted in an increasing trend for the pelagic-to-demersal ratio (P/D). The climate zone of the species-landing data indicated a stable rate from 1991 to 2019, except during two intervals. The first interval, from 2004 to 2006, showed an increase in temperate zone species, while the second interval, from 2018 to 2019, exhibited a decrease in temperate zone species (Figure 4C).
The hierarchical clustering dendrogram for CONISS could be divided into four main intervals based on the Bray–Curtis dissimilarity (where CCC = 0.71), as shown in Figure 5A. These intervals were characterized in the PCA plot (Figure 5B). The older years had lower PC axis 1 values and higher PC axis 2 values (Figure 5B). A biplot also indicated that Nile tilapia, rare species, and mullet (longer lines = higher contribution) were the dominant and more important species, occasionally in the cluster of the early interval (1991–2003). In contrast, from 2007 to 2017, grass carp became more important (Figure 5B). The PERMANOVA test supported the clustering and ordination results, where a pairwise comparison indicated significant differences among all intervals except cluster 2 (2003–2006) and cluster 4 (2018–2019; Table 2). The non-significance variations among these two clusters indicated minor variations in the relative abundances of the fish species. In general, the temporal changes in the landings could be attributed to changes in the fish community structure due to the overexploitation of target taxa or environmental changes.

3.3. Environmental Impact

The total landing gradually increased from 1991 onward and reached its first peak in 2000. In 2002, the first drop in the total landing occurred (Figure 6A). An exponential increase was observed in the past three decades, which continued until 2017. Between 2018 and 2019, another drop in the total landing occurred (Figure 6A). The total landing was strongly positively and significantly correlated with the fishing effort (total number of licensed boats; R2 = 0.61; Figure 6B).
The most prominent change in the Wadi El-Rayan lakes was the reduction in their areas. Initially, the measured change in the lakes’ levels was positive until the year 2000, as shown in Figure 7A, but then it dramatically decreased. Based on the modeled data, a linear prediction (also depicted in Figure 7A) estimated that there is likely to be a continuous decrease in the lakes’ areas in the next few years. Notably, this area reduction was significantly correlated with the mean yearly temperature, as indicated in Figure 7B. There was a polynomial correlation (R2 = 0.95; Figure 7B), suggesting that climate warming and the associated increase in evaporation rates may play a role, although complex, in the reduction in the lakes’ areas.

4. Discussion

4.1. Historical Changes and Their Drivers

The recent changes in the fish landings of the fish community from the Wadi El-Rayan lakes include a general increasing trend for the landings, a marked temporal variation in the dominant fish species and their percentage abundances, a decrease in the pelagic-to-demersal ratio, an increase in alien species, and an increase in warm-water species, all associated with a reduction in the surface area of the lakes.
Coll et al. [19] suggested that the global change in fish landings in the past half-century was a result of an increased fishing capacity. The marked increase in fish production during the past three decades correlated with the fishing efforts (Figure 6B). However, this trend cannot indefinitely be sustained. In 2018–2019, production began to decrease, which may be an early indicator of a critical point. At this juncture, the production rate could remain unchanged, even if the fishing efforts continue to increase.
The lakes, occasionally the lower one, are closed basins with no marked water outflow. The decrease in the lakes’ areas could be attributed to a decreasing inflow [26] or increasing evaporation. The strategy of water reuse has multiplied in the past few years all over Egypt, and remote-sensing data indicate a marked increase in agriculture and aquaculture in the Wadi El-Rayan area [34]. Anthropogenic activities have negatively affected the balance of water cycles in central Asia [34]. This is the potential scenario for the Wadi El-Rayan lakes, which face both increasing aridity and increasing human activities using the lakes’ water. According to Hereher [35], the lower lake area reduced by 20 km2 from 2000 to 2013. In addition, Afefe et al. [36] indicted that the lower lake area lost more than 29% of its area from 2007 to 2013 (from 48.6 to 34.09 km2).
Increasing temperatures result in higher evaporation rates. Moreover, higher temperatures enable the decomposition of organic matter [37], leading to eutrophication and salinization. The role of elevated evaporation rates in this hyper-arid region has previously been indicated [23,35,37]. Due to temperature increases, the evaporation rate has also increased; consequently, salt has accumulated while the water volume has declined [37].
Environmental changes and anthropogenic impacts may explain the temporal variations in fish landings. Hondorp et al. [38] found that landings of pelagic planktivorous fish species were positively correlated with N but not with hypoxia in semi-enclosed seas. According to Pennino and Bellido [39], the P/D ratio in the Mediterranean appears to be associated with the mean Chl-a value, which has a general increasing temporal trend. They argued this to the availability of nutrients in the water column in addition to the overexploitation of resources. The decline of pelagic taxa (i.e., a decrease in the pelagic-to-demersal ratio) can be attributed to increased eutrophication and the concentration of nitrates and phosphates [40]. These chemicals usually have an anthropogenic origin [12,40]. An increase in temperature can also result in eutrophication.
The change in the P/D ratio could be attributed to an increased deterioration in the water quality (i.e., a eutrophication increase). The drastic decline in the water quantity and quality due to climate change and human activities is a global problem [41]. Benoit and Swain [42] indicated that abiotic factors such as temperature and nutrients are primary drivers of change in the fish community structure. Moreover, they argued that the changes in fish communities can be directly linked to fishing pressure and environmental variables, particularly when both variables act synergistically to shift fish communities.
Alien-species abundances such as silver carp (Hypophthalmichthys molitrix) and grass carp (C. idella) are increasing (Figure 3A). Invasive alien species are exponentially rising globally [43,44]. Biological invasions are a global consequence of globalization, a rise in the human population, expanding aquaculture, and man-made structures that connect the oceans. Invasive alien species now represent a global change [45] and their impact on the ecosystem is not fully understood [46]. They may negatively impact biodiversity and ecosystem services [12,45]. Furthermore, introduced fish may have significant environmental degradation impacts such as reduced yields and decreased water clarity [47].
Mediterranean ecosystems are currently experiencing a combined impact of biological invasion and climate warming. Many alien species have been recorded in the Mediterranean, with alien thermophilic species entering through the Suez Canal of Egypt and extending to the western basins of the Mediterranean. The pronounced expansion of alien thermophilic fish species has been attributed to climate warming [48].
The ideal temperature for common sole (Solea solea) ranges from between 8 and 24 °C [49]. In the northern Adriatic (Italy), Palazzi et al. [50] found that the specific growth rate (SGR) of S. solea at a temperature range of 24–29 °C was the highest, although it was affected by heavy mortality, suggesting that the species with higher SGR rates under higher temperatures could sustain a higher production for a short period. However, increasing temperatures could result in a marked mortality increase over longer time scales. The marked increase in S. solea for the landings of the study area could be attributed to their high SGR. The farming of silver carp in cages in the study area was not attributed to the increase in production.
In aquaculture, Egypt is ranked ninth globally and the first among African countries. Carp is the second target species after tilapia in Egyptian aquaculture. Grass carp appeared from 1991, while silver carp appeared only from 2008 (Supplementary Material). Silver carp (Hypophthalmichthys molitrix) was introduced into Egypt and escaped from cages into the Nile River in the mid-2000s [51]. This could be attributed to the feeding habits of silver carp as it is a plankton feeder and consumes aquatic vegetation without the need of artificial feed (i.e., low production costs [52]). Furthermore, crop rising was the key to the successful development of carp-pond aquaculture [51]).

4.2. Quality of the Data

The value of fisheries in economies is significantly increasing [22,53]. Long-term data provide a valuable tool to monitor biodiversity dynamics and their possible drivers. Fish landings and catch-effort data (i.e., the number of boats, fishing gear, and fishers) are reported by the FAO for many countries and are provided by each country’s national fisheries’ management organizations to the FAO [54]. However, there are considerable challenges regarding the accuracy of the reported data [55]. Fish-landing data provide a vital tool to assess fisheries’ contributions to the economy as well as the total removal of fish and other organisms from the environment. Pauly et al. [56] suggested that the relative abundance of a species in the landing data is correlated with the relative abundance of this species in an ecosystem. The FAO catch data are the most comprehensive for global fisheries. However, the adequacy of these data has been heavily criticized [57]. The by-catch (non-targeted species) may be underestimated compared with the relative abundance of these species in natural ecosystems [58]. Caddy et al. [59] suggested that the assumption of Pauly et al. [56] may be wrong because the relative abundance of a fish species in natural habitats may not necessarily reflect the LC [60]. Moreover, Pinnegar et al. [61] found that high-value fish represent a high proportion of the landing composition, irrespective of their relative abundance. This suggests that landing data tend to minimize/underestimate the corresponding changes in the ecosystem. Additionally, experts sometimes identify only down to a genus level; thus, the species of some genera are categorized together.
Despite the above-mentioned criticism, landing data were recently proven to be a good indicator of natural habitats [62]. Although experts may identify only down to a genus level—thus, the species of some genera are categorized together—the landing catch was successfully implemented to assess the temporal trends of exploited fish communities [63]. The authors analyzed the mean size of a landed catch using Portuguese fisheries’ landing data and indicated that the data were fully applicable. Furthermore, landing data have been correlated with trawl surveys in the past few years [20,21]. The results suggest that the former can safely be used to analyze fish biodiversity. Mcclanahan and Hicks [64] evaluated whether data from fishery-dependent and -independent methods were comparable when assessing fish communities and found small differences. Therefore, landing data can reflect larger ecological differences in natural habitats. One the most straightforward applications of fish-landing data was conducted by Durante et al. [65], who analyzed historical trends in landing data from 1931 to 2015 in New Zealand and found a marked change in exploited fish communities where fish landings increased and similarities between catch compositions decreased. Durante et al. [65] also indicated that both the total catch and the trophic indices of landings decreased after the year 2000, whereas in recent years, smaller catches and lower trophic-level species have become more abundant. This suggests that fish-landing data are valuable when monitoring fisheries and assessing long-term changes in fish communities.

4.3. Limitation and Future Prospects

Fish-landing data can be effectively used to infer associations between fish and their environment [66]. Combining historical data to assess and manage fish stocks and production is an increasing practice worldwide [67]. The total fishing effort and landings of specific fish species may vary seasonally; therefore, we used the total annual landing to remove seasonal variations [68]. Moreover, absolute trending data in fish landings can be influenced by the fishing effort applied, which may vary seasonally. Therefore, we analyzed the trends in the percentages of specific taxa with respect to the total landing; thus, the calculations were independent from the fluctuations in the fishing effort [67].
Despite the known efficiency, sources of biases are still present and need to be resolved. For example, the fishers’ choice of fishing locations, competition within fisheries, variabilities in the fishing effort, target and non-target taxa, cage aquaculture, and market forces may shift or alter temporal trends and may not represent the actual fish community composition and fish stock [69]. Furthermore, these caveats of fishery-landing data can result in a faulty interpretation of the fish community composition and ecosystem status.
The two lakes of Wadi El-Rayan greatly differ in terms of salinity. The landing data for each individual lake are not available, so we could not examine the influences of these differences on the target species. Moreover, although we examined the role of temperature, other hydrological variables such as salinity, pH, heavy metals, and eutrophication levels may have significant influences. However, no data are available regarding the historical changes in these hydrological parameters, suggesting the urgent need for these data in future analyses of fish-landing data.
In general, aquatic ecosystems are now under combined natural and anthropogenic stressors [70,71,72,73,74] and disentangling the role of both types of stressors is challenging [75]. Therefore, historical records prior to human interventions are highly valuable to identify the baselines of these ecosystems for restoration and conservation [76].

5. Conclusions

The quantitative analysis of fish-landing data from the Wadi El-Rayan lakes over the past three decades (1991–2019) aimed to identify temporal variations in fish communities and their drivers. The results revealed that the landings predominantly comprised a few taxa, including Nile tilapia, mullet, and grass carp. The decline in the lakes’ areas and changes in warm-water species’ dominance were attributed to increasing temperatures. Additionally, the fish structure in the lakes shifted, with demersal species increasing in recent years while pelagic ones decreased. Furthermore, alien species proliferated in contrast to native ones. These changes were also linked to elevated eutrophication levels due to water mismanagement, which were further exacerbated by climate warming over the past few decades.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/w16182685/s1. Excel sheet include landings data of Wadi El-Rayan lakes from 1991 to 2019 and annual average temperature.

Author Contributions

Conceptualization, A.A.A.; methodology, M.S.-K., A.M.H., K.H.M.A.-R. and M.S.; validation, E.I., A.A., D.E.A., D.E.G. and H.S.; data curation, M.M.K., A.A.A., A.A. and M.S.A.; writing—review and editing, A.A.A., A.A., M.S. and A.M.H.; visualization, A.A.A., M.M.K. and A.M.H.; supervision, D.E.A. and A.A.A. All authors have read and agreed to the published version of the manuscript.

Funding

This work was funded by the Researchers Supporting Project number (RSP2024R455), King Saud University, Riyadh, Saudi Arabia.

Data Availability Statement

This article has no associated data and all the data used in this study are present in the article.

Acknowledgments

Two anonymous reviewers are highly acknowledged for their constructive comments and numerous useful suggestions. The authors are indebted to the Researchers Supporting Project number (RSP2024R455), King Saud University, Riyadh, Saudi Arabia, for funding this research. We highly acknowledge the General Authority for Fisheries Resources and Development (GAFRD) for supplying the data used in this study.

Conflicts of Interest

The authors declare no conflict of interest.

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Water 16 02685 g001
Figure 1. (A) Location map of Faiyum depression, west of the Nile Valley; (B) close-up view of Faiyum depression, showing Lake Qarun and the Wadi El-Rayan depression; (C) close-up view showing the upper and lower Wadi El-Rayan lakes and the main land use in the area surrounding the lakes; (D) DEM of the Faiyum depression showing the elevation of the Wadi El-Rayan lakes; (E) field photograph showing the waterfalls connecting the Wadi El-Rayan lakes in the Faiyum Oasis.
Figure 1. (A) Location map of Faiyum depression, west of the Nile Valley; (B) close-up view of Faiyum depression, showing Lake Qarun and the Wadi El-Rayan depression; (C) close-up view showing the upper and lower Wadi El-Rayan lakes and the main land use in the area surrounding the lakes; (D) DEM of the Faiyum depression showing the elevation of the Wadi El-Rayan lakes; (E) field photograph showing the waterfalls connecting the Wadi El-Rayan lakes in the Faiyum Oasis.
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Figure 2. (A) Box-plot of the total fish landing (in tons) from 1991 to 2019. Shaded area represents the interval of a non-increasing trend. (B) Box-plot showing the variation in the total landing of the different fish taxa in the Wadi El-Rayan lakes.
Figure 2. (A) Box-plot of the total fish landing (in tons) from 1991 to 2019. Shaded area represents the interval of a non-increasing trend. (B) Box-plot showing the variation in the total landing of the different fish taxa in the Wadi El-Rayan lakes.
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Figure 3. RMA linear regression models showing a significant increasing trend for both alien species (A) and warm-water species (B).
Figure 3. RMA linear regression models showing a significant increasing trend for both alien species (A) and warm-water species (B).
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Figure 4. Temporal changes in proportions of fish taxa grouped by their ecological preferences: (A) water salinity; (B) life mode; (C) climate zone.
Figure 4. Temporal changes in proportions of fish taxa grouped by their ecological preferences: (A) water salinity; (B) life mode; (C) climate zone.
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Figure 5. (A) Bray–Curtis–based CONISS clustered dendrogram showing 4 potential clusters (intervals). (B) PCA plot showing the relationship between the identified intervals and a biplot representing the loading (importance) of the main fish taxa.
Figure 5. (A) Bray–Curtis–based CONISS clustered dendrogram showing 4 potential clusters (intervals). (B) PCA plot showing the relationship between the identified intervals and a biplot representing the loading (importance) of the main fish taxa.
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Figure 6. (A) Catch trends over the study period for the Wadi El-Rayan lakes. (B) RMA linear regression model showing a significant positive relationship between the total landing and the fishing effort.
Figure 6. (A) Catch trends over the study period for the Wadi El-Rayan lakes. (B) RMA linear regression model showing a significant positive relationship between the total landing and the fishing effort.
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Figure 7. (A) Reduction in the area of the Wadi El-Rayan lakes based on measured data [26] and modeled data using satellite-image data [29]. (B) Polynomial regression model showing a significant positive correlation between the mean annual temperature of Faiyum City and the total area of the Wadi El-Rayan lakes.
Figure 7. (A) Reduction in the area of the Wadi El-Rayan lakes based on measured data [26] and modeled data using satellite-image data [29]. (B) Polynomial regression model showing a significant positive correlation between the mean annual temperature of Faiyum City and the total area of the Wadi El-Rayan lakes.
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Table 1. List of the fish species in the fish-landing data and their ecological preferences.
Table 1. List of the fish species in the fish-landing data and their ecological preferences.
Temperature (°C)
Scientific NameEnglish NameFamilyLife ModeDietSalinityStatusZoneMinMaxAvg.
Bagrus bajadBagrus bajadBagridaeDemersalPiscivoreFreshwaterNativeTropical172923
Hemiramphus farBlack-barred halfbeakHemiramphidaeReef ass.HerbivoreBrackish marineNativeTropical252927
Clarias gariepinusCatfishClariidaeBenthopelagicOmnivoreFreshwaterNativeSubtropical232926
Solea soleaCommon soleSoleidaeDemersalOmnivoreBrackish marineNativeSubtropical82416
Anguilla anguillaEuropean eelAnguillidaeDemersalCarnivoreEuryhalineNativeTemperate03015
Dicentrarchus labraxEuropean seabassMoronidaeDemersalCarnivoreEuryhalineNativeSubtropical52817
Sparus aurataGilthead sea breamSparidaeDemersalCarnivoreBrackish marineNativeSubtropical182622
Ctenopharyngodon idellaGrass carpCyprinidaeBenthopelagicOmnivoreFresh–brackishAlienSubtropical203025
Chelon aurataMullet neiMugilidaePelagicOmnivore EuryhalineNativeTemperate122619
Lates niloticusNile perchLatidaeDemersalCarnivore FreshwaterNativeTropical222825
Oreochromis niloticusNile tilapiaCichlidaeBenthopelagicHerbivoreFresh–brackishNativeTropical283431
Oreochromis aureusBlue tilapiaCichlidaeBenthopelagicHerbivoreFresh–brackishNativeTropical283431
Tilapia zilliRedbelly tilapiaCichlidaeBenthopelagicHerbivoreFresh–brackishNativeTropical283431
Hypophthalmichthys molitrixSilver carpXenocyprididaeBenthopelagicHerbivoreFresh–brackishAlienSubtropical222825
Pomadasys stridensStriped piggyHaemulidaeDemersalOmnivoreMarineNativeTropical182120
Table 2. Summary of the PERMANOVA test. Non-significant values are in bold.
Table 2. Summary of the PERMANOVA test. Non-significant values are in bold.
1991–20032004–20062007–20172018–2019
1991–20030
2004–20060.00580
2007–20170.00010.00480
2018–20190.00980.10360.01340
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Abdelhady, A.A.; Samy-Kamal, M.; Ismail, E.; Hussain, A.M.; Gamvroula, D.E.; Ali, A.; Ahmed, M.S.; Abdel-Raheem, K.H.M.; Saibi, H.; Sami, M.; et al. Climate Warming and Mismanagement Drive the Shift of Fish Communities in the Wadi El-Rayan Arid Lakes. Water 2024, 16, 2685. https://doi.org/10.3390/w16182685

AMA Style

Abdelhady AA, Samy-Kamal M, Ismail E, Hussain AM, Gamvroula DE, Ali A, Ahmed MS, Abdel-Raheem KHM, Saibi H, Sami M, et al. Climate Warming and Mismanagement Drive the Shift of Fish Communities in the Wadi El-Rayan Arid Lakes. Water. 2024; 16(18):2685. https://doi.org/10.3390/w16182685

Chicago/Turabian Style

Abdelhady, Ahmed A., Mohamed Samy-Kamal, Esam Ismail, Ali M. Hussain, Dimitra E. Gamvroula, Ahmed Ali, Mohamed S. Ahmed, Khalaf H. M. Abdel-Raheem, Hakim Saibi, Mabrouk Sami, and et al. 2024. "Climate Warming and Mismanagement Drive the Shift of Fish Communities in the Wadi El-Rayan Arid Lakes" Water 16, no. 18: 2685. https://doi.org/10.3390/w16182685

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