Guerrero Gómez, Adrián

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Guerrero Gómez, Adrián

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Guerrero Gómez, Adrián

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Universidad de Murcia. Departamento de Zoología y Antropología Física

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Eutrophication-induced shifts in fish assemblages from a Mediterranean coastal lagoon
(Elsevier, 2025-10-24) Zamora López, Antonio; Guerrero Gómez, Adrián; Torralva Forero, María del Mar; Zamora Marín, José Manuel; Oliva Paterna, Francisco José; Zoología y Antropología Física; Facultad de Biología
Eutrophication remains a critical threat affecting estuarine and coastal lagoon ecosystems, largely driven by intensified anthropogenic pressures and exacerbated by climate change. Understanding the impacts of eutrophic processes on biological communities is essential to ensure effective conservation and management of these vulnerable environments. This study investigates the ecological consequences of eutrophication-induced algal blooms and hypoxia-mediated mass mortality events on fish communities in the Mar Menor coastal lagoon (Western Mediterranean Sea). We assessed temporal changes in fish assemblage structure and composition across three different periods: a baseline reference period (2002–2004), an algal bloom period (2018–2019), and a mass mortalities period (2020–2021). For that purpose, multiple community metrics were assessed, including species richness, abundance, biomass, β-diversity, functional guilds, and species dominance. Significant disturbances in fish abundance and biomass in response to critical eutrophic events were found, though species richness remained stable. Community similarity decreased during warmer seasons of eutrophic periods, but β-diversity values remained constant. Species-specific responses highlighted a marked decline of benthic taxa closely associated with bottom habitats, while zooplanktivores and planktivores became dominant, suggesting the emergence of top-down trophic control mechanisms. Additionally, during hypoxic events, large macrobenthivorous species appeared to seek refuge in shallow and more oxygenated areas, thus leading to evident shifts in fish assemblage composition. These findings provide robust evidence of structural and functional disruption in fish assemblages under eutrophic stress conditions. Our study underscores the relevance of long-term biological monitoring and adaptive management strategies in transitional systems, particularly under future climate and nutrient enrichment scenarios.
Open Access
Unauthorized translocations of threatened fauna in freshwater ecosystems: insights from the Iberian southeast
(Wiley, 2025-07-22) Zamora Marín, José Manuel; Guerrero Gómez, Adrián; Zamora López, Antonio; Torralva, Mar; Oliva Paterna, Francisco José; Sánchez Fernández, David; Zoología y Antropología Física
Unauthorized translocations of native and threatened wildlife are widely conducted for conservation purposes. This illegal practice remains understudied and is poorly considered by wildlife managers despite its important socioecological implications. By focusing on the southeastern Iberian Peninsula as a case study, we combined data from freshwater biodiversity monitoring programs, published records and local expert knowledge to provide a comprehensive assessment of the magnitude of unauthorized translocations in freshwater ecosystems. A total of 14 cases of covertly translocated populations were recorded, involving 10 freshwater vertebrate species (six fish and four amphibians). All these species are classified as threatened taxa (i.e., critically endangered, endangered or vulnerable) at a global, national or regional level, seven of them being Iberian endemisms. At least nine out of these unauthorized translocations have resulted in self-sustaining populations, but their impact on local biodiversity and recipient ecosystems' functioning remains to be assessed. This case study suggests that unauthorized translocations could be an emerging conservation issue in freshwater ecosystems, highlighting the need for implementing integrative management approaches to halt this illegal practice at source. These management approaches should include a more proactive attitude by environmental authorities towards official conservation translocation programs and increased social awareness of the potential impacts of unauthorized translocations.
Open Access
Population dynamics, habitat use and trapping efficiency of the invasive crab Callinectes sapidus in a Mediterranean hypersaline coastal lagoon
(Pensoft Publishers, 2025-10-07) Herrero Reyes, Antonio A.; Guerrero Gómez, Adrián; Zamora López, Antonio; Torralva, Mar; Zamora Marín, José Manuel; Oliva Paterna, Francisco José; Zoología y Antropología Física
The blue crab (Callinectes sapidus) has rapidly invaded several coastal lagoons along the Western Mediterranean. However, there are still no comprehensive assessments of its population biology, habitat use and trapping efficiency in critical habitats. A two-year study (November 2021 – September 2023) was conducted in a natural corridor zone placed between the hypersaline Mar Menor coastal lagoon and the Mediterranean Sea. Our main goal was to assess the population structure, habitat use and trapping efficiency (four types of traps) of the blue crab. The blue crab shows a population dynamic and structure that reflects its full settlement and reproductive movements across the study area. Most captures corresponded to adults and subadults, peaking in summer, and largest crabs were recorded in November. A significant relationship was found between crab size, habitat type (Cymodocea nodosa meadows, Caulerpa prolifera meadows and bare substrates) and trap effectiveness. Trapping efficiency varied with both habitat characteristics and crab size, showing a positive relationship of juveniles and adults with muddy substrates, while water depth had a negative influence on juveniles and subadults. However, results supported great plasticity at the microhabitat scale. Fyke nets were identified as the most effective trapping method. Trap type significantly affected the number of captures as a function of crab size and sex, with subadults and females being predominantly captured in fyke nets. These findings provide novel insights into the species’ population biology in invaded regions and cost-efficient control methods, enabling the design of priority management strategies in shallow waters to minimize impacts from crab invasions and to ensure ecological integrity.
Open Access
First record of winter pregnant males of two pipefish species in a Mediterranean coastal lagoon
(Wiley, 2025-08-22) Guerrero Gómez, Adrián; Zamora López, Antonio; Herrero Reyes, Antonio Andrés; Oliva Paterna, Francisco José; Madrid Ruiz, Jorge; Álvarez-Navarro, Víctor M.; Peñalver Miras, Rocío; Torralva Forero, María del Mar; Zoología y Antropología Física; Facultades de la UMU::Facultad de Biología
Syngnathus abaster Risso, 1827 and Syngnathus typhle L., 1758 are key components of fish assemblages in European transitional waters, with well-documented reproductive cycles typically occurring from spring to autumn. However, recent warming trends in the western Mediterranean has raised questions about potential shifts in their breeding phenology. In January 2025, three pregnant S. abaster males and one S. typhle male were detected in the Mar Menor Coastal lagoon (western Mediterranean), representing the first recorded winter breeding event for both species. The size structure of S. abaster in winter 2025 also contrasted with colder winters, further supporting this interpretation. These findings may reflect a response to recent thermal anomalies and highlight the phenological plasticity of these species. To our knowledge, this is the first indication of potential phenological shifts in syngnathids from transitional waters, with implications for understanding how climate change may influence their reproductive dynamics.
Open Access
Shallow waters as critical habitats for fish assemblages under eutrophication-mediated events in a coastal lagoon
(Elsevier, 2023-07-24) Zamora López, Antonio; Guerrero Gómez, Adrián; Torralva Forero, María del Mar; Zamora Marín, José Manuel; Guillén Beltrán, Antonio; Oliva Paterna, Francisco José; Zoología y Antropología Física
Eutrophication is a major driver of the degradation of transitional waters worldwide, especially in environments with a restricted connection to the sea, such as coastal lagoons. In recent decades, intensive agriculture and urban water inputs around the Mar Menor coastal lagoon (Western Mediterranean) have disturbed this originally oligotrophic aquatic system. The nutrient input into the lagoon has triggered its eutrophication, leading to dystrophic crises and mass mortality events for aquatic biota, transforming it into one of the most eutrophication- impacted transitional waters in the Mediterranean basin. In this study, we applied a fish-based indicator to assess the ecological quality of shallow waters under different eutrophication-mediated environmental stress scenarios (from pre-eutrophic reference periods to critical eutrophic periods), as well as to explore the role of confinement (i.e., water renewal time) and shoreline anthropogenic pressure as factors modulating the indicator response. Despite the high magnitude of the eutrophication impact on the lagoon, the ecological quality of the shallow waters decreased only slightly after the mass mortality events. The level of confinement also had slight effects on the ecological quality of the most confined shallow areas in the summer during eutrophic periods. Hence, shallow waters could play a critical role as refuge habitats, both for fish assemblages and other aquatic taxa, by buffering euxinic conditions during eutrophication processes.”. In fact, shallow waters could act as critical habitats, allowing for the recolonisation of aquatic biota from more impacted areas in the lagoon. This attribute further reinforces the need to properly manage and protect the shoreline areas of transitional waters, particularly under eutrophication scenarios.
Open Access
Spatiotemporal dynamics and species-habitat relationships in syngnathid assemblages from a coastal lagoon under eutrophication stress
(Elsevier, 2025-08-14) Guerrero Gómez, Adrián; Zamora López, Antonio; Zamora Marín, José Manuel; Oliva Paterna, Francisco José; Torralva Forero, María del Mar; Zoología y Antropología Física; Facultad de Biología
Syngnathids are a vulnerable fish group strongly associated with vegetated habitats in transitional waters, yet their population biology and habitat preferences remain poorly understood, particularly in environments subjected to eutrophic conditions. This study examines the spatiotemporal variation and habitat selection of syngnathid populations in the shallow areas of the Mar Menor, a hypersaline coastal lagoon undergoing severe eutrophication, which has led to mass macrophyte mortalities. Seasonal surveys conducted in 2018–2019 revealed a relatively simplified syngnathid assemblage as compared to other large European transitional systems, but highly relevant within the lagoon context. Syngnathus abaster was the dominant species, while Syngnathus typhle and Hippocampus guttulatus were less abundant. Juveniles were particularly prevalent in the vegetated bottoms of shallow areas, reinforcing their function as growing and foraging grounds. Habitat models identified species- and size-specific preferences, with S. abaster and S. typhle closely linked to vegetation metrics, while adult classes showed more complex habitat relationships. In contrast, H. guttulatus exhibited a stronger dependence on water quality predictors. Seascape features also influenced syngnathid distributions. Our findings highlight the key role of seagrass and mixed seagrass-macroalgae meadows in supporting syngnathid populations, particularly under a scenario of habitat degradation. Long-term monitoring is essential to track syngnathid responses to environmental shifts and to inform effective conservation strategies in transitional systems facing increasing anthropogenic pressures.
Open Access
Fish functional responses to eutrophication and mass mortality events in a Mediterranean coastal lagoon
(Elsevier, 2026-03-23) Zamora López, Antonio; Guerrero Gómez, Adrián; Torralva Forero, María del Mar; Zamora Marín, José Manuel; Herrero-Reyes, Antonio Andres; Guerreiro, Pedro Miguel; Oliva Paterna, Francisco José; Zoología y Antropología Física; Facultad de Biología
Coastal lagoons are increasingly vulnerable to anthropogenic pressures, with eutrophication emerging as a key driver of ecological degradation. In systems with restricted marine connectivity, understanding how biological communities respond to critical eutrophic events is essential for preserving ecological functions and guiding effective management strategies. This study applies a fish trait-based approach to assess the functional consequences of mass mortality events caused by eutrophication in the Mar Menor coastal lagoon (Western Mediterranean Sea). Based on 588 surveys, we evaluated long-term functional shifts in fish assemblages across three critical eutrophic phases —Pre-Mortality (2018–2019), Mortality (2020−2021) and Post-Mortality (2022−2023)— compared with a reference period (2002–2004). Four functional diversity indices were assessed —functional richness (FRic), specialization (FSpe), originality (FOri), and divergence (FDiv)— and compared their sensitivity with taxonomic metrics and a multi-metric fish index. FSpe and FOri were the most sensitive indices to critical eutrophic events, indicating declines in the uniqueness of traits and ecological functions. Functional homogenization and the loss of specialist taxa were widespread across the lagoon, with minimal influence from site-specific anthropogenic pressure or spatial confinement. These findings suggest limited recovery of ecological functions under and after persistent critical eutrophic conditions. Our study demonstrates the usefulness of incorporating functional diversity metrics to detect and characterize the ecological responses of fish assemblages to eutrophication and mass mortality events in transitional coastal systems.
Open Access
Population dynamics of resident fish in a coastal lagoon under eutrophication-mediated habitat changes
(Hellenic Centre for Marine Research, 2024-10-09) Guerrero Gómez, Adrián; Zamora López, Antonio; Torralva Forero, María del Mar; Zamora Marín, José Manuel; Guillén Beltrán, Antonio; Oliva Paterna, Francisco José; Zoología y Antropología Física
Coastal lagoons, as transitional ecosystems, are crucial for providing ecosystem services and preserving fish communities, yet they face increasing pressures from anthropogenic activities. The Mar Menor coastal lagoon in the western Mediterranean exemplifies this challenge, as it suffers from severe eutrophication driven by agricultural and urban influences. In this study, we assess changes in the population dynamics of three resident fish species (Apricaphanius iberus, Pomatoschistus marmoratus, and Syngnathus abaster) in the context of human-induced impacts in the Mar Menor. Using long-term monitoring data (the reference period of 2002-2004 vs. the eutrophication period of 2015-2019), we analyze temporal variations in their population dynamics and their relationships with eutrophication-mediated structural changes in shallow waters. Our results suggest that these resident species, which are closely associated with shallow areas, show population dynamics that reflect habitat alterations, underscoring their potential as indicators of eutrophication impacts. This study enhances our understanding of the dynamics within transitional ecosystems and provides a basis for integrated management strategies aimed at promoting effective fish conservation