Search Results (97)

Human exploitation has been a major driver of marine turtle population declines, particularly affecting naturally scarce species such as the pantropical hawksbill turtle. Although hawksbill sea turtles have been documented in the Gulf of California since the early 20th century, data on their historical demography during periods of high exploitation in this region are nonexistent. We investigated the size structure of hawksbill turtles from the Western Central Gulf of California by examining a unique sample of decorative taxidermies, corresponding to 31 specimens captured during fishing operations near Santa Rosalía, Baja California Sur, Mexico, between 1980 and 1990. An analysis of the curved carapace measures revealed a length range (nuchal notch to posterior of supracaudals) of 29.5–59.5 cm (mean = 38.75 ± 6.67 cm) and a width range of 25.0–51.5 cm (mean = 33.63 ± 5.66 cm), with 87% of specimens having lengths between 30 and 45 cm. Based on the carapace length measurements, we estimated the ages to be between 7 and 20 years, indicating that the population included juveniles. Our findings provide baseline data for an understudied period and region, suggesting that this area previously served as an important juvenile habitat. These results contribute essential historical demographic information for conservation planning. Full article

Coral restoration is essential for recovering depleted populations and reef ecological functions. However, its effect on enhancing fish assemblages remains understudied. This study investigated the integration of 3D-printed and natural Staghorn coral (Acropora cervicornis) out-planting to assess their role in enhancing benthic spatial complexity and attracting fish communities. Conducted between 2021 and 2023 at Culebra Island, Puerto Rico, we employed a before-after-control-impact (BACI) design to test four treatments: natural A. cervicornis, 3D-printed corals, mixed stands of 3D-printed and natural corals, and non-restored controls. Fish assemblages were monitored through stationary counts. Results showed that integrating 3D-printed and natural corals enhanced fish assemblages and their ecological functions. Significant temporal changes in fish community structure and biodiversity metrics were observed, influenced by treatment and location. Herbivore abundance and biomass increased over time, especially in live coral and 3D-printed plots. Reefs with higher rugosity exhibited greater Scarid abundance and biomass post-restoration. Piscivore abundance also rose significantly over time, notably at Tampico site. Fishery-targeted species density and biomass increased, particularly in areas with live and 3D-printed coral out-plants. Fish assemblages became more complex and diverse post-restoration, especially at Tampico, which supported greater habitat complexity. Before restoration, fish assemblages showed a disturbed status, with biomass k-dominance curves above abundance curves. Post-out-planting, this trend reversed. Control sites showed no significant changes. The study demonstrates that restoring fast-growing branching corals, alongside 3D-printed structures, leads to rapid increases in abundance and biomass of key fishery species, suggesting its potential role promoting faster ecosystem recovery and enhanced coral demographic performance. Full article

Coral-reef fishes in the South China Sea play a crucial role in sustaining ecosystem stability and delivering essential ecological functions. However, widespread coral degradation has led to habitat loss, intensifying environmental stress on reef-associated fish communities. To better understand their current status and guide conservation efforts, this study conducted a comprehensive, trait-based assessment of coral-reef fish diversity across 19 reef sites in the South China Sea, spanning nearshore (Sanya, Hainan) and offshore (Xisha and Nansha Islands) systems. Significant spatial differences were observed in species composition, functional trait structure, and responses to environmental disturbance. Offshore reefs, particularly in the Nansha Islands, exhibited the highest species richness, trophic complexity, and functional diversity, while nearshore reefs showed simplified community structure dominated by small, sedentary species with high microhabitat dependence. Coral cover was only weakly correlated with fish diversity and failed to reflect functional trait complexity, highlighting the limitation of relying on structural indicators alone. Using community-weighted trait metrics, PCA, and indicator species analysis, this study established a tri-principle framework for identifying priority conservation species based on ecological function, rarity, and vulnerability. Key functional species—including Chlorurus sordidus, Siganus fuscescens, and Cephalopholis urodeta—were identified, along with representative conservation sites such as Meiji Reef, Lingyang Reef, and Luhuitou. These findings underscore the need to integrate species-level and functional diversity into coral reef monitoring and management. The proposed framework provides a science-based foundation for prioritizing species and habitats, enhancing the resilience of reef ecosystems under the dual threats of climate change and anthropogenic pressure. Full article

Understanding the factors influencing amphibian populations is essential for effective freshwater conservation, particularly for species with biphasic life histories. This study examined how pond- and landscape-level characteristics shape larval amphibian occupancy, abundance, and detection in a remnant Tupelo-Cypress wetland in southeastern Illinois. Given the small number of available ponds (n = 4), we standardized survey effort across sites and incorporated robust hierarchical Bayesian models to evaluate environmental effects at both community and species levels. Occupancy probabilities were generally high across species, with canopy cover significantly increasing both community and species occupancy, particularly for salamanders (up to 6.4-fold). Predatory backswimmers and fish substantially reduced occupancy (by 21.7-fold and 6.0-fold, respectively). Anurans, especially Pseudacris spp., were more abundant than salamanders, with abundance positively associated with canopy cover, leaf litter, and pond perimeter. Detection probabilities were generally low and varied by species, with predatory invertebrates reducing detection up to 83.3-fold. These findings underscore the importance of maintaining canopy cover while mitigating predation risks to support amphibian populations. The application of multi-species hierarchical models provides a nuanced understanding of species-specific responses, offering valuable insights for conservation strategies in regions affected by habitat loss and climate change. However, given the limited spatial replication, these findings should be interpreted cautiously and validated through additional studies across broader temporal and spatial scales. Full article

With the escalating frequency and intensity of global wildfires driven by climate change, fire retardants (FRs) have become essential tools in wildfire management. Despite their widespread use, the environmental safety of newer FR formulations—particularly in relation to aquatic ecosystems and developmental toxicity—remains insufficiently understood. In particular, their effects on fish embryos, which represent a sensitive and ecologically important life stage, are poorly characterized. This study investigated the acute toxicity of three commercially available FRs—N-Borate, N-Phosphate+, and N-Phosphate-—on early life stages of zebrafish (Danio rerio), based on an OECD 236 Fish Embryo Toxicity (FET) test. Notably, N-Phosphate- FR exhibited significant toxicity with a 96 h LC50 of 60 mg/L (0.0055%), while N-Borate (>432 mg/L, >0.032%) and N-Phosphate+ (>1181 mg/L, >0.08%) showed substantially lower toxicity. Sublethal effects, including reduced yolk sac absorption and yolk sac darkening, were observed across all FRs, highlighting potential developmental disruptions. The elevated toxicity of N-Phosphate- FR likely stems from its surfactant content. These findings reveal variations in the acute toxicity of different FR formulations, emphasizing the need for ecotoxicological assessments to guide the selection of safer FRs for wildfire management and to protect aquatic biodiversity. The results highlight the importance of incorporating developmental endpoints in FR risk assessments and provide foundational data for regulatory decisions regarding FR application near aquatic habitats. Further research is necessary to elucidate the mechanisms underlying observed effects and to evaluate cross-species toxicity at environmentally relevant concentrations. Full article

Understanding fish habitats is essential for fisheries management, habitat restoration, and species protection. Automated fish detection is a key tool in these applications, which enables real-time monitoring and quantitative analysis. Recent advancements in high-resolution cameras and machine learning technologies have facilitated image analysis automation, promoting remote fish tracking. However, many of these detection methods require large volumes of annotated data, which involve considerable effort and time. Additionally, their practical implementation remains challenging in environments with limited data. Hence, this study proposes an anomaly-based fish detection approach by integrating Patch Distribution Modeling with data augmentation techniques, including Affine Transformations, Neural Filters, and SinGAN. Field experiments were conducted in Lake Izunuma-Uchinuma, Japan, using an electrofishing boat to acquire data. Evaluation metrics, such as AUROC and F1-score, assessed detection performance. The results indicate that, compared to the original dataset (AUROC: 0.836, F1-score: 0.483), Neural Filters (AUROC: 0.940, F1-score: 0.879) and Affine Transformations (AUROC: 0.942, F1-score: 0.766) improve anomaly detection. However, SinGAN exhibited no measurable enhancement, indicating the necessity for further optimization. This shows the potential of the proposed approach to enhance automated fish detection in limited-data environments, supporting aquatic ecosystem sustainability. Full article

The floodplain of a large river plays a crucial role in the river’s ecosystem and serves as an essential microhabitat for river fish to complete their life history events. Over the past four decades, the floodplain represented by the Jingjiang section in the middle reaches of the Yangtze River has experienced a significant reduction in area, complexity, and diversity of fish microhabitats. This study quantitatively analyzed the dynamic changes and geomorphological structure of the floodplain in the Jingjiang reach (JJR) of the Yangtze River using satellite remote sensing images and high-resolution unmanned aerial vehicle (UAV) optical images. We built an enhanced U-Net model incorporating both the CBAM and SE parallel attention mechanisms to classify these images and identify environmental structural units. The accuracy of the enhanced model was 16.39% higher compared to original U-Net model. At the same time, the improved normalized difference water index (mNDWI), enhanced vegetation index (EVI), and normalized difference vegetation index (NDVI) were utilized to extract the flood frequency of the floodplain and analyze the area changes of the floodplain in the JJR. The trend of the flood area in the JJR during the flood season was consistent with the overall trend of flood areas in the flood season, which generally exhibits a downward tendency. In 2022, the floodplain of the JJR underwent substantial anthropogenic disturbances, with 40% of its area comprising anthropogenic environmental units. Compared to historical periods, the impervious surface within the floodplain has increased annually, while ecological units such as riparian forests and trees have gradually diminished or even disappeared, leading to a simplification of structural complexity. These findings provide a critical background and robust data foundation for the protection and restoration of fish habitats and the formulation of strategies for fish population reconstruction in the Yangtze River. Full article

Hydropower development is rapidly expanding in biodiversity-rich regions like the Ecuadorian Andes, raising major concerns about its ecological impacts. This study evaluates fish species composition and habitat characteristics in the Cristal and Dulcepamba Rivers, with a particular focus on the effects of the San José del Tambo Hydroelectric Project on the Dulcepamba River. Sampling conducted during the dry season (November–December 2023) at 15 sites incorporated fish surveys, habitat analyses, and environmental quality evaluation. The results showed marked declines in fish abundance, richness, and diversity in sections of the Dulcepamba River directly affected by water diversions, with species richness reduced to only three species at a site most impacted by discharge reduction. Conversely, the Cristal River, with its unaltered hydrology, supported considerably greater diversity, including 12 species at one site. Environmental integrity indices (Andean–Amazon Biotic Index, Biological Monitoring Working Party Index, Andean Riparian Quality Index, and Fluvial Habitat Index) further underscored the Cristal River’s superior conservation status. In the Dulcepamba River, reduced discharge in the environmental flow of the Hydroelectric Project—below mandated environmental discharge levels—led to river drying, disrupted connectivity, and impaired fish migration. This study provides essential insights into these highly biodiverse yet poorly studied ecosystems, which are increasingly threatened by anthropogenic pressures. The findings highlight the critical need to reconcile energy development with conservation efforts in these vulnerable Andean environments. Full article

Microalgae form the basis of marine food webs, essential in sustaining top predators including seabirds. However, certain species of microalgae synthesize biotoxins, which can accumulate in shellfish and fish and may cause harm to marine animals feeding on them. Toxins produced by dinoflagellates have been previously observed to be poisonous to seabirds. Also, in freshwater and brackish habitats, cyanobacteria have caused bird mortality events. In this work, we analyze the prevalence of six families of biotoxins (paralytic shellfish toxins (PSTs), microcystins (MCs), anatoxins, amnesic shellfish toxins (ASTs), cylindrospermopsin, and tetrodotoxins (TTXs)) in 340 samples from 193 wild birds admitted to a wildlife rehabilitation centre in south Portugal. Furthermore, we consider the clinical picture and signs of 17 birds that presented quantifiable levels of biotoxins in their tissues. The relationship between toxin burdens and the symptomatology observed, as well as possible biotoxin sources, are discussed. Based on previously published research data, we conclude that, in these birds, the biotoxins are unlikely to be the only cause of death but might contribute to some extent to a reduction in birds’ fitness. Full article

Anthropogenic development has historically concentrated in coastal areas to exploit resources from fishing and commercial navigation. In recent centuries, intensive tourism has added pressure on sandy shorelines, leading to their modification. This development model has led to the disappearance of most coastal sand dunes and their rich biodiversity, which includes specialized plant and animal species adapted to sandy substrates, harsh arid conditions, and variable levels of salinity. The European Community’s conservation policies, particularly the Habitats Directive (Council Directive 92/43/EEC), have facilitated the preservation and restoration of the few remaining dune systems. However, these policies have unfortunately overlooked the protection of the adjacent beaches, which are integral to the coastal ecosystem. The loss of biodiversity typical of the beach–dune ecosystems is examined in relation to the anthropogenic disturbance factors, with particular attention to mechanical beach cleaning. Indeed, the metabolizable energy generated by this decomposer biomass is crucial for supporting a diverse trophic network of predators, ranging from insects to birds. The rapid disappearance of the specialized beetle fauna is examined, and some essential criteria for defining standard biotic indices suitable for monitoring these ecosystems are suggested. This approach aims to support more effective conservation programs for these fragile environments. We recommend revising the regulatory framework for safeguarding beach–dune ecosystems, while also proposing some key management principles to be incorporated into the protection guidelines. Full article

Marine organisms produce sounds for various purposes, including spawning, avoidance, and migration, with each species exhibiting unique acoustic characteristics. This study observed the grunt sounds of Pacific cod (Gadus macrocephalus) during the spawning season for the first time using passive acoustic monitoring (PAM) techniques. Acoustic signals were recorded continuously for about one month at an aquaculture fish farm in Korea. From these recordings, 1208 grunt sounds of Pacific cod were extracted using an automatic grunt detector, and statistical time–frequency parameters were estimated. On average, the grunt sounds consisted of 29 pulses at 6.5 ms intervals within a duration of 205 ms, with a pulse rate of 122.6 per second. The periodic pulse-type signal creates multiple harmonic frequencies on the spectrogram, characterized by time-harmonic modulation with a slope of −240 Hz/s. The mth harmonic frequency distribution ranged from 162 to 822 Hz, with a median source level of 122.6 dB re 1 μPa at 1 m. These findings provide essential scientific data for understanding Pacific cod communication during the spawning season and can aid in identifying spawning sites, conserving habitats, and managing biological resources, contributing to marine ecosystem protection and sustainable management. Full article

Heavy metals originating from industrial runoff, agricultural practices, urbanization, and natural geological processes persist in coastal sediments due to their low degradation rates and high stability. Their cycling is influenced by sediment dynamics, water circulation, and complex interactions with biological and chemical factors. Heavy metal pollution demonstrates serious risks to coastal biota, including fish, shellfish, algae, and marine mammals through mechanisms such as bioaccumulation and biomagnification. These processes lead to biodiversity loss, habitat degradation, and reduced ecosystem functionality. Current mitigation strategies for pollution control regulations and remediation techniques show promise but face challenges in implementation. Emerging technologies such as nanotechnology and bioremediation offer innovative solutions but require further validation. Knowledge gaps persist in understanding the long-term ecological impacts of heavy metal contamination and optimizing management strategies for diverse coastal ecosystems. Coastal ecosystems are vital for supporting biodiversity and providing essential ecosystem services, but they are increasingly threatened by heavy metal pollution—a pervasive environmental challenge that demands urgent attention. This review investigates the sources, characteristics, pathways, ecological impacts, and management strategies associated with heavy metal contamination in coastal environments. The review synthesizes findings from recent literature, employing a systematic approach to analyze natural and anthropogenic sources, contamination pathways, and the biogeochemical processes governing heavy metal cycling. Future research should focus on addressing these gaps through interdisciplinary approaches, integrating advanced modeling techniques, stakeholder engagement, and sustainable management practices. By prioritizing these efforts, we can safeguard coastal ecosystems and their essential services from the escalating threats of heavy metal pollution. Full article

Preserving healthy river habitats is essential for maintaining fish diversity. Over time, anthropogenic activities have severely damaged river habitats, leading to notable changes in fish diversity patterns. Conducting thorough and reliable investigations into fish diversity is crucial for assessing anthropogenic impacts on diversity. In August 2023, a water ecology survey was conducted across 20 terraced river sections in the mainstem of the Jialing River, resulting in the collection of 60 environmental DNA water samples. The survey identified 99 fish species, representing 74 genera across 7 orders and 20 families, with the Cyprinidae exhibiting the highest number of species. The fish communities are predominantly composed of species inhabiting slow flowing water, demersal fish, omnivores, and fish spawning adhesive eggs. Overall, small-bodied fish dominate the mainstem of the Jialing River, and the species preferring flowing habitats are relatively scarce. In addition, geographic division analyses revealed minimal variations in fish species composition and diversity among the terraced reservoirs and across the upper, middle, and lower reaches. Notably, the fish compositions in the middle and lower reaches were found to be similar, indicating a certain degree of convergence in these sections of the Jialing River. In conclusion, this study unveils the current status and distribution pattern of fish diversity in the Jialing River and highlights the extent of anthropogenic activities’ impact on fish diversity. Full article

Fish in the Yong River basin have been significantly impacted by pollution, habitat modification and overfishing. In order to facilitate the recovery of freshwater biodiversity, a fishing ban has been implemented in the Yong River basin since 2022. However, the high level of human activity along the waterways of the Yong River basin poses a significant challenge to the monitoring of fish biodiversity using established methods. It is essential, therefore, to have effective monitoring tools to assess the effectiveness of the fishing ban policy. In this study, environmental DNA (eDNA) metabarcoding was employed to assess fish species biodiversity across five river sections of the Yong River basin in October 2022. Additionally, we checked the results against fishing gear (drift gillnets and ground cages) surveys and historical records. A total of twenty-two fish species were found from eDNA metabarcoding, fourteen species were found via fishing, and only two species were found from both methods. The most dominant fish species identified by eDNA was Alburnus mossulensis, present in all river sections. However, a decline in species biodiversity was observed in the whole Yong River basin, with a significant difference in community composition across the Upper Yao River (UYAR) and Yong River (YOR). Moreover, eDNA detected fish and potentially invasive species consistent with their geographic distribution. Overall, the results of this study provide a snapshot of the current fish biodiversity in the Yong River basin, offering baseline data for future evaluations of fishing ban policies in this ecosystem. Full article

Coralligenous bioconstructions are a key Mediterranean ecosystem for their associated biodiversity and role in the blue carbon cycle. They are also sensitive to environmental alterations (e.g., climate change) and other anthropic impacts related to coastal anthropization (e.g., fishing activities). Marine-coastal zone protection, conservation programs and management strategies are essential to guarantee a good ecological status of the coralligenous habitat. In this context, environmental and ecosystem accounting are useful tools to measure natural capital stocks and ecosystem service flows associated with marine ecosystems, conveying their importance in scientific and policy contexts. Indeed, the importance of marine ecosystems is often overlooked due to the difficulty of expressing their value in common units, making it challenging for decision-makers to explore trade-offs between conservation and exploitation of marine ecosystems. In this study, a biophysical and trophodynamic environmental accounting model was used to assess the biophysical value of natural capital stocks of the coralligenous habitat in three Marine Protected Areas (MPAs) of the Campania Region (Southern Italy): Punta Campanella, Santa Maria di Castellabate, and Costa degli Infreschi e della Masseta. The natural capital value per unit area associated with the coralligenous habitat ranged from 2.44 × 10¹² to 4.72 × 10¹² sej m⁻² for Santa Maria di Castellabate and Punta Campanella, respectively. Despite the different intensive values of natural capital calculated for the MPAs, there were no significant differences both in the biomass values of the taxonomic groups and in the biomass-based Shannon diversity index. Additionally, the biophysical values were also converted into monetary units, with the aim of facilitating the understanding of the importance of natural stocks in socio-economic and political contexts. The economic equivalent of natural capital value refers to the total extent of the coralligenous habitat and ranged from about EUR 1 to 15 million for Costa degli Infreschi e della Masseta and Santa Maria di Castellabate, respectively. The results of this study could be useful for local managers and policy makers and may make them more likely to achieve biodiversity conservation and sustainable development goals in MPAs. This is the first study devoted to the assessment of natural capital value of coralligenous habitats. Future studies could complement the results of this study with biophysical and economic assessments of ecosystem service flows generated by coralligenous habitats, focusing on the role they play in human well-being. Full article