Search Results (2,179)

Hyperspectral unmixing (HU) aims to estimate endmembers and their corresponding abundances, a task commonly referred to as blind hyperspectral unmixing (BLU). Nonnegative matrix factorization (NMF) provides a unified framework for their joint estimation. It is widely assumed that more accurate endmember estimation leads to improved abundance estimation, enabling simultaneous optimization of both variables. However, this paper shows that, in practical noisy scenarios, the relationship between endmembers and abundances in NMF-based multi-variable joint optimization problems (NMF-based JOPs) is inherently coupled and significantly more complex, making it difficult to improve both estimation accuracies simultaneously. Furthermore, we demonstrate that the hard abundance sum-to-one constraint (ASC), commonly imposed in NMF-based JOPs, is inconsistent with realistic noisy conditions. To address these limitations, we propose a novel two-stage framework for BLU that decouples the refinement of endmembers and abundances. In the first stage, a strongly convex minimum-volume simplex model is employed to ensure robust and stable endmember extraction. In the second stage, we introduce a novel formulation, L₁_SoftASC, which promotes abundance sparsity and physical interpretability while improving convexity and robustness in abundance estimation. Experimental results on both synthetic and real benchmark datasets demonstrate that the proposed two-stage approach consistently outperforms existing single-stage NMF-based JOP methods in terms of both endmember and abundance estimation accuracy, while providing BLU with greater flexibility in handling ASC. Full article

Introduction: As apex and mesopredators, elasmobranchs help maintain marine ecosystem balance by shaping food-web structure and habitat connectivity, yet more than one-third of species are threatened with extinction. Identifying where and when they aggregate within atoll systems is therefore a prerequisite for spatially explicit conservation planning. Lhaviyani Atoll, in the central Maldives, lies within a recognised Indian Ocean elasmobranch hotspot and hosts two Important Shark and Ray Areas (ISRAs), yet fine-scale information on aggregation sites, habitat partitioning and seasonal use remains limited. Objective: To map persistent activity hotspots, characterise habitat partitioning between sharks and batoids, quantify seasonal and inter-annual dynamics, and provide an ecological basis for habitat-focused conservation in Lhaviyani Atoll. Methodology: Using a seven-year (2017–2024) opportunistic dive-log dataset of 12,732 SCUBA surveys and 142,994 elasmobranch records across 94 dive sites, spatial kernel-density estimation was applied separately to sharks and batoids to identify activity hotspots and visualise spatial overlap. Habitat associations were examined across substrate types and reef geomorphic zones. Seasonal and inter-annual dynamics in relative abundance and diversity (Shannon, Pielou’s evenness) were quantified across monsoon phases and the 2017–2024 period. Results: Twenty-eight species (14 sharks, 14 batoids) were recorded, including 23 listed as threatened on the IUCN Red List (4 Critically Endangered, 12 Endangered, 7 Vulnerable). Four persistent activity hotspots were identified along the northern atoll rim, two overlapping with the Fushifaru Kandu and Kuredhu–Huravalhi–Komandoo ISRAs. Sharks were concentrated along more complex exposed and semi-sheltered slopes and high-flow channels, with significantly higher occurrence on reef and sheltered reef slopes and lower occurrence on rubble and sand substrates; batoids were distributed broadly within lagoonal habitats with no strong substrate or geomorphic preferences. Relative abundance and diversity peaked during the late southwest monsoon (August–September) and declined into the northeast monsoon (December–March); after 2021, diversity and evenness increased while overall abundance declined. Conclusions: Persistent hotspots, contrasting habitat use by sharks and batoids, and consistent monsoonal seasonality support the ecological relevance of existing ISRAs in Lhaviyani Atoll, while providing finer-scale information on habitat partitioning and additional priority areas for threatened elasmobranchs, including four Critically Endangered species. Full article

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a major heat-induced contaminant in protein-rich foods, yet its effects on intestinal barrier homeostasis and luminal microecology remain insufficiently defined. In this study, adult zebrafish were exposed to dietary PhIP for 90 days at estimated intake doses of 0.006, 0.4, and 7.2 mg/kg bw/day to evaluate intestinal injury, microbial dysbiosis, and metabolic remodeling. PhIP exposure impaired growth-related indices and induced progressive intestinal lesions, accompanied by mucus barrier depletion, reduced goblet cell abundance, and downregulation of muc2. Tight junction integrity was disrupted, as indicated by decreased zo-1, occludin, and claudin1 expression, weakened ZO-1 and Claudin-1 immunofluorescence signals, and reduced tight junction-related protein levels. Serum LPS and intestinal pro-inflammatory cytokines were markedly elevated, whereas il-10 expression was suppressed, indicating increased endotoxin burden and inflammatory activation. 16S rRNA gene sequencing revealed Proteobacteria-enriched dysbiosis and exposure-associated shifts in candidate genera, including Chitinilyticum, Shewanella, Aeromonas, Acinetobacter, Microbacterium, and Reyranella. Untargeted metabolomics further identified luminal metabolic remodeling involving lipid-related compounds, organic acids, amino acid metabolism, arachidonic acid metabolism, the citrate cycle, and pathways related to choline and glycerophospholipid metabolism. Association analysis linked genus-level microbial variation and core pathway-related metabolites with LPS, inflammatory cytokines, and tight junction markers. These findings indicate that dietary PhIP exposure disrupts intestinal barrier homeostasis in parallel with Proteobacteria-related dysbiosis and luminal metabolic remodeling, providing an integrated microbiota-metabolite-barrier association framework for evaluating intestinal risks of heat-induced food contaminants. Full article

Hyperspectral imaging (HSI) provides rich spatial and spectral information for remote sensing, mineral exploration, and biomedical analysis, but its limited spatial resolution and sensor imperfections lead to blurred, noisy, and mixed-pixel observations. Addressing these degradations jointly—rather than sequentially—has been shown to improve physical interpretability, yet existing joint deblurring–unmixing methods rely primarily on hand-crafted regularizers that do not fully exploit spatial–spectral structure. Meanwhile, recent plug-and-play (PnP) approaches applied to HSI leverage deep priors but focus solely on either deconvolution or unmixing in isolation. To bridge this gap, we formulate the joint inverse problem of hyperspectral deblurring and spectral unmixing and propose, to our knowledge, the first plug-and-play framework tailored for this coupled task using the Alternating Direction Method of Multipliers (ADMM) and a pretrained deep denoiser (DnCNN) as an implicit PnP prior. Our method uses the natural splitting properties of ADMM to separate a physics-driven subproblem that enforces fidelity to the hyperspectral forward model, which includes linear mixing and blur under a linear, space-invariant convolution approximation, from the data-driven prior step. This synergy of model-based fidelity and learned spatial prior enables more accurate abundance estimates than those obtained with approaches relying solely on analytical regularizers. Experimental results on real hyperspectral datasets demonstrate that the proposed Plug-and-Play Joint Deconvolution and Unmixing (PnP-JDU) method outperforms conventional unmixing baselines, stand-alone PnP unmixing methods, and the Deblurring and Sparse Unmixing via the Alternating Direction Method with Total Variation (DSUnADM-TV) baseline in reconstruction and abundance accuracy metrics. Across the tested datasets and imaging conditions, PnP-JDU achieves lower RMSE, higher PSNR, lower reconstruction and abundance errors, and lower SAD values, while preserving fine spatial details and producing physically meaningful abundance maps. Full article

Small pelagic fishes are essential for artisanal fisheries and food security in São Tomé and Príncipe, yet biological information required for stock assessment remains scarce. This study examined the population dynamics and life-history traits of Caranx crysos, Euthynnus alletteratus, Hemiramphus balao, and Cheilopogon melanurus using 9052 specimens collected from artisanal landings between 2023 and 2025. C. melanurus (35.2%) and H. balao (34.0%) dominated the sampled catches, followed by C. crysos (18.1%) and E. alletteratus (12.7%). Standardized CPUE series modelled using GAMs revealed significant temporal and seasonal variation in relative abundance, with contrasting species-specific trends. Length–weight relationships revealed negative allometric growth in three of the four species examined (75%), with b values ranging from 2.50 to 3.19, while Fulton’s condition factor differed significantly among species (Kruskal–Wallis χ² = 6702.7, p < 0.001). Sex-ratio analyses showed significant deviations from parity in C. crysos and C. melanurus, whereas E. alletteratus and H. balao remained balanced. Gonadosomatic index and maturity-stage distributions indicated year-round reproductive activity with distinct spawning peaks. Length at first maturity (L50) ranged from 30.2 cm to 38.8 cm among species. Growth parameters estimated from length-frequency data using the von Bertalanffy Growth Function fitted through ELEFAN_GA in TropFishR yielded L∞ values of 43.9–68.4 cm and K values of 0.065–0.336 yr⁻¹. Growth performance index (φ′) ranged from 2.48 to 2.99, corresponding to theoretical longevities of 8.9–46.3 years. Length-based cohort analysis indicated biomass concentration in intermediate size classes and increasing fishing mortality towards larger individuals. Exploitation rates revealed contrasting fishing pressures among species, while sensitivity analyses identified growth and mortality parameters as the main sources of uncertainty. These findings provide the first integrated biological baseline for the assessment and management of small pelagic resources in São Tomé and Príncipe. Full article

Immune remodeling within the tumor microenvironment (TME) influences the progression and clinical outcome of uterine corpus endometrial carcinoma (UCEC), but the contribution of chemokine-related regulatory genes remains incompletely characterized. This study aimed to evaluate the prognostic relevance of CXCL13 and its association with immune microenvironmental features in UCEC using publicly available transcriptomic and single-cell datasets. RNA-sequencing profiles and clinical annotations from 589 UCEC cases in The Cancer Genome Atlas (TCGA) were analyzed to assess TME composition using ESTIMATE (Estimation of Stromal and Immune cells in MAlignant Tumours using Expression data) and CIBERSORT (Cell-type Identification By Estimating Relative Subsets Of RNA Transcripts), followed by survival analysis, differential gene expression analysis, protein–protein interaction network construction, Cox regression, and gene set enrichment analysis. A public single-cell RNA-sequencing dataset from the Gene Expression Omnibus (GEO; GSE173682) was further used to infer the cellular sources of CXCL13. Elevated CXCL13 expression was associated with favorable overall survival and enrichment of immune-activation pathways. CIBERSORT-based analysis indicated that high CXCL13 expression correlated with increased estimated fractions of CD8⁺ T cells and plasma cells, together with transcriptional features related to tertiary lymphoid structure-associated immune activation, whereas several immunosuppressive cell populations showed lower estimated abundance. Single-cell analysis suggested that CXCL13 was mainly expressed by follicular helper T cells and exhausted CD8⁺ T cells. These findings indicate that CXCL13 may serve as a prognostic biomarker associated with an immune-active TME in UCEC. Further histological, spatial, and functional validation is warranted to confirm its mechanistic role and translational potential. Full article

This study evaluated how graded dietary nucleotide supplementation (0, 0.25, 0.5, 0.75, 1.0, and 2.0 g/kg) affects growth performance, antioxidant capacity, intestinal morphology, and gut microbiota in swamp eel (Monopterus albus) (initial body weight 10.07 ± 0.92 g). Three hundred sixty fish were randomly assigned to six diets, each in triplicate, for eight weeks. Compared with the control, nucleotide addition significantly increased final body weight, weight gain rate, and specific growth rate, and decreased feed conversion ratio (p < 0.05), with optimal results at 0.75 g/kg (HS3). Survival was 100% in all groups. Supplemented fish showed lower serum and intestinal malondialdehyde levels and higher superoxide dismutase and catalase activities (p < 0.05). Serum total protein, albumin, and triglycerides increased, whereas alanine aminotransferase, aspartate aminotransferase, and γ-glutamyl transpeptidase decreased (p < 0.05), pointing to improved hepatic and lipid metabolism. Intestinal trypsin, lipase, and amylase activities also rose markedly (p < 0.05), peaking in HS3. Histological examination revealed greater mucosal thickness and villus height (p < 0.05); in HS3, these values reached approximately 0.95 mm and 0.87 mm, respectively. Metagenomic analysis showed that 0.75–1.0 g/kg nucleotides increased alpha diversity and restructured the microbial community, enriching Bacteroidetes- and Prevotella-related taxa while reducing Proteobacteria, including Acinetobacter baumannii and Escherichia coli. LEfSe identified dose-specific discriminant taxa, and refined KEGG Level 3 pathway analysis predicted enhanced butyrate and propanoate biosynthesis, starch utilization, and purine/pyrimidine interconversion at moderate doses. Genus-level abundances of Prevotella and Bacteroides correlated inversely with serum oxidative and hepatic stress markers. Quadratic regression estimated the optimal dietary nucleotide level at 764 mg/kg (0.76 g/kg), consistent with the best-performing 0.75 g/kg group. Collectively, 0.75–0.76 g/kg dietary nucleotides optimize growth and intestinal health in M. albus through coordinated improvements in antioxidant status, digestive function, mucosal architecture, and beneficial gut microbiota remodeling. Full article

Introduction: Marine heatwaves are increasing in frequency and intensity, posing major challenges for fishes inhabiting shallow coastal ecosystems. Short-term exposure to extreme warming can alter metabolic performance and thermal tolerance, with potential consequences for species persistence and school composition in thermally variable habitats. Understanding the capacity of coastal fishes to withstand acute warming events is therefore essential for predicting ecological responses to climate change. Objective: We aimed to determine the effects of simulated marine heatwaves on thermal tolerance and metabolic performance in juvenile grey mullets, Chelon labrosus and Chelon aurata, two abundant sympatric species inhabiting the Ria Formosa lagoon (southern Portugal). Methodology: Juvenile mullets acclimated at 17 °C were exposed to simulated heatwave treatments of 23, 27, or 33 °C and sampled either at peak temperature or after 48 h and 1-week recovery at 17 °C. Critical thermal maximum (CTmax, using a 1 °C/min thermal ramp), static oxygen consumption (MO2), and intermittent respirometry parameters were measured. Standard metabolic rate (SMR), maximum metabolic rate (MMR), and aerobic scope (AS) were derived from intermittent respirometry. A complementary temperature-ramp (>3 h at each temperature step 17, 23, 27 and 33 °C) was performed to evaluate routine metabolic rate and estimate Q10 values across increasing temperatures. Additional plasma and tissue analyses are being conducted to assess energetic substrate mobilization and cellular responses to thermal and oxidative stress. Results: CTmax increased significantly with warming in both treatment modes, demonstrating rapid heat hardening in juvenile mullets. Fish exposed to 27 and 33 °C exhibited higher CTmax than control fish, and this elevated tolerance persisted after recovery. Chelon labrosus showed slightly higher CTmax values than C. aurata. Oxygen consumption increased with temperature, with the strongest responses occurring at 33 °C. SMR increased markedly with warming, particularly in heatwave-exposed fish, while MMR increased mainly at the highest temperature treatment. In contrast, AS showed no clear thermal optimum or decline across treatments. Routine metabolic rate increased non-linearly with temperature in the complementary ramp experiment, with a mean Q10 of 2.28, confirming strong thermal dependence of metabolism. Conclusions: Juvenile mullets possess substantial short-term thermal plasticity and can rapidly increase heat tolerance during marine heatwaves but this enhanced tolerance is accompanied by elevated metabolic costs under extreme warming, indicating potential energetic trade-offs near upper thermal limits. Differential physiological responses between species may influence school composition and ecological performance across thermal landscapes. Ongoing plasma and tissue analyses will further clarify the energetic and cellular mechanisms underlying thermal and oxidative stress resilience in coastal fishes. Full article

This study presents a comprehensive data-limited stock assessment of bonga shad (Ethmalosa fimbriata) and lesser African threadfin (Galeoides decadactylus) in the Central Gulf of Guinea using complementary catch- and abundance-based approaches, including Abundance-based Maximum Sustainable Yield (AMSY), Catch-based Maximum Sustainable Yield ++ (CMSY++), and the Bayesian State-space Schaefer Model (BSM). These models were applied because they are suitable for evaluating stock status in data-limited fisheries using catch and abundance information. While AMSY primarily uses abundance information, CMSY++ integrates catch and productivity priors, whereas BSM incorporates state-space error structures to account for observation uncertainty. Catch time series (1990–2021) were extracted from Food and Agricultural Organization (FAO) FishstatJ accessed in 2023, with catch values for 2022–2023 cautiously extrapolated from recent trends due to the temporary absence of updated official statistics. Standardized and scaled relative abundance indices from Cameroonian and Nigerian EEZ were used to support model estimation and assess the stock status. For Ethmalosa fimbriata, the results from CMSY++ and BSM yielded an MSY estimate of 126 × 10³ t and 95.5 × 10³ t, respectively, while for G. decadactylus, MSY from CMSY++ and BSM were 9.1 × 10³ and 13.4 × 10³, respectively. Stock status indicators suggested the stock was fully exploited based on both AMSY (F/F_MSY = 0.83) and CMSY++ (F/F_MSY = 1.03) and overfished based on BSM (F/F_MSY = 1.77). For G. decadactylus, the analysis based on AMSY suggested an overfished stock state (F/F_MSY = 1.2), while under CMSY++ and BSM, the stock is fully exploited. The log scale CPUE was symmetrical within the expected bounds, and the posterior parameter distributions were constrained, indicating that the model passed the convergence test and had robust parameter estimates. The study recommends maintaining catches within MSY-based reference points as the total allowable catch (TAC) and emphasizes the need for improved data continuity, regional collaboration, and precautionary management for long-term sustainability of fisheries resources in the Central Gulf of Guinea. Full article

The seasonal distribution of microplastics, as a representative case, was examined in Mytilus galloprovincialis from a pilot farm in the Gulf of Naples (Italy). The influence of marine parameters on microplastic uptake rate was assessed. A destructive patented method was used, and two microplastic size classes (<10 µm; >10 µm) were defined. Estimated Daily Intakes were calculated for different age groups. Results showed a significant abundance of small microplastics (9683.92 ± 6911 vs. 41.85 ± 13.98). In mussels, the highest levels (19,738.13 ± 3406.04) were detected in summer, and the lowest in autumn (4145.56 ± 2364.93). Summer variations in seawater temperature, oxygen, and pH were significantly different from those in winter and spring. High exposure levels, mainly of microplastics < 10 µm, were observed in the elderly (318.08 ± 227.00), followed by adults (225.29 ± 160.78) and children (212.29 ± 151.50), with the lowest in teenagers (127.51 ± 91.00). Despite the high variability of factors influencing mussel filtration and microplastic uptake, the study provided data on the seasonal microplastic distribution pattern and a size-based screening exposure level. Results highlight the importance of geographic and seasonal conditions, and particle size in assessing microplastic exposure through farmed mussel consumption. Full article

Dietary fibre (DF) and bioactive compounds (BCs) are essential components of a healthy diet and are abundant in plant-rich dietary patterns. Increasing evidence demonstrates that their combined and synergistic actions significantly influence human health, largely through their effects on the gut microbiota. This review highlights the need for more precise terminology regarding DF and BCs, as inconsistent use of these terms can create confusion among both consumers and researchers. The DF complex encompasses all non-digestible food components that have a positive effect on human health, together with the BCs associated with them, recognising that DF often serves as a carrier for these compounds throughout the digestive tract. Although recommended intakes for BCs have not been established, intake levels observed in populations adhering to healthy dietary patterns may serve as useful reference points. Updated data on the intake and estimated intestinal bioaccessibility of polyphenolic compounds in the contemporary Spanish diet are presented. Full article

The potency of urate, an abundant human plasma antioxidant, in preventing oxidative damage caused by the carbonate radical anion CO₃^•−, was studied using quantum chemical calculations. The influence of microhydration of CO₃^•−/CO₃²⁻ and urate⁻/urate^• couples on the thermodynamic and kinetics of the one-electron oxidation process was investigated. Depending on the degree of microhydration, the estimated rate constant for one-electron transfer is in the range of 2.0–7.3 × 10⁹ M⁻¹ s⁻¹, in good agreement with the experimental value of 1.3 × 10⁹ M⁻¹ s⁻¹. Modeling using vertical detachment energy and electron affinity, the driving forces of single electron transfer revealed urate(H₂O)₆⁻ and CO₃(H₂O)₉^•− clusters as the most likely existing species in water. Molecular docking revealed a favorable interaction of urate with the catalytic pocket of SOD1. Urate binds more strongly to the anionic active center of SOD1 than the reference inhibitor LSC-1, indicating its potency to prevent HCO₃⁻-supported CO₃^•− formation. In contrast, the known OGG1 inhibitor TH13264 shows substantially stronger binding than urate, indicating urate’s weaker affinity toward the DNA repair enzyme catalytic pocket. The molecular dynamics data indicate that urate binding does not destabilize either SOD1 or OGG1. In light of increasing evidence that the major source of oxidative stress could be CO₃^•−, rather than the commonly assumed hydroxyl radical HO^•, the obtained results indicate the inherent ability of plasma to combat oxidative stress induced by this selective, milder oxidant. Such an ability with respect to the non-selective, highly reactive HO^• does not exist in vivo. Full article

Introduction: The European catfish (Silurus glanis) has expanded rapidly across Europe, significantly impacting native freshwater biodiversity. Despite its well-documented ecological and economic effects as a top predator, reproductive biology data from non-native populations remain scarce, limiting the development of effective management strategies. Objective: This study examines key reproductive traits, sex ratio, size at first maturity, spawning period, fecundity, and oocyte diameter, of an invasive European catfish population in the Lower Tagus River (LTR), Portugal, approximately 15 years after its establishment. Methodology: A total of 674 individuals were collected monthly from January 2022 to November 2023 using electrofishing, gill nets, baited hook-lines, and catches from professional fishermen. Sex and reproductive stage were assessed via gonadal analysis. Size at first maturity was estimated using logistic regression. Fecundity was determined by the gravimetric method, and oocyte stage and diameter were assessed histologically. The gonadosomatic index (GSI) was used to characterise the reproductive cycle. Results: The sex ratio was significantly female-biased (1.4:1). Size at first maturity (TL₅₀) was 72.9 cm TL for females and 68.8 cm TL for males. The spawning season extended from February to June, coinciding with water temperatures of 11–23 °C, with the highest GSI values reported to date for this species (GSI max = 22.5%). Histological analysis confirmed asynchronous oocyte development. Absolute fecundity ranged from 8364 to 319,000 oocytes per female and was positively correlated with total length and body weight. Mean mature oocyte diameter ranged from 1.50 to 3.21 mm. Conclusions: The European catfish in the LTR exhibits high reproductive plasticity, early maturity, a prolonged spawning season, and elevated fecundity, likely facilitated by warm water temperatures and abundant prey resources. Crucially, these parameters reveal earlier maturation and greater reproductive investment relative to native populations, demonstrating an extreme phenotypic plasticity characteristic of successful invasions in southern European aquatic ecosystems. These findings provide essential biological parameters for targeted management, including selective removal of large females, intensified fishing effort during the spawning season, and population monitoring to prevent compensatory reproductive responses. Full article

Background/Objectives: The present study estimated the potential therapeutic effects of Borassus flabellifer immature endosperm extract (BFE) on the metabolic disorders of diabetes and hypothyroidism using a mixed research design. Methods: Characterization of phytochemicals via GC-MS demonstrated a highly abundant list of bioactive compounds, and it encompassed phenolic derivatives, methylxanthines, fatty acids, and inositol-related compounds. Molecular docking indicated that the major phytoconstituents showed positive binding affinities to the most vital metabolism and endocrine receptors, namely, TRβ1, PPARγ, and AMP-activated protein kinase (AMPK). Notably, both compounds C1 and C2 were highly affined towards TRβ1 (−7.8 and −7.6 kcal/mol), which is attributed to interactions in the active site through hydrogen bonding and hydrophobic responses, which means that the identified compounds were found to have good predicted interactions with some metabolic- and thyroid-associated targets and could be used to form preliminary hypotheses for further mechanistic studies. The in vivo data showed that the disease-induced groups were marked by hyperglycemia, imbalance in thyroid hormones, and dyslipidemia, as well as liver, kidney, and heart dysfunction. BFE caused significant decreases in these changes, which were also observed through improvements in fasting blood glucose, T3, T4, and TSH; partial restoration of lipid profiles; and dampening of liver and kidney injury signalers. The cardiac risk indices were also reduced significantly after BFE administration. Positive changes in body weight gain, feed ratio, and metabolic ratio further reflected better physiological stability. Results: These findings were corroborated by histopathological analysis, which showed that the tissue architecture of the pancreas, liver, kidney, and heart had significantly recovered in the study. BFE still showed constant therapeutic activity even though the magnitude of response was attenuated when combined disease conditions were used. Conclusions: Comprehensively, the results indicate that BFE potentially plays a role in the amelioration of metabolic and endocrine abnormalities of diabetic and hypothyroid conditions. These observations should be regarded as hypothesis-generating, as further mechanistic and translational studies are needed to substantiate their biological relevance. Full article

Grassland ecosystems are among the most threatened habitats in North America, and their degradation has contributed to widespread population declines of grassland-dependent birds. The Burrowing Owl (Athene cunicularia) is a grassland specialist whose populations have shown sustained declines at a continental scale; however, quantitative data on relative abundance remain limited in northern Mexico. We estimated a relative abundance index for the Burrowing Owl in the grasslands of the southern Chihuahuan Desert, Mexico, using vehicle-based line transects expressed as the number of individuals per linear kilometer (ind/km). Additionally, we evaluated the relationship between human disturbance and owl records using a standardized Human Disturbance Index (HDI) based on field indicators of grazing pressure and solid waste. A total of 18 transects (1 km each) yielded 83 detections, with a mean relative abundance of 4.61 ± 5.93 standard deviation (SD) ind/km. A Generalized Linear Model with a Negative Binomial distribution revealed a significant negative effect of the HDI on owl abundance (β = −1.27, z = −3.81, p = 0.0001; incidence rate ratio (IRR) = 0.28, 95% confidence interval (CI): 0.14–0.51). Our results provide a baseline abundance estimate for the Burrowing Owl in the southern Chihuahuan Desert and highlight the importance of habitat disturbance metrics to assess population status in fragmented and human-impacted grassland landscapes. Full article