Assessing water quality in lotic ecosystems using biological indicators is essential for their conservation. This study analyzed the influence of physicochemical parameters (pH, conductivity, dissolved oxygen, total nitrogen, nitrates, total phosphorus, phosphates, alkalinity, and hardness) on the diversity, abundance, and distribution of protozoa in 15 sites of the upper Soto la Marina River basin, Tamaulipas, Mexico, including the Corona, Purificación, Pilón, San Felipe rivers and the Vicente Guerrero Reservoir. Through bimonthly sampling over an annual cycle (February-December), 24 protozoan morphospecies were identified, with a dominance of Ciliophora (10 morphospecies) and Amoebozoa (4 morphospecies). Chi-square analyses revealed that morphospecies frequency was significantly dependent on the sampling site (χ² = 246.72, df = 69, p < 0.001) but independent of seasonality (χ² = 0.86, df = 15, p = 1.0). Beta diversity (Sorensen-Dice index) showed low faunistic similarity among most sites (<60%), suggesting high species turnover and a local environmental filter. Using Outlying Mean Index (OMI) analysis, most morphospecies exhibited a generalist niche (low marginality, high tolerance), showing no significant relationship with the measured environmental variables. However, Vorticella sp. emerged as an exception, showing a significant association (p = 0.0329) and positive correlation with maximum pH and alkalinity values, and at sites with high NO₃⁻ and PO₄³⁻ concentrations, suggesting its potential as a bioindicator of organic enrichment conditions in the region. The lack of a strong environmental signal in most species underscores the complexity of these systems and the need to integrate multiple levels of bioindicators. This study provides the first baseline on the protozoan community in the area and discusses its relevance for water quality monitoring in a region of high conservation value, such as the area of influence of the Sierra de Tamaulipas.

Artisanal fisheries in Mexico frequently operate with limited data, lacking historical catch and effort series. In this context, the population status of the dogfish (Rhizoprionodon terraenovae) was evaluated for the first time in Priority Marine Regions 45–46 and the area of influence of the Wetland of International Importance Playa Tortuguera Rancho Nuevo, Tamaulipas, using methods based on size frequencies. Between November 2018 and February 2020, 541 artisanal fishing organisms were analyzed in La Barra del Tordo using FISAT II. The von Bertalanffy growth parameters for combined sexes were: L∞ = 105 cm, k = 0.59 years⁻¹, t₀ = −0.195 years. Total (Z), natural (M) and fishing (F) mortalities were 4.13, 0.467 and 3.22 years⁻¹, respectively. The average exploitation rate (E = F/Z) was 0.78 (95% CI: 0.745–0.805), exceeding the reference point of 0.5 indicating severe overexploitation. The parameters showed biological consistency (Ø′ = 3.81; M/k = 0.79), and natural mortality was within the range reported for the species. This finding, in a priority region for conservation under the regime of the Conservation Sector of the Marine Ecological Management Program, shows the urgent need to implement fisheries management with an ecosystem approach that guarantees the sustainability of the fishery and the integrity of the coastal ecosystem. The study demonstrates that, even with limited data, it is possible to obtain robust estimates to inform management decisions in natural protected areas

Artisanal fisheries in Mexico frequently operate under data-limited conditions, lacking historical time series of catch and effort. The Atlantic sharpnose shark (Rhizoprionodon terraenovae) is caught by artisanal fisheries in Marine Priority Regions 45-46 and the influence area of the Playa Tortuguera Rancho Nuevo Wetland of International Importance, Tamaulipas, where it acts as a natural predator of Kemp's ridley sea turtle (Lepidochelys kempii) hatchlings, a critically endangered species. In this data-limited context, the population status of R. terraenovae was assessed for the first time using length-frequency based methods. Between November 2018 and February 2020, 541 organisms from the artisanal fishery in La Barra del Tordo were analyzed using FISAT II. The von Bertalanffy growth parameters for combined sexes were: L∞ = 105 cm, k = 0.59 yr⁻¹, t₀ = -0.195 yr. Total (Z), natural (M), and fishing (F) mortality rates were 4.13, 0.467, and 3.22 yr⁻¹, respectively. The mean exploitation rate (E = F/Z) was 0.78 (95% CI: 0.745-0.805), exceeding the reference point of 0.5 (Gulland, 1971), indicating severe overexploitation. The parameters showed biological consistency (Ø' = 3.81; M/k = 0.79), and natural mortality (0.467 yr⁻¹) fell within the range reported for the species. This finding, in a priority conservation region under the Conservation Sector regime of the Marine Ecological Zoning Program, evidences the urgent need to implement ecosystem-based fisheries management. The study demonstrates that, even with limited data, it is possible to obtain robust estimates that reconcile fisheries sustainability with L. kempii conservation in protected natural areas.

The Tilapia (Oreochromis aureus) sustains more than 90% of the fishery value and volume in the Vicente Guerrero Reservoir (VGR), Northeast Mexico, but stock status is uncertain due to lack of assessments. A total of 1,792 individuals (2020-2021) were analyzed. Von Bertalanffy growth, total (Z), natural (M) and fishing (F) mortality, and exploitation rate (E) were estimated. Under a data-limited framework, four complementary approaches were applied: the LBB model, length-based indicators, empirical reference points, and ecological risk assessment. Growth was negatively allometric (b=2.89). Estimated parameters were: L∞=464 mm, K=0.2275 yr⁻¹, Z=3.591 yr⁻¹, M=0.3894 yr⁻¹, F=3.302 yr⁻¹, E=0.892. The LBB model estimated a relative biomass B/B₀=0.057 (95% CI: 0.042-0.072) and an F/M ratio of 8.48. Only 7.5% of individuals exceeded maturity length, 4.8% were at optimal length, and 2.6% were mega-spawners. Estimated fishing mortality exceeded the reference points (F_MSY=0.339 yr⁻¹; F_limit=0.508 yr⁻¹; F_crash=0.678 yr⁻¹) by 9.7, 6.5, and 4.9 times, respectively, classifying the stock as extreme high risk. The O. aureus stock in VGR is in biological collapse (B/B₀=5.7%; F/M=8.48). Increasing minimum capture length to at least 290 mm and reducing fishing effort by 80-90% is urgently required. The convergence of independent methods validates data-limited approaches for artisanal fisheries.

Tap water quality is a critical public health concern because microbiological contamination in water distribution systems may pose risks to consumers. Therefore, this study seeks to integrate conventional and molecular approaches. Traditional methods, including the Most Probable Number (MPN) and selective culture media, were used to detect microbial indicators of contamination, while molecular analysis using Polymerase Chain Reaction (PCR) was used to identify Escherichia coli at 5 sites within the city’s water distribution network. Metagenomic analysis was performed at two of the five sites selected based on the consistent presence of microorganisms and resource constraints. Sequencing was used to characterize the broader microbial community that may not be detected by culture-based methods. Traditional analyses revealed the presence of thermotolerant coliforms, suggesting potential fecal contamination, while PCR confirmed the presence of Escherichia coli. Metagenomic analysis identified a diverse bacterial community, with the families Moraxellaceae, Pseudomonadaceae and Enterobacteriaceae among the predominant taxa. The combined use of conventional and molecular methods provided complementary information for assessing tap water quality and bacterial taxa of potential sanitary importance.

Assessing water quality in lotic ecosystems using biological indicators is essential for their conservation. This study analyzed the influence of physicochemical parameters (pH, conductivity, dissolved oxygen, total nitrogen, nitrates, total phosphorus, phosphates, alkalinity, and hardness) on the diversity, abundance, and distribution of protozoa at 15 sites in the upper Soto la Marina River basin, Tamaulipas, Mexico, including the Corona, Purificación, Pilón, and San Felipe rivers and the Vicente Guerrero Reservoir. Through bimonthly sampling over the annual cycle of 2021 (February–December), 24 protozoan morphospecies were identified, with dominance of Ciliophora (10 morphospecies) and Amoebozoa (4 morphospecies). Chi-square analyses revealed that morphospecies frequency was significantly dependent on sampling site (χ² = 246.72, df = 69, p < 0.001) but independent of seasonality (χ² = 0.86, df = 15, p = 1.0). Beta diversity (Sørensen–Dice index) showed low faunistic similarity among most sites (<60%), suggesting high species turnover and a local environmental filter. Using Outlying Mean Index (OMI) analysis, most morphospecies exhibited a generalist niche (low marginality, high tolerance), showing no significant relationship with the measured environmental variables. However, Vorticella sp. emerged as an exception, showing a significant association (p = 0.0329) and positive correlation with maximum pH and alkalinity values and occurring at sites with high NO₃⁻ and PO₄³⁻ concentrations, suggesting its potential as a bioindicator of organic enrichment conditions in the region. The absence of a strong environmental signal in most species underscores the complexity of these systems and the need to integrate multiple levels of bioindicators. This study provides the first baseline on the protozoan community in the area and discusses its relevance for water quality monitoring in a region of high conservation value, such as the area of influence of the Sierra de Tamaulipas.