Jorge Homero Rodríguez-Castro

Small-scale fisheries management is a critical challenge for global fisheries sustainability. This study diagnoses the institutional failures behind overexploitation and regulatory non-compliance in Mexico’s shark-cazón fishery (predominantly Rhizoprionodon terraenovae). Using the Institutional Analysis and Development (IAD) Framework and Ostrom’s Social-Ecological Systems (SES) approach, we assessed the catch series (1976–2014) and institutional robustness. Results show a 77% surplus over the Maximum Sustainable Yield (MSY), with an average catch of 51,417 tonnes per year against a biological limit of 29,040 tonnes. The diagnosis reveals undefined access limits, exclusively state-run monitoring, sanctions provided for in law but not applied participatorily, and the absence of local conflict-resolution mechanisms. These findings suggest that overexploitation is not an inevitable biological failure but the outcome of a command-and-control design that inhibits collective action and erodes rule legitimacy. This study contributes to the common-pool resource governance literature by extending Ostrom’s framework and Hønneland’s compliance model to a previously underrepresented Latin American elasmobranch context. Based on this diagnosis, we recommend transitioning toward polycentric governance—with nested community monitoring, effectively enforced graduated sanctions, and local conflict-resolution mechanisms—as a strategy for improving regulatory compliance in data-limited fisheries.

Artificial wetlands are a critical replacement habitat for waterbirds in arid regions, but little is known about how elevation and seasonality jointly structure these communities. The objective of this study was to assess the combined effects of elevation, seasonality, and agricultural disturbance on the richness, diversity, and composition of waterbird communities in artificial wetlands. We surveyed 36 permanent artificial wetlands across three elevational strata (low, intermediate, and high) in Poanas, Durango, Mexico, using variable-radius point counts over a complete annual cycle, and assessed richness, alpha diversity, beta diversity, indicator species, and their relationship with environmental variables. Estimated richness (Chao 1, Jackknife 1) and alpha diversity (Simpson, Shannon; Kruskal–Wallis H = 7.63, p = 0.022) decreased significantly in the high stratum relative to the low and intermediate strata, with no differences between the latter two. Beta diversity showed a similar pattern: the high stratum was significantly distinct from the other two (Permutational Multivariate Analysis of Variance, F = 3.225, p = 0.001). Canonical Correspondence Analysis revealed that community composition was more strongly associated with cropland areas (r = 0.6) than with elevation (r = −0.33). Seasonally, abundance was higher in winter, associated with migratory species; a two-way PERMANOVA confirmed that elevation and seasonality had comparable and largely independent effects on community composition (R² = 7.78% and 7.11%, respectively; both p < 0.001). These results indicate that elevation and seasonality act as complementary environmental filters and that surrounding agricultural management can be as determinant as topography for the conservation of waterbirds in artificial wetlands. These findings have direct implications for the design of conservation strategies in agropastoral landscapes and open new avenues of research on the relative role of anthropogenic disturbance versus topography in artificial wetland systems in arid regions.

The striped mullet (Mugil cephalus) and white mullet (Mugil curema) support artisanal fishing at the mouth of the Soto La Marina River, Gulf of Mexico, an area of great ecological value within the Laguna Madre and Rio Bravo Delta Protected Natural Area, the Terrestrial Priority Region RTP-83, and the Marine Priority Region RMP-44. Given the absence of historical catch and effort time series—a typical constraint of data-limited fisheries—a length-based frequency approach was used to estimate growth parameters, mortality rates, and the exploitation rate (E = F/Z). During 2018–2019, 1134 specimens of M. cephalus and 339 of M. curema were sampled. Due to sexual dimorphism in M. cephalus, analyses were performed separately for females, males, and combined sexes, while M. curema was analyzed with sexes combined. Growth (L∞, k) and mortality (Z, M, F) parameters for combined sexes were: M. cephalus (562 mm, 0.14 year⁻¹; 3.72, 0.21, 3.51 year⁻¹) and M. curema (329 mm, 0.15 year⁻¹; 1.46, 0.25, 1.21 year⁻¹). Exploitation rates (E) substantially exceeded Gulland (E = 0.5) and Patterson (E = 0.4) reference points: M. cephalus females (0.891), males (0.915), combined sexes (0.944), and M. curema (0.828). It is concluded that both stocks show strong evidence of growth overfishing, with exploitation rates well above established reference points, revealing a disconnect between the area’s conservation designations and the actual condition of the resource.

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 (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.

Oyster spat recruitment is a key process controlling the persistence of natural populations. However, the relative influence of environmental gradients on spat recruitment remains poorly understood in estuaries of the Gulf of Mexico, especially along the Mexican coast. The aim of this study was to analyze the influence of some environmental factors on the spat recruitment of the eastern oyster ( Crassostrea virginica ) along the subtropical estuary of the Soto la Marina River, Gulf of Mexico. Six sampling sites were selected along the estuary, ranging from 1 km (Site 1) up to 22.8 km (Site 6) from the river mouth. Monthly, samples (April 2020–March 2021) of oyster spat ( C. virginica ) were collected from each site using an artificial spat collector. Water temperature, salinity, dissolved oxygen, pH, and Secchi depth were measured at the same time as oyster spat were collected for each site. Spatial and seasonal variations in the number of oyster spat were evaluated using a generalized linear mixed model (GLMM). Additionally, the relationship between spat recruitment and environmental variables was assessed using multiple linear regression analyses. Salinity was the unique environmental variable with significant differences between sites, showing a decreasing gradient from the river mouth to the upstream locations. The mean density of oyster spat decreased significantly from Site 1 to Site 5; however, they were absent at Site 6. Salinity and temperature were the environmental factors that explained the spatio-temporal variation of spat recruitment, showing a positive relationship with spat density on the collectors. Since temperature did not show significant differences between sampling sites, salinity is considered the primary environmental condition influencing the spat recruitment along the estuary. These findings provide a basis for identifying optimal areas and periods for oyster spat collection, supporting efforts in oyster reef restoration and the development of oyster aquaculture.

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 (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.

The striped mullet (Mugil cephalus) and white mullet (Mugil curema) support artisanal fishing at the mouth of the Soto La Marina River, Gulf of Mexico, an area of great ecological value within the Laguna Madre and Rio Bravo Delta Protected Natural Area, the Terrestrial Priority Region RTP-83, and the Marine Priority Region RMP-44. Given the absence of historical catch and effort time series—a typical constraint of data limited fisheries—a length based frequency approach was used to estimate growth parameters, mortality rates, and the exploitation rate (E = F/Z). During 2018–2019, 1,134 specimens of M. cephalus and 339 of M. curema were sampled. Due to sexual dimorphism in M. cephalus, analyses were performed separately for females, males, and combined sexes, while M. curema was analyzed with sexes combined. Growth (L∞, k) and mortality (Z, M, F) parameters for combined sexes were: M. cephalus (562 mm, 0.14 year⁻¹; 3.72, 0.21, 3.51 year⁻¹); M. curema (329 mm, 0.15 year⁻¹; 1.46, 0.25, 1.21 year⁻¹). Exploitation rates (E) substantially exceeded Gulland (E = 0.5) and Patterson (E = 0.4) reference points: M. cephalus females (0.891), males (0.915), combined sexes (0.944); M. curema (0.828). It is concluded that both stocks are experiencing severe overexploitation, revealing a disconnect between the area's conservation designations and the actual condition of the resource.

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.

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.