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A systematic review and meta-analysis of on farm management and water quality as risk factors triggering pathogen outbreaks in tilapia culture is presented. A total of 121 papers from 28 countries, 37 devoted to management and 84 to water quality associated with the presence of pathogens in tilapia culture were analysed. Most of research has been made on ponds, focusing on bacteria and metazoans. Meta-analysis reveals the proportion of research showing statistical inferences between management (34%), water quality (38% for bacteria and 16.2% for metazoans) and pathogen outbreaks. The most cited parameters related to pathogens outbreaks were temperature (30°C), dissolved oxygen (5.0 mg/L), pH (8.0) and ammonia (1.0mg/L) 65, 38, 32 and 34 papers, respectively. However, statistical inference was20%. Meta-analysis reveals tendencies between high temperatures (30-35°C), low dissolved oxygen (5 mg/L) and high NH

La tilapia, originaria de África, ha sido introducida en cientos de países con fines de cultivo, generando un importante mercado, cubriendo necesidades alimentarias de amplios sectores de la población. La introducción de la tilapia ha traído problemas de invasiones en prácticamente todos los ambientes acuáticos tropicales de América y otros continentes, afectando la biodiversidad. Su cultivo ha generado necesidad de agua en altas cantidades, por lo que frecuentemente se emplean aguas poco aptas y sin tratamiento previo; además el agua que se emplea en los cultivos comúnmente es regresada al medio sin ningún tratamiento agudizando el problema. La mala calidad del agua produce estrés en los peces, volviéndolos susceptibles a enfermedades parasitarias, produciendo bajos rendimientos y mortalidad. Otro problema que se enfrenta respecto a las enfermedades parasitarias es la falta de conocimiento de los productores para identificar, prevenir y contrarrestar estas enfermedades. La capacitación y seguimiento de las actividades acuícolas por parte de expertos, así como compartir experiencias es fundamental para reducir estos riesgos. Existen miles de artículos científicos y técnicos que abordan estas problemáticas, pero la mayoría no está al alcance de los productores que, al no estar preparados para el manejo y control de enfermedades, sufren pérdidas económicas y desmotivación. El objetivo de este ensayo es dar al lector una visión general de la relación entre el manejo, calidad del agua y diversas enfermedades parasitarias que atacan a la tilapia en las prácticas de cultivo.

Nile tilapia is the most commercially important fish in Chiapas as well as in other parts of the world. An understanding of parasite infection dynamics in tilapia may assist in applying proper prophylactic measures for reducing the loss of fish caused by parasitic diseases. Different environments and culture systems may imply different infection dynamics; therefore, the present study identified and compared the infection parameters (prevalence, mean abundance, and intensity) of parasites of Oreochromis niloticus cultured in floating cages and ponds. A total of 18 metazoan parasite taxa were recovered from gills, skin, fins and intestines of 310 specimens from floating cages and ponds. Fourteen species of parasites were found in floating cages: 8 monogenean species, 1 nematode, 1 digenea, 1 crustacea, 3 protozoans. In ponds, 16 parasite taxa were reported: 11 were monogeneans species, 4 protozoans and 1 crustacean. In both systems, monogeneans (Cichlidogyrus sclerosus, C. tilapiae, Gyrodactylus cichlidarum) and protozoans (Trichodina compacta) were most prevalent. Tilapia in ponds sustained higher parasitic infections than those in floating cages (p 0.05). The Canonical Correspondence Analysis showed two groups: the first grouped the ponds, associated with high values of nitrite, nitrate, ammonia, conductivity, temperature, and the abundance of the ectoparasites C. halli, C. dossoui, Scutogyrus longicornis, C. sclerosus and T. compacta. The second group grouped the cages, associated with Clinostomum marginatum, Apiosoma piscicola, Lernea sp., and Contracaecum sp. and a high dissolved oxygen concentration. Our findings suggest that monitoring programs are required to improve the sanitary conditions of tilapia cultures in Chiapas.

De Jesús-Carrillo, Rosa María, Ocaña, Frank A., Hernández-Ávila, Iván, Mendoza-Carranza, Manuel, Sánchez, Alberto J., Barba-Macías, Everardo (2020): Mollusk distribution in four habitats along a salinity gradient in a coastal lagoon from the Gulf of Mexico. Journal of Natural History 54 (19-20): 1257-1270, DOI: 10.1080/00222933.2020.1785030, URL: http://dx.doi.org/10.1080/00222933.2020.1785030

Land use change threatens the ecological integrity of tropical rivers and streams; however, few studies have simultaneously analyzed the taxonomic and functional responses of tropical macroinvertebrates to riparian forest conversion. Here, we used community structure, functional diversity, and stable isotope analyses to assess the impacts of riparian deforestation on macroinvertebrate communities of streams in southern Mexico. Monthly sampling during the dry season was conducted in streams with riparian forest (forest streams), and in streams with pasture dominating the riparian vegetation (pasture streams). Samples were collected for water quality (physical-chemical variables, nutrient concentrations, and total suspended solids), organic matter (leaf litter abundance and algal biomass), and macroinvertebrate abundance and diversity. Higher temperature, conductivity, suspended solids, and chlorophyll a were detected in pasture streams, while nitrate concentrations and leaf litter biomass were greater in forest streams. Macroinvertebrate density was higher in pasture sites, while no differences in taxonomic diversity and richness were found between land uses. Functional evenness was greater in forest streams, while richness and divergence were similar between land uses, despite differences in taxonomic composition. Environmental variables were associated with taxa distribution but not with functional traits, suggesting current conditions still promote redundancy in ecological function. Isotopic analyses indicated consumers in pasture streams were enriched in 13C and 15N relative to forest streams, potentially reflecting the higher algal biomass documented in pasture systems. Isotopic niches were broader and more overlapped in pasture streams, indicating more generalist feeding habits. No significant losses of taxonomic or functional diversity were detected in pasture streams. However, changes in trophic ecology suggest landscape-level processes are altering macroinvertebrate feeding habits in streams. The changes we observed in habitat, water quality, and macroinvertebrate community were related to the removal of the riparian vegetation, suggesting the structure and function of the focal systems would benefit from riparian restoration.

Aim: The current paper aims to present and discuss some hypothesis about why in Mexico and in particular the Mexico City the epidemy of COVID-19 seems to be slower than other countries. Subject and methods: We compared daily UVI maximum and the reported COVID cases in Mexico City, New York, and Los Angeles and performed an ADONIS permutation test to look for significant differences between case numbers and its relationship with the UV index. We performed a quantile regression to explain the relation between UVI and daily COVID cases. We also investigated and analyzed other possible factors contributing to this slowdown because UVI cannot be the only explanation. Results: Although Mexican authorities have applied one of the smaller numbers of tests in the world, it is possible to identify a slowdown in Mexico's rate of infections. We found a negative and significant difference between the UV and registered cases among the three cities analyzed. However, this slowdown cannot be explained by a single factor. It is possible to hypothesize about the confluence of other factors as Vitamin D levels in Mexican population, lack of central air conditioning and the ventilation in houses and metropolitan transportation systems. Also, the Bacillus Calmette–Guérin vaccination could be part of the explanation of this phenomenon. Conclusions: Single parameter models as solar irradiation can explain partially the complicated spread of COVID-19 in different parts of the world. However, it is necessary to extend our scientific understanding of environmental effects, city infrastructure, population age, vaccination schemes, socioeconomic conditions, social and political behavior on COVID-19 epidemic dynamics.

Natural Protected Areas (NPAs) are very important among other attributes because of their high biodiversity, in addition to the ecosystem services they provide. The Centla Wetland Biosphere Reserve (CWBR) in Tabasco, Mexico, is one of the most extensive wetlands of Mesoamerica, where the two rivers converge with the greatest flow to the Gulf of Mexico, the Grijalva and Usumacinta Rivers. The CWBR presents several problems caused by anthropogenic activities. One of these is fishing; in this reserve, there is a problem caused by the numeric dominance of the invasive non-native genus of the armored catfish (Pterygoplichthys spp.) even with a minimal economic importance. In addition, the local and regional overfishing of the blue land crab (Cardisoma guanhumi) has affected its reproductive cycle. Results of research projects on the environmental and socioeconomic situation of both resources are exposed here as well the perception of this situation by fishermen in the area. The situation of each resource is exposed, on the one hand how to control and reduce the damage caused by the armored catfish and on the other hand how to regulate the exploitation of the blue land crab through the proposal of legal mechanisms such as the closure and regulation of catches.

A Bathytoshia centroura female of 181 cm disk width was found during the monitoring of small scale fishery in the state of Tabasco, Mexico. The specimen was caught by a gill net vessel at 32 km northeastern of the port of Sanchez Magallanes, at 78 m depth. Large size and spacing of mid-dorsal bucklers, conspicuous tubercles on the outer parts of disc and tail with numerous rows of small spines were used to verify the identification. The presence of this species in the southeast of the Gulf of Mexico is reported, increasing up to five, the number of the species of the subfamily Dasyatinae in this zone.

Fish assemblages in tropical lowland rivers are characterized by a high richness of species that feed on a diverse array of food resources. Although closely related species often have similar feeding ecology, species within the family Cichlidae display a broad spectrum of trophic niches, and resource partitioning has been inferred from studies conducted in Neotropical rivers. We investigated interspecific variation in food resource use and its relationship to morphological variation among cichlid fishes within the Pantanos de Centla Biosphere Reserve, a coastal area encompassing the delta of the Grijalva-Usumacinta River in Tabasco, Mexico. Most species consumed benthic crustaceans, aquatic insect larvae, and detritus, but some were more herbivorous, and one species was a specialized piscivore. Dietary niche overlap among species was higher than expected for one assemblage, and similar to random expectations for another, suggesting a lesser role for resource partitioning than has been shown for some cichlid assemblages, perhaps due to availability of abundant resources, even in low-water conditions. Canonical correspondence analysis revealed that greatest morphological differences am7ong species involved functional traits directly associated with resource use. Relationships between feeding ecology and morphology were similar to those described for other riverine cichlids. Strong ecomorphological relationships facilitate inferences about the ecology of cichlid species, including species that currently lack data from field studies. Knowledge of ecological relationships will be important for conservation in the Pantanos de Centla, an ecosystem of global significance for biodiversity and ecosystem services.

To have a better understanding of the influence of topographic, climatic, and, especially, anthropogenic factors on hydrological discharge and flooding, this study proposes a new framework approach using a set of methods to answer the questions why, where, when, and how flooding occurs. Including conditional inference tree (CIT), cross-correlation, and double-mass curves analysis, the approach is demonstrated in an application to the Wei River Basin, China. From the CIT analysis, dam construction period was identified as the most important factor (why), and the sub-catchment farthest upstream contributed the most to the flooding of the downstream floodplain (where). We then analysed the effect of the periods of dam construction on the time lag change (when) and the precipitation-discharge relationship (how) using cross-correlation analysis and double-mass curves analysis, respectively. The results suggested that the dam construction delayed the precipitation for 0.4days on average compared to before the dam construction period, and the discharge at the outlet of the basin was reduced by 44%. This framework approach is promising as it can quantitatively evaluate the importance of multiple factors on multiple years of flooding, while many studies evaluate single flooding events.

The feeding rate and feeding preference of the crab Aratus pisonii regarding three mangrove species, red ( Rhizophora mangle ), white ( Laguncularia racemosa ) and black ( Avicennia germinans ), under two leaf conditions (fresh and senescent), were recorded in two laboratory experiments. Feeding rates were determined considering the dry weight of the food before feeding minus the dry weight of the remaining food after feeding, standardised on the fresh weight of each crab. A factor for the conversion of fresh weight to dry weight of each mangrove species and leaf condition was applied in order to obtain the dry weight of the food. Preferences were determined based on the consumption of one of the mangrove species when offered the three species simultaneously, under two leaf conditions. Results showed that the feeding rates of A . pisonii were high in the case of the fresh leaves of A . germinans (0.03 ± 0.06 g psh /g phi ) and R . mangle (0.02 ± 0.03 g psh /g phi ) and of the senescent leaves of L. racemosa (0.05 ± 0.04 g psh /g phi ), indicating that the crabs chose both fresh and senescent leaves of the species L. racemosa . Regarding sex, the females fed more than the males in all the experiments. Feeding rates were: with fresh leaves, A . germinans and R . mangle (0.04 ± 0.06 and 0.03 ± 0.03 g psh /g phi , respectively) and with senescent leaves, L . racemosa and R . mangle (0.06 ± 0.05 and 0.04 ± 0.04 g psh /g phi , respectively). Feeding preferences were: with fresh leaves, L . racemosa (0.06 ± 0.06 g psh /g phi ) and with senescent leaves, L . racemosa and R . mangle (0.05 ± 0.05 and 0.03 ± 0.03 g psh /g phi , respectively). Under laboratory conditions, the crabs chose both fresh and senescent leaves of L. racemosa as food, and recorded greater feeding rates with fresh leaves of A . germinans and R . mangle when they had no other feeding option.

Tropical coastal ecosystems of the southern Gulf of Mexico including marshes, mangroves and seagrasses of Centla Wetlands and Terminos Lagoon (Grijalva-Usumacinta delta) are known to host a high diversity of aquatic consumers. Nevertheless, the limited research focusing on the energy fluxes that sustain consumers has as yet neither considered the strong seasonality of these systems, nor the linkage of the trophic flow patterns with ecosystem functioning. The present work analyses and compares stable isotope ratios (δ13C and δ15N) of consumers during the dry and rainy season at different wetland sites to determine their resource utilization. The sites compared comprise three fluvio-lagoons and a coastal mangrove creek that differ in vegetational characteristics, distance to the sea, and freshwater input. The results support the hypothesis that a larger isotopic niche breadth of consumers prevails during the rainy season, when resource availability is supposedly higher. This translates into an increase in resource use diversification by consumers and corroborates the flood pulse concept (FPC), which can be particularly applied to those habitats with high riverine influence in the study area (e.g., fluvio-lagoons). However, the FPC alone cannot be applied to understand the main factors influencing the fate and utilization of basal resources in areas interacting more actively with the sea, and therefore further extensions and/or complementary conceptual approaches considering marine systems highly interconnected with coastal floodplains should be considered.

Se evaluó la germinación y supervivencia in situ y ex situ de plántulas de Aspidosperma megalocarpon, Eugenia sp., Lonchocarpus castilloi, Manilkara zapota, Ormosia macrocalyx y Rollinia mucosa. En campo se sembraron 2 160 semillas en nueve bloques de 5 m x 20 m distribuidos en bosque tropical, acahual maduro y acahual joven. El experimento se replicó en condiciones de vivero bajo sombra de 40, 60 y 80%. Los tipos de cobertura vegetal no mostraron diferencias significativas en las tasas de germinación y de crecimiento; sin embargo, estos sí influyeron en la capacidad de germinación de A. megalocarpon y O. macrocalyx, y en las tasas de depredación de M. zapota y L. castilloi. En el acahual joven se presentó la mayor depredación de semillas, sin embargo, las plántulas remanentes presentaron mayor supervivencia que en las otras coberturas vegetales. En el vivero no se encontró diferencia en la proporción de semillas germinadas, ni en las tasas de germinación y de crecimiento. R. mucosa, fue la única especie que presentó menor supervivencia (42%). Las condiciones ambientales de las diferentes clases de cobertura vegetal en el área de estudio mantienen condiciones adecuadas para el proceso de germinación, crecimiento y establecimiento de plántulas de las especies estudiadas, lo cual permite sugerir su utilización en la rehabilitación de áreas degradadas del bosque original sembrando de manera directa, siempre y cuando se realice de manera inmediata después de la recolecta. Es necesario continuar con estos estudios para promover el uso de especies nativas en la rehabilitación y restauración de bosques tropicales.

Regional ecological information is relevant to the international management of vulnerable species such as sharks. On the basis of monthly fishery data (2007–2010) from two small-scale multispecies fleets, namely, the bottom longline fleet (MLL) and vertical line+shark-specific longline fleet (VL+SSL) operating on the Campeche Bank, we recorded 19 shark species. The occurrence of immature stages of 15 species, gravid females of Carcharhinus leucas, three Endangered species (Sphyrna mokarran, S. lewini, Isurus oxyrinchus) and three Vulnerable and six Near-threatened species emphasises the importance of this area. Rhizoprionodon terraenovae (42.01% of total abundance), S. lewini (24.82%) and S. tiburo (14.57%) were the most abundant species. The commercial logbooks (2007–2012) for one fleet recorded 6517 for MLL and 1617 for VL+SSL fishery trips. The general additive model indicated a maximum of shark catch rate (CR) for MLL and SSL during 2011 (mean±s.e., 49.94±8.44 and 91.38±16.07kg per 100 hooks respectively). Monthly CR for MLL was highly variable; the maximum was observed in February (15.45±21.43kg per 100 hooks), the maximum monthly CR for SSL was in January (88.04±14.85kg per 100 hooks). For MLL, a positive relation was observed between effort and CR, whereas, for SSL, no clear relation was observed.

La cuenca del Usumacinta es uno de los principales sistemas hidrologicos de Mexico, posee una alta diversidad de flora y fauna, y constituye el ultimo rio vivo en el pais, por consiguiente la generacion de info rmacion que ayude a su aprovechamiento sustentable es urgente. El objetivo de esta investigacion es analizar la diversidad de especies asociada a la pesca en la cuenca del Usumacinta, haciendo enfasis en la importancia de las especies introducidas en relacion a la diversidad de especies explotadas. La cuenca fue dividida en 3 regiones (selva, lagunas y costa). En toda la cuenca, la pesca de pequena escala explota 35 especies (30 especies de peces y 5 de crustaceos). La mojarra pinta (Parachromis managuensis), la tilapia (Oreochromis niloticus), el bobo escama (Ctenopharyngodon idella), la carpa comun (Cyprinus carpio), la carpa roja (Carassius auratus) y los plecos (Pterygoplichthys spp.) son especies introducidas, representando 20.7% del total. En la zona selva, las especies introducidas alcanzaron altas tasas de captura, siendo las carpas las mas capturadas. A pesar de que estas especies son parte fundamental de las pesquerias del Usumacinta, sus efectos sobre el ecosistema deben ser analizados, especialmente especies con altas abundancias y nula importancia comercial como los plecos.

Tropical small-scale fisheries are typical for providing complex multivariate data, due to their diversity in fishing techniques and highly diverse species composition. In this paper we used for the first time a supervised Self-Organizing Map (xyf-SOM), to recognize and understand the internal heterogeneity of a tropical marine small-scale fishery, using as model the fishery fleet of San Pedro port, Tabasco, Mexico. We used multivariate data from commercial logbooks, including the following four factors: fish species (47), gear types (bottom longline, vertical line+shark longline and vertical line), season (cold, warm), and inter-annual variation (2007–2012). The size of the xyf-SOM, a fundamental characteristic to improve its predictive quality, was optimized for the minimum distance between objects and the maximum prediction rate. The xyf-SOM successfully classified individual fishing trips in relation to the four factors included in the model. Prediction percentages were high (80–100%) for bottom longline and vertical line + shark longline, but lower prediction values were obtained for vertical line (51–74%) fishery. A confusion matrix indicated that classification errors occurred within the same fishing gear. Prediction rates were validated by generating confidence interval using bootstrap. The xyf-SOM showed that not all the fishing trips were targeting the most abundant species and the catch rates were not symmetrically distributed around the mean. Also, the species composition is not homogeneous among fishing trips. Despite the complexity of the data, the xyf-SOM proved to be an excellent tool to identify trends in complex scenarios, emphasizing the diverse and complex patterns that characterize tropical small scale-fishery fleets.

Tropical coastal habitats like marshes, mangroves, and submerged grasses comprise diverse plant and animal communities and a certain degree of connectivity with other ecosystems. We compared the food web structure of a fringing mangrove-seagrass habitat and three fluvio-lagoons with marsh-eelgrass and mangrove-bare sediments during a dry season in Terminos Lagoon and Centla Wetlands, Southern Gulf of Mexico. Analysis of δ13C and δ15N stable isotopes in tissues of aquatic consumers, primary producers, and other carbon sources, in combination with isotope-based Bayesian methods, were performed to determine the main food sources and the isotopic niche of the consumers’ communities. Consumers in the mangrove-seagrass site showed high dependence on phytoplankton (average contribution 31 %), macroalgae (20 %) and organic matter derived from seagrasses (17 %). In the fluvio-lagoons, consumers showed high dependence on marginal vegetation (16–46 %). Phytoplankton and mangrove epiphytes comprised other important resources at these sites (with contributions of 24–44 %). The isotopic niche of consumers from the fringing mangrove-seagrass site did not overlap with those from the fluvio-lagoons. Moreover, despite the predominance of generalist consumers in all sites, differences in their isotopic niche area were observed, with consumers from the marsh-eelgrass site showing the narrowest. This suggests that consumer resource availability greatly differs in these habitats. Our results provide valuable information that help increase our understanding about the trophic structure in these important estuarine systems.

Assessments of trophic diversity are critical for evaluating ecological integrity of habitats, but interpretations of such assessments require an understanding of variation across natural environmental gradients. This can be problematic when comparing structure of assemblages in under-studied regions or habitats, such as watersheds in dry tropical forests. Here, we compared assemblage-wide trophic metrics and intraspecific variation for a subset of consumer traits across rivers and among different ecosystem types within the Grijalva and Usumacinta River basins of Mexico. The two rivers differ with respect to flow-regime alteration and climate: the Grijalva River has been hydrologically altered by a series of dams and has wet and dry tropical forests in its watershed, whereas the Usumacinta River remains unimpounded with a watershed dominated by tropical wet forest. Use of allochthonous resources was pervasive in Usumacinta basin tributaries, with stable isotope signatures suggesting that many fishes directly consumed riparian plants and detritus. In contrast, fish assemblages in Grijalva basin tributaries were supported by higher proportions of in-stream production. Food-chain length was highest in a Grijalva River reservoir fish assemblage, although trophic diversity was low in the impounded system compared to the mainstem Usumacinta River, where fishes consumed the broadest variety of food resources. We also observed differences in trophic ecology and body nutrient content within taxa across habitat types and basins. The differences we observed suggest that even in relatively intact watersheds, expectations for trophic structure in tropical streams should be adjusted based on factors such as discharge, climate, and riparian forest cover.

Los elasmobranquios son depredadores activos que dependen de un sistema visual bien desarrollado. Los ojos de la raya latigo americana, Dasyatis americana, estan adaptados a intensidades de luz variables en zonas costeras. En este estudio se utilizan caracteres morfologicos y metodos moleculares (ADNmt COI) para describir el hallazgo de un morfotipo con ausencia de ojos en la raya D. americana, en un area costera marina tropical. La descripcion esta basada en seis ejemplares sin ojos colectados a partir de muestreos de flotas de pesca de pequena escala que operan en el Banco de Campeche al sur del Golfo de Mexico. Mediante comparacion de las diferentes caracteristicas fenotipicas (color, numero de dientes, forma de la aleta pelvica y de los espiraculos) entre los morfotipos sin ojos y los morfotipos regulares, se encontraron diferencias contrastantes. Tanto los machos como hembras de los morfotipos sin ojos presentaron organos reproductivos internos completos y funcionales. Utilizando los resultados obtenidos a traves de analisis geneticos provenientes del codigo de barras genetico, se confirma que los individuos sin ojos pertenecen a D. americana. Este es el primer reporte de individuos sin ojos de D. americana o de especies cercanas que son reproductivamente funcionales, y que viven simpatricamente con individuos de D. americana de morfotipo regular en el sur del Golfo de Mexico.

Salinity tolerance is one of several important physiological attributes that determine invasion success and the pattern of dispersal of introduced aquatic organisms. Introduced freshwater fishes able to tolerate elevated salinities have the potential to invade and exploit brackish-water (mixohaline) environments and use estuaries and coastal waters as ‘bridges’ for dispersing from one coastal river system to another. Several members of the neotropical suckermouth armoured catfish genus Pterygoplichthys (Siluriformes: Loricariidae) have established non-native populations in inland waters of North and Central America, Asia and islands in the Caribbean, and Pacific and Indian oceans. Loricariids are generally considered to be strictly freshwater; but a few naturally occur in mesohaline habitats. Catch and habitat data from 2004–2005 and 2009–2011 fish surveys in the Grijalva–Usumacinta River delta region (south-eastern Mexico) confirmed that introduced Pterygoplichthys populations established in upstream freshwater sites (where these catfish are abundant) have recently dispersed into downstream oligohaline and mesohaline estuarine habitats. During 2009–2011 surveys, these non-native catfish – tentatively identified as P. pardalis or its hybrids – were found in sites with salinities ranging from 1 to 8 ppt (mean 5.2 ppt). Acute-salinity experiments were conducted with Pterygoplichthys (110–302 mm standard length, N = 140) captured in the Grijalva–Usumacinta Basin to determine upper salinity tolerance levels. Tests demonstrated that individuals maintained in salinities of 0.2 ppt were able to survive abrupt (acute) exposure to salinities up to 10 ppt with little mortality over 10 days (240 h experimental endpoint). A few individuals survived abrupt exposure to 11 and 12 ppt for 20 or more hours, although none survived more than a few hours at 16 ppt or greater. These field and experimental results provide quantitative evidence that non-native Pterygoplichthys are physiologically capable of surviving mesohaline conditions for extended periods and that non-native populations in Mexico are invading and presumably exploiting estuarine and other coastal environments, perhaps as feeding areas and potentially as dispersal routes. Copyright © 2011 John Wiley & Sons, Ltd.

In Southeastern Mexico, Centropomus undecimalis is an important fish species of sport and commercial fisheries for coastal and riverine communities. Fisheries along rivers and coasts depend on migratory habits of this species, and these movements are probably related to reproduction. In spite of its economic importance, few studies have been conducted focusing on its reproductive biology, and this research aims to analyze these habits. Samples (fork length, somatic and gonads weight, and macroscopic maturity stages) were obtained from organisms collected by fishermen from the largest fishing cooperatives along the coastal and riverine areas of Tabasco, from July 2006 to March 2008. Fish size ranged from 34 to 112cm fork length, with an average age of 6.42 years for males and 9.12 years for females. In riverine areas, fish sizes ranged from 30 to 85cm and the average age was 5.5 years for males and 6.6 years for females. Significant differences were recorded between lengths of males and females from the two areas (Kruskal-Wallis, p0.05). A curve for eviscerated weight was calculated for both sexes, for coastal fishes SW=0.0059(FL) 3.07, and the riverine ones SW=0.0086(FL) 2.98, with an isometric growth (b=3). The period of maximum reproduction was from July to August, with temperatures of 28 to 30°C. A significant correlation between the gonadosomatic index (GSI) and rainfall was recorded for samples of both males and females from coastal areas (r=0.63, r=0.70) whereas only one positive correlation was recorded for riverine females (r=0.57). The size at first maturity (L50) was estimated at 60cm and 80cm (FL), corresponding to 5.5 and 8.5 years of age, for males and females, respectively. An important proportion of mature females of eight years and older, suggests that these ages contribute significantly to the reproductive biomass. The results indicate that due to changes in the exploitation period, we recommend to protect populations of the common snook. Rev. Biol. Trop. 59 (2): 669-681. Epub 2011 June 01.En este estudio, se analizó la biología reproductiva y poblacional del robalo blanco (Centropomus undecimalis). El material biológico se obtuvo en los desembarcos de la pesca artesanal de las cooperativas de mayor contribución en la zona costera y ribereña durante julio de 2006 a marzo de 2008. En la zona costera las tallas oscilaron entre 34 a 112cm (LF) y en la zona ribereña entre 30 a 85cm. Se encontraron diferencias significativas entre las longitudes de machos y hembras en ambas zonas de estudio (Kruskal-Wallis, p0.05). El periodo máximo reproductivo fue de julio a agosto. En la zona costera, se encontró una correlación significativa entre el iGS y precipitación pluvial para machos y hembras (r=0.63, r=0.70), en la zona ribereña solo se encontró un correlación positiva en las hembras (r=0.57). La talla de primera madurez (L50) se estimó a los 60cm para hembras y 80cm (LF) para machos correspondiendo a 5.5 y 8.5 años de edad respectivamente. Los resultados sugieren un cambio en el periodo de explotación para la conservación de las poblaciones del robalo blanco y su producción.

Mangrove and seagrass habitats are important components of tropical coastal zones worldwide, and are conspicuous habitats of Centla Wetland Biosphere Reserve (CWBR) in Tabasco, Mexico. In this study, we examine food webs in mangrove- and seagrass-dominated habitats of CWBR using stable isotope ratios of carbon and nitrogen. Our objective was to identify the importance of carbon derived from mangroves and seagrasses to secondary production of aquatic consumers in this poorly studied conservation area. Carbon and nitrogen isotope ratios of basal sources and aquatic consumers indicated that the species-rich food webs of both habitats are dependent on riparian production sources. The abundant Red mangrove Rhizophora mangle appears to be a primary source of carbon for the mangrove creek food web. Even though dense seagrass beds were ubiquitous, most consumers in the lagoon food web appeared to rely on carbon derived from riparian vegetation (e.g. Phragmites australis). The introduced Amazon sailfin catfish Pterygoplichthys pardalis had isotope signatures overlapping with native species (including high-value fisheries species), suggesting potential competition for resources. Future research should examine the role played by terrestrial insects in linking riparian and aquatic food webs, and impacts of the expanding P. pardalis population on ecosystem function and fisheries in CWBR. Our findings can be used as a baseline to reinforce the conservation and management of this important reserve in the face of diverse external and internal human impacts. Manguezais e pradarias de gramíneas são importantes componentes das zonas costeiras tropicais em todo o mundo, sendo habitats comuns nos ''Pântanos de Centla'', uma Reserva da Biosfera localizada em Tabasco, México. Nesse trabalho, são investigadas as teias alimentares de habitats dominados por manguezais e pradarias de gramíneas, através de isótopos estáveis de carbono e nitrogênio, tendo como objetivo identificar a importância do carbono derivado desses produtores para a produção aquática secundária nessa unidade de conservação tão pouco estudada. As razões isotópicas de carbono e nitrogênio das fontes basais e dos consumidores aquáticos indicam que as teias alimentares, ricas em espécies, de ambos os habitats, são dependentes da produção ripária. O abundante mangue-vermelho Rhizophora mangle parece ser a fonte primária de carbono no habitat dominado por manguezais. Em contraste, muito embora as pradarias de gramíneas sejam conspícuas no ambiente lagunar estudado, muitos dos consumidores da teia alimentar nessa região parecem depender do carbono oriundo da vegetação ripária (e.g. Phragmites australis).A espécie de bagre exótica Pterygoplichthys pardalis possui assinaturas isotópicas que se sobrepõem a das espécies nativas (incluindo algumas de elevado valor comercial na pesca), sugerindo competição potencial por recursos. Novas investigações deveriam avaliar o papel dos insetos terrestres como elo de conexão entre as teias alimentares da mata ripária e do ambiente aquático, bem como os impactos da expansão da população de P. pardalis sobre o funcionamento do ecossistema e das pescarias no ''Pântano de Centla''. Considerando os múltiplos impactos antrópicos na região, os resultados obtidos no presente trabalho podem ser utilizados como uma base de referência em programas de gerenciamento e conservação da diversidade nessa importante Reserva da Biosfera.

Subsistence fishing was surveyed in the communities of Nueva Esperanza and Loma Bonita of the Lacandon Forest in the Usumacinta River Basin of Chiapas, Mexico from March to August 2005. Thirty fish species, four turtles and two crustaceans were harvested. The most prevalent species in terms of biomass extracted were the pantano cichlid, Herichthys pearsei (Hubbs), grass carp, Ctenopharyngodon idella (Valenciennes), northern checkmark cichlid, Vieja intermedia (Gunther), bigmouth sleeper, Gobiomorus dormitor Lacepede, machaca, Brycon guatemalensis Regan, and blue catfish, Ictalurus furcatus (Lesueur). Ten fishing gears were employed in four habitat types. Fishing patterns, fishing gears employed, species harvested, biomass extracted and catch rates differed between localities. The uniqueness of local fisheries should be considered in further studies and management policies for conservation of fish populations.

Ontogenetic diet changes (prey species richness and size) in juveniles of white sea catfish(Genidens barbus)were tested in three southern Brazilian estuaries: Mampituba (29°12′S), Tramandaí (30°02′S), Chuí (33°44′S). Cluster analysis revealed that white sea catfish juvenile populations in the three estuaries are composed of two feeding groups. These two feeding groups are coincident with a bimodal size–age distribution of the juveniles of white sea catfish. In small catfish (5 to 10 cm TL) copepods were the most numerous prey (Chuí = 86.66%N, Tramandaí = 85.52%N and Mampituba = 52.34%N). In large catfish (10 to 20 cm TL) the most abundant and frequent prey was fish (Chuí: 73.19%N and 74.56%FO; Tramandaí: 85.92%N and 73.33%FO; Mampituba: 52.34%N and 61.54%FO). The Morisita overlap index among small and large fish was low in all estuaries; high values of Morisita's similarity index were observed among same size catfish groups. In all cases, no differences were observed among prey bio-volume curves of same size predator groups (small, F = 0.41,P = 0.65; large, F = 2.19,P = 0.11). In all estuaries, prey size increased significantly with increasing predator size. The 90th regression quantile estimated with most precision the predator–prey size relationship.

We test the hypothesis that predatory benthic fishes play a similar ecological role in different estuaries by displaying the same feeding strategy. We used whitemouth croaker (Micropogonias furnieri) populations in four southern Brazilian estuaries (Mampituba (29°12′ S), Tramandai (30°02′ S), Patos Lagoon (32°10′ S) and Chui (33°44′ S)) as a model. We compared feeding strategies based on a graphical method proposed by Amundsen et al. [(1996) J Fish Biol. 48:607–614], with confidence intervals of frequency of occurrence of prey (FO) and prey-specific abundance (PSA) estimated by bootstrap analyses. We test differences among diets in the four estuaries used the ANOSIM and SIMPER analyses. We minimize the effect of fish size on prey selectivity by restricting the diet analysis to 70–130 mm size classes. Across all estuaries, infaunal prey was the dominant item in the whitemouth croaker’s diet. Most individuals fed on dominant infaunal prey such as Polychaetes (Chui: FO = 0.55 ± 0.018 SD; PSA = 0.88 ± 0.016 and Mampituba: FO = 0.73 ± 0.037; PSA = 0.56 ± 0.056), Bivalves (Tramandai: FO = 0.58 ± 0.032; PSA = 0.92 ± 0.024) and Tanaidaceans (Patos Lagoon: FO = 0.63 ± 0.027; PSA = 0.62 ± 0.043). A between-phenotype contribution to the niche width was observed in all four estuaries, where individuals generally consumed relatively large amounts of different prey types in the same habitat and season. Whitemouth croaker have a zoobenthivore feeding strategy and seemed to maintain the same feeding strategy in all the four estuaries. Specialization on consuming infaunal prey displayed by juveniles of whitemouth croaker could be an important factor leading to the successful colonization of South American estuaries.

Despite the increasing impact of heavy metal pollution in southern Mexico due to urban growth and agricultural and petroleum activities, few studies have focused on the behavior and relationships of these pollutants in the biotic and abiotic components of aquatic environments. Here, we studied the bioaccumulation of heavy metals (Cd, Cr, Ni, Pb, V, Zn) in suspended load, sediment, primary producers, mollusks, crustaceans, and fish, in a deltaic lagoon habitat in the Tabasco coast, with the aim to assess the potential ecological risk in that important wetland. Zn showed the highest concentrations, e.g., in suspended load (mean of 159.58 mg kg 1 ) and aquatic consumers (15.43e171.71 mg kg 1 ), particularly Brachyura larvae and ichthyoplankton (112.22e171.71 mg kg 1 ), followed by omnivore Callinectes sp. crabs (113.81e128.07 mg kg 1 ). The highest bioconcentration factors (BCF) of Zn were observed for planktivore and omnivore crustaceans (3.06e3.08). Zn showed a pattern of distribution in the food web through two pathways: the pelagic (where the higher concentrations were found), and the benthic (marsh plants, sediment, mollusk, fish). The other heavy metals had lower occurrences in the food web. Nevertheless, high concentrations of Ni and Cr were found in phytoplankton and sediment (37.62 e119.97 mg kg 1 ), and V in epiphytes (68.64 mg kg 1 ). Ni, Cr, and Cd concentrations in sediments surpassed international and national threshold values, and Cd entailed a “considerable” potential risk. These heavy metals are most likely transferred into the food web up to fishes through the benthic pathway. Most of the collected fishes are residents in this type of habitat and have commercial importance. Our results show that the total potential ecological risk in the area can be considered as “moderate”. Nevertheless, heavy metal values were similar or surpassed the values from other highly industrialized tropical coastal regions. info:eu-repo/semantics/publishedVersion

"Una pieza clave para diseñar estrategias que reviertan el deterioro de los recursos naturales es contar con información ambiental consistente y actualizada, en especial sobre ecosistemas de alta complejidad e importancia económica y social como las lagunas costeras. El objetivo de este trabajo de revisión fue identificar y ordenar las publicaciones especializadas sobre los ecosistemas lagunares de Tabasco, México, y así poder analizar las tendencias de investigación que dan sustento al manejo estatal de los recursos costeros. Mediante un análisis bibliométrico y una descripción multicriterio de la literatura, se encontró que los artículos científicos y las tesis son las publicaciones dominantes y que ambos se han enfocado principalmente en documentar, mediante diagnosis disciplinarias, el deterioro de las especies económicamente importantes y de los ecosistemas lagunares ante impactos debidos a actividades humanas. También, que los trabajos publicados permanecen puntuales y esporádicos, ocasionando que la producción científica sea espacial y temáticamente heterogénea; los vacíos de información incluyen sistemas lagunares y temáticas de investigación, así como a los acercamientos académicos interdisciplinarios. Los resultados ayudaron a describir las particularidades del conocimiento científico sobre las lagunas costeras tabasqueñas, y también a identificar espacios de oportunidad que, de ser atendidos con investigación científica sistemática y publicable, ayudarían a formar una línea base para el manejo sostenible de estos ecosistemas de Tabasco."