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, p<0.05). The male:female ratio was 1:0.68 in the coast, and 1:0.16 in riverine areas. The length-weight relationship did not vary between both sexes among areas (ANCOVA, p>0.05). 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 (L 50) 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.

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In Mexico, aquaculture is a growing sector, but it continues to be developed using non‐native species. The natural ecosystems of the lowland humid tropics of southeastern Mexico have been well‐described by ecologists and are host to a very high diversity of species, including a substantial ichthyofauna. Cichlid fish, commonly known in southeast Mexico as ‘mojarras’, are an important fish resource and are widely consumed. Several species are now under considerable pressure and consequently the generation of biotechnology for the culture of native fish species is necessary and worthwhile. This paper examines and describes the experiences and knowledge generated over recent years regarding the aquaculture of native cichlids in the southeast of Mexico. Although the scientific and technological capacity for research and development for native species culture exists, there is an evident lack of information on new technologies among producers, as scientific research is not translating fully into technical assistance. Research and extension should be emphasized in order to develop a comprehensive knowledge base on native species and to enable their cultivation.

Análisis del cambio de uso del suelo en un ecosistema urbano en la zona de drenaje del río Grijalva, México Resumen E l cambio de uso del suelo de la ciudad de Villahermosa, Tabasco, se analizó con base en el efecto provocado por el crecimiento urbano sobre la vegetación arbórea y los ecosistemas acuáticos. Se hizo un análisis multitemporal mediante el modelador de cambio de uso del suelo (Land Change Modeler for Ecological Sustainability) y el módulo CrossTab del software IDRISI Selva® y se calcularon tasas de cambio. De acuerdo con los resultados, durante casi tres décadas se perdieron 4,008 ha de suelo ocupado por vegetación arbórea y 289 ha de humedales, debido al crecimiento acelerado de los pastizales y la zona urbana. Mediante modelos de transición estocástica (cadenas de Markov y autómatas celulares) se proyectó una pérdida de 1,171 ha de vegetación arbórea y 247 ha de humedales entre el periodo 2008 y 2030. Es probable que esta tendencia se mantenga por el incesante crecimiento del pastizal y la zona urbana.Received: March 31, 2016 / Accepted: November 9, 2016. Palabras clave:Vegetación arbórea, humedales, crecimiento urbano, cadenas de Markov, autómatas celulares.

Constructed wetland is a technically feasible, economically viable and environmentally sustainable natural technology that contributes at reducing greenhouse gases in the wastewater treatment. In this context, a pilot-scale subsurface horizontal-flow constructed wetland (HF-CW) was evaluated by using Thalia geniculata as native vegetation. The reactor operated with an average flow rate of 204 ± 66 L/ day of wastewater, with gravel support medium diameter of 2.8 ± 0.8 cm, porosity of n = 56.3 ± 3.5 and density of 1,666.7 ± 119.3 kg/m 3 , with 4.2 days as a hydraulic retention time. The HF-CW weighs approximately 2,600 kg, considering 1,108 kg of gravel, 850 kg of water and the weight of the container (carbon steel). The kinetic behavior was observed to be first order with k = −0.43 days −1 , favoring the efficiency of biological oxygen demand removal up to 90%. During the experiments, it was shown that the bacterial biomass attached to the support material decreased its concentration from influent to effluent (33,000 to 2,000 mg/kg, mg of fixed biomass attached to each kg of gravel). For the electrical conductivity, color and turbidity, values were found to decrease in the order of 7.2 ± 4.8%, 86.7 ± 6.8% and 90.3 ± 5.8%, respectively. From the current experimental results, it was demonstrated that constructed wetlands, involving native species as vegetation, are highly efficient for the removal of basic pollutants.