ResumenLa cuenca del río Usumacinta se caracteriza por su gran extensión, heterogeneidad ecológica y alta biodiversidad. Con el objetivo de documentar de manera integral la riqueza y distribución de la ictiofauna, se incluyen en este trabajo los registros para la cuenca depositados en la Colección de Peces (ECOSC), además de la revisión bibliográfica y de los registros de otras bases de datos nacionales e internacionales. Adicionalmente y con la finalidad de analizar la diversidad y abundancia, se realizaron muestreos (2014 y 2015) en 3 zonas: selva, planicie y delta. La ictiofauna se compone de 2 clases, 28 órdenes, 50 familias y 172 especies, de las cuales 3 son nuevos registros. De acuerdo a su afinidad ecológica, 75 especies son dulceacuícolas, 8 estuarinas y 89 marinas. La zona selva tuvo más especies dulceacuícolas exclusivas y la zona delta registró la mayor riqueza de peces marinos. Los cambios observados en la diversidad a lo largo de las 3 zonas están influidos por la historia geológica, dinámica hidrológica y su conectividad con el golfo de México. Es necesario continuar con el estudio de la ictiofauna en función de la complejidad geomorfológica para entender patrones biogeográficos, así como procesos ecológicos importantes para su conservación. AbstractThe Usumacinta Basin is characterized by its large size, ecological heterogeneity and high diversity of fish. The purpose of this work was to examine the richness and distribution of the fish fauna, and analyze the diversity

The characterisation of digestive proteases in native freshwater fish such as the Mayan cichlid Cichlasoma urophthalmus provides scientific elements that may be used to design balanced feed that matches with the digestive capacity of the fish. The purpose of this study was to characterise the digestive proteases, including the effect of the pH and the temperature on enzyme activity and stability, as well as the effect of inhibitors using multienzymatic extracts of the stomach and intestine of C. urophthalmus juveniles. Results showed that the optimum activities of the acid and alkaline proteases occurred at pH values of 3 and 9, respectively, whereas their optimum temperatures were 55 and 65 °C, respectively. The acid proteases were most stable at pH values of 2–3 and at temperatures of 35–45 °C, whereas the alkaline proteases were most stable at pH values of 6–9 and at 25–55 °C. The inhibition assays recorded a residual activity of 4% with pepstatin A for the acid proteases. The inhibition of the alkaline proteases was greater than 80% with TPCK, TLCK, EDTA and ovalbumin, and of 60 and 43.8% with PMSF and SBT1, respectively. The results obtained in this study make it possible to state that C. urophthalmus has a sufficiently complete digestive enzyme machinery to degrade food items characteristic of an omnivorous fish species, although specimens showed a tendency to carnivory.

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We revise the historic context of freshwater pearl culture in Asia, updating the present situation and perspectives of this activity in Mexico, and, possibly, in some Latin American countries. The review is based on the results of ten years of research conducted in southeast Mexico (state of Tabasco) to firstly determine the demography of freshwater mussel stocks and, based on this information, identify a target species with a higher potential for pearl farming: the fatmucket mussel Psoronaias crocodilorum. The main advances relative to the seeding technique for keshi pearl production and composite technique for half-pearl (mabe) production are detailed and placed under perspective with China, as today's greatest producer of freshwater pearls. After ten years, several cohorts of keshi and mabe pearls have been produced, representing the first of their kind in Latin America. Although the yield and quality of these pearls has gradually been improved, some aspects of the keshi technique (preparation and seeding of the donor's mantle into the host's mantle) still require further optimisation. To promote social development, one of the goals of the project included the involvement of local communities in the manufacture and selling of handcrafts made from the shell. The other goal was to share the main outcomes derived from the keshi and mabe techniques with academics, producers, and government authorities through a series of training workshops aimed to create awareness in the local communities for the potential of freshwater pearl culture in Tabasco as an aquaculture-based, environmentally friendly and viable model for socioeconomic development.

El robalo blanco (Centropomus undecimalis) es una especie demersal con característica protándrica hermafrodita y hábitos diadrómicos. Se distribuye desde el norte de Florida E.U.A., hasta el sur de Río de Janeiro, Brasil; en el Golfo de México, es abundante en los estados de Tamaulipas, Veracruz y Tabasco. En su área de distribución, el robalo blanco presenta alta importancia comercial y deportiva, esto debido a sus características alimenticias, abundancia, alto valor en el mercado local y regional, así como a la facilidad de obtenerlo por parte de las comunidades pesqueras. En los últimos diez años, el incremento de la demanda en el consumo regional y nacional, así como la modificación de sus hábitats, ha causado que sus niveles de explotación sean altos en el Golfo de México, reduciendo las tallas de captura y la captura por unidad de esfuerzo.