Seasonal variations in food web dynamics of floodplain lakes with contrasting hydrological connectivity in the Southern Gulf of Mexico

Hydrobiologia - Floodplains are some of the most productive and diverse ecosystems on Earth. The Usumacinta River Basin, in the Southern Gulf of Mexico, hosts several floodplain lakes, whose...     

Spatial distribution of cichlids in Tzendales River,Biosphere Reserve Montes Azules,Chiapas, Mexico

Located within Mexico’s Montes Azules Biosphere Reserve, the Tzendales River is part of the Usumacinta River Basin, which supports the largest diversity of cichlid fishes in Middle America. We evaluated temporal and spatial variation of species richness and distribution of cichlids in the Tzendales River; we collected 14 species with nine native and five endemic. The species with greatest relative abundances and broadest spatial distributions were Vieja intermedia and Amphilophus nourissati; and the rarest and most spatially restricted species were Thorichthys meeki and Parachromis friedrichsthalii. Environmental characteristics varied seasonally although fish assemblages and distributions were relatively stable over time. Based on habitat use patterns, three species associations were observed: (1) Amphilophus nourissati, Petenia splendida, Vieja argentea, V. bifasciata, V. intermedia, V. pearsei, V. synspila and V. ufermanni; (2) ‘Cichlasoma’ salvini and Parachromis friedrichsthalii; and (3) Thorichthys helleri and Thorichthys meeki. Two rheophilic species, Theraps lentiginosus and Theraps irregularis, had low habitat overlap with all of the other cichlid species. Canonical correspondence analysis showed that the depth, current speed and quantity of rocks in the substrate defined the spatial distribution of species in dry season. Cichlids of the Tzendales River appear to partition habitat in a manner that reduces resource competition.     

Economic valuation of the commercial aquaculture of Sarcopeltis skottsbergii in Southern Chile

In this study we analyze the economic feasibility of commercial cultivation of Sarcopeltis skottsbergii, a red seaweed endemic in southern Chile with commercial interest as a source of carrageenan. To this end, a dynamic bioeconomic model was built that comprises three submodels, namely, a biological, a technical, and an economic one. The cultivation was by using a method where they are hung in the sea, with juveniles attached to lines. The site is located in the Bay of Ancud, in the Los Lagos Region of southern Chile. The sensitivity analysis showed that cultivation is profitable for a private investor when the price and growth of the biomass are substantially higher than the parameters established for the baseline model. The results suggest that greater technological development is required to make a culture of this type profitable and, thus, reduce the extractive pressure that is currently exerted on natural habitats.