New record of Vallisneria americana Michx. in the transitional zone in the Usumacinta river system

Vallisneria americana is a submersed rooted macrophyte with ample geographic distribution in North America, which as a structured habitat, shelters high biodiversity of aquatic fauna and helps to sink Carbon. However, their populations have drastically decreased or disappeared in the free-flowing Usumacinta river system. Physico-chemical parameters in water, measurements of quantitative habitat complexity, and records of the fish collected were quantified in the unique path of V. americana. This patch of 4 m 2 registered a low average density (96 ∓ 48 stems/m 2), 61.7 ∓ 0.9 g ash free dry weight /m 2 of biomass, and 192 ∓ 42.3 masculine inflorescences/m 2. Six fish species of the Poecillid and Cichlid families were caught, with an average density of 19 ∓ 1.9 fish/m 2 , all of them less than 6.3 cm of standard length. This first record of V. americana in the transitional longitudinal zone (20-60 MASL) of the Usumacinta river system strengthens the relevance of the Wanhá Biosphere Reserve, as it was mainly decreed for their records of relictual inland of red mangrove populations, and high diversity of tropical swamp woody communities. Moreover, the American eelgrass patch represents a nursery area for at least six native fish of Poeciliids and Cichlids, which are the two more diverse fish families in Middle America. Moreover, Cichlid´s fishery is a relevant component to environmental sustainability.