Overview
The last San Marcos gambusia was found in 1983 and all evidence indicates that the species is extinct. A proposed rule to delist the species was published in the Federal Register on September 30, 2021. The San Marcos gambusia was described as a new species from the upper San Marcos River system in 1969, and was subsequently listed as endangered on July 14, 1980. At the time the species was listed, small and declining populations, lowered water tables, pollution, bottom plowing and cutting of vegetation were cited as threats to the species.
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Characteristics
Habitat
The San Marcos gambusia preferred quiet waters adjacent to moving water, but seemingly of greatest importance, thermally constant waters. The San Marcos gambusia was found mostly over muddy substrates, but generally not silted habitats. Shade from over-hanging vegetation or bridge structures is a factor common to all sites along the upper San Marcos River, where apparently suitable habitats for this species occur.
A natural body of running water.
Timeline
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