Type locality, Provincia de La Rioja, Departamento San Blas de los Sauces, Río Hualco, FML 2601 (holotype of Trichomycterus hualco, 6.87 cm SL). Known only from the type locality that lies within a region with few drainage systems and a depauperate ichthyofauna. This is the third species apparently endemic to La Rioja Province (with T. riojanus and T. pseudosilvinichthys). The type locality is a small, clear water stream that flows down a small rocky canyon into a small pool. Stream and pool depth range, approximately 0.2 to 0.6 m deep and 1.0 to 1.5 m wide; both had rock and pebble bottoms and with limited adjoining terrestrial vegetation among the surrounding boulders. The type locality (Río Hualco) seeps into the soil downstream from the pool and is apparently isolated from adjoining drainages throughout the year. The specimens were collected both above and below an approximately three-meter high waterfall within the stream and in the pool, none were observed in the small outflow stream that drains the pool. Stomach contents include dipteran larvae (Chironomidae and Ceratopogonidae), this diet of autochthonous benthic macroinvertebrates is common to species of Trichomycterus. T. alterus was also collected from this site. Local inhabitants utilize the Río Hualco as a recreation site and on occasion as a bathing area, hence such activities put it at risk of ecological alteration, a threat common to many other aquatic habitats within those portions of the Andes especially for this species, given its apparent restriction to that small drainage system (Ref. 80457).