In 1936, Paul Needham, a fisheries biologist with the U.S. Bureau of Fisheries began a series of explorations (1936, 1937 and 1938) into the Rio Santo Domingo drainage in Baja California seeking to bring back live specimens of the Baja rainbow trout as hatchery stock and further study.

Needham's explorations led to the publication of Rainbow Trout of Mexico and California (1959) with coauthor Richard Gard.

[5] The Mexican golden trout is sexually dimorphic; males can easily be identified from females due to their much longer jaws or kype.

Mexican golden trout are brightly colored with blue parr marks on both males and females along the side of the body.

Due to their small range and highly sensitive, isolated habitat, Mexican golden trout are considered vulnerable.

The biggest threats are human development and the possibility of competition/interbreeding with introduced rainbow trout (Oncorhynchus mykiss).

Sanitation practices in the region where the golden trout is found is minimal, so much of its home water is polluted with residential sewage and trash.