Mexican golden trout

The Mexican golden trout (Oncorhynchus chrysogaster) is a species of fish in the family Salmonidae. The species is endemic to high-elevation headwaters of the Fuerte River, Sinaloa River, and Culiacán River drainages in the Sierra Madre Occidental in Mexico. 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. Although live specimens reached U.S. hatcheries, none ever survived to spawn. In 1952, 1955 and 1956 Needham again explored the Sierra Madre Occidental tributaries of the Gulf of California. Needham's explorations led to the publication of Rainbow Trout of Mexico and California (1959) with coauthor Richard Gard. It contains the first full color drawing of the Mexican golden trout. In 1964, Needham and Gard's proposed binomial name Salmo chrysogaster was accepted as the scientific name for a new species of trout, the Mexican golden trout. The specific name chrysogaster is derived from the Greek for "golden belly". In 1989, morphological and genetic studies indicated trout of the Pacific basin were genetically closer to Pacific salmon (Oncorhynchus species) than to the Salmos—brown trout (S. trutta) or Atlantic salmon (S. salar)—of the Atlantic basin. Thus, in 1989, taxonomic authorities moved the rainbow, cutthroat and other Pacific basin trout, including the Mexican golden trout, into the genus Oncorhynchus. 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. Purple scaling is visible along the lateral line. Both sexes also have bright golden-yellow belly coloration. The top of the fish and the tailfin are covered in small black spots with much larger spotting on the dorsal fin.