The Mexican golden trout (''Oncorhynchus chrysogaster'') is a species of

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

in the family

Salmonidae Salmonidae is a family of ray-finned fish that constitutes the only currently extant family in the order Salmoniformes . It includes salmon (both Atlantic and Pacific species), trout (both ocean-going and landlocked), chars, freshwater whitefis ...

. The species is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to high-elevation

headwaters The headwaters of a river or stream is the farthest place in that river or stream from its estuary or downstream confluence with another river, as measured along the course of the river. It is also known as a river's source. Definition The ...

of the

Fuerte River The Fuerte River is a river in the state of Sinaloa, in northwestern Mexico. It flows from headwaters in the Sierra Madre Occidental to the Pacific Ocean in the Gulf of California. Course It begins at the junction of the Rio Verde (also called ...

Sinaloa River The Sinaloa River is a river of Mexico. It runs across the state of Sinaloa from northeast to southwest, beginning in the Sierra Madre Occidental and emptying into the Gulf of California. Its flow is interrupted mostly by the Bacurato Dam which c ...

, and

Culiacán River The Culiacán River is a river that is formed at the confluence of the Tamazula River and Humaya River, located in Culiacán city of Sinaloa state, in northwestern Mexico. The river flows from the Sierra Madre Occidental headwaters confluence ge ...

drainages in the

Sierra Madre Occidental The Sierra Madre Occidental is a major mountain range system of the North American Cordillera, that runs northwest–southeast through northwestern and western Mexico, and along the Gulf of California. The Sierra Madre is part of the American C ...

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

Taxonomy

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 Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

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 The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja Ca ...

. 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 The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

were genetically closer to Pacific salmon (''Oncorhynchus'' species) than to the ''

Salmo ''Salmo'' is a genus of ray-finned fish from the family Salmonidae. The single ''Salmo'' species naturally found in the Atlantic North America is the Atlantic salmon, whereas the salmon and trout of the Pacific basin belong to another genus, ''O ...

s''–

brown trout The brown trout (''Salmo trutta'') is a European species of salmonid fish that has been widely introduced into suitable environments globally. It includes purely freshwater populations, referred to as the riverine ecotype, ''Salmo trutta'' morph ...

(''S. trutta'') or

Atlantic salmon The Atlantic salmon (''Salmo salar'') is a species of ray-finned fish in the family Salmonidae. It is the third largest of the Salmonidae, behind Siberian taimen and Pacific Chinook salmon, growing up to a meter in length. Atlantic salmon are ...

(''S. salar'') of the

Atlantic basin The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Africa, Europe and ...

. Thus, in 1989, taxonomic authorities moved the rainbow, cutthroat and other Pacific basin trout, including the Mexican golden trout into the genus ''Oncorhynchus''.

Description

The Mexican golden trout is

sexually dimorphic Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

, 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 The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

. 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 A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

. The pectoral fins, pelvic fin and anal fin are light orange in color with white tips. Due to their harsh and small stream habitat the Mexican golden trout remains small even when fully grown. Adults rarely reach over a foot long with the maximum size probably being 10 inches (25 cm). Overall body shape and fin placement nearly identical to Rainbow trout. Juvenile banding ("Parr marks") usually remains distinct throughout the fish's life.

Distribution

Mexican golden trout have an extremely limited range, being found only in the pristine high-elevation

of the

, and

drainages in the

. This fish is highly restricted, and only known from 15 localities, one in the Sinaloa, four in the Culiacan, and ten in the Fuerte.

Habitat

Mexican golden trout are limited to small streams created by small cienegas (spring-fed marshes) above . The surrounding landscape is dominated by deep canyons, scrub forest, evergreens and hardwoods.

Status and threats

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 The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributaries of the Pacific Ocean in Asia and North America. The steelhead (sometimes called "steelhead trout") is an anadromous (sea-run) form of the coasta ...

. This trout is also an example of the negative effects of habitat abuse and destruction. The primary use for the Mexican Golden trout is as food by the local indigenous people. Some of the local people use dynamite to stun the fish and collect them as they float to the top of the water. This is especially harming to the golden trout populations because of the mass harvest. 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. What happens now in Mexican Golden trout water is similar to what happened to so many North American trout waters in the 19th and early 20th centuries as far as decline in populations is concerned.

Economic benefits

The scenic area and rugged mountainous landscape have started a budding tourism industry for this area. Being able to conserve and promote the sustainable harvesting of these native trout can help the people of the area as well as the Golden Trout. Setting up regulations on the harvesting of the fish and restrictions on polluting the head waters these fish inhabit would greatly improve the region. In Arizona and New Mexico there was 512 million dollars that was spent on trips and equipment for fishing. This revenue could be a major contributor to helping the area grow and being able to conserve the local environment from destruction.

References

{{Taxonbar, from=Q3235091 Oncorhynchus Endemic fish of Mexico Trout, Mexican golden Trout, Mexican golden Fauna of the Sierra Madre Occidental Fish described in 1964 Taxonomy articles created by Polbot