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

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

in the family

Salmonidae Salmonidae (, ) is a family (biology), family of ray-finned fish, the only extant member of the suborder Salmonoidei, consisting of 11 extant genera and over 200 species collectively known as "salmonids" or "salmonoids". The family includes salmo ...

. The species is

endemic Endemism is the state of a species being found only 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 foun ...

to high-elevation

headwaters The headwater of a river or stream is the geographical point of its beginning, specifically where surface runoff water begins to accumulate into a flowing channel of water. A river or stream into which one or many tributary rivers or streams flo ...

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 ...

, 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 ...

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, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

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, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...

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 (), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Vermejo''), is a marginal sea of the Pacific Ocean that separates the Baja California peninsula from ...

. 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 Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

''chrysogaster'' comes from

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

χρυσός (''khrusós''), meaning "gold", and γαστήρ (''gastḗr''), meaning "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 Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

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

Salmo ''Salmo'' is a genus of ray-finned fish from the subfamily Salmoninae of family (biology), family Salmonidae, and is part of the tribe (biology), tribe Salmonini along with the sister genera ''Salvelinus'' and ''Salvethymus''. Almost all ''Salmo ...

s''—

brown trout The brown trout (''Salmo trutta'') is a species of salmonid ray-finned fish and the most widely distributed species of the genus ''Salmo'', endemic to most of Europe, West Asia and parts of North Africa, and has been widely introduced globally ...

(''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 Hucho taimen, Siberian taimen and Pacific Chinook salmon, growing up to a meter in length. Atlan ...

(''S. salar'')—of the

Atlantic basin The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

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

Etymology

The

genus name Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial spec ...

''Oncorhynchus'' comes from

ὄγκος (''ónkos''), meaning "bend", and ῥύγχος (''rhúnkhos''), meaning "snout". The

''chrysogaster'' comes from

χρυσός (''khrusós''), meaning "gold", and γαστήρ ''gastḗr''), meaning "belly".

Description

The Mexican golden trout is

sexually dimorphic Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

; 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 epithelia ...

. 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 on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

. 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 are nearly identical to those of 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 tributary, tributaries of the Pacific Ocean in North America and Asia. The steelhead (sometimes called steelhead trout) is an Fish migration#Classification, ...

(''Oncorhynchus mykiss''). 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 harmful 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 is happening now in Mexican golden trout water is similar to what happened to so many other 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 Mexican 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, 512 million dollars 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