Trout Diversity in Mexico sensu Morphological and Molecular Studies by Truchas Mexicanas

Index to Descriptive information and Images

Yaqui and Guzman Trout Species
Rio Tomochic Trout
Rio Mayo Trout
Mexican Golden Trout
San Lorenzo Trout
Piaxla Trout
Presidio Trout
Baluarte Trout
Acaponeta Trout
Conchos Trout


Yaqui and Guzman Trout – Native trout are widespread in the Rio Yaqui basin, with 46 localities known (of which two were discovered during 2005). Our collections indicate that at least two species of native trout inhabit the Rio Yaqui basin, a Bavispe form that includes tributaries that drain into the Rio Bavispe sub-basin (Papigochic, Gavilan, Nutria, Arcos), and another from the Rio Tomochic treated separately below. Yaqui trout have strong golden hues on the sides and have many prominent black spots above and between the parr marks. The reddish-pink lateral “band” is discontinuous (unlike typical rainbow trout) and broken into a series of spots – there being no reddish pigment in the space occupied by the parr marks. This condition typically persists even once the parr marks have faded on large individuals. A variety exists in the Rio Arcos with a continuous lateral band and a more densely spotted body. Yaqui trout typically have an orange cutthroat mark under the dentary bone. The pelvic, anal, and pectoral fins are typically orange. The dorsal fin is sometimes tipped with orange. A similar trout is known from three localities in the adjacent Guzman basin, but it is not yet known if this trout is native, or was stocked from the adjacent Yaqui watershed. An early report of trout from the New Mexico portion of the Guzman Basin (Emory 1848) suggests the former, but anecdotal information from Mormon settlers in the basin supports of the latter.  This must be further examined with morphological and molecular comparisons in a phylogenetic analysis.  Given that there are multiple non-game aquatic species that share this biogeographic pattern there may exist a native trout in the Guzman basin.

Illustration of Yaqui Trout by J.R. Tomelleri (copyrighted).

Illustration of Guzman Trout by J.R. Tomelleri (copyrighted).

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Rio Tomochic trout – Trout from this Yaqui sub-basin are a soft lemon yellow on the sides as opposed to gold, have a row of bright pinkish spots along the lateral “band,” and have less prominent black spots mostly restricted to above the lateral line – with many shaped like the letter ‘x’ instead of the typical oval or round shape. We have collected trout from only two tributaries of the Tomochic, but know that they have formerly been collected from the mainstem. We do not know if the trout from the Tomochic intergrade with those from the Bavispe sub-basin, or if there is a thermal barrier or behavior differences that prevent hybridization. Tomochic trout also have a slight pinkish/orange cutthroat mark under the dentary bone. The ventral fins are typically orange.

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Rio Mayo trout – Trout from the Rio Mayo are most similar to the Tomochic trout. The males are strongly suffused with bright pink and lavender on the cheeks and have the same bright pink spots along the lateral “band” and the ‘x’ shaped spots as the Tomochic trout. The ventral fins are orange or pinkish orange. We have only collected Mayo trout from one location (in 1997 and 2005); this about 10 km above the falls of the Basaseachi, and only three localities are known. Most of the watershed remains unexplored for trout.

Illustration of Mayo Trout by J.R. Tomelleri (copyrighted).

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Mexican Golden trout (Oncorhynchus chrysogaster) – This is the only native Mexican trout with a formal scientific name. The complex is poorly known, and the species description is based on a handful of collections. Three vast Pacific watersheds comprise its distribution: Rio Fuerte to the north, the Rio Sinaloa, and the Rio Culiacan to the south. Both morphological studies (Ruiz-Campos, unpubl. data) and molecular data suggest that the species is polytypic, and at least 2 species may comprise the Mexican Golden trout complex. In contrast to the Yaqui/Mayo trout, the Mexican golden trout has a continuous reddish lateral band. Females and young are typically silvery with conspicuous charcoal blue parr marks, and sometimes exhibit an almost blue-black lateral stripe through the parr marks. Spawning males are bright golden-yellow on the sides and upper belly, and have a bright orange belly. Anal, pelvic, and pectoral fins are bright orange in males. The black spots are numerous but small, and are mostly restricted to back and upper sides. This form is highly restricted, and only known from 15 localities, one in the Sinaloa, four in the Culiacan, and ten in the Fuerte.

Illustration of Mexican Golden Trout (male above, female below) by J.R. Tomelleri (copyrighted).

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Rio San Lorenzo trout – The distribution of trout within the San Lorenzo watershed is poorly known, and the largest sub-basin, the San Gregorio, is remote and remains unexplored for trout. Of the ten localities known from the San Lorenzo, seven were discovered during our 2004 expedition. San Lorenzo trout are silvery with bright blue and purple reflections, often with only a faint (and sometimes no) pink coloration on the opercle and lateral band. Faint yellow/cream coloration is sometimes developed on the lower sides of these trout, but is lacking in many of the specimens we have collected. The ventral fins are light pinkish-gray. The black spots are well-developed, oval, angled anteriorly and are almost wholly restricted to above the lateral line. San Lorenzo trout typically have from 12 – 16 oval parr marks, in contrast to most other North American trout, which usually have from 8 – 11 parr marks. The body is heavily marked below the lateral line by auxiliary parr marks, which are the same dark slate-gray as the principal parr marks. We have also made several collections from above and below the falls at Arroyo la Sidra, and suggest that there may originally have been a unique trout in this watershed that has subsequently been hybridized by hatchery rainbows that have escaped or been purposefully introduced into this arroyo. In 2004 we collected two albino O. mykiss from a side channel of the A. la Sidra above two large waterfalls upstream of the hatchery, a find we cannot attribute to natural patterns of dispersal.

Illustration of San Lorenzo Trout by J.R. Tomelleri (copyrighted).

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Rio Piaxtla trout – The trout of the Rio Piaxtla watershed are similar to those of the San Lorenzo, but are more brightly colored with orange, red, and gold. Specimens from Arroyo El Granizo (a population discovered in 2004) have a continuous bright orange lateral band, and those from the Arroyo Santa Barbara have a muted brick-red/orange band. Piaxtla trout have more parr marks than any other known trout, typically with 13 or 14, and as many as 18. The number of auxiliary parr marks below the lateral line typically numbers more than 100. The anal, pelvic, and pectoral fins range from bright orange to brick-orange. The dorsal and anal fins are more broadly tipped with white than other species of Mexican trout. The distribution of Piaxtla trout is poorly known because of the remote location and the difficulty of accessing streams. Residents of Puentecillas told us that they had made intra-basin transfers of trout from Arroyo El Granizo, but had never stocked any exotic trout. Of the five localities known from the Piaxtla, three were discovered during our 2004 expedition.

Illustration of trout from Rio Piaxtla, Durango, by J.R. Tomelleri (copyrighted).

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Presidio Trout – The origins of trout in the Rio del Presidio watershed has been debated for many years. Robert Rush Miller believed them to have been stocked from railroads in the late 19th or early 20th century. In March of 2004, we had a lengthy discussion in Ciudad Durango with Walter Bishop II of Durango, Mexico. Mr. Bishop related how his father (American vice-consul to Durango) had caught trout along the Durango/Mazatlán trail in the early 1900’s, a largely undisturbed and remote wilderness at the time. Mr. Bishop was certain that the trout were native, and said that he had never heard of the practice of “stocking” trout in this area. Further, Mr. Bishop had for years served as manager of the El Salto Lumber Company, and consequently knew the area and surrounding mountains very well. He related how the railroad had not reached the Presidio headwaters until the late l920s, arriving with the lumber companies and settlers, and making the streams virtually inaccessible to stocking with technology of the time even if someone had otherwise wanted to stock these streams. Mr. Bishop’s father, Walter Bishop I, originally collected trout from the Presidio headwaters in l907 and shipped them to Edward W. Nelson at the Smithsonian Institution, presumably at the latter’s request. Presidio trout that we have collected are variable. Individuals from Arroyo Nogales show bright orange-red fins and lateral stripes, but those collected in Quebrada de Vega in 2004 are less brightly colored and more sparsely spotted. At Walter Bishop’s suggestion, we also collected trout in Arroyo la Rosilla, trout which Mr. Bishop implied were “different” from the native trout below the waterfall at El Salto. Some variability in the trout could be due to geological and thermal isolation of the various populations. Of the eleven localities are known from the Presidio, two were discovered during our 2004 expedition.

Illustration of Presidio Trout by J.R. Tomelleri (copyrighted).

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Baluarte Trout – Prior to our original collection in October 2000, the Baluarte trout were unknown to science. Our group made subsequent collections in Feb. 2004 from Arroyo Santa Barbara, a barranca southwest of El Salto, Durango. Baluarte trout are spectacular for their lemon-gold coloration, orange bellies, and their bright red spots in lieu of a lateral band. Many specimens also exhibit a unique greenish hue on their anterior parr marks. The anal, pelvic and pectoral fins are bright yellow-orange. Our guides to the arroyo insisted that there were 2 forms of trout in the Rio Baluarte watershed.. Our collections were intriguing, consisting almost entirely of male trout, a sparsely -spotted variety and another form that was more densely spotted. It is not known if this variation is natural or if it is caused by introgression from introduced rainbows. Only three localities are known from the Rio Baluarte; one discovered during 2004.

 

Illustration of trout from Rio Baluarte, Durango, by J.R. Tomelleri (copyrighted).

Acaponeta Trout – As with the Baluarte trout, the Acaponeta trout was unknown prior to 2001. We collected Acaponeta trout from three additional arroyos in 2004. These trout are unusual for their large, round auxiliary parr marks. Acaponeta trout are typically silvery, and lack the strong yellow, gold, and red coloration of the neighboring Baluarte trout. Specimens from Arroyo las Moras were an unusual green coloration in the back and had few black spots, clustered principally on the peduncle. The ventral fins of the Acaponeta trout are a light pinkish-gray, or light creamy orange. Some of the larger adults that we collected showed the same pattern of red spots along the side as the Rio Baluarte trout (a pattern also seen in trout from the rios Conchos, Yaqui, and Mayo). As in Rio Baluarte trout, there seems to be two forms in the Acaponeta tributaries – a sparsely spotted form and a densely spotted variety.

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Conchos Trout – The first scientific collections of Conchos trout were made in Feb. 2005. This trout (like the Mayo, Yaqui, Baluarte and Acaponeta trout) has a distinct series of red spots along its lateral line (in lieu of the typical red band found in rainbow trout), and has strong lemon/gold coloration on its side and upper belly. Our specimens were small, less than 150 mm total length, and had few black spots on the tail, sides and upper body. The pelvic, anal, and pectoral fins are orange. A unique characteristic of the Conchos trout is the lemon-yellow cutthroat mark under the jaw.

Illustration of Conchos Trout by J.R. Tomelleri (copyrighted).

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