ed. note -- this article was written in the summer of 2004.  In February, 2005, a tiny native population of Conchos trout was located in the upper Conchos watershed by members of Truchas Mexicanas.  By March 2006, after an extensive and fruitless search of the same stream, that population was believed extirpated.  However, after interviewing local Rarámuri and conducting exhaustive sampling, another small but viable population was located in another arroyo.  These rare trout are the first  native trout known to science on Mexico's Atlantic slopes, and appear related to the trout of the rios Mayo and Tomochi (Yaqui watershed).  For more information on the urgency of protecting this unique trout, read the Conchos "White Paper."   Donations from Trout Unlimited, The Native Fish Conservancy, NANFA, and many individuals have allowed the World Wildlife Fund to promote conservation of native fishes in the immediate region.   A Rarámuri streamkeeper has been hired, and critical habitat of the stream has been fenced to keep livestock out of the arroyo.   With permission of the local ejido, a transplant program to a nearby stream could begin as early as fall of 2008.

In April of 2007, again following advice of the indigenous Rarámuri, another native trout was discovered on Mexico's Atlantic slope.  This trout was located on our third collecting trip into a remote arroyo, having made earlier attempts in the same stream in 2002 and 2006.   This "southern" Conchos trout differs from the "northern" trout found in 2005 and 2006, and is more closely related to the Mexican golden trout. The population is some 200 stream miles south of the aforementioned "northern" Conchos trout.  Repeat sampling in 2008 suggests that the known range of this "southern" species is about 3 km of spring-fed streams.

      In 1886, the noted naturalist and paleontologist Edward Drinker Cope, published a one paragraph note in the American Naturalist journal.  Entitled "The Most Southern Salmon," Cope implied that cutthroat trout were native to Chihuahua, Mexico.

"I owe to my friend, Professor Lupton, two specimens of a black-spotted trout from a locality far south of any which has hitherto yielded Salmonidae.  They are from streams of the Sierra Madre, of Mexico, at an elevation of between 7000 and 8000 feet, in the southern part of the State of Chihuahua, near the boundaries of Durango and Sinaloa.  The specimens are young, and have teeth on the basihyal bones, as in Salmo purpuratus, which they otherwise resemble.

Cope's choice of words should not be misconstrued.  The term "black-spotted trout" was  used not as a reference to any trout with black spots, but rather was the common name of the time for cutthroat trout.   Cope never formally described these trout as a "species," and the specimens were subsequently lost, evidently never having been examined by others.  If Cope's trout were cutthroats, they probably were collected in the headwaters of the Rio Conchos -- the largest watershed in the state of Chihuahua, and a tributary to the Rio Grande.  His references to "teeth on the basihyal bones" and "Salmo purpuratus" suggest that Cope  believed the trout to be "black-spotted trout," a relative of the Rio Grande cutthroat.  Though all trout have teeth on the tongue, only cutthroats (and the occasional redband trout)  have teeth on the "basihyal bones," or on the "base of the tongue" [basibranchial teeth in modern parlance].  [ed. note -- some undescribed trout from southern Durango, Mexico also have weakly developed basibranchial teeth.]  The only species of trout known from southern Chihuahua is the Mexican golden trout, Oncorhynchus chrysogaster, which has no teeth on the base of the tongue.   Cope's comparison to Salmo purpuratus is  intriguing and somewhat problematic.  The species "purpuratus" included at the time all known "red-throated trouts" (cutthroats) and also encompassed the redband trouts (relatives of rainbows) as we now know them.   In fact, Cope wrote in an 1883 paper on Great Basin fishes that he found "Salmo purpuratus"  in "great abundance" in the Chewaucan River.    We now know these trout to be redband trout, though they were purported in literature to be cutthroats almost to the middle of the last century.   David Starr Jordan originally believed that the Kamchatkan species described as Salmo mykiss  by Pallas in 1814 (and later referred to S. mykiss purpuratus) was a coastal cutthroat, the same as found in Alaska and the Pacific northwest, thus the purpuratus name became attached to cutthroats.    Jordan discovered in the late 1890's that the Pallas specimen was actually a steelhead, a species with no basihyal (or "basibranchial") teeth.  So S. mykiss became the name for steelhead, and all cutthroat trout were properly relegated to  S. clarkii.  

Cope was also familiar with rainbow trout (a close relative of Mexican goldens), having visited Baird Station (McCloud River Hatchery) in California in 1879, even writing a detailed article complete with illustration about the lateral line system in hatchery trout from the McCloud.  He was also an avid fisherman and a remarkable  naturalist.  The bulk of his 1300 + publications pertained to paleontology, but he was a keen observer of nature and was profoundly fascinated with its detail.  His ability as an artist was unmatched among his peers.  Cope published many dozens of papers on mammals, birds, and reptiles.  The wealth of his papers on fishes, both fossil and living, would constitute a decent career for lesser biologists. 

In 1885 at the American Association for the Advancement of Science, noted ichthyologist Tarleton Bean presented a paper whereby he recognized  that in addition to having smaller scales, the S. spilurus/purpuratus (cutthroat) group could be distinguished from the S. gairdneri/irideus trouts (rainbows and steelheads) by the presence of hyoid (=basihyal) teeth.  [ Bean published his paper in 1888 as "Distribution and some Characters of the Salmonidae," referencing Lupton's trout and Cope's note upon them.]      Cope also attended this 1885 meeting, and his 1886 publication was his first published use of the term "basihyal" in describing trout.   Cope is presumed to have had intimate knowledge of fish osteology, and he distinguished between teeth on the tongue (referring to them as "glossohyal" teeth) and teeth on the hyoid or basihyal bones.  Cope published descriptions for an incredible 424 nominal species of fish, and even proposed his own formal classification of living fishes.   In 1872 he wrote a species description of Salmo spilurus (Rio Grande cutthroat) , a species reported by George Brown Goode in 1887 to be a close relative of Salmo purpuratus.    Both Goode and  David Starr Jordan (American Food and Game Fishes) thought S. spilurus to have NO "basihyal teeth."  We now know that the Rio Grande cutthroat do have such teeth, though they are typically fewer and more weakly developed than other cutthroats.   In the late 1800's and early l900's, it was widely assumed and published (based solely on Cope's article) that Rio Grande cutthroat trout occurred in the mountains of Chihuahua.

Could the two specimens collected by Lupton simply have been Mexican golden trout, a species unknown to science at the time?   Perhaps, small Mexican golden trout (less than 4 inches long) might not have a spotting pattern as distinct as the adult trout. Most every large ichthyological collection in the United States contains specimens which were misidentified at one time or another.  These misidentifications of specimens though, are typically of small, cryptic species -- such as minnows -- which can be difficult to identify.     Unhybridized native trout should present a clearer picture.   Could Cope have made a mistake noticing the presence of "basihyal teeth," or is there an unusual and undiscovered population of trout in southern Chihuahua with these teeth?   Even if  Cope's description of the "basihyal teeth" is ignored, one should be able to distinguish the Mexican golden trout from southern cutthroat trout.  The Mexican golden has a spotting pattern that is decidedly "rainbow trout," and it is somewhat similar to that species.  The golden has small spots, profusely and regularly distributed above the lateral line, including MANY spots on the top of the head, in contrast to the Rio Grande and many other  cutthroats which have larger spots that are more or less clustered on the peduncle, and few (typically none) on the head.  In fact, Cope's original description of Salmo spilurus from 1872 mentions the diagnostic spotting pattern in specific detail: 

"...the caudal peduncle from the middle of the anal fin, with the caudal and dorsal fins, thickly spotted with large, irregularly disposed black spots.  Those on the caudal peduncle are darkest between the scales; each one having, therefore, a reticulated appearance.  Above the lateral line they extend to the dorsal fin, continually contracting their distribution from the lateral line upward.  A few scattered spots are found all the way to the head, and four or five mark the side of the latter." 

ed. note -- Collections we made in 2005, 2006, 2007, and 2008 provided the first scientific voucher specimens of native trout from the Rio Conchos watershed.   These trout DO have orange/yellow cutthroat marks; however, they lack basibranchial teeth and are NOT cutthroats.   Still today, there are no cutthroat trout from Mexico in any museum collections.  Cope's description of the trout's habitat does fit well with headwaters streams of southwest Chihuahua that drain to the Pacific Ocean.  These streams, tributaries to the Rio Fuerte, and rios Sinaloa and Culiacan, are home to the native Mexican golden trout -- unknown to science at the time of Cope's description.  However, the high and remote headwaters of the rios Balleza and Porvenir (both Conchos tributaries) interdigitate with headwater streams of the Fuerte in southwest Chihuahua, suggesting that the Conchos too could have, and may yet be home to Cope's trout.   Next  1  2  3  4  Home