RARE and ENDANGERED SPECIES; the RIO GRANDE TROUT (Seim° Clarkii Virrinalis)

RARE AND ENDANGERED SPECIES; THE RIO GRANDE TROUT (Seim° clarkii virRinalis) Robert Behnke Colorado Cooperative Fishery Unit Colorado State University Fort Collins, Colorado January, 1967 Introduction The cutthroat trout native to the Rio Grande River basin, is listed as endangered by the Bureau of Sport Fisheries and Wildlife. So little is known about this trout regarding original distribution, taxonomy, or its present status, that perhaps the category "status unknown" would be more appropriate. Evermann and Kendall (1895) reviewed the scattered bits of information on the Rio Grande trout and concluded; "The distribution of the trout of the Rio Grande basin furnishes very interesting and proper subject for investigation." No such investigation has yet been attempted. Virtually the whole taxonomic foundation of this trout found in present day keys and check lists can be traced to the comments of Jordan (1891), who examined two specimens from the Rio Grande at Del Norte, Colorado, in 1889. The original distribution, characters distinguishing it from other cutthroat trout, and variability of populations is not known. Drastic en- vironment changes wrought by the use and misuse of water; the introduction of exotic fish species, particularly rainbow trout and other subspecies of cutthroat trout which hybridize with the native trout, make an evaluation of the present status of the Rio Grande trout 4 difficult task. Relatively few specimens of native Rio Grande trout were collected and permanently preserved in museum collections, and these were from a rather -2- restricted geographical area. Thus, there is little available material representing the original Rio Grande trout for comparative taxonomic studies. Some interesting fragments of information have been accumulated and data obtained from 68 specimens of Rio Grande trout to provide a summary of the present knowledge of this trout. Mainly, however, the goal of this report is to stimulate an interest to know more about the Rio Grande trout, hoping to generate more information and the collection of specimens, allow- ing a thorough evaluation and an authoritative statement on its present status and taxonomic position. Historical Considerations The name: Reference to the Rio Grande cutthroat trout is probably the earliest mention of trout in the New World. An account of Coronado's expedition in 1539 related that: "There were very good trout in the upper Pecos River" (Rostlund, 1952:25). In 1852 the U.S. Army established Fort Massachusetts on Utah Creek (now Ute Creek) in Costilla County, Colorado. Ute Creek flows westward from the Sangre de Cristo Mountains, joining Sangre de Cristo Creek which then enters Trinchera Creek, tributary to the Rio Grande in the San Luis Valley. Fort Massachusetts was abandoned in 1858 and replaced by Fort Gar- land, six miles to the south and closer to Sangre de Cristo Creek. In 1853 a Pacific Railroad Survey expedition made the first collection of Rio Grande trout for scientific purposes. These trout were taken from Ute Creek at Fort Massachusetts. On examining these specimens, Girard (1856) described a new species, "Salar virainalis." Additional specimens were later collected and sent from Fort Garland. Cope (1a72) studied the specimens from -3- Fort Garland and also described a now species, "Salmo spilurus." The type locality for spilurus is listed as Sangre de Cristo Pass (probably from Sangre de Cristo Creek). Cope knew of Girard's description of virginalis from approximately the same locality, but at that time the typologist con- cept and criteria of a species was prevalent in systematic work. Trout with their great variability in color, spotting, and general morphology were especially susceptible to the naming of a rash of invalid species. Cope decided that spilurus was a distinct species because it was: "not so slender" as visginalis. He believed "S. pleuriticus" (the Colorado River cutthroat) also occurred in the Rio Grande basin and listed it from Fort Garland (Cope and Yarrow, 1875). For several years thereafter the name spilurus was ap- plied to Rio Grande cutthroat trout and virginalis erroneously used for Bonneville basin trout. The name virginalis given by Girard in 1856, clearly is the first valid scientific name used for Rio Grande trout. There is no contention at present that the Rio Grande trout is a member of the wide ranging cutthroat species, Salmo clarkii. If the Rio Grande trout is suf- ficiently distinct from other cutthroat trout to warrant subspecific des- ignation, the name Salmo clarkii virginalis should be used. Distribution Cope (1886) reported receiving two black spotted trout, resembling a cutthroat trout, with: "teeth on the basihyal bones," from southern Chihuahua, Mexico. Subsequently, most 041PA1,Ihed distributional records extended the range of the Rio Grande trout south to Chihuahua. These two Mexican specimens mentioned by Cope have significante concerning the original distribution of Rio Grande trout and for trout systematics and zoo- geography in general. Unfortunately, the fate of these specimens and their -4- precise collection locality are unknown. The locality given by Cope: "streams of the Sierra Madre, at an elevation of 7,000 and 8,000 feet, in the southern part of the State of Chihuahua near the boundaries of Durango and Sinaloa," could be in the Rio Conchos drainage which is tributary to the Rio Graade in Chihuahua, or it could refer to streams draining westward into the Gulf of California. Needham and Gard (1959) described trout collected from the Pacific Coast streams (Rio Fuerte, Rio Sinaloa, and Rio Culiacan). A distinctive golden colored trout inhabits these streams; it was named Salmo chrysogaster by Needham and Gard (1964). Salmo chrysogaster does not appear to be derived from, or closely related to, the Rio Grande cutthroat trout. Needham and Gard (1959) compared a sample of trout collected from the headwaters of the Rio Casas Grandes in northern Chihuahua, a dis- rupted tributary of the Rio Grande. These trout are not of the cutthroat species, but are almost identical to the trout of the Rio Yaqui, tributary to the Gulf of California. The Rio Yaqui and Rio Cases Grandes have many species in common (Miller, 1958). The Rio Yaqui and Rio Cases Grandes trout appear intermediate between the Mexican golden trout, S. chrysogaster, and the Gila trout, S. gilae, but are not closely related to Rio Grande cutthroat trout. The probability remains that during the colder periods of the Pleistocene, cutthroat trout did range throughout the Rio Grande system into Mexico and may yet persist in isolated colonies in the Rio Conchos. Cope l s calling attention to the "basihyal" teeth on the Mexican specimens indicates that these specimens were true cutthroat trout and not the "golden trout" from the Pacific drainage of Chihuahua. 'The basihyal bone to be anatomically correct is the bone forming the base of the tongue and sometimes tongue teeth are called basihyal teeth. However, since. all -5- trout have teeth on the tongue, Cope's specific reference to basihyal teeth probably means basibranchial (=hyoid) teeth which distinguish cutthroat trout from other species of the genus Salo). At present, this is the only evidence that a Rio Grande cutthroat occurred south into Mexico. No specimens of cutthroat trout have been collected from Mexico since Cope's note of 80 years ago. Just how far south in the Rio Grande basin the native cutthroat ranged has not been accurately determined. Clark Hubbs (1957) said there are no authentic records of native trout ever occurring in Texas, and at present only one stream, McKittrick Creek in the Guadalupe Mountains, maintains a self-reproducing population of introduced rainbow trout. There are some old reports relating tales of native trout from far outside the present known distribution. Daniel (1878) in a letter to the sportsmen's journal, Forest and Stream, recalled his fishing experiences while serving as Assistant Surgeon in the Second Texas Rifles during the Civil war. He believed he remembered catching trout at San Felipe Springs (tributary to the Rio Grande near Del Rio on the Mexican border, Val Verde Co.). Daniel had a "distinct recollection" of taking "speckled trout" from the Devil's River while stationed at Fort Hudson (tributary of Rio Grande, Val Verde Co.). He claimed to have caught many trout from the Limpia River (tributary of Pecos R., Jeff Davis Co.) during his duty at Fort Davis in Texas. In southern New Mexico, at Fort Stanton, Daniel recalled trout in the Rio Bonito (tributary to the Pecos, Lincoln Co.). Daniel had lived in New Haven, Connecticut, and wrote that he was familiar with the eastern brook trout (Salvelinus fontinalis); he thought the trout he saw in Texas and New Mexico to be the same. Another correspondent to Forest and Stream (Taylor, 1878) supplied further information on trout in Texas. Inquiry was made with Dr. D.I. Hunter, -6- a Confederate Army surgeon, who was stationed at Fort Davis on the Limpia River during the Civil War. A fish, believed to be the eastern brook trout (Salvelinus fontinalis) was said to be abundant in the Limpia and in streams to the north. The Limpia was described as a clear, cool, sparkling stream flowing through a region about 5,000 ft. elevation. A buffalo hunter told Taylor of catching "wagon loads" of "speckled trout" in the Panhandle region of Texas, from headwater streams of the Canadian and Red rivers. Major D.W. Hinkle formerly with Emory's Boundary Survey and familiar with the Panhandle region, verified the Buffalo hunter's story according to Taylor. At that time the Texas border extended the Panhandle region of Texas westward into part of present day New Mexico and would have included suitable trout habitat in the Canadian River basin. The report of trout in the Red River basin, I would consider, more dubious.

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