Publications by Year: 2019

2019
Garrett, Gary, Timothy Birdsong, Megan Bean, and Benjamin J. Labay. “Chihuahuan Desert Native Fish Conservation Areas: A multispecies and watershed approach to preservation of freshwater fish diversity.” Multispecies and Watershed Approaches to Freshwater Fish Conservation, edited by Daniel C. Dauwalter, Timothy W. Birdsong, and Gary P. Garrett, 91: 231–252. Bethesda, Maryland, USA: American Fisheries Society, 91, 231–252. Publisher's VersionAbstract
With 95% of the land in Texas privately owned, conservation of the aquatic resources is particularly daunting and is exemplified by the fact that 48% of the 191 native freshwater fishes in Texas are now of conservation concern. Partnerships with private landowners is not only sensible, but often the only way to achieve long-term conservation goals. In the Chihuahuan Desert region of Texas, 55% of the native fishes are of conservation concern or already lost to extirpation or extinction. Although there are numerous contributing factors, habitat degradation and loss are the primary culprits. For decades, research and restoration have focused on some of the more imperiled species and their habitats. From reestablishing ciénegas, to landowner partnerships, to Conservation Agreements, much has been accomplished. Unfortunately, the challenges increase faster than our accomplishments. Our latest, and most promising, approach has been to develop six Native Fish Conservation Areas in the Chihuahuan Desert. These NFCAs represent an ecologically-focused conservation prioritization of watershed segments that serve as native fish “strongholds” and they function as priority areas for conservation investments to promote integrated, holistic conservation strategies that enable the long-term persistence of freshwater biodiversity. Current and future conservation of aquatic resources in Texas emphasizes a landscape-scale approach, working primarily with private landowners to provide conservation best management practices and support on-the-ground projects to maintain or restore habitats to sustain functional ecosystems.
Hendrickson, Dean A.IUCN Red List of Threatened Species: Cyprinella xanthicara.” IUCN Red List of Threatened Species, no. e.T6141A3104687. Publisher's VersionAbstract
Established in 1964, the IUCN Red List of Threatened Species has evolved to become the world’s most comprehensive information source on the global conservation status of animal, fungi and plant species.
Hendrickson, Dean A., Arcadio Valdes Gonzales, and Steven Norris. “IUCN Red List of Threatened Species: Cyprinodon pisteri.” IUCN Red List of Threatened Species, no. e.T191305A1975352. Publisher's VersionAbstract
Established in 1964, the IUCN Red List of Threatened Species has evolved to become the world’s most comprehensive information source on the global conservation status of animal, fungi and plant species.
Pérez‐Miranda, Fabian, Omar Mejía Guerrero, and Dean A. Hendrickson. “IUCN Red List of Threatened Species: Herichthys minckleyi.” IUCN Red List of Threatened Species, no. e.T4836A3012480. Publisher's VersionAbstract
Established in 1964, the IUCN Red List of Threatened Species has evolved to become the world’s most comprehensive information source on the global conservation status of animal, fungi and plant species.
Lyons, Kathleen, and David M. Hillis. “Exploring the Distribution of Groundwater Salamanders and Catfish with Environmental DNA.” Austin, Texas, U.S.A.: University of Texas at Austin, Contract \#504920, 29.Abstract
We designed and tested environmental-DNA (eDNA) probes to identify the presence of species of groundwater salamanders (genus Eurycea) and the Mexican blindcat (Prietella phreatophila) from environmental samples. Environmental samples were screened for the target species using the eDNA probes and quantitative PCR (qPCR). Custom probes were designed to amplify species-specific regions of the mitochondrial cytochrome b gene. A new cytochrome b gene tree was created to ensure full probe coverage of all the recently revised central Texas Eurycea species. Probes were optimized and tested on tissue samples of Eurycea and P. phreatophila species. We developed successful probes for each of the described, as well as the known but undescribed, species of central Texas Eurycea (is a few cases, one probes detects a few closely related species), and for P. phreatophila. We confirmed that these probes are highly species-specific, so they can be used not just for detection of Eurycea, but for species identication. Twenty-six sites across central Texas and Coahuila, Mexico, were subjected to water sampling for the purposes of environmental DNA (eDNA) analysis. These springs, caves, and wells were potential sites for karst aquifer-dwelling salamanders (genus Eurycea) and Mexican blindcat (Prietella phreatophila). To detect the presence of these rare species, volumes of water were pumped through a fine filter which was returned to a lab at the University of Texas - Austin. A DNA extraction was promptly performed on each filter to yield an eDNA sample. The presence of P. phreatophila was detected at a known site for the species in Val Verde County, Texas, validating both the detection method and the molecular probe. Eurycea sp. 1 was detected at a new spring for the species close to a known sample site. An additional positive control site was Eliza Spring of the Barton Springs complex, where E. sosorum was detected. However, we did not detect the target species at several other sites of known occurrence. We conclude that positive results (the presence of a species) are meaningful (we detected no false negatives), but negative results (no species detection) do not necessarily mean that the target species is not present (we did sample known localities for the target species that produced false negatives).
Hendrickson, Dean A., and Arcadio Valdes Gonzales. “IUCN Red List of Threatened Species: Cyprinodon bifasciatus.” IUCN Red List of Threatened Species, no. e.T6147A3104843. Publisher's VersionAbstract
Established in 1964, the IUCN Red List of Threatened Species has evolved to become the world’s most comprehensive information source on the global conservation status of animal, fungi and plant species.
Hendrickson, Dean A.IUCN Red List of Threatened Species: Dionda argentosa.” IUCN Red List of Threatened Species, no. e.T191262A130199481. Publisher's VersionAbstract
Established in 1964, the IUCN Red List of Threatened Species has evolved to become the world’s most comprehensive information source on the global conservation status of animal, fungi and plant species.
Hendrickson, Dean A., and Steven Norris. “IUCN Red List of Threatened Species: Gila eremica.” IUCN Red List of Threatened Species, no. e.T191266A1974611. Publisher's VersionAbstract
Established in 1964, the IUCN Red List of Threatened Species has evolved to become the world’s most comprehensive information source on the global conservation status of animal, fungi and plant species.
Matamoros, Wilfredo, Dean A. Hendrickson, and Maria Vega-Cendejas. “IUCN Red List of Threatened Species: Xiphophorus gordoni.” IUCN Red List of Threatened Species, no. e.T23157A2784873. Publisher's VersionAbstract
Established in 1964, the IUCN Red List of Threatened Species has evolved to become the world’s most comprehensive information source on the global conservation status of animal, fungi and plant species.
Hendrickson, Dean A., and Joseph R. Tomelleri. “Oncorhynchus chrysogaster.” The IUCN Red List of Threatened Species 2019 (e.T142674122A145641611). Publisher's VersionAbstract
TAXONOMIC NOTES The taxon Oncorhynchus chrysogaster currently includes the drainages of the ríos Fuerte, Sinaloa, and Culiacán. Here we treat only the Río Fuerte subpopulations as O. chrysogaster. Sinaloa and Culiacán subpopulations are different phenotypically from each other and from those subpopulations in the Fuerte watershed. JUSTIFICATION This species is known from a number of localities within the Urique, Loera, and Verde sub-basins in Chihuahua, Mexico. Its extent of occurrence (EOO) is estimated to be 3,289 km² and its area of occupancy (AOO) is estimated to be 44 km². Anecdotal evidence suggests population decline and possible extirpation in some areas where this species. However, it is still considered common in the Río Verde and Loera sub-basins. Primary threats include deforestation, livestock overgrazing, hybridization with Rainbow Trout, and localized fishing pressure. Therefore, this species is assessed as Near Threatened (NT) because it meets the threshold for a threatened category under B1 and B2 and there is evidence of continuing decline in the area, extent, and quality of available habitat, but it occurs in more than 10 locations, the population is not severely fragmented, and currently there is no evidence of major range-wide population decline. GEOGRAPHIC RANGE INFORMATION This species is known from 22 localities and more than 10 locations in the sub-basins Urique, Loera, and Verde in Chihuahua, Mexico. It is found in headwater streams of all three sub-basins and in the mainstem of the Río Verde above about 1,900 m. The Río Verde and its tributaries have the largest populations of this trout. Arroyo las Truchas in the Loera basin also has a strong population. Extent of occurrence (EOO) for the species is estimated to be 3,289 km² and area of occupancy (AOO) is estimated to be 44 km². The population is not considered to be severely fragmented. POPULATION INFORMATION Total population size is unknown for this species. Range-wide population trend is unknown, but it is suspected to be declining at a rate that precludes this species from being assessed in a threatened category under criterion A. Mexican Golden Trout are rare and possibly have been eliminated from the upper Urique basin. Trout in the Los Loera system are common in the Arroyo las Truchas, but other streams in that area have not been surveyed. The Río Verde sub-basin populations appear to be stable. Trout are rare in Arroyo San Vincente, and appear different phenotypically from the rest of the basin. The Río Verde and its tributaries have the largest populations of this trout. Arroyo las Truchas in the Loera basin also has a strong population. HABITAT AND ECOLOGY INFORMATION Mexican Golden Trout prefers cold, clear streams above 1,900 m altitude. Their preference appears to be for deeper water beneath boulders and undercuts. Spawning individuals have been taken in mid-February. The specific habitat uses, basic life history, and basic ecology of this species are uncertain and require additional research. THREATS INFORMATION There are multiple threats to the Mexican Golden Trout. Habitat degradation from the effects of overgrazing and logging is principal. These activities cause siltation and warming of the stream waters, and increase flash flooding which can disturb spawning regimens. The Río Verde populations are easily accessed from the highway and are subject to exploitation by anglers. Grow-out facilities in the Fuerte basin are common and Rainbow Trout (Oncorhynchus mykiss) escape from these operations is likely to lead to introgression. To date we have not collected any Mexican Golden Trout that we suspected were hybridized with Rainbow Trout. Future genetic introgression with Rainbow Trout is expected, given government initiatives that promote the development of hatcheries within the region. USE AND TRADE INFORMATION This species is not traded. It is occasionally targeted in subsistence and sport fisheries. However, the magnitude of harvest is unknown. CONSERVATION ACTIONS INFORMATION Currently there are no species-specific conservation measures directed towards Mexican Golden Trout. Recommended conservation actions include implementation of harvest limits in the Rio Verde, and education and encouragement of of cattle ranchers to reduce accessibility to riparian vegetation. More information regarding population size, population trend, and the impacts of major threats would be useful in guiding future conservation action.
Hendrickson, Dean A., and Joseph R. Tomelleri. “Oncorhynchus sp. nov. 'Acaponeta Trout'.” The IUCN Red List of Threatened Species 2019 (e.T142674476A145641646). Publisher's VersionAbstract
TAXONOMIC NOTES There is evidence that most populations of native Acaponeta trout are likely to be introgressed with Rainbow Trout. JUSTIFICATION This species is known only from the headwaters of four streams (arroyos los Metates, Cebollas, Tanquecitos, and Las Moras) at high elevation in the Sierra Madre Occidental, Durango, Mexico. Severe population fragmentation is likely, given the most widespread and major threat to this species is genetic introgression with Rainbow Trout. Its area of occupancy (AOO) and extent of occurrence (EOO) are both highly restricted and this species is not thought to occur in more than four locations. Decline in the number of mature individuals, as well as continued decline in EOO and AOO are inferred. As such, this species is listed as Critically Endangered (CR) under criterion B2ab(i,ii,iii,v). GEOGRAPHIC RANGE INFORMATION This species is known only from the headwaters of four streams (arroyos los Metates, Cebollas, Tanquecitos, and Las Moras) at high elevation in the Sierra Madre Occidental, Durango, Mexico. Area of occupancy (AOO) for the species is estimated at 8 km² and its extent of occurrence (EOO) is estimated at 187 km², based on available georeferenced point records. Both EOO and AOO are inferred to be in decline due to introgression with Rainbow Trout (Oncorhynchus mykiss). This species occurs at four locations, given that the spread of Rainbow Trout is likely to affect each stream separately. POPULATION INFORMATION There is no information regarding trends of the populations. This species was common at Tanquecitos and las Cebollas. Given its highly restricted range, total population size is suspected to be small. HABITAT AND ECOLOGY INFORMATION This species occurs only in headwater streams in the Río Acaponeta watershed. Elevation of habitat ranges from 2,300-2,800 m asl. The specific habitat uses, basic life history, and basic ecology of this species are uncertain and require additional research. THREATS INFORMATION The unique phenotype of the Acaponeta trout shows the population to have a native component that is in danger of introgression with Rainbow Trout (Oncorhynchus mykiss). Future genetic introgression with Rainbow Trout is expected, given government initiatives that promote the development of hatcheries within the region. USE AND TRADE INFORMATION This species is not utilized. CONSERVATION ACTIONS INFORMATION There are no conservation actions currently in place. Education of the populace about the native trout regarding the potential impact of introgression may be an effective course of action. Additionally, more research regarding distribution, population size, and population trend would be useful in guiding future conservation action.
Hendrickson, Dean A., and Joseph R. Tomelleri. “Oncorhynchus sp. nov. 'Culiacán Golden Trout'.” The IUCN Red List of Threatened Species 2019 (e.T142674166A145641621). Publisher's VersionAbstract
TAXONOMIC NOTES The Culiacán Trout is phenotypically and meristically distinct from Oncorhynchus chrysogaster in the rios Fuerte and Sinaloa. JUSTIFICATION The Culiacán trout is restricted to headwater streams in the Río Culiacán basin, Chihuahua and Durango, Mexico and occurs in no more than six locations. This species can be locally common, however, collection localities are few and far between. Localized threats include logging and livestock grazing, both of which have resulted in a continued decline in the extent, area, and quality of available habitat. Subpopulations are fragmented and cannot intermix due to thermal barriers in main river channels. Total population size has been severely diminished in the last 40 years and continuing decline in the number of mature individuals is inferred, but exact estimates of decline are unknown. Its extent of occurrence (EOO) and area of occupancy (AOO) are both highly restricted. Therefore, this species is assessed as Endangered (EN) under criterion B1ab(i,ii,iii,v)+2ab(i,ii,iii,v). GEOGRAPHIC RANGE INFORMATION This species is restricted to headwater tributaries in the Río Culiacán basin. It is most common in arroyos Agua Blanca, El Desecho, and El Río. Extent of occurrence (EOO) for this species is estimated to be 207 km² and area of occupancy (AOO) is estimated to be 14 km², based on current collection records. Continued decline of both EOO and AOO is inferred, based on a reduction in the quality, area, and extent of suitable habitat. This species occurs in fewer than 10 subpopulations and is restricted to no more than six locations. Habitat is restricted to elevations between 2,300-2,800 m asl. POPULATION INFORMATION There is no information available about population trends as no collection sites have been revisited in recent years. This species can be locally common, however, collection localities are few and far between. Total population size is suspected to be less than 1000 with approximately 200 individuals in the largest subpopulation.. Thermal barriers in the mainstem rivers prevent movement of the trout between headwater streams, and therefore subpopulations are considered severely fragmented. HABITAT AND ECOLOGY INFORMATION Virtually nothing is known of the biology of this species. They inhabit clear, cold headwater streams, particularly between 2,300-2,800 m asl. THREATS INFORMATION Localized threats include deforestation of the watershed through logging/road building and grazing of livestock in the riparian. These threats have resulted in an observed reduction in the area, extent, and quality of suitable habitat. Logging and grazing increase silt loads in the stream and decrease clarity of the water and have the potential to smother spawning gravels. Future genetic introgression with rainbow trout is expected, given government initiatives that promote the development of hatcheries within the region. USE AND TRADE INFORMATION This species is not utilized. CONSERVATION ACTIONS INFORMATION There are currently no known conservation actions in place. Education of the local people about the native trout is likely to be the most effective from of mitigation. Additionally, more research regarding distribution, total population size, population trend, and the magnitude of threats would be useful in guiding future conservation action.
Hendrickson, Dean A., and Joseph R. Tomelleri. “Oncorhynchus sp. nov. 'Mayo Trout'.” The IUCN Red List of Threatened Species 2019 (e.T142674103A145641606). Publisher's VersionAbstract
TAXONOMIC NOTES The Mayo trout is most closely related to the Yaqui trout. JUSTIFICATION The Mayo Trout is restricted to four streams (13 collection localities) and is abundant only in one location. This location is a headwater stream that is threatened by mining interests. Additional threats include subsistence harvest, human encroachment, and subsequent declines in water quality and habitat availability. Subpopulations are fragmented and cannot intermix. Total population size has been severely diminished in the last 40 years and continuing decline in the number of mature individuals is inferred, but exact estimates of decline are unknown. Its extent of occurrence (EOO) and area of occupancy (AOO) are both highly restricted. Therefore, this species is assessed as Endangered (EN) under criterion B1ab(i,ii,iii,v)+2ab(i,ii,iii,v). GEOGRAPHIC RANGE INFORMATION This species is restricted to small streams above Basaseachi falls, and to a few headwater streams (above 2,000 m) that intersect the Río Mayo below the falls. One individual was collected below Basaseachi in 2008 (L. Findley Pers. Comm. 2008). Arroyo El Concheño appears to have the strongest population. Extent of occurrence (EOO) for the species is estimated to be 240 km² and area of occupancy (AOO) is estimated to be 26 km²; both are inferred to be declining due to adjacent mining activity, human encroachment, subsistence harvest, and reductions in habitat quality. This species is reported from 13 collection localities. However, threats are acting at the stream scale and the number of locations is unlikely to exceed four. POPULATION INFORMATION The Mayo Trout is rare throughout its range. Cursory surveys show it to be common only in Arroyo El Concheño. The species is decreasing in abundance above Basaseachi falls because of developments and encroachment of civilization. Severe fragmentation is inferred based on habitat type and dispersal ability. HABITAT AND ECOLOGY INFORMATION The Mayo Trout needs cold, clear water. Virtually nothing is known of the spawning habits or behavior of this species. THREATS INFORMATION Mining is a threat to the Mayo Trout in Arroyo El Concheño. Effluent from new mining efforts have killed much of the aquatic life immediately downstream of a mine on El Concheño. There are still trout immediately above a waterfall that is adjacent to the mine. Mayo trout are uncommon above Basaseachi falls, are absent from the mainstem of the river, and are decreasing in the headwaters due to encroaching civilization and developments along the streams. Water quality and catch from local anglers are affecting the populations. Future genetic introgression with rainbow trout is expected, given government initiatives that promote the development of hatcheries within the region. USE AND TRADE INFORMATION This species may occasionally be taken in subsistence fisheries. CONSERVATION ACTIONS INFORMATION There are currently no conservation actions in place. It is imperative that mining not be expanded on Arroyo El Concheño. Education of the local populace may be of help in preserving the small populations above Basaseachi. Additionally, more research regarding distribution, population size, population trend, life history and ecology, and the magnitude of threatening factors will be useful in guiding future conservation action.
Hendrickson, Dean A., and Joseph R. Tomelleri. “Oncorhynchus sp. nov. 'Northern Conchos Trout'.” The IUCN Red List of Threatened Species 2019 (e.T145640871A145641651). Publisher's VersionAbstract
TAXONOMIC NOTES Undescribed species. Affinity appears to be with Yaqui trout in the adjacent basin, but genetic work shows this trout to be unique. JUSTIFICATION Extensive surveys show the trout to occupy only one section of a tiny headwater stream in the Hojasichi sub-basin of the Río Conchos. Habitat is evidently restricted to 1 km of stream and the population has not expanded its range in the past 14 years, despite some protections. the total population size is unlikely to exceed 250 individuals. Threats include fishing pressures, livestock overgrazing, and inbreeding. Given its highly restricted extent of occurrence and area of occupancy, an observed decline in the area, extent, and quality of available habitat in the recent past, and expected future declines, this species is assessed as Critically Endangered (CR) under criterion B1ab(iii)+2ab(iii). GEOGRAPHIC RANGE INFORMATION This species is currently known from about 1 km of stream in the Hojasichi sub-basin of the Río Conchos. Its extent of occurrence (EOO) does not exceed 2.33 km² (although for the purpose of the Red List assessment, this measurement is raised to 4 km² to ensure the EOO is not smaller than the area of occupancy). Its area of occupancy (AOO) is 4 km² (but the actual area occupied by the species does not exceed 2 km²). It occurs in one location. John Woodhouse Audubon (1906) mentioned trout in the Conchos basin seen during his 1849 overland trip through Chihuahua. POPULATION INFORMATION Pennington (1963) described a fish which could only be referred to trout, while studying the culture of the Rarámuri near Sisoguichi. Anecdotal reports of "aparique" (trout) are frequently reported by the indigenous Rarámuri, but they typically mention that they haven't seen the fish for 10 or 20 years. Flechsig noted that residents of Panalachi told him of existence of a trout but were unable to produce the fish because of severe drought in the early 1950s (A. Flechsig Pers. Comm. 2004). We found native trout in 2005 near Panalachi, but subsequent trips to that site over the next 11 years failed to produce any trout. A tiny population was found in a remote stream to the north of Panalachi in 2006. That population is restricted to about 1 km of stream in a remote area, but appears not to be expanding it's range, and is the only known population of this species despite repeated efforts to find more. Total population size is unlikely to exceed 250 mature individuals. HABITAT AND ECOLOGY INFORMATION This species is currently thought to be restricted to a single headwater stream in the northern Río Conchos, excluding the Río Balleza sub-basin. Historical reports suggest it was more widespread in the upper Conchos proper. The single location where this species occurs is between an elevation of 2350-2400 masl. Basic life history and basic ecology are uncertain and require additional research. THREATS INFORMATION Historical declines are the result of overfishing, particularly anglers that take the fish by poisoning the waters, either with clorox, lime, or poisonous roots. Overgrazing by livestock has degraded stream banks and helped to eliminate the fish from most of its former range. Currently, these are not considered major threats to this population because access to the public and livestock is restricted. However, a recent trip showing some fish with a severe overbite suggests that the population has become inbred. Use of detergents in the streams by native peoples washing clothes may also have contributed to the reduction in range of this species. Future genetic introgression with rainbow trout is expected, given government initiatives that promote the development of hatcheries within the region. USE AND TRADE INFORMATION Historically, this species was targeted by subsistence fisheries through the use of clorox, lime, and other indiscriminate fishing methods. Currently, there is no known trade in this taxon. CONSERVATION ACTIONS INFORMATION Currently the species is known to subsist only in one stream, a northerly flowing tributary to the Río Hojasichi. Sections of this stream are crudely fenced with barbed wire to keep livestock out of the riparian, and there is currently a "streamkeeper" (hired by the WWF) that lives on the stream to control public access. Continued site protection is imperative to the survival of this species. Future conservation should seek to employ habitat restoration, species recovery, and education and awareness initiatives.
Hendrickson, Dean A., and Joseph R. Tomelleri. “Oncorhynchus sp. nov. 'Baluarte Trout'.” The IUCN Red List of Threatened Species 2019 (e.T142674469A145641641). Publisher's VersionAbstract
TAXONOMIC NOTES Some museum specimens appear to be introgressed with Rainbow Trout. JUSTIFICATION This species is currently known only from three localities in the headwaters of the Baluarte watershed. Total population size and population trend are unknown as there have been no repeat collections at any sites within the Baluarte, and the purity (extent of ingression) of current collections are uncertain. Severe population fragmentation is likely, given the most widespread and major threat to this species is genetic introgression with Rainbow Trout (Oncorhynchus mykiss). Its area of occupancy (AOO) and extent of occurrence (EOO) are both highly restricted and this species is not thought to occur in more than three locations. Decline in the number of mature individuals, as well as continued decline in EOO and AOO are inferred. As such, this species is listed as Critically Endangered (CR) under criterion B2ab(i,ii,iii,v). Additional field research in the Baluarte watershed may find more native populations. More information regarding population status, distribution, and the impact of introgression would be useful in guiding future conservation action. GEOGRAPHIC RANGE INFORMATION This species is known only from three collection localities in the Sierra Madre Occidental, Durango, Mexico. Arroyo Santa Barbara represents the largest subpopulation. at high elevation in the Sierra Madre Occidental, Durango, Mexico. The area of occupancy (AOO) for the species is estimated at 6 km² and its extent of occurrence (EOO) is estimated at 113 km², based on available georeferenced point records, and both are inferred to be declining based on apparent introgression with Rainbow Trout (Oncorhynchus mykiss). We expect that more field research in the Baluarte watershed would find additional native populations. POPULATION INFORMATION There is insufficient information to establish trends regarding the population status of this species. It is suspected that the pure populations of Baluarte trout are under threat of introgression with introduced Rainbow Trout. HABITAT AND ECOLOGY INFORMATION This species is restricted to the headwaters of the Baluarte watershed in the Sierra Madre Occidental. Elevation ranges from 2,500-2,700 m asl. Basic life history and basic ecology are uncertain and require additional research. THREATS INFORMATION The presence of, and introgression with native Rainbow Trout (Oncorhynchus mykiss) is an immediate threat to the species, and is expected to have resulted in declines in the extent of occurrence, area of occupancy, habitat quality, and the number of remaining mature individuals. Future genetic introgression with Rainbow Trout is expected, given government initiatives that promote the development of hatcheries within the region. USE AND TRADE INFORMATION There is no known trade in this fish CONSERVATION ACTIONS INFORMATION No conservation actions currently in place. One reasonable option would be to isolate a native population and try to reproduce that in a troutless stream that is inaccessible to upstream movement of Rainbow Trout. Additionally, more research regarding distribution, population status, and the effects of introgression are needed.
Hendrickson, Dean A., and Joseph R. Tomelleri. “Oncorhynchus sp. nov. 'Bavispe Trout'.” The IUCN Red List of Threatened Species 2019 (e.T142673841A145641601). Publisher's VersionAbstract
TAXONOMIC NOTES The Yaqui Trout is the only native salmonid in the Río Yaqui watershed. There is some evidence that the Yaqui trout in the Bavispe, Papigochi and the Tutuaca sub-basins are differentiated from each other phentotypically. Rainbow trout are raised as food in grow-out facilities in the Yaqui basin, and have escaped into the wild. Hybridization with the Yaqui trout has occurred but is of localized occurrence. JUSTIFICATION The Yaqui Trout occurs in a number of locations throughout the Yaqui and Guzmán basins at elevations ranging from 1,600-2,200 m above sea level. Extent of occurrence (EOO) for this species is estimated to be 7,339 km² and area of occupancy (AOO) is estimated to be 120 km². Population size is unknown, but presumably exceeds 10,000. Population trend is suspected to be stable or declining at a rate that precludes this species from being listed under a threatened category under criterion A. Subpopulations are not considered fragmented, given a higher thermal tolerance when compared to close congeners, and the ability to disperse through thermal barriers in lower elevation, mainstem rivers. Localized threats include deforestation and livestock overgrazing which have resulted in increased runoff, siltation, and higher stream temperatures, hybridization with rainbow trout, and mild fishing pressure. However, many of the localities where this species occurs are isolated and difficult to access. Therefore, this species is assessed as Near Threatened (NT), because it meets the thresholds for a threatened category under criteria B1 and B2 and there is evidence of decline in the area, extent and quality of habitat, but it occurs in greater than 10 localities and subpopulations are not fragmented. GEOGRAPHIC RANGE INFORMATION Yaqui Trout are common in the Bavispe and Tutuaca sub-basins, and in tributaries of the Río Tomochi (Papigochi sub-basin). The Bavispe has more than a dozen arroyos with strong and stable populations with Arroyo Yenquin and Arroyo Nutria being among the best. Habitat extends from headwaters to about 1,600 m asl. In general, the watershed appears to be among the best in Chihuahua/Sonora from an overall management perspective. Extent of occurrence (EOO) for this species is estimated to be 7,339 km² and area of occupancy is estimated to be 120 km², based on known collection localities. Threats are localized and expected to affect localities independently. Therefore, the number of locations where this species occurs exceeds 10. POPULATION INFORMATION Total population size is unknown but presumably exceeds 10,000. Population trend is suspected to be stable or slowly declining, principally because the watershed is sparsely settled and there is not a lot of fishing pressure on the species. A "duplicate" subpopulation exists in the Guzman basin to the east, having been transplanted there from the Bavispe sub-basin in the early 1900s. Subpopulations are not considered fragmented, given an potentially higher thermal tolerance for warm water and capabilities to disperse through and even live within lower elevation mainstem rivers. HABITAT AND ECOLOGY INFORMATION This species typically occupies small, cold water tributaries with northerly or eastward flow. Major tributaries are often thermal barriers to dispersal for close congeners. However, because the Yaqui trout may exhibit some tolerance to warmer waters, it is occasionally found in mainstem rivers such as rios Tomochi and Gavilan at lower altitudes (1,600 m asl). Basic life history and basic ecology are uncertain and require additional research. THREATS INFORMATION The principal threat to Yaqui Trout is logging and associated runoff. While there is no known instance of clear cutting in the area, extensive logging in the mid-1900s prompted Aldo Starker Leopold to remark that the Río Gavilan had undergone extensive degradation, including sawdust in runoff and flash flooding. Removal of streamside trees also contributes to warming of the stream waters. Trout generally require higher dissolved oxygen than other native fishes, and are therefore particularly susceptible to warming waters. Some pastures are overgrazed which also contributes to flash flooding of streams and rivers and can interrupt spawning and decrease visibility in the streams. Hybridization with non-native Rainbow Trout is a concern, and could eventually lead to widespread introgression. Currently, hybrids are uncommon and are localized near grow-out facilities for Rainbow Trout. Future genetic introgression with rainbow trout is expected, given government initiatives that promote the development of hatcheries within the region. USE AND TRADE INFORMATION There is no known trade of the taxon. It is occasionally targeted in subsistence fisheries. However, fishing pressure at these localities is low because human development is sparse and localities are sometimes remote. CONSERVATION ACTIONS INFORMATION There are currently no species-specific conservation actions in place. Good forest management (e.g. selective logging) is recommended. Reductions in cattle stocking densities would help mitigate the effects of rapid runoff and higher silt loads in the runoff.
Hendrickson, Dean A., and Joseph R. Tomelleri. “Oncorhynchus sp. nov. 'Piaxtla Trout'.” The IUCN Red List of Threatened Species 2019 (e.T142674424A145641631). Publisher's VersionAbstract
TAXONOMIC NOTES The Piaxtla Trout is the closest relative to the San Lorenzo trout, but is phenotypically distinct and Escalante et al. (2015) report genetic differences. JUSTIFICATION This species is restricted to few headwater streams of the Río Piaxtla drainage between 2,100-2,700 m asl in Durango, Mexico. While its extent of occurrence and area of occupancy are both restricted, this species appears to be abundant where it occurs and population status is suspected to be stable. There are no known major pervasive threats. Therefore, this species is assessed as Near Threatened because it meets the threshold for a threatened category under criteria B1 and B2, subpopulations are likely severely restricted, but there is no indication of major population or habitat decline. GEOGRAPHIC RANGE INFORMATION This species is found in a few headwater streams of the Río Piaxtla drainage between 2,100-2,700 m asl. The largest populations appear to be in Arroyo El Granizo, Arroyo Santa Barbara, and Arroyo de la Plazuela. Extent of Occurrence (EOO) for this species is estimated to be 334 km² and area of occupancy (AOO) is unlikely to exceed 10 km. Threats are expected to act independently on stream headwaters, therefore the number is locations is expected to be fewer than 10. Distribution is not considered to be very restricted, given a lack of major plausible threats with the capacity to drive this species towards extinction within a short period of time. There is one instance of intra-basin transfer of Piaxtla Trout to a fishless stream. However, the status of that introduction is unknown. POPULATION INFORMATION This species appears to be locally abundant at the few collection localities where it occurs. Current population trend is suspected to be stable. However, populations are inferred to be severely restricted, given they do not occur in main river reaches and likely encounter thermal barriers that limit the dispersal of individuals between headwater reaches. HABITAT AND ECOLOGY INFORMATION The Piaxtla Trout occupies cold and clear headwater streams. Virtually nothing is known of its reproductive or behavioural traits. THREATS INFORMATION Currently, there are no known major pervasive threats to this species. There are no known grow-out facilities for rainbow trout in the Piaxtla basin. However, future genetic introgression with Rainbow Trout is expected, given government initiatives that promote the development of hatcheries. Sportfishing occurs in the basin but is not thought to present a major threat at this time. USE AND TRADE INFORMATION There is no known trade in the taxon. CONSERVATION ACTIONS INFORMATION There are no known conservation actions in place at this time. Education of the local populace about the native trout is recommended. More research regarding distribution, population size, population status, and the impacts of potential threats would be useful in guiding future conservation action.
Hendrickson, Dean A., and Joseph R. Tomelleri. “Oncorhynchus sp. nov. 'Presidio Trout'.” The IUCN Red List of Threatened Species 2019 (e.T142674431A145641636). Publisher's VersionAbstract
TAXONOMIC NOTES Hendrickson and Tomelleri (In Press) discussed the provenance of trout in the Presidio basin, and determined that trout were indeed native to the drainage. JUSTIFICATION This species historically occurred in isolated headwater streams of the Río del Presidio. Based on current collection records, this species exhibits a restricted extent of occurrence (EOO) and area of occupancy (AOO). Recent collections show strong introgression in the watershed. More collections need to be made to determine the range and purity of remaining populations. Native trout from Arroyo Hondo (Quebrada de Vega) were historically abundant, but collections from 2004 show that stream to be compromised by Rainbow trout. Therefore, it is uncertain if this species still exists in pure form. As such, it is assessed as Data Deficient (DD) until more information regarding the distribution, populations status, and magnitude of introgression is available. GEOGRAPHIC RANGE INFORMATION Trout occur sporadically throughout the Río del Presidio in isolated headwater streams. It is unknown at this time which populations represent pure Presidio Trout. POPULATION INFORMATION Trout are locally common in isolated populations. However, it is not known which, if any of these populations represent pure Presidio trout populations. Trout were first collected from the Presidio watershed in 1906 by Walter C. Bishop (Needham and Gard, 1959). Later collections were made by Ralph G. Miller in 1946, and by "P.R. Needham and party" in 1952. Subsequent collections in the 2000s are suspected to show strong signs of introgression and lead to doubts as to whether any of these recent collections represent pure native Presidio trout. HABITAT AND ECOLOGY INFORMATION This species occurs in cold and clear headwater arroyos and canyons in the upper Río del Presidio watershed. Elevation ranges from 1800-2700 masl. Basic life history and basic ecology are uncertain and require additional research. THREATS INFORMATION The principal threat of overriding concern is hybridization with rainbow trout. There is uncertainty regarding the extent of introgression in the various subpopulations, but introgression is suspected to be widespread throughout the watershed (Escalante et al. 2014). Future genetic introgression with rainbow trout is expected, given government initiatives that promote the development of hatcheries within the region. USE AND TRADE INFORMATION There is no known trade in the taxon. CONSERVATION ACTIONS INFORMATION There are no species-specific conservation actions in place. The prevalence of hatcheries and grow-out facilities in the Presidio watershed present an obstacle to recovery. To conserve this species, it is necessary to document a pure lineage of Presidio trout and use it as a founder population for subsequent reintroductions. More research regarding taxonomy, distribution, population size, and population status of Presidio trout are needed to guide future conservation action.
Hendrickson, Dean A., and Joseph R. Tomelleri. “Oncorhynchus sp. nov. 'San Lorenzo Trout'.” The IUCN Red List of Threatened Species 2019 (e.T142674185A145641626). Publisher's VersionAbstract
TAXONOMIC NOTES JUSTIFICATION This species is restricted to cold, high elevation headwater streams in the Remedios sub-basin of the San Lorenzo drainage. Its extent of occurrence (EOO) and area of occupancy (AOO) are both restricted. Continual declines in EOO and AOO are inferred based on the most serious threats, which include widespread introgression with rainbow trout, and declines in the quality, area, and extent of habitat resulting from deforestation and livestock overgrazing. Subpopulations are severely fragmented with limited to no genetic exchange due to thermal barriers outside of headwater habitat. Localized threats are likely to affect stream subpopulations independently and the number of locations where this species occurs is estimated to be six. Therefore, this species is assessed as Endangered (EN) under criterion B1ab(i,ii,iii)+2ab(i,ii,iii). GEOGRAPHIC RANGE INFORMATION Known populations reside within the Remedios sub-basin of the San Lorenzo. Río Truchas would appear to have the most significant population. Arroyo la Sidra has a peculiar morphotype above the waterfall near Vencedores that is genetically unique. The San Gregorio arm of the San Lorenzo is complimentary in size to the Remedios, but is unexplored for trout. Extent of occurrence (EOO) for this species is estimated to be 4,662 km² and area of occupancy (AOO) is estimated to be 18 km², based on known collection localities. Given the scope of potential threats, the number of locations is estimated to be six. POPULATION INFORMATION Total population size is uncertain, but unlikely to exceed 1,000. Population trend is uncertain but likely to be declining at a rate that precludes listing under a threatened category under criterion A. San Lorenzo trout are common in the Río Truchas. Trout in Arroyo la Sidra above the falls are not common, and are in danger of introgression due to the release of rainbow trout from a nearby grow-out facility. Other disjunct populations occur in small headwater tributaries of the Remedios. Subpopulations are considered severely fragmented, given specific habitat requirements and an inability to migrate across thermal barriers in river mainstreams. HABITAT AND ECOLOGY INFORMATION This species occurs in cold and clear high mountain streams, headwaters and larger arroyos at elevations between 2,300-2,700 m asl. Biological habits, niche, and reproductive characteristics have not been studied for San Lorenzo trout. THREATS INFORMATION Hybridization with rainbow trout is rampant in Arroyo la Sidra below the main falls. Escapes from the grow-out facility are frequent. Hybridization may pose a threat to other populations in the San Lorenzo where populations are not fragmented by thermal barriers. Logging and livestock are present in adjacent areas and may create runoff problems in the watershed. Future genetic introgression with rainbow trout is expected, given government initiatives that promote the development of hatcheries within the region. USE AND TRADE INFORMATION There is no known trade in the taxon. CONSERVATION ACTIONS INFORMATION There are currently no species-specific conservation measures in place. Recommended conservation measures include encouraging ejidos to limit access of livestock to streams, and prevention of future rainbow trout releases to reduce future introgression outside of Arroyo la Sidra. More research regarding distribution, population size, population trend, and the magnitude of potential threats would be useful in guiding future conservation action.
Hendrickson, Dean A., and Joseph R. Tomelleri. “Oncorhynchus sp. nov. 'Sinaloa Golden Trout'.” The IUCN Red List of Threatened Species 2019 (e.T142674143A145641616). Publisher's VersionAbstract
TAXONOMIC NOTES The Sinaloa trout is phenotypically and meristically distinct from Oncorhynchus chrysogaster specimens in the rios Fuerte and Culiacán, and is therefore treated separately from those taxa. JUSTIFICATION This species is restricted to headwater tributaries in the Río Sinaloa basin between 2,600-2,800 m asl, exhibits a restricted extent of occurrence (EOO) and area of occupancy (AOO), and occurs at less than 10 locations. Total population size is unknown but suspected to be relatively small. Population trend is unknown. Subpopulations are inferred to be severely fragmented, given specific habitat requirements for cold, clear water, and an inability to disperse across mainstem river thermal barriers. Localized threats include siltation due to livestock overgrazing, deforestation, and introgression with hatchery raised rainbow trout, which has resulted in a continued decline in the area, extent, and quality of available habitat, and a projected continued decline in EOO and AOO. Therefore, this species is assessed as Endangered (EN) under criterion B1ab(i,ii,iii)+2ab(i,ii,iii). GEOGRAPHIC RANGE INFORMATION This species is restricted to headwater tributaries in the Río Sinaloa basin between 2600-2800 masl. Arroyos El Soldado, Casa Quemada, and El Potrero appear to have the most broadly distributed populations. Extent of occurrence (EOO) for this species is estimated to be 368 km² and area of occupancy (AOO) is estimated to be 18 km². This species is known from nine localities and major threats are expected to impact each locality separately. Therefore, the number of locations where this species occurs is nine. Both EOO and AOO are projected to undergo continuing decline if threats are not mitigated. Edward William Nelson saw trout in streams on the slopes of Mt. Mohinora in 1898, and we suspect that he was in the Sinaloa drainage at the time. POPULATION INFORMATION Information on population size and trends is limited, as most of these streams have been collected once in the last 50 years. This species is localized to tiny headwater streams, and therefore population size is suspected to be less than 1,000. Observation of degraded habitat and the difficulty of finding viable populations suggests that this species was more widespread in historical times. It is suspected that more intensive collecting would produce more sites at lower altitudes for Sinaloa Trout. Subpopulations are considered severely fragmented, given habitat requirements and the presence of thermal barriers in mainstem rivers that prevent dispersal. HABITAT AND ECOLOGY INFORMATION This species requires cold, clear water in headwater streams, with gravel for spawning. The specific habitat uses, basic life history, and basic ecology of this species are uncertain and require additional research. THREATS INFORMATION Overgrazing by livestock has caused siltation in Sinaloa tributaries and remains an ongoing problem. The watershed is logged, but does not appear to be heavily so. One locality (Arroyo Rancho en Medio) contained hybrids between Sinaloa Trout and hatchery Rainbow Trout. The hybrids were localized near a grow-out facility that contained hatchery trout. A waterfall prevented the movement of rainbow trout upstream, but no such barriers exist to downstream dispersion. Future genetic introgression with Rainbow Trout is expected, given government initiatives that promote the development of hatcheries within the region. USE AND TRADE INFORMATION There is no trade in the taxon. CONSERVATION ACTIONS INFORMATION There are currently no species-specific conservation measures in place. Education of the local population to prevent livestock from degrading riparian areas, and encouraging the production of native trout in grow-out facilities to eliminate hybridization with rainbow trout are priority conservation actions. More research regarding distribution, population size, population trend, and the impacts of localized threats would be useful in guiding future conservation action.

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