Status, Distribution, and Conservation of Native Freshwater Fishes of Western North America

ABSTRACT The fundamental charge of conservation biology is to preserve biological diversity. Yet, efforts to accomplish this goal have focused too narrowly on reversing the slide toward extinction in already threatened or endangered species. In this review, we argue that conservation biologists and fisheries managers should broaden their vision to include efforts to preserve the ecological and evolutionary processes that ultimately give rise to new biodiversity. Our view is based upon the simple observation that biological diversity is a function of both the rate at which new taxa originate as well as the rate at which established taxa are lost to extinction. Efforts to stem extinction that fail to maintain the ecological and evolutionary processes of speciation are ultimately unsustainable. We suggest that common, widespread species are particularly important to the origin of new diversity and argue that conservation biologists should pay particular attention to the evolution of diversity within such species. We illustrate several key points to this argument using the desert minnow, Utah chub <em>Gila atraria</em>, as a model system. In particular, we show that conservation efforts in common species must focus on clearly delineating conservation unit boundaries and that particular care should be paid to unique ecological and evolutionary diversity within such species.We also show the importance of understanding and conserving the range of ecological and evolutionary interactions that are common hallmarks of abundant and widespread taxa.We conclude our review by suggesting several specific areas of future research in Utah chub that would help more clearly define conservation and management priorities in this species.

Status, Distribution, and Conservation of Native Freshwater Fishes of Western North America

ABSTRACT Three native trouts occur in the southwestern United States. The Rio Grande cutthroat trout <em>Oncorhynchus clarkii virginalis</em> persists in New Mexico and southern Colorado on the Santa Fe, Carson, and Rio Grande national forests and private lands. The Gila trout <em>O. gilae</em> and the Apache trout <em>O. gilae apache</em> (also known as <em>O. apache</em>) occur in isolated headwater streams of the Gila and Little Colorado rivers on the Gila and Apache- Sitgreaves national forests and Fort Apache Indian Reservation in southwestern New Mexico and east-central Arizona, respectively. For more than two decades, intensive management has been directed at the Apache, Gila, and Rio Grande cutthroat trouts. Despite the efforts, their decades-long listed status remains unchanged for the Gila and Apache trouts, and the Rio Grande native is under consideration for listing. The objectives of this paper are to review the literature and management activities over the past quarter of a century in order to delineate why recovery and conservation have been so difficult for southwestern trout.

Status, Distribution, and Conservation of Native Freshwater Fishes of Western North America

ABSTRACT Populations of the four Bear Lake endemic species, Bonneville cisco <em>Prosopium gemmifer</em>, Bonneville whitefish <em>P. spilonotus</em>, Bear Lake whitefish <em>P. abyssicola</em>, and Bear Lake sculpin <em>Cottus extensus</em>, were monitored by Utah Division of Wildlife Resources and/or Utah State University. Bonneville cisco populations have been monitored annually since 1990 using hydroacoustic sampling. The population has ranged from 1.9 to 9.7 million fish. Because no reliable method was available to determine whitefish species identification prior to 1999, the whitefish population was monitored from 1973 to 1998 by lumping the catches of both species and referring to them as the “whitefish complex.” In 1999, the Utah Division of Wildlife Resources began recording the percentage of gill-net catch comprised by Bonneville and Bear Lake whitefish. Bonneville whitefish comprised between 84% and 94% of the gill-net catch while Bear Lake whitefish comprised between 6% and 16%. Relative abundance of Bear Lake sculpin was monitored biennially since 1998 using catch rates from bottom trawling. Average catch per 20-min trawl at both the top and bottom of the thermocline at three different sites ranged from 37 fish to 79 fish.

Status, Distribution, and Conservation of Native Freshwater Fishes of Western North America

ABSTRACT Outside of anadromous salmonids and a few endangered species, the biology of native freshwater fishes of western North America is poorly known. What do we need to know to effectively manage native species and avoid decline and extinction? A recent analysis of the role of science in the Pacific salmon controversy outlines a clear framework for biological evaluation and management of native species. This framework has three components: (1) determine the status of populations based on genetic and ecological variation, (2) identify and quantify threats to populations, and (3) determine actions to alleviate threats and promote conservation of populations.We use our studies of leatherside chub <em>Gila copei</em> (also known as <em>Snyderichthys copei</em>), a small cyprinid native to the Bonneville basin and upper Snake River drainage, as a case study to illustrate the application of this research and management framework. Recent surveys have revealed dramatic reductions in range of leatherside chub over the last 50 years. Genetic, morphometric, and ecological studies all indicate that leatherside chub comprise two distinct species. Leatherside chub is threatened by both habitat degradation and introduced brown trout <em>Salmo trutta</em>, and the interaction between these two threats exacerbates negative effects.We conclude by showing how studies of leatherside chub can inform and influence management, conservation, and habitat restoration activities.

Status, Distribution, and Conservation of Native Freshwater Fishes of Western North America

ABSTRACT The Lewis and Clark expedition crossed the Continental Divide in 1805 on the way west to the Pacific Ocean. Based on journal entries, members of the expedition probably encountered two species of resident salmonids and four of the six species of anadromous salmonids and steelhead (Family Salmonidae, genus <em>Oncorhynchus</em>). The salmonid species were called common salmon (now known as Chinook salmon <em>O. tshawytscha</em>), red charr (sockeye salmon <em>O. nerka</em>), white salmon trout (coho salmon [also known as silver salmon] <em>O. kisutch</em>), salmon trout (steelhead <em>O. mykiss</em>), and spotted trout (cutthroat trout <em>O. clarkii</em>). There was no evidence of the expedition encountering pink salmon <em>O. gorbuscha</em>, chum salmon <em>O. keta</em>, or species of true char <em>Salvelinus</em> spp. Common fishes procured from Indian tribes living along the lower Columbia River included eulachon <em>Thaleichthys pacificus</em> and white sturgeon <em>Acipenser transmontanus</em>. The identity of three additional resident freshwater species is questionable. Available descriptions suggest that what they called mullet were largescale sucker <em>Catostomus macrocheilus</em>, and that chubb were peamouth <em>Mylocheilus caurinus</em>. The third questionable fish, which they called bottlenose, was probably mountain whitefish <em>Prosopium williamsoni</em>, although there is no evidence that the species was observed in the Columbia River drainage. Missing from the species list were more than 20 other fishes known to Sahaptin-speaking people from the mid-Columbia region. More complete documentation of the icthyofauna of the Pacific Northwest region did not occur until the latter half of the 19th century. However, journals from the Lewis and Clark expedition provide the first documentation of Columbia River fishes.

Status, Distribution, and Conservation of Native Freshwater Fishes of Western North America

ABSTRACT Of 55 fish species that were likely native to the Great Plains region of Montana, Wyoming, and Colorado, 33 (60%) species have been given some kind of conservation designation by at least one of the state fisheries management agencies because they are rare or in decline. The species with conservation designations were generally fishes that inhabit large rivers of the upper Missouri River drainage (14 species); live in small, cool- or clear-water streams (9 species); or reside in a wide array of habitats but occur at the edge of their ranges in individual states (10 species). Changes in riverine habitats due to construction of reservoirs on large rivers and introduction of exotic piscivorous fishes to reservoirs are major causes of decline of riverine species in the Great Plains region of Montana, Wyoming, and Colorado. Fishes that occur as disjunct, relict populations in small cool- or clear-water streams or at the periphery of their range in individual states are susceptible to local extirpations caused by habitat alterations and introductions of exotic piscivorous fishes but may have significant conservation value due to their genetic diversity. Given the large proportion of native Great Plains fishes that are declining or threatened with extirpation in individual states, a region-wide effort to maintain native fish assemblages is warranted.

Status, Distribution, and Conservation of Native Freshwater Fishes of Western North America

ABSTRACT The bonytail <em>Gila elegans </em>is endemic to the Colorado River drainage of the American West. In the lower basin, this unique cyprinid historically occurred in the Colorado River main stem and its tributaries from Glen Canyon Dam downstream into Mexico. The species is distinct morphologically and genetically although intermediate forms have been noted from the upper basin. Today, wild individuals may persist in the lower basin in Lake Mojave, Arizona–Nevada. Management activities include broodstock development, the development of grow-out ponds and native fish habitats, and the stocking of bonytail into lakes Mojave and Havasu. Smaller bonytail (<10 cm) were first stocked in Lake Mojave in 1980. Very few of these bonytail have been collected during annual monitoring of the lake during the last 25 years. Today, larger fish (>25 cm) are stocked after being passive integrated transponder-tagged. Predation, particularly on the smaller fish, is thought to be the main reason for the lack of recruitment. Bonytail were stocked in Lake Havasu in 1994 using fish greater than 25 cm. To date, 19 fish have been collected. Although this is a small number of individuals, their recapture is encouraging and suggests that bonytail can be established by stocking larger individuals. A management plan for the big-river fishes of the lower Colorado River basin has been completed by a multi-agency committee.

Status, Distribution, and Conservation of Native Freshwater Fishes of Western North America

ABSTRACT A life cycle model was employed to identify the response of an adfluvial bull trout <em>Salvelinus confluentus</em> population to chronic and catastrophic losses of subadults. The model simulates the bull trout population within Rimrock Lake, Washington, a reservoir on the Tieton River impounded by Tieton Dam. Subadult bull trout are entrained during summer water releases for irrigation, and the dam has no fish passage facilities to enable those fish to return upstream. Suitable spawning and rearing habitat is primarily upstream of the dam. Tagging studies of adult bull trout passing weirs in the two major tributaries to the reservoir were used to estimate model parameters for survival, maturity rates, reproductive capacity, and initial abundance. Sampling data and the deterministic model simulations indicated that the population was capable of rebounding quickly from intermittent catastrophic events. Resilience of the bull trout population resulted from high adult longevity and repeat spawning. The accumulation of mature adults across multiple age-classes led to egg deposition that fully seeded rearing capacity of the natal tributaries, even when several consecutive broods of juveniles exhibited poor survival. Catastrophic events simulated to entrain 50% of the subadults every 15 years caused a 40% reduction in adult abundance within 4 years of the event, followed by a full recovery to maximum production within 9 years. Even during the low point of adult abundance, 15 times more eggs were deposited than were needed to fully seed juvenile tributary habitat. Because the population was already producing juveniles at capacity, simulations for opening fish passage over Rimrock Dam showed that the sustained spawner population would increase by only two adults. However, simulations for expanded juvenile habitat by 14% indicated that the sustainable adult population would increase by 14%. Thus, habitat improvements that target juvenile rearing capacity appear to have the greatest potential to increase population size.

Status, Distribution, and Conservation of Native Freshwater Fishes of Western North America

ABSTRACT Population abundance estimates conducted from 1998 to 2000 were completed for adult (>200 mm) humpback chub <em>Gila cypha</em> and roundtail chub <em>G. robusta</em> in Westwater Canyon on the Colorado River, Utah. Sampling was conducted annually using a three-pass mark–recapture approach. The primary method of capture was trammel netting with supplemental electrofishing on one pass per year. Separate abundance estimates were generated for each year of the study using the null estimator (M_o) within Program CAPTURE. Results showed a decline in the adult humpback chub population between 1998 and 1999 and no change in abundance between 1999 and 2000. The adult roundtail chub population abundance in Westwater Canyon during this time period was relatively stable. Catch per unit effort (CPUE) data from this study and historic interagency standardized monitoring indicated a continued declining trend in mean CPUE for humpback chub that was significant. Mean CPUE for roundtail chub also showed a continued declining trend, but it was not statistically significant. The results of this study provide information to assess the current status of these two species and a point of reference for future population estimates of chub in the upper Colorado River basin.

Status, Distribution, and Conservation of Native Freshwater Fishes of Western North America

ABSTRACT Native Hawaiian stream fishes are represented by only five species belonging to two families, Gobiidae (‘o’opu nakea Awaous <em>guamensis</em>, ‘o’opu ‘alamo’o <em>Lentipes concolor</em>, ‘o’opu nopili <em>Sicyopterus stimpsoni</em>, and ‘o’opu naniha <em>Stenogobius hawaiiensis</em>) and Eleotridae (‘o’opu ‘akupa <em>Eleotris sandwicensis</em>). All species are found on each of the main Hawaiian Islands, and none is currently threatened or endangered. These animals are not true freshwater fishes, but rather share an amphidromous life cycle where adults live and reproduce in streams and larvae develop at sea. Techniques developed for sampling (electroshocking, seining) and assessment (e.g., index of biotic integrity, instream flow incremental methodology) in continental U.S. streams are inappropriate for Hawaiian streams. Thus, procedures were developed specifically for fishes in streams on oceanic islands of the tropical Pacific where amphidromy is the predominant life history mode. Geographical information systems-compatible data from ongoing statewide native stream fish surveys can soon be viewed on the Web site for the Hawai’i Division of Aquatic Resources (http://www.hawaii.gov/dlnr/dar). The 2000 Hawai’i Supreme Court decision on the Waiahole Water Dispute specifically provides for the maintenance of optimum flow for native stream fishes, and the Division of Aquatic Resources has adopted policies guiding instream water use decisions: (1) no net loss of habitat for native fishes, (2) use of a watershed or ahupua’a perspective, and (3) maintenance of an open corridor between the stream and the ocean to facilitate native species migrations. The preservation of indigenous Hawaiian stream fishes now has been elevated to the highest level of protection in the state.