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At least 1,225 records · Page 68Linked to original sources
USGS2023

Fish life-history traits predict abundance-occupancy patterns in artificial lakes

Life-history traits of a species have been postulated as a factor in abundance and occupancy patterns. Understanding how traits contribute to the ubiquity and rarity of taxa can facilitate the development of effective conservation policy by establishing a connection between species requirements and resource. The goal was to evaluate fish assemblages in artificial lakes for evidence of the abundance-occupancy patterns reported in natural environments and, if evident, to explore if observed patterns of abundance and occupancy could be attributed to species traits. Fish abundance and occupancy were estimated over 1990–2018 in 22 artificial lakes impounded within the Tennessee River basin, USA. Consistent with reports for many other taxonomic groups in natural environments, there was a positive association amidst 114 fish species between abundance and occupancy in artificial lakes ( R 2 = 0.78). This result indicates that the fish assemblages that develop in these anthropized environments follow the fundamental abundance-occupancy patterns uncovered in natural environments, despite assemblages having been disfigured by the dramatic rearrangement of habitats brought by impoundment. Moreover, a redundancy analysis focusing mostly on reproductive and habitat traits adequately predicted abundance-occupancy patterns of fish assemblages in artificial lakes ( R 2 = 0.69). Species abundance-occupancy is influenced by the interplay between life-history traits and habitat availability, even in artificial lakes, and by extension, possibly other artificial ecosystems.

Alabame, Georgia, Kentucky, Mississippi, North Car↗
USGS2012

Immunity to fish rhabdoviruses

Members of the family Rhabdoviridae are single-stranded RNA viruses and globally important pathogens of wild and cultured fish and thus relatively well studied in their respective hosts or other model systems. Here, we review the protective immune mechanisms that fish mount in response to rhabdovirus infections. Teleost fish possess the principal components of innate and adaptive immunity found in other vertebrates. Neutralizing antibodies are critical for long-term protection from fish rhabdoviruses, but several studies also indicate a role for cell-mediated immunity. Survival of acute rhabdoviral infection is also dependent on innate immunity, particularly the interferon (IFN) system that is rapidly induced in response to infection. Paradoxically, rhabdoviruses are sensitive to the effects of IFN but virulent rhabdoviruses can continue to replicate owing to the abilities of the matrix (M) protein to mediate host-cell shutoff and the non-virion (NV) protein to subvert programmed cell death and suppress functional IFN. While many basic features of the fish immune response to rhabdovirus infections are becoming better understood, much less is known about how factors in the environment affect the ecology of rhabdovirus infections in natural populations of aquatic animals.

Viruses↗
USGS2023

Antimycin A species sensitivity distribution: Perspectives for non-indigenous fish control

The global transfer of aquatic biota outside their native geographical range has resulted in dramatic changes to biological communities. Many nonnative species introductions are facilitated by human activity and then spread intra-continentally through connected watersheds once established. Resource managers therefore utilize multiple control technologies, such as management chemicals, for fisheries management to remove non-indigenous fishes. Antimycin-A (ANT-A) is a management chemical, previously registered in the United States, that has been extensively studied and used to control non-indigenous fishes. The present study examines ANT-A species sensitivity among fish and aquatic invertebrates and summarizes factors that influence toxicity. ANT-A species sensitivity distributions 20th percentile hazard concentrations (HC20) for acute studies ≤ 24 h demonstrated fish (0.088 µg/L) are 174-fold more sensitive to ANT-A than invertebrates (15.35 µg/L). Similar to previous reports, toxicity was demonstrated to be influenced by water pH, temperature, and fish mass. Therefore, the present study and results characterize ANT-A toxicity for aquatic resource managers and future use in fisheries management.

Management of Biological Invasions↗
USGS2017

The thermal regime and species composition of fish and invertebrates in Kelly Warm Spring, Grand Teton National Park, Wyoming

We evaluated the thermal regime and relative abundance of native and nonnative fish and invertebrates within Kelly Warm Spring and Savage Ditch, Grand Teton National Park, Wyoming. Water temperatures within the system remained relatively warm year-round with mean temperatures >20 °C near the spring source and >5 °C approximately 2 km downstream of the source. A total of 7 nonnative species were collected: Convict/Zebra Cichlid ( Cichlasoma nigrofasciatum ), Green Swordtail ( Xiphophorus hellerii ), Tadpole Madtom ( Noturus gyrinus ), Guppy ( Poecilia reticulata ), Goldfish ( Carassius auratus ), red-rimmed melania snail ( Melanoides tuberculata ), and American bullfrog tadpoles ( Lithobates catesbeianus ). Nonnative fish (Zebra Cichlids and Green Swordtails), red-rimmed melania snails, and bullfrog tadpoles dominated the upper 2 km of the system. Abundance estimates of the Zebra Cichlid exceeded 12,000 fish/km immediately downstream of the spring source. Relative abundance of native species increased movingdownstream as water temperatures attenuated with distance from the thermally warmed spring source; however, nonnative species were captured 4 km downstream from the spring. Fish diseases were prevalent in both native and nonnative fish from the Kelly Warm Spring pond. Clinostomum marginatum, a trematode parasite, was found in native species samples, and the tapeworm Diphyllobothrium dendriticum was present in samples from nonnative species. Diphyllobothrium dendriticum is rare in Wyoming. Salmonella spp. were also found in some samples of nonnative species. These bacteria are associated with aquarium fish and aquaculture and are generally not found in the wild.

Wyoming↗
USGS2018

Necropsy-based wild fish health assessment

Anthropogenic influences from increased nutrients and chemical contaminants, to habitat alterations and climate change, can have significant effects on fish populations. Adverse effects monitoring, utilizing biomarkers from the organismal to the molecular level, can be used to assess the cumulative effects on fishes and other organisms. Fish health has been used worldwide as an indicator of aquatic ecosystem health. The necropsy-based fish health assessment provides data on visible abnormalities and lesions, parasites, condition and organosomatic indices. These can be compared by site, season and sex, as well as temporally, to document change over time. Severity ratings can be assigned to various observations to calculate a fish health index for more quantitative assessment. A drawback of the necropsy-based assessment is that it is based on visual observations and condition factors, which are not as sensitive as tissue and subcellular biomarkers for sublethal effects. Additionally, it is rarely possible to identify causes or risk factors associated with observed abnormalities. So, for instance a raised lesion or "tumor" on the fins, lips or body surface may be a neoplasm. However, it could also be a response to a parasite, chronic inflammation or hyperplasia of normal cells in response to an irritant. Conversely, neoplasms, certain parasites, other infectious agents and many tissue changes are not visible and so may be underestimated. However, during the necropsy-based assessment, blood (plasma), tissues for histopathology (microscopic pathology), genomics and other molecular analyses, and otoliths for aging can be collected. These downstream analyses, together with geospatial analyses, habitat assessments, water quality and contaminant analyses can all be important in comprehensive ecosystem evaluations.

Journal of Visualized Experiments↗
USGS2013

Effects of summer drawdown on the fishes and larval chironomids in Beulah Reservoir, Oregon

Summer drawdown of Beulah Reservoir, Oregon, could adversely affect fish and invertebrate production, limit sport fishing opportunities, and hinder the recovery of threatened species. To assess the impacts of drawdown, we sampled fish and Chironomidae larvae in Beulah Reservoir in the springs of 2006 to 2008. The reservoir was reduced to 68% of full pool in 2006 and to run-of-river level in 2007. From spring 2006 to spring 2007, the catch per unit effort (CPUE) of fyke nets decreased significantly for dace [Rhinichthys spp.] and northern pikeminnow [Ptychocheilus oregonensis], increased significantly for suckers [Catastomus spp.] and white crappies [Pomoxis nigromaculatus], and was similar for redside shiners [Richardsonius balteatus]. CPUE of gillnets either increased significantly or remained similar depending on genera, and the size structure of redside shiners, suckers, and white crappies changed appreciably. From 2007 to 2008, the CPUE of northern pikeminnow, redside shiners, suckers, and white crappies decreased significantly depending on gear and the size structure of most fishes changed. Springtime densities of chironomid larvae in the water column were significantly higher in 2006 than in 2008, but other comparisons were similar. The densities of benthic chironomids were significantly lower in substrates that were frequently dewatered compared to areas that were partially or usually not dewatered. Individuals from frequently dewatered areas were significantly smaller than those from other areas and the densities of benthic chironomids in 2008 were significantly lower than other years. Summer drawdown can reduce the catch and alter the size structure of fishes and chironomid larvae in Beulah Reservoir.

Oregon↗
USGS1982

Some observations on the ecology and fish management of reservoirs in the United States

By 1980 there were 1,608 reservoirs (over 202 ha each) with a surface area of 4 million ha in the United States. Construction of new reservoirs has decreased in recent years because of the lack of suitable sites and the opposition of environmental interests. Reservoirs have characteristics of both lacustrine and riverine ecosystems. Reservoirs have been segmented into riverine, transitional and lacustrine zones for simulation modelling.Fish and plankton production increases rapidly after initial impoundment and then decreases and stabilizes at lower levels. Decreases in the number of fish species and in fish biomass following impoundment are caused by reduced quantity and quality of spawning and nursery habitat and decreased detrital input. Plankton populations can be followed downstream in a series of reservoirs and increases in abundance were associated with the inundation of vegetation or the introduction of nutrients.In addition to water level management, the most effective fish management programs have included introducing new fishes, developing vegetation or building structures on the reservoir bottom. Considerable progress has been made in predicting the effects of environmental parameters on fish production.

Montana, Nebraska, North Dakota, South Dakota↗
USGS2009

Warmwater fish in rivers

Large warmwater rivers are complex ecosystems and often contain numerous species and habitats. We loosely define a large river as having a drainage area greater than 50,000 km2 and a stream order great than six. Further, these rivers typically have mean discharges greater than 1,500 m3/s. Channel patterns are highly variable among and within large rivers, generally forming a meandering pattern. Currently, many large rivers are confined by bank stabilization and are characterized by a straight channel because of anthropogenic alterations. Further, most large rivers in North America have altered hydrographs because of main-stem dams or dams within the drainage area. Large rivers that have been modified to reduce meandering and flooding present challenges for deployment and operation of fish sampling gear. Water temperature in large rivers is highly variable across North America and varies longitudinally within a river. For example, the Missouri River originates in the Rocky Mountains and terminates at the confluence with the Mississippi River near St. Louis, Missouri. Thus, mean water temperature in the headwaters is considerably different than the confluence. As a result, we defined warmwater by the dominant fish assemblage found in the river. Most fish species can be categorized into broad categories, such as coldwater, coolwater, or warmwater, based on water temperature in the natural environments where they occur. We define warmwater rivers as rivers that were naturally void of coldwater fishes such as trouts, salmons, and ciscoes. This is appropriate because it disregards zoogeographic boundaries that may limit the inclusion of rivers in the warmwater category. For example, the Colorado River is in a different zoogeographic subdivision than the Ohio River (Moyle and Cech 2000), but both rivers contain warmwater fish assemblages.

Book chapter↗
USGS2009

Coldwater fish in large standing waters

Large coldwater lakes are defined here as standing freshwater bodies with surface area greater than 200 ha that support coldwater fishes such as trouts and salmons throughout the year. These large water bodies can be exposed to extensive wind fetch, which will affect the timing, mobility, and safety of personnel and gear. These considerations become important constraints for deploying, locating, and retrieving sampling gear. Wind and wave energy affect the timing, duration, and stability of thermal stratification, and they can create transient upwellings, thermal fronts, seiches, and other internal waves that affect vertical and horizontal thermal structure and dissolved oxygen availability. Thermal stratification affects seasonal distribution and productivity patterns for most aquatic organisms. When waters are destratified, movements and distributions of fishes can vary considerably, particularly during thermocline formation in spring and destratification during autumn. During thermal stratification, species with similar thermal responses tend to concentrate more predictably within certain depth-temperature strata, and segregate from species with different thermal responses. In mesotrophic and eutrophic lakes, hypoxia below the thermocline (sometimes encroaching into the thermocline) forces coldwater fishes into shallower, warmer depths than they would otherwise inhabit. Seasonal and diel changes in light and turbidity conditions affect the activity levels, behaviors, and distributions of fishes (e.g., schooling, diel vertical or horizontal migrations, refuge-seeking) and influence their ability to detect and evade certain types of sampling gear, such as gill nets and trawls. Major tributaries and outlets can form habitat conditions that differ considerably from the rest of the littoral zone. Tributary mouths form shallow sand-silt deltas with perceptible flow-through channels and groundwater inflows. Localized thermal pockets can develop if the temperature from incoming surface plumes or groundwater differs substantially from the lake water. Inlets are also point sources for recruitment and for delivering turbidity or prey generated from stream, riparian, or terrestrial sources. Because these habitat features tend to attract fishes, inlets and outlets should generally be considered distinct strata in a lake sampling program.

Book chapter↗
USGS2009

Coldwater fish in wadeable streams

Standardizing sampling methods for fish populations across large regions is important for consistent measurement of large-scale effects of climate or geography. In addition, pooling samples creates larger sample sizes and can facilitate data sharing among scientists and land managers. Sampling freshwater fish has largely not been standardized due to the diversity of fish and habitats. USGS aquatic ecologist Jason Dunham and co-authors contributed a chapter about sampling coldwater fish in wadeable streams to a new book that details common methods, protocols, and guidelines for sampling fish across North America. Topics include three common sampling methods: electrofishing, snorkeling, and nest counts. Each method provides complementary information about different species and life stages. The information will be useful for initiating new or fine-tuning ongoing sampling programs.

Book chapter↗
USGS2024

Indices for common North American fishes

One of the greatest advantages to the standardization of fisheries sampling methods is the comparable data they produce (Bonar et al. 2017). Following American Fisheries Society (AFS) standardized sampling methods, fisheries professionals can more easily compare their data with standardized data collected across North America to address both small- and large-scale fisheries questions. For example, access to standardized data can allow fisheries managers to evaluate if a fish species is within an expected range for weight or length in a particular water body, providing them with valuable information about the baseline health of their fish population. Additionally, given that fish can take years to respond to certain management actions (Meals et al. 2010), access to standardized data over time can be used to assess the effectiveness of these actions. Finally, standardized fisheries data can be analyzed over large geographic regions and provide increased sample sizes to evaluate management actions that cross local or state borders, such as habitat improvements or regulations, as well as the effects of large-scale transformations such as climate change on fish growth or body condition. Ultimately, the use of standardized data enhances the ability of fisheries professionals to address both small- and large-scale threats currently facing freshwater ecosystems and the fishes they support.

Book chapter↗
USGS1939

Migratory fish, a problem of interstate cooperation?

Bobwhite quail chicks, when given a choice of balanced diets in which the essential difference was the protein supplement, showed preferences for one diet containing 49 per cent peanut oil meal, another containing a mixture of 9 per cent meat and bone scraps (50% protein) with 38 per cent soybean oil meal, and a third (control) diet containing a mixture of 16 per cent dried buttermilk with 42 per cent soybean oil meal, in contrast to diets containing sardine meal or menhaden fish meal. ....Feeding tests during the first five weeks of life showed that diets containing 14 per cent sardine fish meal consistently gave high live weights, low mortality, and high efficiency of feed utilization. Diets with 9 to 10 per cent menhaden meal produced nearly as good results....Live weights, survival, and efficiency of feed utilization were markedly better on a diet containing 9 per cent meat and bone scrap (50% protein) than on one with 9 per cent meat scrap (55% protein), but not as good as with diets containing fish meal without meat....The chicks grew and survived more successfully on diets containing either soybean oil meal or peanut oil meal as the sole protein supplement, than on diets containing either linseed oil meal, cottonseed oil meal, or dried buttermilk as the sole protein concentrate. None of these was as satisfactory as the diets containing fish meal.....All chicks died on diets containing either linseed oil meal, cottonseed oil meal, or dried buttermilk as the sole source of protein. All three of these concentrates, however, gave satisfactory results, when used as 10 per cent of the diet. In fact, survival and efficiency of feed utilization were nearly as good on a diet containing 10 per cent dried buttermilk, 10 per cent linseed oil meal, 10 per cent peanut oil meal, and 27 per cent soybean oil meal, as on diets containing fish meal.

Transactions of the North American Wildlife Confer↗
USGS1979

Annotated list of the fishes of the Lake Ontario watershed

This annotated list of the fishes of Lake Ontario and its watershed is based on published distribution records, museum collections, and reports of fish surveys that confirm the occurrence of fish species dating back to the 1850's. It includes 130 forms (129 spp. + the hybrid splake), 20 of which have disappeared or are extremely rare today. Considering species present only in the lake proper, 64 were reported in 1929, and 51 of those remained in 1972-73 (13 having disappeared). Seventeen species and the splake are fishes not known to have occurred in the lake in 1929 or were introduced since then. A list of 86 references pertinent to the study of the fish fauna of the watershed is given. The present list, started in 1972, includes some information from as late as 1976.

Technical Report↗
USGS1998

Contaminant effects on Great Lakes' fish-eating birds: a population perspective

Preventing environmental contaminants from reducing wildlife populations is the greatest concern in wildlife toxicology. In the Great Lakes, environmental contaminants have a history of reducing populations of many species of fish-eating birds. Endocrine effects may have contributed to declines in fish-eating bird populations, but the overriding harm was caused by DDE-induced eggshell thinning. Toxic effects may still be occurring today, but apparently they are not of a sufficient magnitude to depress populations of most fish-eating birds. Once DDE levels in the Great Lakes declined, eggshells of birds began to get thicker and reproductive success improved. Populations of double-crested cormorants (Phalacrocorax auritus) and ring-billed gulls (Larus delawarensis) have increased dramatically since the bans on DDT and other organochlorine pesticides. Bald eagles (Haliaeetus leucocephalus) are still not reproducing at a normal rate along the shores of the Great Lakes, but success is much improved compared to earlier records when eggshell thinning was worse. Other species, such as herring gulls (Larus argentatus) and black-crowned night-herons (Nycticorax nycticorax), seem to be having improved reproductive success, but data on Great Lakes'-wide population changes are incomplete. Reproductive success of common terns (Sterna hirundo), Caspian terns (Sterna caspia), and Forster's terns (Sterna forsteri) seems to have improved in recent years, but, again, data on population changes are not very complete, and these birds face many habitat related problems as well as contaminant problems. Although contaminants are still producing toxic effects, and these effects may include endocrine disfunction, fish-eating birds in the Great Lakes seem to be largely weathering these effects, at least as far as populations are concerned. A lack of obvious contaminant effects on populations of fish-eating birds in the Great Lakes, however, should not be equated with a lack of any harm to these birds or with a conclusion that certain contaminants do not need additional control.

Book chapter↗
USGS1995

Effects of fish density and relative abundance on competition between larval lake herring and lake whitefish for zooplankton

Competition for zooplankton between larval lake herring ( Coregonus artedi ) and lake whitefish ( C. clupeaformis ) was compared in mesocosm experiments in a small lake. Both species were combined in test enclosures at relative abundances of 1:1 or 1:4 lake herring to lake whitefish at densities of 500; 1, 000; and 2, 000 fish per cage, and were allowed to feed ad libitum on available zooplankton. After 60 days, at 500 fish per cage and a 1:1 ratio, lake whitfish were significantly larger than lake herring. At 1, 000 and 2, 000 fish per cage, lake herring and lake whitefish exhibited similar depressed growth rates. Survival was lower (30-50%) in the nets with 2, 000 fish than in the lower fish densities. We suspect that diet similarities of juvenile lake herring and lake whitefish in addition to the larger size and more aggressive behavior of larval lake whitefish resulted in the depressed growth and poorer survival for lake herring.

Book chapter↗
USGS1989

Acid rain publications by the U.S. Fish and Wildlife Service, 1979-1989

Pollution of aquatic and terrestrial ecosystems has been a concern to society since the burning of fossil fuels began in the industrial revolution. In the past decade or so, this concern has been heightened by evidence that chemical transformation in the atmosphere of combustion by-products and subsequent long-range transport can cause environmental damage in remote areas. The extent of this damage and the rates of ecological recovery were largely unknown. "Acid rain" became the environmental issue of the 1980's. To address the increasing concerns of the public, in 1980 the Federal government initiated a 10-year interagency research program to develop information that could be used by the President and the Congress in making decisions for emission controls. The U.S. Fish and Wildlife Service has been an active participant in acid precipitation research. The Service provided support to a number of scientific conferences and forums, including the Action Seminar on Acid Precipitation held in Toronto, Canada, in 1979, an international symposium on Acidic Precipitation and Fishery Impacts in Northeastern North America in 1981, and a symposium on Acidic Precipitation and Atmospheric Deposition: A Western Perspective in 1982. These meetings as well as the growing involvement with the government's National Acidic Precipitation Assessment Program placed the Service in the lead in research on the biological effects of acidic deposition. Research projects have encompassed water chemistry, aquatic invertebrates, amphibians, fish, and waterfowl. Water quality surveys have been conducted to help determine the extent of acid precipitation effects in the northeast, Middle Atlantic, and Rocky Mountain regions. In addition to lake and stream studies, research in wetland and some terrestrial habitats has also been conducted. Specific projects have addressed important sport species such as brook trout (Salvelinus fontinalis), Atlantic salmon (Salmo salar), and striped bass (Morone saxatilis). Trace metal accumulation in fish has been investigated and a symposium sponsored on related work. U.S> Fish and Wildlife Service scientists serve as advisors and participants in research being conducted by industry, nonprofit groups, State and other Federal agencies. Researcher have worked closely with colleagues in Canada, England, Norway, Scotland, the Soviet Union, and Sweden to gain additional understanding of the problem. In 1982, the Service implemented a mitigation research program to provide resource managers with information to help them protect sensitive ecosystems, and rehabilitation methods for resources already affected by acidification. An international workshop was convened to outline the research needs. Several conferences were organized to develop appropriate field and laboratory procedures. Scientists with the mitigation research program are evaluating the ecological effects of liming (addition of base material) surface waters and surrounding watershed to provide buffering against acidic inputs. Through long-term cooperative project with States and other organizations, investigations are studying possible abatement methods for regions most affected by acidic deposition. To date, more than 200 reports the describe these studies have been published. These products include conference proceedings, journal articles, and in-house scientific publications. An education poster describing the effects of acid rain on aquatic ecosystems was developed and distributed to individuals, conservations and State organizations, and the public education system. This annotated bibliography lists current publications by Service authors, cooperators, or contractors on acid rain and related quality. Entire are arranged alphabetically by author surname. For further information about the research program, contact the U.S. Fish and Wildlife Service, Acid Precipitation Section, National Fishery Research Center -- Leetown, Box 700, Kearneysville, WV 25430.

Biological Report↗
USGS2002

Resident fish assemblages in shallow shorelines of a Columbia River impoundment

During May-September 1995, we replicated an earlier (1984-85) study of fishes in shoreline habitats of the John Day Reservoir, Columbia River, to investigate fish assemblage structure at several spatial and temporal scales. A total of 37,400 resident fishes representing 24 taxa was collected in 359 beach seine hauls. Fish catch composition during 1984 and 1985 was very similar, but was greatly different from catch in 1995. During 1984-1985, four native taxa (chiselmouth, northern pikeminnow, suckers, and sand rollers) constituted more than 90% of the combined main-channel catch, with introduced taxa comprising only 1.3% of the main-channel catch. In contrast, during 1995 only 37.7% of the main-channel catch comprised chiselmouth, northern pikeminnow, suckers, and sand rollers, while 33.9% were introduced taxa, primarily sunfishes and yellow perch. This shift in catch composition was greatest in the lower reservoir where the 1995 catch was 61% introduced taxa. Although changes in species composition of near-shore reservoir fish assemblages over the 10-yr period appeared to be substantial, we are unsure of annual variability since we have only one season of sampling for comparison with the earlier study. The differences we observed could be a long-term response to reservoir aging, a short-term reaction to annual differences in hydrologic and thermal regimes, or simply the naturally varying reproductive success of some species.

Northwest Science↗
USGS2005

Historical and current perspectives on fish assemblages of the Snake River, Idaho and Wyoming

The Snake River is the tenth longest river in the United States, extending 1,667 km from its origin in Yellowstone National Park in western Wyoming to its union with the Columbia River at Pasco, Washington. Historically, the main-stem Snake River upstream from the Hells Canyon Complex supported at least 26 native fish species, including anadromous stocks of Chinook salmon Oncorhynchus tshawytscha, steelhead O. mykiss, Pacific lamprey Lampetra tridentata, and white sturgeon Acipenser transmontanus. Of these anadromous species, only the white sturgeon remains in the Snake River between the Hells Canyon Complex and Shoshone Falls. Today, much of the Snake River has been transformed into a river with numerous impoundments and flow diversions, increased pollutant loads, and elevated water temperatures. Current (1993-2002) fish assemblage collections from 15 sites along the Snake River and Henrys Fork contained 35 fish species, including 16 alien species. Many of these alien species such as catfish (Ictaluridae), carp (Cyprinidae), and sunfish (Centrarchidae) are adapted for warmwater impounded habitats. Currently, the Snake River supports 19 native species. An index of biotic integrity (IBI), developed to evaluate large rivers in the Northwest, was used to evaluate recent (1993-2002) fish collections from the Snake River and Henrys Fork in southern Idaho and western Wyoming. Index of biotic integrity site scores and component metrics revealed a decline in biotic integrity from upstream to downstream in both the Snake River and Henrys Fork. Two distinct groups of sites were evident that correspond to a range of IBI scores-an upper Snake River and Henrys Fork group with relatively high biotic integrity (mean IBI scores of 46-84) and a lower Snake River group with low biotic integrity (mean IBI scores of 10-29). Sites located in the lower Snake River exhibited fish assemblages that reflect poor-quality habitat where coldwater and sensitive species are rare or absent, and where tolerant, less desirable species predominate. Increases in percentages of agricultural land, total number of diversions, and number of constructed channels were strongly associated with these decreasing IBI scores.

American Fisheries Society Symposium↗