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At least 1,297 records · Page 72Linked to original sources

USGS2002

Genetic structure of Columbia River redband trout populations in the Kootenai River drainage, Montana, revealed by microsatellite and allozyme loci

We describe the genetic divergence among 10 populations of redband trout Oncorhynchus mykiss gairdneri from the upper Columbia River drainage. Resident redband trout from two watersheds in the Kootenai River drainage and hatchery stocks of migratory Kamloops redband trout from Kootenay Lake, British Columbia, were analyzed using allele frequency data from microsatellite and allozyme loci. The Kamloops populations have significantly different allele frequencies from those of the Kootenai River drainage. Of the total genetic variation detected in the resident redband trout, 40.7% (microsatellites) and 15.5% (allozymes) were due to differences between populations from the two Kootenai River watersheds. The divergence among populations within each watershed, however, was less than 3.5% with both techniques. Our data indicate that watershed-specific broodstocks of redband trout are needed by fisheries managers for reintroduction or the supplementation of populations at risk of extinction.

Idaho, Montana↗

USGS2003

Physiological responses of juvenile rainbow trout to fasting and swimming activity: Effects on body composition and condition indices

The physiological traits that allow fish to survive periods of limited food resources are poorly understood. We assessed changes in proximate body composition, relative organ mass, blood metabolites, and relative weight (Wr) of sedentary and actively swimming (15 cm/s) juvenile rainbow trout (154-182 mm total length) over 147 d of fasting. Fasting caused measurable responses that were augmented when fish were swimming. Lipids and plasma triacylglycerides declined over time. Proteins were catabolized simultaneously with lipid reserves, but ammonia concentrations in plasma did not increase. The liver somatic index (LSI) did not change substantially over 105 d, suggesting that gluconeogenesis maintained blood glucose concentrations and hepatic glycogen reserves for a substantial period of fasting. The gut somatic index (GSI) and Wr declined linearly during fasting, but the LSI did not decline until after 105 d of fasting. Consequently, the use of different body condition indices could lead to different conclusions about the condition of juvenile rainbow trout. Swimming activity caused fish to have lower lipid and protein reserves than those of sedentary fish. No mortalities were observed among sedentary fish, but mortalities occurred among actively swimming fish after 97 d of fasting when 3.2% or less lipid remained in their bodies. Body condition indices did not account for differences in proximate body composition between sedentary and actively swimming fish and were relatively poor predictors of lipid content and risk of mortality. The probability of mortality was most accurately predicted by percent lipid content. Therefore, we suggest that fisheries scientists consider using percent lipid content when evaluating the physiological status and risk of mortality due to starvation among juvenile rainbow trout.

Transactions of the American Fisheries Society↗

USGS1992

Evaluating enhancement of striped bass in the context of potential predation on anadromous salmonids in Coos Bay, Oregon

We describe an approach for evaluating the predation on anadromous salmonids that could result from enhancement of striped bass Morone saxatilis in Coos Bay, Oregon. Predation by striped bass on juvenile salmonids has been documented there since 1930. To provide a basis for the decision about enhancement of striped bass in Coos Bay, we estimated the losses of anadromous salmonids in 1950 and 1960–1964. In this evaluation, we used information on striped bass in Coos Bay and collateral information about striped bass in other waters. Estimated numbers of juvenile salmonids consumed by striped bass in Coos Bay (April–June) ranged from more than 41,000 in 1950 to about 383,000 in 1963. Estimated losses of adult salmonids ranged from about 1,000 in 1950 to about 46,000 in 1963. This approach was useful in conveying the potential consequences of large‐scale striped bass enhancement to decision makers and to the public. The evaluation also helped identify information needs that are now considered in managing the fishery and in evaluating impacts on salmonids.

Oregon↗

USGS1994

Declining survival of lake trout stocked during 1963-1986 in U.S. waters of Lake Superior

The average catch per effort (CPE) values for the 1963–1982 year-classes of stocked lake trout Salvelinus namaycush caught at age 7 in gill nets and for the 1976–1986 year-classes caught at ages 2–4 in trawls declined significantly in U.S. waters of Lake Superior. The declines in CPE were not explained by reduced stocking, but rather by significant declines in survival indices of the year-classes of stocked lake trout. Increases in mortality occurred in year-classes before the fish reached ages 2–4, before they were recruited into the sport and commercial fisheries, and before they reached sizes vulnerable to sea lamprey predation. We conclude that declining abundance of stocked lake trout resulted from increased mortality, which may have been caused by competition, predation, or by a combination of these and other factors. Restoration of lake trout in Lake Superior may now depend on prudent management of naturally reproducing stocks rather than on stocking of hatchery-reared fish.

North American Journal of Fisheries Management↗

USGS1994

Development of an antimycin-impregnated bait for controlling common carp

The common carp Cyprinus carpio is a major problem for fisheries and wildlife managers because its feeding behavior causes degradation of valuable fish and waterfowl habitat. This study was designed to evaluate the effectiveness of an antimycin‐impregnated bait for control of common carp. The toxic bait contained fish meal, a binder, antimycin, and water. The ingredients were mixed together and made into pellets. This bait was force‐fed to common carp or administered in a pond environment, where fish voluntarily fed on the bait. The lowest lethal dose in the force‐feeding study was 0.346 mg antimycin/kg of fish and doses that exceeded 0.811 mg antimycin/kg were toxic to all fish. On three occasions, adult common carp held in 0.004‐ha concrete ponds were offered 10 g of toxic bait containing 5.0, 7.5, and 10 mg antimycin/g of bait and the mean mortalities 96 h later were 21, 35, and 51%, respectively. Three tests were conducted in 0.04‐ha earthen ponds each containing 100 adult common carp; these fish were offered 50 g of the toxic bait that contained 10 mg antimycin/g, and the mean mortalities (96 h) were 19, 32, and 74%. Toxic baits should be used in conjunction with other management techniques, and only when common carp are congregated and actively feeding, and when few nontarget bottom‐feeding species are present.

North American Journal of Fisheries Management↗

USGS2011

Trends in relative weight of walleye stocks in Wyoming reservoirs

The relative weight ( W r ) index of body condition provided insight into the stock dynamics of walleye Stizostedion vitreum in six reservoirs in the North Platte River drainage of Wyoming. The three most upstream reservoirs are managed as both walleye and trout ( Oncorhynchus spp. and Salmo spp.) fisheries; trout are stocked annually. The three downstream reservoirs are managed for coolwater and warmwater fishes, and walleye fry are stocked almost annually in two of the reservoirs. Positive relations between stocking densities of trout and W r of walleyes and between water levels and W r of walleyes were observed. Length-related trends in W r within walleye stocks over time were related to prey availability.

Wyoming↗

USGS2001

Summer habitat use by Columbia River redband trout in the Kootenai River drainage, Montana

The reported decline in the abundance, distribution, and genetic diversity of Columbia River redband trout Oncorhynchus mykiss gairdneri (a rainbow trout subspecies) has prompted fisheries managers to investigate their habitat requirements, identify critical habitat, and develop effective conservation and recovery programs. We analyzed the microhabitat, mesohabitat, and macrohabitat use and distribution of Columbia River redband trout by means of snorkel surveys in two watersheds in the Kootenai River drainage, Montana and Idaho, during the summers of 1997 and 1998. Juvenile (36–125 mm total length, TL) and adult (>=126 mm TL) fish preferred deep microhabitats (>=0.4 m) with low to moderate velocities (<=0.5 m/s) adjacent to the thalweg. Conversely, age-0 (<=35 mm) fish selected slow water (<=0.1 m/s) and shallow depths (<=0.2 m) located in lateral areas of the channel. Age-0, juvenile, and adult fish strongly selected pool mesohabitats and avoided riffles; juveniles and adults generally used runs in proportion to their availability. At the macrohabitat scale, density of Columbia River redband trout (35 mm) was positively related to the abundance of pools and negatively related to stream gradient. The pool: riffle ratio, gradient, and stream size combined accounted for 80% of the variation in density among 23 stream reaches in five streams. Our results demonstrate that low-gradient, medium-elevation reaches with an abundance of complex pools are critical areas for the production of Columbia River redband trout. These data will be useful in assessing the impacts of land-use practices on the remaining populations and may assist with habitat restoration or enhancement efforts.

Montana↗

USGS2003

Evidence of sexually dimorphic introgression in Pinaleno Mountain Apache trout

The high-elevation headwater streams of the Pinaleno Mountains support small populations of threatened Apache trout Oncorhynchus apache that were stocked following the chemical removal of nonnative salmonids in the 1960s. A fisheries survey to assess population composition, growth, and size structure confirmed angler reports of infrequent occurrences of Oncorhynchus spp. exhibiting the external morphological characteristics of both Apache trout and rainbow trout O. mykiss. Nonlethal tissue samples were collected from 50 individuals in the headwaters of each stream. Mitochondrial DNA (mtDNA) sequencing and amplification of nuclear microsatellite loci were used to determine the levels of genetic introgression by rainbow trout in Apache trout populations at these locations. Sexually dimorphic introgression from the spawning of male rainbow trout with female Apache trout was detected using mtDNA and microsatellites. Estimates of the degree of hybridization based on three microsatellite loci were 10-88%. The use of nonlethal DNA genetic analyses can supplement information obtained from standard survey methods and be useful in assessing the relative importance of small and sensitive populations with a history of nonnative introductions.

North American Journal of Fisheries Management↗

USGS2003

Effect of swimming activity on relative weight and body composition of juvenile rainbow trout

Fisheries managers often assess body condition using relative weight (Wr) because it provides a comparative measure of fish plumpness among individuals and populations. However, it is not known whether the morphological information that Wr summarizes reflects physiological measures, such as relative lipid reserves, in rainbow trout Oncorhynchus mykiss. The purpose of this study was to determine whether swimming activity affects either the Wr or proximate body composition of juvenile (total length, 170-260 mm) rainbow trout. When rainbow trout from a hatchery were fed ad libitum for 147 d, inactive (no current) and active (15 cm/s current velocity) fish did not differ in Wr However, inactive rainbow trout maintained relatively constant lipid levels, whereas active fish declined in lipid content. Relative weight may provide a comparable measure of body form, but it is not an accurate index of lipid content between active and inactive rainbow trout fed an excess ration. For assessing the physiological condition of rainbow trout, measurement of proximate body composition appears to be more accurate than indices based on length and weight.

North American Journal of Fisheries Management↗

USGS2003

Relative contribution of stocked walleyes in Tennessee reservoirs

Since the mid-1950s, fisheries biologists with the Tennessee Wildlife Resources Agency have stocked walleyes Stizostedion vitreum in several tributary reservoirs of the Cumberland and Tennessee rivers to augment declining native stocks; however, the efficacy of these management actions has never been formally evaluated. The contribution of stocked walleyes in four Tennessee reservoirs was evaluated during 1999 and 2000 by marking fry and fingerlings through oxytetracycline (OTC) immersion. Stocking densities were 13-48 fingerlings/ha, and marking efficacy was high for fish marked as fry (mean = 98%; SE = 1.7%) and fingerlings (mean = 99%; SE = 0.6%). Nearly all (94-100%; N = 509) of the age-1 and age-2 walleyes collected in the four reservoirs were OTC-marked. Based on these findings, fingerling walleyes must be stocked annually to sustain the walleye populations in these tributary impoundments.

North American Journal of Fisheries Management↗

USGS2004

Stock-specific migration timing of adult spring-summer Chinook salmon in the Columbia River basin

An understanding of the migration timing patterns of Pacific salmon Oncorhynchus spp. and steelhead O. mykiss is important for managing complex mixed-stock fisheries and preserving genetic and life history diversity. We examined adult return timing for 3,317 radio-tagged fish from 38 stocks of Columbia River basin spring-summer Chinook salmon O. tshawytscha over 5 years. Stock composition varied widely within and between years depending on the strength of influential populations. Most individual stocks migrated at similar times each year relative to overall runs, supporting the hypotheses that run timing is predictable, is at least partially due to genetic adaptation, and can be used to differentiate between some conspecific populations. Arrival timing of both aggregated radio-tagged stocks and annual runs was strongly correlated with river discharge; stocks arrived earlier at Bonneville Dam and at upstream dams in years with low discharge. Migration timing analyses identified many between-stock and between-year differences in anadromous salmonid return behavior and should and managers interested in protection and recovery of evolutionary significant populations.

North American Journal of Fisheries Management↗

USGS2005

Morphology and aging precision of statoliths from larvae of Columbia river basin lampreys

The general morphology and precision associated with age determination of statoliths from larval Pacific lampreys Lampetra tridentata and western brook lampreys L. richardsoni found within the Columbia River basin were examined. Significant positive correlations were observed between the size of left and right statoliths from individuals. Principal components analysis indicated an allometric relationship between lamprey length and statolith size as well as a potential species grouping based on these measurements. Discriminant analysis was able to correctly classify more than 94% of Pacific lampreys and 92% of western brook lampreys based on lamprey length and statolith size, and Pacific lamprey statoliths tended to be larger than western brook lamprey statoliths for lampreys of a given size. Reader bias in age estimates of statoliths was greater for older lampreys. Multiple independent age readings of both statoliths from individual lampreys indicated that the overall average percent error was 16.7% for Pacific lampreys and 33.0% for western brook lampreys. Within-individual average percent error ranged from 5.1% to 20.1% among species and readers. Within-reader average percent error ranged from 6.4% to 17.8% among species and readers. The average percent error observed in this study was greater than that observed in studies of other species of lampreys; however, statoliths that were ambiguous or difficult to read were not excluded from this study. In general, the modal separation of age-groups observed in length-frequency distributions for lampreys is poor, as seen in this study; therefore, statolith-based ages may verify or provide better estimates of population age structure. These data demonstrate that estimates of precision are necessary before management actions founded on statolith-based age structure determination are implemented. ?? Copyright by the American Fisheries Society 2005.

Oregon↗

USGS2005

Distribution and abundance of black bass in Skiatook Lake, Oklahoma, after introduction of smallmouth bass and a liberalized harvest regulation on spotted bass

We conducted a 3-year study to examine the trends in abundance and distribution of three sympatric black bass species ( Micropterus ) in an Oklahoma reservoir after implementation of a differential harvest regulation to reduce the abundance of spotted bass M. punctulatus and after stocking nonnative smallmouth bass M. dolomieu . Largemouth bass M. salmoides were stocked in Skiatook Lake, Oklahoma, immediately after its creation in 1984 to supplement the existing population in the watershed. Nonnative smallmouth bass were stocked in 1990, and their abundance and distribution have increased ever since. Native spotted bass, which have less fishery value than the other two black bass species, increased fivefold in abundance in 1994, became the predominant black bass species by at least 1996, and appeared to displace largemouth bass from many habitats. From boat-mounted electrofishing sampling conducted in April and May 1997–1999, we found that spotted bass abundance (proportion and catch per hour) had decreased while smallmouth bass abundance and distribution within the reservoir steadily increased. Largemouth bass abundance did not change among years. Throughout our study period, spotted bass was always the most abundant black bass species where differences in abundance were found. Our results suggest that the continually expanding smallmouth bass population is displacing spotted bass from many of their formerly used habitats, much like spotted bass had displaced largemouth bass by 1996.

Oklahoma↗

USGS2005

A sampler for capturing larval and juvenile Atlantic menhaden

Interest in capturing larval and juvenile Atlantic menhaden Brevoortia tyrannus for use in laboratory studies required the design and construction of a sampling device that would allow us to make collections of live fish from open-water areas. Our device for capturing 1-2.5-in larval-juvenile fish was constructed of a stainless steel frame that supported a 9.84-ft-long (3-m-long)5 cone plankton net with a 3.28-ft-diameter (1-m-diameter) opening and a 0.04-in (1-mm) mesh size. Although the plankton net was similar to that used during typical larval fish collections, the cod end was constructed of Plexiglas and was nearly watertight; this prevented impingement and injury to larval fish and provided a calm-water environment. The cod end was designed for quick release from the plankton net, and the entire cod end could be submerged into a 75-gal onboard holding tank. This design and technique obviated the netting or emerging of fish from the water until they were returned to the laboratory. ?? Copyright by the American Fisheries Society 2005.

North American Journal of Fisheries Management↗

USGS2005

A new sampler design for measuring sedimentation in streams

Sedimentation alters aquatic habitats and negatively affects fish and invertebrate communities but is difficult to quantify. To monitor bed load sedimentation, we designed a sampler with a 10.16-cm polyvinyl chloride coupling and removable sediment trap. We conducted a trial study of our samplers in riffle and pool habitats upstream and downstream of highway construction on a first-order Appalachian stream. Sediment samples were collected over three 6-week intervals, dried, and separated into five size-classes by means of nested sieves (U.S. standard sieve numbers 4, 8, 14, and 20). Downstream sediment accumulated in size-classes 1 and 2, and the total amount accumulated was significantly greater during all three sampling periods. Size-classes 3 and 4 had significantly greater amounts of sediment for the first two sampling periods at the downstream site. Differences between upstream and downstream sites narrowed during the 5-month sampling period. This probably reflects changes in site conditions, including the addition of more effective sediment control measures after the first 6-week period of the study. The sediment sampler design allowed for long-term placement of traps without continual disturbance of the streambed and was successful at providing repeat measures of sediment at paired sites. ?? Copyright by the American Fisheries Society 2005.

North American Journal of Fisheries Management↗

USGS2005

Recent water temperature trends in the lower Klamath River, California

Elevated water temperatures have been implicated as a factor limiting the recovery of anadromous salmonids in the Klamath River basin. This article reviews evidence of a multi-decade trend of increasing temperatures in the lower main-stem Klamath River above the ocean and, based on model simulations, finds a high probability that water temperature has been increasing by approximately 0.5??C/decade (95% confidence interval [Cl] = 0.42-0.60??C/decade) since the early 1960s. The season of high temperatures that are potentially stressful to salmonids has lengthened by about 1 month over the period studied, and the average length of main-stem river with cool summer temperatures has declined by about 8.2 km/decade. Water temperature trends seem unrelated to any change in main-stem water availability but are consistent with measured basinwide air temperature increases. Main-stem warming may be related to the cyclic Pacific Decadal Oscillation, but if this trend continues it might jeopardize the recovery of anadromous salmonids in the Klamath River basin. ?? Copyright by the American Fisheries Society 2005.

North American Journal of Fisheries Management↗

USGS2005

Effect of block net use and time of sampling on backpack electrofishing catches in three Kansas reservoirs

Using backpack electrofishing in three Kansas reservoirs, we investigated the need for block nets when estimating density (fish/ha) and species diversity and determined whether time of sampling affected catch rates (fish/h) of age-0 largemouth bass Micropterus salmoides and age-0 Lepomis spp. and species diversity. Block nets were used to enclose or buoys were used to mark the boundaries of 149 m2 of reservoir surface area. Species richness, diversity, and density of age-0 largemouth bass and Lepomis spp. did not differ significantly between areas enclosed with block nets and areas marked with buoys, but species richness, diversity, and catch rates differed significantly between day and night sampling. Age-0 largemouth bass and Lepomis spp. catch rates, species richness, and species diversity were all significantly higher during night sampling. Our results indicate that use of block nets may not be necessary to estimate age-0 largemouth bass and Lepomis spp. densities, species richness, or diversity in reservoir littoral areas. We recommend night sampling because of significantly higher catch rates and better representation of the littoral fish assemblage. ?? Copyright by the American Fisheries Society 2005.

North American Journal of Fisheries Management↗

USGS2005

Evaluation of a prototype surface flow bypass for juvenile salmon and steelhead at the powerhouse of Lower Granite Dam, Snake River, Washington, 1996-2000

A surface flow bypass takes advantage of the natural surface orientation of most juvenile salmon Oncorhynchus spp. and steelhead O. mykiss by providing a route in the upper water column that downstream migrant fishes can use to pass a hydroelectric dam safely. A prototype structure, called the surface bypass and collector (SBC), was retrofitted on the powerhouse of Lower Granite Dam and was evaluated annually with biotelemetry and hydroacoustic techniques during the 5-year life span of the structure (1996-2000) to determine the entrance configuration that maximized passage efficiency and minimized forebay residence time. The best tested entrance configuration had maximum inflow (99 m 3/s) concentrated in a single surface entrance (5 m wide, 8.5 m deep). We identified five important considerations for future surface flow bypass development in the lower Snake River and elsewhere: (1) an extensive flow net should be formed in the forebay by use of relatively high surface flow bypass discharge (>7% of total project discharge); (2) a gradual increase in water velocity with increasing proximity to the surface flow bypass (ideally, acceleration 3 m/s) to entrain the subject juvenile fishes; (4) the shape and orientation of the surface entrance(s) should be adapted to fit site-specific features; and (5) construction of a forebay wall to increase fish availability to the surface flow bypass should be considered. The efficiency of the SBC was not high enough (maximum of 62% relative to passage at turbine units 4-5) for the SBC to operate as a stand-alone bypass. Anywhere that surface-oriented anadromous fish must negotiate hydroelectric dams, surface flow bypass systems can provide cost-effective use of typically limited water supplies to increase the nonturbine passage, and presumably survival, of downstream migrants. ??Copyright by the American Fisheries Society 2005.

Washington↗