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At least 775 records · Page 43Linked to original sources
USGS2000

Drifting invertebrates, stomach contents, and body conditions of juvenile rainbow trout from fall through winter in a Wyoming tailwater

We investigated the availability of drifting invertebrates and the stomach contents and body conditions of stocked (hatchery) and naturally spawned (wild) juvenile (20-25 cm total length) rainbow trout from fall through winter in the Big Horn River downstream from Boysen Dam in Wyoming. When the density and biomass of drifting invertebrates declined with water temperature during the fall, stomach contents and body conditions substantially decreased among both wild and stocked fish. During the coldest portion of the winter, the density of small drifting invertebrates increased as did the body conditions of both wild and hatchery trout. We suggest that the perceived increase in body conditions during late winter was due to survival of fish with higher body conditions and not growth of fish from fall to late winter.

Transactions of the American Fisheries Society↗
USGS2000

Ictalurid populations in relation to the presence of a main-stem reservoir in a midwestern warmwater stream with emphasis on the threatened Neosho madtom

Ictalurid populations, including those of the Neosho madtom Noturus placidus , have been monitored in the Neosho River basin since the U.S. Fish and Wildlife Service listed the Neosho madtom as threatened in 1991. The Neosho madtom presently occurs only in the Neosho River basin, whose hydrologic regime, physical habitat, and water quality have been altered by the construction and operation of reservoirs. Our objective was to assess changes in ictalurid densities, habitat, water quality, and hydrology in relation to the presence of a main-stem reservoir in the Neosho River basin. Study sites were characterized using habitat quality as measured by substrate size, water quality as measured by standard physicochemical measures, and indicators of hydrologic alteration (IHA) as calculated from stream gauge information from the U.S. Geological Survey. Site estimates of ictalurid densities were collected by the U.S. Fish and Wildlife Service annually from 1991 to 1998, with the exception of 1993. Water quality and habitat measurements documented reduced turbidity and altered substrate composition in the Neosho River basin below John Redmond Dam. The effects of the dam on flow were indicated by changes in the short- and long-term minimum and maximum flows. Positive correlations between observed Neosho madtom densities and increases in minimum flow suggest that increased minimum flows could be used to enhance Neosho madtom populations. Positive correlations between Neosho madtom densities and increased flows in the winter and spring months as well as the date of the 1-d annual minimum flow indicate the potential importance of the timing of increased flows to Neosho madtoms. Because of the positive relationships that we found between the densities of Neosho madtoms and those of channel catfish Ictalurus punctatus , stonecats Noturus flavus , and other catfishes, alterations in flow that benefit Neosho madtom populations will probably benefit other members of the benthic fish community of the Neosho River.

Arkansas, Kansas, Missouri, Oklahoma↗
USGS2000

Seasonal movement and habitat use by striped bass in the Combahee River, South Carolina

Adult striped bass Morone saxatilis (N = 30, 656-906 mm total length) were captured by electrofishing during January-March 1998 in the Combahee River, South Carolina, and fitted with radio transmitters. Their exact locations were recorded biweekly through December. From January to early April, striped bass were located in the tidally influenced lower region of the river in water temperatures ranging from 9??C to 18??C. The fish then moved an average of 38.5 km upstream from late April to the end of May when water temperatures ranged from 18??C to 26??C. Striped bass remained in the upper region of the river from late May to September when water temperatures were as much as 5??C lower than in the river's lower regions. Striped bass began to move downstream and were spread throughout the river during September and October in water temperatures ranging from 19??C to 27??C. Combahee River striped bass appear to follow a migratory pattern typical of other southern striped bass stocks. Habitat preference appears to be strongly influenced by temperature. Combahee River temperatures are stable and remain close to the preferred temperatures of striped bass during summer extremes. Therefore, unlike northern populations, southern populations are more likely to remain within riverine habitat during the summer months. Discrete thermal refugia, such as springs, apparently are not used or are absent in the Combahee River. It is possible that striped bass in the Combahee River depend on the entire upper region of the river as a thermal refuge.

Transactions of the American Fisheries Society↗
USGS2000

Reduction in recruitment of white bass in Lake Erie after invasion of white perch

Recruitment to the adult population of white bass Morone chrysops in Lake Erie sharply declined during the early 1980s. To explain this phenomenon, we formulated the following four hypotheses: (1) the biological characteristics of adult spawners changed during the early 1980s, so that the ability to produce eggs decreased; (2) the decrease in phosphorus loadings to Lake Erie during the 1970s resulted in a lower abundance of crustacean zooplankton and thus in reduced survival of age-0 white bass; (3) the increase in the population of adult walleyes Stizostedion vitreum in Lake Erie during the 1970s and 1980s led to reduced survival of age-0 white bass; and (4) establishment of the white perch Morone americana population in Lake Erie during the early 1980s led to reduced survival of the early life stages of white bass. The growth, maturity, and fecundity of adults during the period 1981–1997 were compared with the same characteristics found by earlier studies. The mean length, weight, and condition factors that we calculated were higher than those reported for Lake Erie in 1927–1929 for all age groups examined, and white bass in Lake Erie matured at an earlier age during 1981–1997 than during 1927–1929. Fecundity estimates ranged from 128,897 to 1,049,207 eggs/female and were similar to estimates from other populations. Therefore, the first hypothesis was rejected. With respect to the second hypothesis, zooplankton surveys conducted during 1970 and 1983–1987 indicated that the abundance of crustacean zooplankton in Lake Erie did not change between the two time periods. However, these results were not conclusive because only a single-year survey was conducted before 1980. Based on walleye diet studies and estimates of walleye population size, walleye predation pressure on age-0 white bass in Lake Erie during 1986–1988 was just slightly higher than that during 1979–1981. Thus, such pressure can explain only a minor portion of the reduction in white bass recruitment. To test the fourth hypothesis, intervention analysis was applied to the long-term abundance series for white bass. The abundance of age-0 white bass in Lake Erie between 1982 and 1997 was significantly lower than that between 1969 and 1981. The catch per unit effort of adult white bass in commercial trap nets between 1987 and 1997 was significantly lower than it was before 1987. Moreover, the period of reduced recruitment for white bass in Oneida Lake, New York, which extends from 1955 to the present, coincides with occupation of the lake by white perch. Thus, of the four hypotheses entertained, the most plausible explanation for the reduction in white bass recruitment in Lake Erie is that white perch reduced the survival of white bass during its early life history.

Michigan, New York, Ohio, Ontario, Pennsylvania↗
USGS2000

Seasonal movement of brown trout in a southern appalachian river

Radio telemetry was used to evaluate the seasonal movement, activity level, and home range size of adult brown trout Salmo trutta in the Chattooga River watershed, one of the southernmost coldwater stream systems in the United States. In all, 27 adult brown trout (262-452 mm total length) were successfully monitored from 16 November 1995 to 15 December 1996. During the day, adult brown trout were consistently found in small, well-established home ranges of less than 270 m in stream length. However, 8 of a possible 18 study fish made spawning migrations during a 2-week period in November 1996. The daytime locations of individual fish were restricted to a single pool or riffle-pool combination, and fish were routinely found in the same location over multiple sampling periods. Maximum upstream movement during spawning was 7.65 km, indicating that brown trout in the Chattooga River have the ability to move long distances. Spawning brown trout returned to their prespawning locations within a few days after spawning. Brown trout maintained larger home ranges in winter than in other seasons. When spawning-related movement was deleted from the analysis, brown trout moved more on a weekly basis in fall than in summer. Brown trout were more active in fall and winter than in spring and summer. Apart from spawning migrations, displacement from established home ranges was not observed for any fish in the study. Although summer water temperatures reached and exceeded reported upper thermal-preference levels, brown trout did not move to thermal refuge areas in nearby tributaries during the stressful summer periods.

Transactions of the American Fisheries Society↗
USGS2000

Identification of juvenile fall versus spring chinook salmon migrating through the lower Snake River based on body morphology

We tested the use of body morphology to distinguish among subyearling fall-run, subyearling spring-run, and yearling spring-run smolts of chinook salmon Oncorhynchus tshawytscha at two lower Snake River dams during the summer emigration. Based on principal-components analysis, subyearling fall-run chinook salmon had smaller heads and eyes, deeper bodies, and shorter caudal peduncles than yearling spring-run chinook salmon. Subyearling spring-run chinook salmon had characteristics of both subyearling fall-run and yearling spring-run chinook salmon. Subyearling fall-run and yearling spring-run chinook salmon were classified with more than 80% accuracy by means of discriminant analysis. Classification accuracy for subyearling spring-run chinook salmon was only 26%. We conclude that body morphology can be used to accurately identify the age of chinook salmon smolts but not the run. Therefore, genetic analyses are the only means of reliably determining the run composition of summer migrants in the lower Snake River.

Transactions of the American Fisheries Society↗
USGS2001

Determining a regional framework for assessing biotic integrity of virginia streams

The utility of an index of biotic integrity (IBI) depends on its ability to distinguish anthropogenic effects on biota amid natural biological variability. To enhance this ability, we examined fish assemblage data from least-disturbed stream sites in Virginia to determine the best way to regionally stratify natural variation in candidate IBI metrics and their scoring criteria. Specifically, we examined metric variation among physiographic regions, U.S. Environmental Protection Agency ecoregions, and drainage basins to judge their utility as regions in which to develop and use distinct versions of the IBI for Virginia warmwater streams. Statewide, metrics differed most among physiographic regions; thus, we recommend their use as IBI regions. Largest differences were found for taxonomic metrics between coastal plain and mountain sites, particularly in numbers of native minnow (Cyprinidae), sunfish (Centrarchidae), and darter (Percidae) species. Trophic and reproductive metrics also differed between coastal plain and more-upland streams, presumably reflecting differences in functional adaptations of fishes to upland versus lowland stream habitats. We suggest three preliminary regional IBis for Virginia, each having a distinctive set of taxonomic, trophic, and reproductive metrics and corresponding scoring criteria.

Transactions of the American Fisheries Society↗
USGS2001

Buoyancy compensation of juvenile chinook salmon implanted with two different size dummy transmitters

We investigated the effect of two different sizes of surgically implanted transmitters on the buoyancy compensation of juvenile chinook salmon Oncorhynchus tshawytscha. We determined buoyancy by measuring the density of fish with a filled air bladder in graded salinity baths. In addition, we examined the effect of pressure changes on buoyancy by measuring the pressure reduction (PR) at which fish became neutrally buoyant. We found no significant difference between the density of control and tagged groups, indicating that fish were able to compensate for the transmitter by filling their air bladders. However, both groups of tagged fish had significantly lower PR than control fish. Regression analysis of fish density on PR indicated that density of the tagged groups changed at a higher rate than that of the controls. As a result, tagged fish attained neutral buoyancy with less pressure reduction even though the tagged and control groups exhibited similar densities. This relation was confirmed by using Boyle's law to simulate buoyancy changes with change in depth. Although fish compensated for the transmitter, changes in depth affected the buoyancy of tagged fish more than that of untagged fish. Reduced buoyancy at depth may affect the behavior and physiology of tagged juvenile salmonids, and researchers should be aware of this potential bias in telemetry data. In addition, there was little difference in PR or the slope of the density - PR regression lines between tagged groups. This was caused by the small difference in excess mass (i.e., weight in water) of the two transmitters. Thus, although two transmitters may not weigh the same, their effects on buoyancy may be similar depending on the excess mass.

Transactions of the American Fisheries Society↗
USGS2001

Early life history of the northern pikeminnow in the lower Columbia River basin

The northern pikeminnow Ptychocheilus oregonensis is a large, native cyprinid in the Columbia River basin that has persisted in spite of substantial habitat alterations. During the months of June to September 1993-1996, we investigated the temporal and spatial patterns of northern pikeminnow spawning, along with describing larval drift and characterizing larval and early juvenile rearing habitats in the lower Columbia River (the John Day and Dalles reservoirs and the free-flowing section downstream of Bonneville Dam) as well as in the lower sections of two major tributaries (the John Day and Deschutes rivers). The density of newly emerged drifting larvae was higher in dam tailraces (a mean of 7.7 larvae/100 m3 in surface tows) than in the lower reservoirs (0.3 larvae/100 m3), indicating that tailraces were areas of more intense spawning. Density was particularly high in the Bonneville Dam tailrace (15.1 larvae/100 m3), perhaps because adult northern pikeminnow are abundant below Bonneville Dam and this is the first tailrace and suitable main-stem spawning habitat encountered during upriver spawning migrations. Spawning also occurred in both of the tributaries sampled but not in a backwater. Spawning in the Columbia River primarily took place during the month of June in 1993 and 1994, when the water temperature rose from 14??C to 18??C, but occurred about 2 weeks later in 1995 and 1996, possibly because of cooler June water temperature (14-15??C) in these years. The period of drift was brief (about 1-3 d), with larvae recruiting to shallow, low-velocity shorelines of main-channel and backwater areas to rear. Larvae reared in greatest densities at sites with fine sediment or sand substrates and moderate- to high-density vegetation (a mean density of 92.1 larvae/10 m3). The success of northern pikeminnow in the Columbia River basin may be partly attributable to their ability to locate adequate spawning and rearing conditions in a variety of main-stem and tributary locations.

Oregon; Washington↗
USGS2001

[Book review] A Review and Synthesis of Effects of Alterations to the Water Temperature Regime on Freshwater Life Stages of Salmonids, with Special Reference to Chinook Salmon, by D.A. McCullough

Review of: A Review and Synthesis of Effects of Alterations to the Water Temperature Regime on Freshwater Life Stages of Salmonids, with Special Reference to Chinook Salmon. By Dale A. McCullough. Columbia River Inter-Tribal Fish Commission. 22 February 1999. REPORT #: EPA 910-R-99-010.

Transactions of the American Fisheries Society↗
USGS2001

The effects of electroshock on immune function and disease progression in juvenile spring chinook salmon

Although much is known about the effects of electroshock on fish physiology, consequences to the immune system and disease progression have not received attention. Our objectives were to determine the effects of electroshock on selected immune function in juvenile spring chinook salmon Oncorhynchus tshawytscha, the mechanism of any observed alteration, and the effects of electroshock on disease progression. We found that the ability of anterior kidney leukocytes to generate antibody-producing cells (APC) was suppressed 3 h after a pulsed-DC electroshock (300 V, 50 Hz, 8 ms pulse width) but recovered within 24 h. This response was similar in timing and magnitude to that of fish subjected to an acute handling stress. The mechanism of suppression is hypothesized to be via an elevation of plasma cortisol concentrations in response to stress. Other monitored immune functions, skin mucous lysozyme levels, and respiratory burst activity were not affected by exposure to electroshock. The progression of a Renibacterium salmoninarum (RS) infection may have been altered after exposure to an electroshock. The electroshock did not affect infection severity or the number of mortalities, but may have accelerated the time to death. The limited duration of APC suppression and lack of effects on lysozyme and respiratory burst, as well as infection severity and mortality levels in RS-infected fish, led us to conclude that electrofishing under the conditions we tested is a safe procedure in regards to immunity and disease.

Transactions of the American Fisheries Society↗
USGS2001

Standardized seawater rearing of chinook salmon smolts to evaluate hatchery practices showed low statistical power

We examined, under standardized conditions, seawater survival of chinook salmon Oncorhynchus tshawytscha at the smolt stage to evaluate the experimental hatchery practices applied to their rearing. The experimental rearing practices included rearing fish at different densities; attempting to control bacterial kidney disease with broodstock segregation, erythromycin injection, and an experimental diet; rearing fish on different water sources; and freeze branding the fish. After application of experimental rearing practices in hatcheries, smolts were transported to a rearing facility for about 2-3 months of seawater rearing. Of 16 experiments, 4 yielded statistically significant differences in seawater survival. In general we found that high variability among replicates, plus the low numbers of replicates available, resulted in low statistical power. We recommend including four or five replicates and using ?? = 0.10 in 1-tailed tests of hatchery experiments to try to increase the statistical power to 0.80.

Transactions of the American Fisheries Society↗
USGS2001

Empirical assessment of indices of prey importance in the diets of predacious fish

Determining the importance of prey taxa in the diets of predacious species is a frequent objective in fisheries research. Various indices of prey importance are in common use, and all give different results because of their emphasis on different aspects of fish diets. We explored these differences by empirically comparing four well-known indices-percent weight (%W), percent occurrence (%O), percent number (%N), and percent index of relative importance (%IRI)-as well as a modified %IRI (%MIRI), as applied to an extensive data set on the diets of six fish species in Spirit Lake, Iowa. Correlations among all indices were positive but were weaker among component indices (%W, %O, and %N) than between the two compound indices (%IRI and %MIRI); correlations among component indices were also weaker than correlations of compound with component indices. Correlation strength of %MIRI with the three component indices varied greatly (%N %O %W), whereas the correlation strength of %IRI with component indices was similar. Importance values based on %W, %MIRI, and %N depend more on prey size than those based on %IRI and %O. The %W and %MIRI emphasized the importance of large prey taxa, whereas %N emphasized small prey in diets; %IRI and %O were similarly unbiased with respect to prey size. The %O yielded substantially higher importance values than all other indices. Thus, for use as a general index of dietary importance, we believe %IRI provides the optimal balancing of frequency of occurrence, numerical abundance, and abundance by weight of taxa in fish diets.

Transactions of the American Fisheries Society↗
USGS2001

Effects of suspended sediment on the reproductive success of the tricolor shiner, a crevice-spawning minnow

Excessive sedimentation of rivers and creeks has been linked to increasing levels of imperilment in the diverse fish fauna of the southeastern United States. In particular, benthic-spawning fishes have decreased in both numbers and range. The tricolor shiner Cyprinella trichroistia is a crevice-spawning minnow that is widespread in the eastern Mobile River drainage above the Fall Line. While they are less sensitive to perturbation than the federally threatened blue shiner C. caerulea, tricolor shiners have decreased in numbers and range during the past few decades. This experiment examined the effects of 0 (control), 100, 300, and 600 mg/L initial concentrations of suspended sediment on the reproductive success of the tricolor shiner. Increasing levels of suspended sediment caused decreasing levels of reproductive success (fewer spawns and fewer eggs laid when spawning occurred). Increasing levels of suspended sediment also delayed the onset of spawning, resulting in distinct frequency distributions of clear eggs, eyed eggs, and larvae across treatments. Mortality of eggs and larvae was not a factor in the experiment. We examined daily sediment concentration data recorded at three sites in the upper Coosa River over the April-August spawning season of 1963. By weighting our experimental results by the number of days above each sediment concentration, we estimated that 20% fewer eggs were laid than would have been laid if conditions had been like those of the controls. Albeit our model is simplistic, it provides insight into how excessive sedimentation contributes to population extirpation. Mitigation of suspended sediments is an important management action for the conservation of southern Appalachian fishes that spawn in benthic habitats.

Transactions of the American Fisheries Society↗
USGS2001

Spawning migration of lacustrine-adfluvial bull trout in a natural area

We investigated the spawning migration of lacustrine-adfluvial bull trout Salvelinus confluentus in the North Fork Skokomish River in Olympic National Park (Washington State) during 1996. Day-snorkeling and electrofishing were conducted to determine timing and duration of the migration and the distribution and abundance of bull trout. The primary spawning migration began in early October and was waning by December. Bull trout migrated 6 km or less up the river from Lake Cushman. Increased river discharge and decreased water temperature appeared to be the primary environmental variables corresponding to the initiation of the migration. Mean length of migratory bull trout increased from June to December. Comparisons with other lacustrine-adfluvial bull trout populations in Oregon, Montana, Idaho, and British Columbia suggested that these populations exhibit specific migratory strategies related to local environmental conditions.

Washington↗
USGS2002

Isolation of thiaminase-positive bacteria from alewife

Evidence pointing to thiamine deficiency as a primary factor in early mortality syndrome in feral salmonids from the Great Lakes and New York's Finger Lakes continues to mount. Such deficiency is believed to be the result of the consumption of nontraditional forage fish, such as alewife Alosa pseudoharengus , that contain thiaminase activity. The source of thiaminase within these forage fish has not been reported. In this study, we report finding thiaminase-positive Paenibacillus thiaminolyticus and other Paenibacillaceae that are closely related to P. thiaminolyticus in the viscera of frozen alewives. Thiaminase-positive bacteria associated with alewife viscera have not previously been reported. Because viable thiaminase-positive cultures were found in only 25% of the fish, bacteria should be considered as only one potential source of thiaminase in alewives.

Transactions of the American Fisheries Society↗
USGS2002

Observations of the distributions of five fish species in a small Appalachian stream

The notion has been growing that resident stream fishes exhibit a greater capacity for movement than was previously thought. In this study, we recorded the distributions of four resident fish species (longnose dace Rhinichthys cataractae , blacknose dace R. atratulus , mottled sculpin Cottus bairdi , and rainbow trout Oncorhynchus mykiss ) and one nonresident species (central stoneroller Campostoma anomalum ) in Rock Creek, a small tributary of Cosby Creek in Great Smoky Mountains National Park, over the period 1979-1995. During this study, 1,998 individuals of resident species were collected from stream sections considered to be within a common area of distribution for each species. Forty-five individuals of resident and nonresident species were captured upstream of these areas, and eight of these fish were considered to be larger than individuals considered typical for each species. Small mammal dispersal theory concepts were used to classify and describe fish movements outside of common areas of distribution. These movements were identified as important in maintaining population connectivity within stream drainages, contributing to reducing the potential for local extinctions of populations and to the recolonization of unoccupied habitats. This study highlights the need for continued study of fish movements in stream drainages and for development of appropriate resource management strategies based partly on the spatial dynamics of fish populations and communities.

Cosby Creek, Rock Creek↗