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At least 1,279 records · Page 71Linked to original sources

USGS1994

Effects of elevated water temperature and immunosuppressant treatment on prevalence and titer of infectious pancreatic necrosis virus in naturally infected brook trout

Using fingerlings of brook trout Salvelinus fontinalis naturally infected with infectious pancreatic necrosis virus (IPNV), we demonstrated that elevated water temperature and treatment with the immunosuppressant triamcinolone acetonide (generic Kenalog®) significantly increases the titer of IPNV and probably also the prevalence of the infection. Stress-promoting treatments could potentially enhance the capability to detect various fish viral agents.

Journal of Aquatic Animal Health↗

USGS1997

Recurrent amoebic gill infestation in rainbow trout cultured in a semiclosed water recirculation system

Five lots of commercially purchased juvenile rainbow trout Oncorhynchus mykiss (17–44 g) stocked in a continuous-production water recirculation system became infested with gill amoebae. The amoebae were introduced into the recirculation system, as evidenced by their presence on gills of fish held in quarantine tanks. Based on their morphology, as seen in histological sections and by electron microscopy, the amoebae appeared to be more closely related to the family Cochliopodiidae than to other taxa of free-living amoebae. Attempts to culture the amoebae in different media, at different temperatures of incubation, and in fish cell culture were not successful. Initial treatment of the recirculation system with formalin at 167 parts per million (ppm) for 1 h eliminated amoebae from the gills. Subsequent treatments of the entire system with formalin at 50–167 ppm reduced the intensity of further infestations.

Journal of Aquatic Animal Health↗

USGS2000

The dose-dependent effect on protection and humoral response to a DNA vaccine against Infectious Hematopoietic Necrosis (IHN) virus in subyearling rainbow trout

A dose–response study that used the DNA vaccine pIHNw-G against infectious hematopoietic necrosis virus (IHNV) showed that complete and highly significant ( P < 0.001) protection against a virus injection challenge can be attained in subyearling rainbow trout Oncorhynchus mykiss (145–160 g, 8- to 10-months-old) 6 weeks after a single intramuscular injection with doses as low as 1 μg. Complete protection was also reproducibly demonstrated at higher vaccine doses; however, no protection was observed with a 0.1-μg dose. Virus-neutralizing antibody titers were detected in fish that had been vaccinated with different doses of the DNA vaccine and then sham-infected; there appeared to be a dose-dependent effect, with higher titers obtained with higher doses of vaccine. The DNA-vaccinated animals that survived virus challenge had significantly ( P < 0.05) higher neutralizing antibody titers than sham-infected, DNA-vaccinated control fish. Additionally, the titers detected in the IHN survivors exhibited a significant ( P < 0.05) dose-dependent effect, with the highest titers being present in fish that received the highest vaccine doses.

Journal of Fish Diseases↗

USGS1990

Sample size requirements and analysis of tag recoveries for paired releases of lake trout

A simple chi-square test can be used to analyze recoveries from a paired-release experiment to determine whether differential survival occurs between two groups of fish. The sample size required for analysis is a function of (1) the proportion of fish stocked, (2) the expected proportion at recovery, (3) the level of significance (∝) at which the null hypothesis is tested, and (4) the power (1 – β) of the statistical test. Detection of a 20% change from a stocking ratio of 50: 50 requires a sample of 172 (∝ = 0.10; 1 – β = 0.80) to 459 (∝ = 0.01; 1 – β = 0.95) fish. Pooling samples from replicate pairs is sometimes an appropriate way to increase statistical precision without increasing numbers stocked or sampling intensity. Summing over time is appropriate if catchability or survival of the two groups of fish does not change relative to each other through time. Twelve pairs of identical groups of yearling lake trout Salvelinus namaycush were marked with coded wire tags and stocked into Lake Ontario. Recoveries of fish at ages 2–8 showed differences of 1–14% from the initial stocking ratios. Mean tag recovery rates were 0.217%, 0.156%, 0.128%, 0.121%, 0.093%, 0.042%, and 0.016% for ages 2–8, respectively. At these rates, stocking 12,100–29,700 fish per group would yield samples of 172–459 fish at ages 2-8 combined.

North American Journal of Fisheries Management↗

USGS1993

Preservation of genetic variation in the Green Lake strain lake trout derived from remnant domestic and feral populations

The Green Lake, Wisconsin, strain of lake trout Salvelinus namaycush was discontinued as a hatchery brood stock in 1976 after Lake Michigan was stocked with the 1975 year‐class. In 1982, a decision was made to restore the Green Lake strain as a production brood stock. Five groups were produced by spawning marked fish that were survivors from the 1976 stocking of southern Lake Michigan. A sixth group was produced from a remnant of the Green Lake brood stock held at the Genoa (Wisconsin) National Fish Hatchery. Hatchery accidents reduced both the number of groups and the effective population number of each group. We studied a procedure for reconstructing a composite Green Lake brood stock from individuals of these six groups. Genetic variability was evaluated by allozyme electrophoresis in five of these groups. Twelve of 18 loci were polymorphic. Allelic frequencies were similar in all five groups; however, significant differences occurred in nine systems. Heterozygosity level (mean ± SE) was lowest in the domestic group (0.119 ± 0.043) and ranged from 0.139 ± 0.043 to 0.166 ± 0.052 in the feral groups. Cluster analysis of genetic distances grouped the four feral groups together, but separate from the domestic group. Progeny from fish captured on Black Can Reef, Lake Michigan, in 1986 and 1988 were the most similar. A modified diallel mating design was developed to produce a composite brood stock from remnant feral and domestic fish. Pooled families from 1991 and 1992 diallel matings will be reared to maturity, then reciprocal crosses of the two year‐classes will be made to form the new composite Green Lake brood stock.

Wisconsin↗

USGS2000

Observations of health indices used to monitor a tailwater trout fishery

Health of the population of rainbow trout Oncorhynchus mykiss in the San Juan River tailwater was monitored to determine the effects of potential crowding from a reduced winter flow test at Navajo Dam, northwestern New Mexico. A systematic necropsy-based health profile provided a rapid method to detect gross changes in the health of the fish population. The health assessment index (HAI) was calculated to quantify the necropsy system and allow statistical comparisons of data sets. Other suborganismic indices were selected to encompass a range of responses specific to the stress of environmental alterations: physiology assessment using total protein and percent muscle lipids, an immune assessment using serum lysozyme, and a cellular-based evaluation using histology. The HAI values showed no clear trend in fish health, although significant differences occurred among fish samples during the test. Significant declines in condition factors and percent muscle lipids throughout the study suggested a seasonal effect. Total protein and lysozyme levels were variable, showing no discernible patterns. Most histological observations appeared to be incidental during the study. Although there was no clear demonstrable effect of altered flow on fish health, this study revealed the sensitivities of various health indicators, which may help in designing future studies and supporting or interpreting results using these approaches.

New Mexico↗

USGS2001

Proposed standard-weight equations for brook trout

Weight and length data were obtained for 113 populations of brook trout Salvelinus fontinalis across the species' geographic range in North America to estimate a standard-weight (Ws) equation for this species. Estimation was done by applying the regression-line-percentile technique to fish of 120-620 mm total length (TL). The proposed metric-unit (g and mm) equation is log10Ws = -5.186 + 3.103 log10TL; the English-unit (lb and in) equivalent is log10Ws = -3.483 + 3.103 log10TL. No systematic length bias was evident in the relative-weight values calculated from these equations.

North American Journal of Fisheries Management↗

USGS2009

Survival and passage of ingested New Zealand mudsnails through the intestinal tract of rainbow trout

We conducted laboratory trials to determine the transit time and survival of New Zealand mudsnails Potamopyrgus antipodarum in the gastrointestinal tract of rainbow trout Oncorhynchus mykiss. To assess the rate of snail passage, we force-fed groups of fish a known quantity of snails and then held them in tanks. At selected intervals we removed individual fish from the test tanks and recorded the number of snails, their condition (live or dead), and their location in the gastrointestinal tract (stomach, anterior intestine, and posterior intestine). Feces were removed from tanks and examined for live snails. We repeated evaluations of passage rate and snail survival to determine the effects of varying the number of snails ingested, fish size, snail size, and feeding a commercial diet to fish after snail ingestion. We plotted and modeled gut evacuation using a stochastic model for ordinal data to consider each test variable. Snail passage rates were faster in fish that were fed smaller snails. Surprisingly, fish fed snails and then administered rations of commercial fish feed retained the snails longer in their stomach than did fish that were not administered fish feeds after being fed snails. Increased retention time of snails in the stomach decreased the probability of snail survival when voided in fecal material. Snails that passed through the gastrointestinal tract within 12–24 h of ingestion were often recovered live in fecal samples. However, no live snails were recovered from the posterior intestine or fecal material collected 24 h after ingestion. Using our results we propose potential management options that could reduce the risks of introducing live snails into new locations when stocking fish from infested hatcheries.

Idaho↗

USGS2004

Immunomodulation and disease resistance in postyearling rainbow trout infected with Myxobolus cerebralis, the causative agent of whirling disease

Myxobolus cerebralis , the myxosporean parasite that causes whirling disease, has a number of deleterious effects on its salmonid host. Although it is well established that juvenile salmonids in the active stages of whirling disease mount an immune response to the pathogen, the occurrence and longevity of any related immunomodulatory effects are unknown. In this study, postyearling rainbow trout Oncorhynchus mykiss infected with M. cerebralis were examined for leukocyte functions and for resistance to Yersinia ruckeri , a bacterial pathogen of salmonids. Compared with uninfected controls, M. cerebralis -infected fish showed lower proliferative lymphocyte responses to four mitogens (concanavalin A, pokeweed mitogen, phytohemagglutinin, and lipopolysaccharide). Conversely, M. cerebralis -infected fish displayed greater bactericidal activity of anterior kidney macrophages than did uninfected fish. After bath challenges with Y. ruckeri , M. cerebralis -infected fish had slightly lower survival and a more rapid onset of mortality than did the control fish. Renal tissue and fecal samples from M. cerebralis -infected and uninfected survivors were cultured for the presence of Y. ruckeri , and no difference in prevalence was noted between the two groups. Because immunomodulatory changes in the M. cerebralis -infected fish involved functional enhancement and suppression of different leukocyte populations, disease resistance among M. cerebralis -infected fish in the later stages of whirling disease will probably vary with the secondary pathogen and the nature of immune response the pathogen evokes.

Journal of Aquatic Animal Health↗

USGS2004

The influence of hook type, angler experience, and fish size on injury rates and the duration of capture in an Alaskan catch-and-release rainbow trout fishery

Owing to concerns about the high incidence of past hooking injuries in Alagnak River rainbow trout Oncorhynchus mykiss, fish were captured with spin- and fly-fishing gear with barbed and barbless circle and "J" hooks to determine gear types contributing to injury. Landing and hook removal times were measured for a portion of fish captured, and the anatomical hooking location, hooking scar locations, bleeding intensity, angler experience, and fish size were recorded for all captured fish. Approximately 62% of fish captured experienced at least one new hooking injury, and 29% of fish had at least one past hooking injury. Small fish sustained higher new injury and bleeding rates, but large fish had higher past injury rates. Injury rates were higher for barbed J hooks, barbed J hooks took longer to remove, and fish caught by spin-fishing were injured more frequently than fish caught by fly-fishing. Fewer fly-fishing-caught fish were injured using circle hooks, and circle hooks tended to hook fish in only one location, generally in the jaw. Barbed J hooks were more efficient at landing fish, and J hooks were more efficient at landing fish than circle hooks. Novice anglers injured proportionally more fish than experienced anglers, primarily during hook removal. Landing time was positively correlated with fish size, and experienced anglers took longer to land fish than novices because they captured larger fish. These results suggest that a reduction in hooking injuries may be achieved by using circle hooks as an alternative to J hooks and barbless J hooks to reduce injury and handling time, yet catch efficiency for both methods would be reduced. Although fish captured with barbless J hooks and circle hooks had fewer injuries, it is important to note that each hook type also caused significant injury, and angler education is recommended to promote proper hook removal techniques.

North American Journal of Fisheries Management↗

USGS2005

Validation of abundance estimates from mark–recapture and removal techniques for rainbow trout captured by electrofishing in small streams

Estimation of fish abundance in streams using the removal model or the Lincoln - Peterson mark - recapture model is a common practice in fisheries. These models produce misleading results if their assumptions are violated. We evaluated the assumptions of these two models via electrofishing of rainbow trout Oncorhynchus mykiss in central Idaho streams. For one-, two-, three-, and four-pass sampling effort in closed sites, we evaluated the influences of fish size and habitat characteristics on sampling efficiency and the accuracy of removal abundance estimates. We also examined the use of models to generate unbiased estimates of fish abundance through adjustment of total catch or biased removal estimates. Our results suggested that the assumptions of the mark - recapture model were satisfied and that abundance estimates based on this approach were unbiased. In contrast, the removal model assumptions were not met. Decreasing sampling efficiencies over removal passes resulted in underestimated population sizes and overestimates of sampling efficiency. This bias decreased, but was not eliminated, with increased sampling effort. Biased removal estimates based on different levels of effort were highly correlated with each other but were less correlated with unbiased mark - recapture estimates. Stream size decreased sampling efficiency, and stream size and instream wood increased the negative bias of removal estimates. We found that reliable estimates of population abundance could be obtained from models of sampling efficiency for different levels of effort. Validation of abundance estimates requires extra attention to routine sampling considerations but can help fisheries biologists avoid pitfalls associated with biased data and facilitate standardized comparisons among studies that employ different sampling methods.

Idaho↗

USGS2011

Hepatic heat shock protein 70 and plasma cortisol levels in rainbow trout after tagging with a passive integrated transponder

This study examined the potentially stressful effects of tagging juvenile rainbow trout Oncorhynchus mykiss with passive integrated transponder (PIT) tags by measuring short-term (<120-h) changes in plasma concentrations of cortisol and hepatic heat shock protein 70 (hsp70). In a laboratory experiment, plasma cortisol levels were measured in fish before they were tagged (0 h) and at 2, 6, 24, and 120 h after being tagged. Hepatic hsp70 levels were measured at 0, 24, and 120 h. All results were compared with those for fish that were handled but not tagged. Plasma cortisol levels were significantly higher in both treatment groups (tagged and handled but not tagged) at 2 h than in the pretreatment groups (0 h). Plasma cortisol levels in the treatment groups returned to near pretreatment levels by 6 h. However, there was a significant difference in plasma cortisol levels between treatment groups at 6 h. There were no significant differences in hepatic hsp70 levels among the two treatment groups, and hepatic hsp70 levels did not change through time. Our results suggest that PIT tagging is a low-impact tagging procedure for juvenile salmonids. ?? Copyright by the American Fisheries Society 2008.

Transactions of the American Fisheries Society↗

USGS2005

Effects of selected polybrominated diphenyl ether flame retardants on lake trout (Salvelinus namaycush) thymocyte viability, apoptosis, and necrosis

Polybrominated diphenyl ether (PBDE) flame-retardants have been identified as an emergent contaminants issue in many parts of the world. In vitro analyses were conducted to test the hypothesis that selected PBDEs congeners affect viability, apoptosis, and necrosis of thymocytes from laboratory-reared lake trout ( Salvelinus namaycush ). At current environmental levels (<1 mg/L), effects of the tested PBDEs on thymocytes were negligible. However, at 100 mg/L, major effects were seen for congener brominated diphenyl ether 47 (BDE-47) and minor effects were seen for congener BDE-99.

Environmental Toxicology and Chemistry↗

USGS2007

Influence of in-stream diel concentration cycles of dissolved trace metals on acute toxicity to one-year-old cutthroat trout (Oncorhynchus clarki lewisi)

Extrapolating results of laboratory bioassays to streams is difficult, because conditions such as temperature and dissolved metal concentrations can change substantially on diel time scales. Field bioassays conducted for 96 h in two mining‐affected streams compared the survival of hatchery‐raised, metal‐näive westslope cutthroat trout ( Oncorhynchus clarki lewisi ) exposed to dissolved (0.1‐μm filtration) metal concentrations that either exhibited the diel variation observed in streams or were controlled at a constant value. Cadmium and Zn concentrations in these streams increased each night by as much as 61 and 125%, respectively, and decreased a corresponding amount the next day, whereas Cu did not display a diel concentration cycle. In High Ore Creek (40 km south of Helena, MT, USA), survival (33%) after exposure to natural diel‐fluctuating Zn concentrations (range, 214–634 μg/L; mean, 428 μg/L) was significantly ( p = 0.008) higher than survival (14%) after exposure to a controlled, constant Zn concentration (422 μg/L). Similarly, in Dry Fork Belt Creek (70 km southeast of Great Falls, MT, USA), survival (75%) after exposure to diel‐fluctuating Zn concentrations (range, 266–522 μg/L; mean, 399 μg/L) was significantly ( p = 0.022) higher than survival (50%) in the constant‐concentration treatment (392 μg/L). Survival likely was greater in these diel treatments, both because the periods of lower metal concentrations provided some relief for the fish and because toxicity during periods of higher metal concentrations was lessened by the simultaneous occurrence each night of lower water temperatures, which reduce the rate of metal uptake. Based on the present study, current water‐quality criteria appear to be protective for streams with diel concentration cycles of Zn (and, perhaps, Cd) for the hydrologic conditions tested.

Environmental Toxicology and Chemistry↗

USGS2009

Metabolism and elimination of benzocaine by rainbow-trout, Oncorhynchus mykiss

1. Branchial and urinary elimination of benzocaine residues was evaluated in adult rainbow trout, oncorhynchus mykiss, given a single dorsal aortic dose of c-14-benzocaine hydrochloride.^2. Branchial elimination of benzocaine residues was rapid and accounted for 59.2% Of the dose during the first 3 h after dosing. Renal elimination of radioactivity was considerably slower; the kidney excreted 2.7% Dose within 3 h and 9.0% Within 24 h. Gallbladder bile contained 2.0% Dose 24 h after injection.^3. Of the radioactivity in radiochromatograms from water taken 3 min after injection, 87.3% Was benzocaine and 12.7% Was n-acetylated benzocaine. After 60 min, 32.7% Was benzocaine and 67.3% Was n-acetylated benzocaine.^4. Of the radioactivity in radiochromatograms from urine taken 1 h after dosing, 7.6% Was para-aminobenzoic acid, 59.7% Was n-acetylated para-aminobenzoic acid, 19.5% Was benzocaine, and 8.0% Was n-acetylated benzocaine. The proportion of the radioactivity in urine changed with time so that by 20 h, 1.0% Was para-aminobenzoic acid and 96.6% Was n-acetylated para-aminobenzoic acid.^5. Benzocaine and a more hydrophobic metabolite, n-acetylated benzocaine, were eliminated primarily through the gills; renal and biliary pathways were less significant elimination routes for benzocaine residues.

Xenobiotica↗

USGS1983

Map showing aeromagnetic interpretation of the Golden Trout Wilderness, Tulare and Inyo counties, California

The Golden Trout Wilderness covers 457 mi 2 in the rugged forested part of the southern Sierra Nevada. It is bounded on the east by Owens Valley, on the north by Sequoia National Park, and on the west and south by U.S. Forest Service multiple-use lands. The east side of the area is accesible from U.S. Highway 395, while the remainder is reached by state, county, and Forest Service roads from the San Joaquin Valley.

California↗

USGS1976

Estimation of stream discharges preferred by steelhead trout for spawning and rearing in western Washington

Determined during the study of selected stream reaches used for spawning and rearing by steelhead trout were (1) stream discharges that cover the greatest areas of the streambeds with water at both the depths and the velocities preferred by spawning steelhead; (2) discharges that cover selectively reduced streambed areas with water at both the depths and velocities preferred by spawning steelhead; (3) discharges that cover the greatest streambed areas with water at velocities preferred by spawning steelhead; (4) rearing discharges that cover the streambed, but not the banks of the channel, with water; and (5) average wetted perimeters of the channels at water stages corresponding to the rearing discharges. These discharges and wetted perimeters were determined by measurements at 54 study reaches on 18 streams representative in size and location of those used by steelhead for spawning and rearing. Using multiple-regression techniques and the measured discharges and wetted perimeters, equations were developed for estimating the spawning and rearing discharges and the wetted perimeter for rearing at unmeasured stream sites. The independent parameters used were drainage area, mean altitude of the basin, reach altitude, reach slope, and average width of reach at toe of bank. Standard errors of estimate for the equations ranged from 26 to 50 percent for discharges corresponding to the greatest areas of preferred depths and velocities, from 32 to 46 percent for discharges corresponding to reduced areas of preferred depths and velocities, from 44 to 68 percent for discharges corresponding to the greatest areas of preferred velocities, from 46 to 57 percent for rearing discharges, and from 20 to 41 percent for the rearing wetted perimeter.

Washington↗

USGS2009

Relation between Streamflow of Swiftcurrent Creek, Montana, and the Geometry of Passage for Bull Trout (Salvelinus confluentus)

Operation of Sherburne Dam in northcentral Montana has typically reduced winter streamflow in Swiftcurrent Creek downstream of the dam and resulted in passage limitations for bull trout (Salvelinus confluentus). We defined an empirical relation between discharge in Swiftcurrent Creek between Sherburne Dam and the downstream confluence with Boulder Creek and fish passage geometry by considering how the cross-sectional area of water changed as a function of discharge at a set of cross sections likely to limit fish passage. With a minimum passage window of 15 x 45 cm, passage at the cross sections increased strongly with discharge over the range of 1.2 to 24 cfs. Most cross sections did not satisfy the minimum criteria at 1.2 cfs, 25 percent had no passage at 12.7 cfs, whereas at 24 cfs all but one of 26 cross sections had some passage and 90 percent had more than 3 m of width satisfying the minimum criteria. Sensitivity analysis suggests that the overall results are not highly dependent on exact dimensions of the minimum passage window. Combining these results with estimates of natural streamflow in the study reach further suggests that natural streamflow provided adequate passage at some times in most months and locations in the study reach, although not for all individual days and locations. Limitations of our analysis include assumptions about minimum passage geometry, measurement error, limitations of the cross-sectional model we used to characterize passage, the relation of Sherburne Dam releases to streamflow in the downstream study reach in the presence of ephemeral accretions, and the relation of passage geometry as we have measured it to fish responses of movement, stranding, and mortality, especially in the presence of ice cover.

Scientific Investigations Report↗