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At least 451 records · Page 25Linked to original sources
USGS1987

Testing of male sockeye salmon ( Oncorhynchus nerka ) and steelhead trout ( Salmo gairdneri ) for infectious hematopoietic necrosis virus

Infectious hematopoietic necrosis (IHN) virus has been isolated only rarely from whole milt samples of male sockeye salmon ( Oncorhynchus nerka ). In 3 yr of testing, virus incidences in males ranged from 0 to 13% when milt was sampled but were 60–100% with spleen or kidney. When IHN virus was isolated from sockeye salmon milt at titers less than 3.00 log 10 plaque-forming units (pfu)/mL, the level of virus in the kidney or spleen exceeded 7.00 log 10 pfu/g. Higher rates of IHN virus isolation from kidney or spleen than from milt were also generally found in steelhead trout ( Salmo gairdneri ), although the differences were less pronounced than in sockeye salmon. Furthermore, virus was sometimes isolated from steelhead trout milt when the level of virus in kidney or spleen samples was very low, and was recovered from some milt samples when none was isolated from the corresponding spleen sample. When male salmonids are tested for IHN virus, kidney or spleen samples are superior to whole milt, but milt should be included for critical examinations.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1987

Snowpack ion accumulation and loss in a basin draining to Lake Superior

The objective of this study was to relate winter precipitation ionic inputs, snowpack retention, and change in first-order stream chemistry with spring snowpack melt. During winter 1982–83, measurement of precipitation inputs, snowpack concentration and loading, and streamwater concentration and discharge of Ca2+, K+, H+, NO3−, and SO42− from a 176-ha watershed reveals that only H+ might be lost from the snowpack before first thaw. Above-freezing soil temperature beneath the snowpack may be a factor in H+ loss. An initial 1-d thaw resulted in loss of over one third (6 eq∙ha−1) of the snowpack Ca2+. Over one half the snowpack load of K+, H+, NO3−, and SO42−, was lost in a subsequent midwinter freeze–thaw period. Snowpack loading of ionic species was reduced by 70–90% before peak spring melting and stream discharge. Ecosystem H+ retention and biological uptake of NO3− further mitigate ionic "pulses" in streamwater. Sulfate discharge exceeds bulk inputs, which suggests significant dry deposition input and little forest soil retention of this anion. The snowpack was relatively small, which limits wider application of these results to the region.

Lake Superior↗
USGS1988

Digestive tract evacuation in northern squawfish ( Ptychocheilus oregonensis )

Digestive tract evacuation in northern squawfish ( Ptychocheilus oregonensis ) (170–1900 g) was studied in fish allowed to feed voluntarily on salmon (4–70 g) at three water temperatures (10, 15, and 20 °C). Squawfish were sacrificed at 1- or 2-h intervals until evacuation approximated 90%. Amount of food evacuated for a given time interval increased approximately three times as the temperature was increased and as the prey weight was increased and two times as the predator weight was increased. The 90% emptying time (ET 90 ) decreased by about two thirds as the temperature doubled and by about one half as the predator weight increased 10 times, but approximately doubled when the prey weight increased 4 times. Two-fish meals (17–20 g each, 35–39 g total) were evacuated more slowly than meals of one fish weighing 17–20 g, but at the same rate as meals of one fish weighing 35–40 g. Equations derived are easily applied to a wide range of water temperatures, prey weights, and predator weights.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1988

Assessment of sea lamprey ( Petromyzon marinus ) predation by recovery of dead lake trout ( Salvelinus namaycush ) from Lake Ontario, 1982-85

During 1982-85, 89 dead lake trout ( Salvelinus namaycush ) were recovered with bottom trawls in U.S. waters of Lake Ontario: 28 incidentally during four annual fish-stock assessment surveys and 61 during fall surveys for dead fish. During the assessment surveys, no dead lake trout were recovered in April-June, one was recovered in August, and 27 were recovered in October or November, implying that most mortality from causes other than fishing occurred in the fall. The estimated numbers of dead lake trout between the 30- and 100-m depth contours in U.S. waters ranged from 16 000 (0.08 carcass/ha) in 1983 to 94 000 (0.46 carcass/ha) in 1982. Of 76 carcasses fresh enough to enable recognition of sea lamprey ( Petromyzon marinus ) wounds, 75 bore fresh wounds. Assuming that sea lamprey wounding rates on dead fish were the same as on live ones of the same length range (430-740 mm), the probability of 75 of the 76 dead lake trout bearing sea lamprey wounds was 3.5 x 10 -63 if death was independent of sea lamprey attack, thus strongly implicating sea lampreys as the primary cause of death of fish in the sample. The recovery of only one unwounded dead lake trout also suggested that natural mortality from causes other than sea lamprey attactks is negligible.

Lake Ontario↗
USGS1989

Genetic variation in steelhead ( Salmo gairdneri ) from the north coast of Washington

Steelhead ( Salmo gairdneri ) collected from various sites in nine drainages in northwestern Washington were genetically characterized at 65 protein-coding loci by starch-gel electrophoresis. Genetic differentiation within and among drainages was not significant, and genetic variation among drainages was much less than that reported in British Columbia; these results may be the consequence of gene flow from hatchery stocks that have been released in Washington since the 1940's. Allele frequencies varied significantly among year-classes (hence, genetic characterization studies must include data from several year-classes), and also between hatchery fish (including a stock developed with local wild fish) and wild fish, indicating that few wild fish have been successfully and routinely included in hatchery brood stocks. Conservation of genetic diversity along the north coast of Washington should be facilitated by reducing the numbers of hatchery fish that spawn in streams and by including wild fish in hatchery brood stocks.

Washington↗
USGS1989

Concentration of infectious hematopoietic necrosis virus from water samples by tangential flow filtration and polyethylene glycol precipitation

Infectious hematopoietic necrosis virus (IHNV) was concentrated from water samples by polyethylene glycol (PEG) precipitation, tangential flow filtration (TFF), and by a combination of TFF followed by PEG precipitation of the retentate. Used alone, PEG increased virus titers more than 200-fold, and the efficiency of recovery was as great as 100%. Used alone, TFF concentrated IHNV more than 20-fold, and average recovery was 70%. When the two techniques were combined, 10-L water samples were reduced to about 300 mL by TFF and the virus was precipitated with PEG into a 1 to 2 g pellet; total recovery was as great as 100%. The combined techniques were used to isolate IHNV from water samples taken from a river containing adult sockeye salmon ( Oncorhynchus nerka ) and from a hatchery pond containing adult spring chinook salmon ( O . tshawytscha ). The combination of these methods was effective in concentrating and detecting IHNV from water containing only three infectious particles per 10-L sample.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1990

Pattern of solute movement from snow into an upper Michigan stream

Precipitation, snowpack, snowmelt, and streamwater samples were collected in a small gauged watershed draining into Lake Superior during winter 1987–88 to assess the importance of snowmelt pattern and meltwater pathways in the occurrence of solute pulses in streamwater. The snowpack along the south shore of Lake Superior can contain 50% of annual precipitation inputs and 38% of annual ionic inputs including moderate levels of strong acids. Throughout winter, thawed surface soils and small but steady snowpack moisture release promoted movement of snowpack solutes to surface mineral soils. Preferential elution of K + , NH4 + , and H + from the snowpack occurred with the initial thaw. Most ions exhibited pulses in snowmelt. Transport of snowpack solutes to the stream during snowmelt was through near-surface soil macropores and overland flow. For those ions with concentrations higher in the snowpack than in the premelt streamwater, K + , NH 4 + , and H + , the earliest snowmelt pulses had the greatest influence on streamwater chemistry. Unlike other portions of the region with resistant bedrock, the widespread presence of alkaline glacial till provides excess stream acid neutralization capacity (ANC) to buffer acidic inputs. Peak winter streamwater ANC reduction was caused principally by spring melt dilution of base cations and associated alkalinity, constant high SO 4 2- levels, and an increase in NO 3 - . The maximum reduction in stream ANC was concurrent with overland flow. Relative to its snowmelt concentration, NO 3 - was highest in streamwater with some stream input likely the result of nitrification and N mineralization.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1990

Denitrification in sediments from the hyporheic zone adjacent to a small forested stream

Denitrifying potentials increased with increasing distance from the stream channel. Dissolved oxygen was 100% of the concentration expected in equilibrium with the atmosphere in water obtained from monitoring wells immediately adjacent to the stream but was as low as 7% of the expected value in water 11.4 m inland. Both nitrate and dissolved organic carbon decreased over summer in wells at the base of the alder-forested slope. A 48-h injection of nitrate-amended stream water into hyporheic water 8.4 m inland stimulated nitrous oxide production in the presence of acetylene. Nitrous oxide was generated as nitrate and acetylene were co-transported to a well 13 m down-gradient. Acetylene-block experiments coupled with the chemistry data suggest that denitrification can modify the chemistry of water during passage through the hyporheic zone. -from Authors

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS2011

Testing a bioenergetics-based habitat choice model: bluegill ( Lepomis macrochirus ) responses to food availability and temperature

Using an automated shuttlebox system, we conducted patch choice experiments with 32, 8–12 g bluegill sunfish ( Lepomis macrochirus ) to test a behavioral energetics hypothesis of habitat choice. When patch temperature and food levels were held constant within patches but different between patches, we expected bluegill to choose patches that maximized growth based on the bioenergetic integration of food and temperature as predicted by a bioenergetics model. Alternative hypotheses were that bluegill may choose patches based only on food (optimal foraging) or temperature (behavioral thermoregulation). The behavioral energetics hypothesis was not a good predictor of short-term (from minutes to weeks) patch choice by bluegill; the behavioral thermoregulation hypothesis was the best predictor. In the short-term, food and temperature appeared to affect patch choice hierarchically; temperature was more important, although food can alter temperature preference during feeding periods. Over a 19-d experiment, mean temperatures occupied by fish offered low rations did decline as predicted by the behavioral energetics hypothesis, but the decline was less than 1.0 °C as opposed to a possible 5 °C decline. A short-term, bioenergetic response to food and temperature may be precluded by physiological costs of acclimation not considered explicitly in the behavioral energetics hypothesis.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1990

Influence of exchange flow between the channel and hyporheic zone on nitrate production in a small mountain stream

Variation in local exchange of flows between the channel and hyporheic zone produced temporally shifting concentration gradients of dissolved oxygen, nitrate, and ammonium in subsurface waters of a small, gravel-cobble bed stream. Channel water advected laterally supplied dissolved oxygen, and groundwater supplied ammonium to support hyporheic nitrification. Nitrate production was highest in sediment slurries from aerobic hyporheic sites, was absent at nearly anoxic sites, and was stopped by nitrification inhibitors (chlorate and nitrapyrin). Ammonium amendment to sediment slurries only slightly enhanced nitrate production indicating that sorption competed with biota for available substrate. Nitrate concentration increased from 75–130 μg N/L during 9 d of ammonium amendment to a hyporheic subsurface flow. Ammonium concentration rose slowly relative to a sulfate tracer initially, and declined slowly after cutoff as ammonium desorbed. Nitrate levels remained elevated for 6 d after cutoff as desorbed ammonium became biotically available. Interactions between the channel's hydrology, lithology, and biology such as we observed in nitrate production are probably more common than reported. However, the magnitude of the resulting nutrient flux will depend on factors which determine the depth and lateral extension of suitable hyporheic habitat.

California↗
USGS1991

Evaluation of a mark-recapture method for estimating mortality and migration rates of stratified populations

We simulated mark–recapture experiments to evaluate a method for estimating fishing mortality and migration rates of populations stratified at release and recovery. When fish released in two or more strata were recovered from different recapture strata in nearly the same proportions, conditional recapture probabilities were estimated outside the [0, 1] interval. The maximum likelihood estimates tended to be biased and imprecise when the patterns of recaptures produced extremely "flat" likelihood surfaces. Absence of bias was not guaranteed, however, in experiments where recapture rates could be estimated within the [0, 1] interval. Inadequate numbers of tag releases and recoveries also produced biased estimates, although the bias was easily detected by the high sampling variability of the estimates. A stratified tag–recapture experiment with sockeye salmon ( Oncorhynchus nerka ) was used to demonstrate procedures for analyzing data that produce biased estimates of recapture probabilities. An estimator was derived to examine the sensitivity of recapture rate estimates to assumed differences in natural and tagging mortality, tag loss, and incomplete reporting of tag recoveries.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1991

Acoustic measures of the abundance and size of pelagic planktivores in Lake Michigan

Based on acoustic data taken at night and vertically stratified by bottom depth (3–110 m only), the total number (± 95% Cl) of pelagic fishes in Lake Michigan was 43.4 ± 10.1 x 10 9 or 226.0 ± 55.2 kt in spring (mean density 0.7–3.8 fish·m -2 or 1.6–12.8 ga·m -2 ) and 115.8 ± 18.3 x 109 or 313.2 ± 74.3 kt in late summer, 1987 (mean density 1.1–7.0 fish·m -2 or 3.0–13.2 g·m -2 ); approximately 30% of this increase in numbers (35% of biomass) occurred within Green Bay. Abundance estimates from horizontally stratified (by water column depth) data were within 9-11% of vertically stratified estimates during spring but over 20% higher during summer. By extrapolation to all water depths, we estimated total pelagic biomass as 274.6 kt for spring and 410.8 kt for summer. During both seasons, smaller fishes were nearer to the surface and nearer shore than larger individuals, and acoustic measures of size approximated the sizes of fishes caught in trawls. Bioenergetic model simulations suggest that 60% of the available production of alewife (Alosa pseudoharengus) was either consumed by stocked salmonines (52.9%) or commercially harvested (7.1%) in 1987. Underwater acoustics proved a valuable tool for lakewide assessments of fish abundances in the Great Lakes.

Michigan↗
USGS1991

A sigmoid model to predict gastric evacuation rates of smallmouth bass Micropterus dolomieui fed juvenile salmon

Laboratory experiments were conducted to examine the effects of water temperature, predator size, prey size, and prey number on gastric evacuation of smallmouth bass ( Micropterus dolomieui ) fed juvenile salmon. The smallmouth bass were allowed to feed voluntarily after 24–48 h of starvation and stomachs were pumped at intervals of 1–4 h until 90% of the stomach contents were evacuated ( E 90 ). Evacuation approximated an S -shaped curve over time, and a sigmoid model was developed to predict evacuation at varying water temperatures, total meal weights, predator sizes, and prey number. The rate of evacuation increased with increasing water temperature, meal weight, or predator size. The E 90 increased with larger meal weights but decreased with increasing temperature or predator size. E 90 ranged between 4 and 95 h, depending upon conditions. E 90 was slower than those estimated previously for another predator of salmon, the stomachless northern squawfish ( Ptychocheilus oregonensis ).

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1991

Tumor frequencies in walleye ( Stizostedion vitreum ) and brown bullhead ( Ictalurus nebulosus ) and sediment contaminants in tributaries of the Laurentian Great Lakes

To better characterize neoplasm epizootics in the Great Lakes basin and their association with families of contaminants, we sampled five locations: the Fox and Menominee rivers, Lake Michigan; Munuscong Lake, St. Mary's River; and the Black and Cuyahoga rivers, Lake Erie. Frequencies of external and liver tumors were determined for brown bullhead ( Ictalurus nebulosus ) from all locations except the Black River and for walleye ( Stizostedion vitreum ) from the Lake Michigan and St. Mary's River sites. Sediment samples were analyzed for metals, polychlorinated aromatics, and polynuclear aromatic hydrocarbons (PAH). Liver neoplasms occurred in brown bullhead from the Cuyahoga River and Munuscong Lake; brown bullhead captured from Munuscong Lake were older than those collected from the other locations. Brown bullhead from these same two rivers had elevated hepatosomatic indexes. No liver neoplasms were found in brown bullhead from the Fox and Menominee rivers, although polychlorinated aromatics were highest in both Fox River sediment and Fox and Menominee brown bullhead, and arsenic was highest in Menominee River sediment and fish. Liver neoplasms in brown bullhead from the Cuyahoga River fit the prevailing hypothesis that elevated PAH in sediment can induce cancer in wild fish. The cause of the liver neoplasms in Munuscong Lake brown bullhead is undetermined.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1991

Nature and time course of acclimation to aluminum in juvenile brook trout ( Salvelinus fontinalis ): II. Gill histology

Gill samples from juvenile brook trout ( Salvelinus fontinalis ) acclimated to low-level aluminum at pH 5.2 showed severe damage by day 4, with necrosis and fusion of secondary lamellae and hyperplasia and hypertrophy of mucous cells. Over the following 20 d, there was a continual process of repair with proliferation and hypertrophy of mucous cells. Qualitative analysis of gill samples plus physiology and mortality data collected in a companion study indicated progressive development (by day 10 onward) of increasing acclimation to Al. Quantitative analysis of gill samples on day 13 showed that mucous cell volume density had tripled and mucous cell area had doubled in Al-exposed fish compared with control fish. A lamellar fusion index showed evidence of fusion in Al-exposed fish by day 4 with recovery to nearly control levels by day 13. Physiological disturbances appear to be directly related to the histological changes observed in the gill epithelium. At the cellular level, changes in either mucous cell production and secretion or changes in mucus chemistry contribute, in part, to acclimation to Al.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1991

U.S. federal policies, legislation, and responsibilities related to importation of exotic fishes and other aquatic organisms

Within the Federal government, the U. S. Fish and Wildlife Service (Service) has primary responsibility for legal and policy responsibility for introduced exotic species. The Lacey Act of 1900 authorizes the Service to prohibit the importation of species that are potentially injurious to native fish and wildlife. However, regulations under authority of the Lacey Act cover only a few species. The Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990 established a Task Force co-chaired by the Director of the Service and Under Secretary of Commerce for Oceans and Atmosphere. The Task Force consults with the Secretary of Transportation to develop regulations to prevent the importation and spread of aquatic nuisance species into the Great Lakes through exchange of ballast water. Federal agencies must comply with Presidential Executive Order 1198, Exotic Organisms, that prohibits Federal agencies or activities they fund or authorize from introducing exotic species. The Service conducts research and evaluation of exotic species to support Federal, State, and local efforts to prevent further importation of harmful species. Effective regulation will also depend on the full cooperation with Canada.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1992

Phosphate and iron limitation of phytoplankton biomass in Lake Tahoe

Bioassays were carried out to assess the response of inoculated, single-species diatom populations (Cyclotella meneghiniana and Aulocosiera italica) to additions of synthetic chelators and phosphate. A chemical speciation model along with the field data was also used to predict how trace metal speciation, and hence bioavailability, was affected by the chelator additions. Results suggest that phosphate was limiting to phytoplankton biomass. Other solutes, Fe in particular, may also exert controls on biomass. Nitrate limitation seems less likely, although Fe-limiting conditions may have led to an effective N limitation because algae require Fe to carry out nitrate reduction. -from Authors

Canadian Journal of Fisheries and Aquatic Sciences↗