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At least 541 records · Page 30Linked to original sources
USGS1974

Residues of DDT in lake trout (Salvelinus namaycush) and coho salmon (Oncorhynchus kisutch) from the Great Lakes

Concentrations of DDT residues were higher in lake trout ( Salvelinus namaycush ) from southern Lake Michigan in 1966–70 (average 18.1 ppm in fish 558–684 mm long) than in lake trout of the same size-class from Lake Superior in 1968–69 (4.4 ppm), and higher in adult coho salmon ( Oncorhynchus kisutch ) from Lake Michigan in 1968–71 (averages for different year-classes, 9.9–14.0 ppm) than in those from Lake Erie in 1969 (2.2 ppm). Residues were significantly higher in lake trout from southern Lake Michigan than in those from the northern part of the lake. In lakes Michigan and Superior, the levels increased with length of fish and percentage oil. In Lake Michigan coho salmon, the residues remained nearly stable (2–4 ppm) from September of the 1st yr of lake residence through May or early June of the 2nd yr, but increased three to four times in the next 3 mo. Residues in Lake Erie coho salmon did not increase during this period, which preceded the spawning season. Although the concentrations of total residues in whole, maturing Lake Michigan coho salmon remained unchanged from August 1968 until near the end of the spawning season in January 1969, the residues were redistributed in the tissues of the spawning-run fish; concentrations in the loin and brain were markedly higher in January than in August. This relocation of DDT residues accompanied a marked decrease in the percentage of oil in the fish, from 13.2 in August to 2.8 in January. Concentrations of residues were relatively high in eggs of both lake trout (4.6 ppm) and coho salmon (7.4–10.2 ppm) from Lake Michigan. The percentage composition of the residues ( p , p ′DDE, o , p ′/DDT, p , p ′DDT, and p , p ′DDT) did not differ significantly with life stage, size, age, or locality, or date of collection of lake trout or coho salmon.

Journal of the Fisheries Research Board of Canada↗
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↗
USGS1995

Effect of predation by Sacramento squawfish (Ptychocheilus grandis) on habitat choice of California roach (Lavinia symmetricus) and rainbow trout (Oncorhynchus mykiss) in artificial streams

We studied the effects of predatory Sacramento squawfish ( Ptychocheilus grandis ) on habitat choice of juvenile California roach ( Lavinia symmetricus ), adult roach, and juvenile rainbow trout ( Oncorhynchus mykiss ) in artificial streams. In single-prey trials, the proportion of fish found in pool habitat declined in the presence of squawfish for juvenile roach (from 0.55 to 0.00), adult roach (from 0.88 to 0.13), and juvenile rainbow trout (0.70 to 0.15). The presence of squawfish did not affect the use of riffle and edge habitats. Of the fish found in shallow water, the proportion found in edge habitat declined from juvenile roach (0.95) to adult roach (0.80) to juvenile rainbow trout (0.23). We also conducted experiments designed to simulate invasion of an area by squawfish, in which adult roach and juvenile rainbow trout were tested together in the presence and absence of squawfish. The proportion of prey in pool habitat in the presence of squawfish was greater in the two-prey trials than in the single-prey trials for both adult roach (0.31 and 0.13, respectively) and juvenile rainbow trout (0.33 and 0.15, respectively). These results support field evidence that squawfish are an important force in determining the spatial structure of native stream fish assemblages.

California↗
USGS2014

Use of oviduct-inserted acoustic transmitters and positional telemetry to estimate timing and location of spawning: a feasibility study in lake trout, Salvelinus namaycush

Background Oviduct-inserted transmitters have shown promise for determining precise location of spawning in fishes. Use of traditional manual tracking to locate expelled oviduct transmitters is laborious and accurate estimates of time of transmitter expulsion require frequent surveys. We tested the feasibility of using oviduct-inserted transmitters with positional telemetry to estimate time and location of spawning in lake trout (Salvelinus namaycush). Three assumptions were tested: (1) oviduct transmitters remain within fish until spawning, (2) oviduct transmitters are expelled with the eggs during spawning, and (3) time and location of oviduct transmitter expulsion can be accurately determined. Results In the laboratory, 39 of 44 (89%) lake trout retained an oviduct transmitter until end of the spawning period and all premature transmitter expulsions occurred before maturation. Natural spawning in the laboratory was not feasible; however, of 35 ripe trout that retained transmitters, 31 (89%) expelled their transmitter with eggs when subjected to manual stripping. Ability to position transmitters with a telemetry array at known spawning sites in Lake Huron (North America) was poor when oviduct transmitters were placed in the substrate compared to transmitters suspended 1 m above substrate - 78% of transmitters in substrate could not be positioned. However, in simulations, time and location of spawning were determined with reasonable accuracy by double-tagging trout with one transmitter that is expelled with the eggs during spawning while another transmitter remains in the fish. Accuracy of estimated time and location of transmitter spatial separation varied with distance traveled from spawning site and swimming speed, and was dependent on transmission delay. Conclusions Our results satisfied the three assumptions of oviduct tagging and suggested that oviduct transmitters can be used with positional telemetry to estimate time and location of spawning in lake trout and other species. In situations where oviduct transmitters may be difficult to position once expelled into substrate, pairing oviduct transmitters with a normal-sized fish transmitter that remains in the fish is recommended, with spawning inferred when the two tags separate in space. Optimal transmitter delay will depend on expected degree of spawning site residency and swim speed.

Lake Huron↗
USGS1979

Excretion of the lampricide Bayer 73 by rainbow trout

Urinary excretion of the 2-aminoethanol salt of 2′, 5-dichloro-4′-nitrosalicylanilide (Bayer 73) in rainbow trout ( Salmo gairdneri ) was measured after exposure of the trout to Bayer 73 and also after intraperitoneal (ip) injection of the lampricide. Fish exposed to 0.05 mg/litre of Bayer 73 for 12 h quickly began to excrete residues in the urine. The largest amount of Bayer 73 was excreted during the 12-h exposure, but the trout continued to excrete Bayer 73 beyond 60 h after exposure. After rainbow trout were given ip injections of 200 µ g of Bayer 73 in corn oil, they excreted up to 25 percent of the injected dose in the urine, and 20 percent was recovered in the bile at the end of the study. In both groups of fish most of the renal excretion of Bayer 73 was as the glucuronide conjugate. The exposure of rainbow trout to Bayer 73 at the doses studied had no effect on the urine output or on the renal excretion of sodium (Na + ), potassium (K + ), calcium (Ca 2+ ), magnesium (Mg 2+ ), and chloride (Cl - ).

Conference Paper↗
USGS1991

Response of rainbow trout to soy lecithin, choline and autoclaved isolated soy protein

Fry of rainbow trout ( Oncorhynchus mykiss ) were fed, from first feeding (mean weight, 0.12 g), basal diets containing either a nonautoclaved (raw) sodium proteinate form of isolated soy protein (ISP) or the same ISP autoclaved at 0.56 kg/cm 2 and l 10°C for 30 min. In the three‐way factorial, 16‐week study, I measured the effects of autoclaving ISP on the growth, survival, and chemical composition of rainbow trout at three levels of soy lecithin (0, 4, and 8%) and two levels of choline (0 and 0.3%). Fish fed raw ISP grew no faster with or without choline than did those fed the basal diet, but those fed heated ISP with choline showed a quantitatively small but significant advantage in weight gain. Whereas fish fed 4% lecithin with raw ISP more than tripled weight gain compared with fish fed the basal diets, fish fed 4% lecithin with heated ISP grew seven times as fast as those fed no lecithin or choline. Rainbow trout fed choline and 4% lecithin with heated ISP (but not raw ISP) grew significantly faster than those fed heated ISP and 4% lecithin alone. The higher level (8%) of lecithin promoted no more growth than the 4% lecithin with either raw or heated ISP. Among rainbow trout fed heated ISP, 4 and 8% supplemental lecithin – either with or without choline – reduced mortality to the same level, but 8% lecithin was the only concentration that significantly reduced the mortality of fish fed raw ISP. The results of calorimetry and determination of nitrogen with larger (235–375 g) rainbow trout individually held in metabolism chambers indicated that autoclaved ISP enhanced the growth and survival responses offish to lecithin by increasing digestible protein and energy and metabolizable energy. This higher amount of bioavailable energy and protein increased the deposition of body fat.

Progressive Fish-Culturist↗
USGS1991

Effects of orally administered steroids on lake trout and Atlantic salmon

Lake trout ( Salvelinus namaycush ) and Atlantic salmon ( Salmo salar ) fed 30 mg β‐estradiol/kg of feed for 100 d from first feeding had liver and kidney pathology similar to but much less severe than that previously reported for rainbow trout ( Oncorhynchus mykiss ). Mortality was not affected. Both lake trout and Atlantic salmon treated with estradiol weighed significantly less than control fish at the end of the treatment period and at 200 d posttreatment. Testosterone‐treated fish of both species weighed less than control fish at the end of the treatment period. By day 200 posttreatment, testosterone‐treated and untreated lake trout weighed the same, but testosterone‐treated Atlantic salmon were heavier than control fish. Estradiol treatment produced an all‐female population of Atlantic salmon but not of lake trout. Testosterone at 5 mg/kg feed increased the ratio of males to females in both species.

Progressive Fish-Culturist↗
USGS1938

The food of the lake trout (Cristivomer namaycush namaycush) and of the lawyer (Lota maculosa) of Lake Michigan

This paper reports on a qualitative and quantitative analysis of the contents of 4,979 lake trout stomachs (593 examined in 1930 and 1,253 collected in 1931 from southern Lake Michigan, 1,446 from northern Lake Michigan and 1,687 from Green Bay in 1932), and of a total of 1,528 lawyer stomachs (172 examined in 1930 and 734 collected in 1931 from southern Lake Michigan, 612 from northern Lake Michigan and 10 from Green Bay in 1932). The food of the trout consisted of 98 per cent by volume of fish of which Cottidae and Coregonidae were the principal constituents. Cottidae were dominant in southern Lake Michigan (72 per cent by volume), Coregonidae in northern Lake Michigan (51 per cent) but the lake shiner, Notropis atherinides, was most important in Green Bay in the spring of the year (64 per cent). The lawyer food consisted of 74 per cent by volume of fish and 26 per cent invertebrates. Dominant items were Cottidae (76 per cent by volume) in southern Lake Michigan, Coregonidae (51 per cent) and Pontoporeia (37 per cent) in northern Lake Michigan, and Percopsis (34 per cent) and Mysis (26 per cent) in Green Bay. Data are also presented on the frequency of occurrence (number of stomachs) of the food items and its variation with the sizes of the trout and lawyers, depths of water, seasons, and localities; on the number of individual fish of each species destroyed by the trout and lawyers; and on the calculated volume of the food fishes preceding digestion. The lake trout and lawyer are competitors for the same food, are both predators of the commercially important Coregonidae, and the lawyer through its consumption of invertebrates is a food competitor of the Coregonidae.

Transactions of the American Fisheries Society↗
USGS1980

Handling as a factor in mortality of trout with or without furunculosis

Mortalities of brook trout ( Salvelinus fontinalis ), brown trout ( Salmo trutta ), and rainbow trout ( Salmo gairdneri ) in 1978 and 1979 were significantly higher in clinically diseased than in subclinically diseased or healthy fish in both years. Mortalities in diseased fish within 24 h after sampling were not statistically different from those in specific-pathogen-free controls; however, the crowding offish lots for stocking resulted in significantly higher mortalities in furunculosis -infected brown trout in 1979. Crowding and handling for stocking thus caused higher mortality in diseased fish than just sampling. Healthy trout were able to tolerate more handling stress.

Progressive Fish-Culturist↗
USGS1982

Furunculosis in brook trout: Infection by contact exposure

In juvenile brook trout (Salvelinus fontinalis) challenged by applying about 10 9 virulent Aeromonas salmonicida cells to an abraded area along the lateral line, or held in aquarium water containing about 10 5 cells per milliliter, mortalities were 50 and 60%, respectively, within 7 days after exposure. Neither feeding the bacterium to the fish nor applying it directly to the gills caused systemic bacterial infection. Two consistent experimental challenges were developed for inducing furunculosis in juvenile brook trout: (1) 15‐min contact (bath) exposures of trout to about 10 6 A. salmonicida cells per milliliter of spring water, and (2) 60‐s dip exposures of the fish to 10 9 A. salmonicida cells per milliliter. These challenge procedures produced 70‐100% and 74‐88% mortality, respectively, within 14 days after exposure. Results obtained with a strain of brook trout from Owhi Lake, Washington, by the dip exposure method were affected by neither the age of the fish (up to 1 year) nor the source of the population. The challenge was also effective for Atlantic salmon (Salmo salar) but not for rainbow trout (S. gairdneri).

Progressive Fish-Culturist↗
USGS1983

Survey of stocking policies for tailwater trout fisheries in the southern United States

A survey of the 16 southern states showed that 48 tailwaters in 13 states were stocked with trout in 1980. Of the almost 3.7 million trout released in these waters, 81% were of catchable size and 19% were fingerlings (< 150mm). Tailwaters received 32% of all trout stocked in the South; nearly 95% of the tailwater fish were rainbow trout ( Salmo gairdneri ). A trend away from "put-grow-and-take" fisheries toward "put-and-take" fisheries was noted. Limited creel data confirmed that fishing pressure in southern tailwaters was heavy, and that 25 to 90% of the trout stocked were recovered by anglers

Progressive Fish-Culturist↗
USGS1989

Electrofishing mark-recapture and depletion methodologies evoke behavioral and physiological changes in cutthroat trout

We examined the behavioral and physiological responses of wild and hatchery-reared cutthroat trout Oncorhynchus clarki subjected to a single electroshock, electroshock plus marking, and multiple electroshocks in natural and artificial streams. In a natural stream, cutthroat trout released after capture by electrofishing and marking showed distinct behavioral changes: fish immediately sought cover, remained relatively inactive, did not feed, and were easily approached by a diver. An average of 3–4 h was required for 50% of the fish to return to a seemingly normal mode of behavior, although responses varied widely among collection sites. Using the depletion method, we observed little change in normal behavior offish remaining in the stream section (i.e., uncaptured fish) after successive passes with electrofishing gear. In an artificial stream, hatchery-reared and wild cutthroat trout immediately decreased their rates of feeding and aggression after they were electroshocked and marked. Hatchery fish generally recovered in 2–3 h; wild fish required at least 24 h to recover. Analysis of feeding and aggression data by hierarchical rank revealed no distinct recovery trends among hatchery fish of different ranks; among wild cutthroat trout, however, socially dominant fish seemed to recover faster than intermediate and subordinate fish. Physiological indicators of stress (plasma cortisol and blood lactic acid) increased significantly in cutthroat trout subjected to electroshock plus marking or single or multiple electroshocks. As judged by the magnitude of the greatest change in cortisol and lactate, multiple electroshocks elicited the most severe stress response; however, plasma concentrations of both substances had returned to unstressed control levels by 6 h after treatment. It was evident that electrofishing and the procedures involved with estimating fish population size elicited a general stress response that was manifested not only physiologically but also behaviorally. These responses may affect the accuracy of population size estimates by violating key assumptions of the methods, especially the assumption of equal catchability offish.

Transactions of the American Fisheries Society↗
USGS1997

Cutthroat trout avoidance of metals and conditions characteristic of a mining waste site: Coeur d'Alene River, Idaho

The South Fork basin of the Coeur d'Alene River, Idaho has been an area of heavy mining activity since the 1880s. The mining operations have resulted in elevated concentrations of metals in surface water, most notably cadmium, lead, zinc, and, to a lesser extent, copper. The metals affected surface water quality downstream in the Coeur d'Alene basin and are suspected to be one of the primary reasons for the reduction in populations of native westslope cutthroat trout Oncorhynchus clarki lewisi. The avoidance response of a surrogate species, Snake River cutthroat trout O. clarki (unnamed subspecies), was evaluated against conditions simulating those in the Coeur d'Alene River basin. Cutthroat trout avoided a metals mixture of these concentrations: Cd (0.30 ??g/L), Cu (6.0 ??g/L), Pb (0.6 ??g/L), and Zn (28 ??g/L). The avoidance response to either Cu or Zn alone was similar to the avoidance response to the mixture, suggesting that avoidance to the mixture was due to these metals. After acclimation to Zn at 55 ??g/L for 90 d, cutthroat trout detected and preferred a lower Zn concentration of 28 ??g/L. The lowest Zn concentrations avoided (28 ??g/L) were 1/6 to 1/78 the Zn concentrations measured in the South Fork and lower Coeur d'Alene River basins. Avoidance of metals-contaminated habitats by cutthroat trout may be, in part, responsible for reduced fish populations.

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

Identification of steelhead and resident rainbow trout progeny in the Deschutes River, Oregon, revealed with otolith microchemistry

Comparisons of strontium:calcium (Sr:Ca) ratios in otolith primordia and freshwater growth regions were used to identify the progeny of steelhead Oncorhynchus mykiss (anadromous rainbow trout) and resident rainbow trout in the Deschutes River, Oregon. We cultured progeny of known adult steelhead and resident rainbow trout to confirm the relationship between Sr:Ca ratios in otolith primordia and the life history of the maternal parent. The mean (??SD) Sr:Ca ratio was significantly higher in the otolith primordia of the progeny of steelhead (0.001461 ?? 0.00029; n = 100) than in those of the progeny of resident rainbow trout (0.000829 ?? 0.000012; n = 100). We used comparisons of Sr:Ca ratios in the primordia and first-summer growth regions of otoliths to determine the maternal origin of unknown O. mykiss juveniles (n = 272) collected from rearing habitats within the main-stem Deschutes River and tributary rearing habitats and thus to ascertain the relative proportion of each life history morph in each rearing habitat. Resident rainbow trout fry dominated the bi-monthly samples collected from main-stem rearing habitats between May and November 1995. Steelhead fry dominated samples collected from below waterfalls on two tributaries in 1996 and 1998.

Transactions of the American Fisheries Society↗
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↗
USGS1994

Observations on the occurrence of bacterial gill disease and amoeba gill infestation in rainbow trout cultured in a water recirculation system

Spontaneous outbreaks of bacterial gill disease (BGD) occurred in 17-44-g rainbow trout Oncorhynchus mykiss after they were placed in a water recirculation system. In each of five groups stocked from September 1991 through July 1992, BGD occurred within 6–8 d after stocking. In each instance, BGD was followed by a secondary amoeba infestation. The spontaneous BGD outbreaks did not occur among previously stocked groups that had recovered from earlier BGD disease outbreaks. Examination of gill tissue by Gram stain and indirect fluorescent antibody technique showed increased numbers of filamentous bacteria associated with BGD after the rainbow trout were stocked into the system. Bacterial numbers decreased after a 1-h treatment with chloramine-T at concentrations of 9–15 mg/L but increased within 2 d after treatment. Although the chloramine-T treatments controlled mortality related to BGD, the amoeba infestation persisted. Histological examination of gills showed some focal hyperplasia before the rainbow trout were placed into the recirculation system, but hyperplasia became more extensive and lamellar fusion and mild telangiectasis developed within a week after placement in the system. The density at which the fingerling rainbow trout were stocked and the suspended solids present in tank water may have contributed to the BGD outbreaks. Exposure of juvenile rainbow trout to tank water from the recirculation system before they were placed into the system did not afford them protection against BGD after stocking.

Journal of Aquatic Animal Health↗
USGS2000

Conserving inland cutthroat trout in small streams: how much stream is enough?

We examined the prognosis for long-term persistence of isolated populations of cutthroat trout Oncorhynchus clarki and the feasibility of using barriers to protect them from nonnative salmonids. In so doing, we estimated minimum stream lengths (MSL) required by cutthroat trout populations of varying abundances and rates of population loss to emigration and mortality. Using 2,500 individuals (>75 mm) as the target population size—corresponding to an effective population size, N e , of 500—we estimated that more than 8 km of stream were required to maintain a population with high fish abundances (0.3 fish/m), and 25 km of stream were required to maintain a population of low abundance (0.1 fish/m). Incorporating a population loss rate of 10% increased MSL to 9.3 km for the high and 27.8 km for the low abundances. Our results suggest that many isolated populations may not persist over the long term because insufficient space exists to maintain the required N e . Barrier construction to protect cutthroat trout from nonnative salmonids may be a necessary short-term solution, but it involves a long-term risk for maintaining viable cutthroat trout populations. We propose a watershed-based framework for cutthroat trout conservation in the central and southern Rocky Mountains that emphasizes protection of strong core populations.

North American Journal of Fisheries Management↗