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At least 811 records · Page 45Linked to original sources
USGS1992

Effects of sodium and calcium on acute toxicity of un-ionized ammonia to Atlantic salmon and lake trout

Acute, static 6-hour toxicity tests were conducted on two sizes each of lake trout and Atlantic salmon in the presence of three levels each of NaCl and CaCl 2 . Calcium did not protect smolts from NH 3 toxicity but had no effect on the tolerance of Atlantic salmon fry to NH 3 . Both cations increased the tolerance of 8-g lake trout fingerlings to NH 3 , but neither significantly affected the toxicity of NH 3 to 0.9-g lake trout fry. These results suggest that the mitigating effects of solution cations of NH 3 toxicity may be related to species, size, and life stage.

Journal of Applied Aquaculture↗
USGS1953

An epizootic among rainbow trout

An epizootic among rainbow trout ( Salmo gairdnerii ) in a private trout farm, resulting from a species of Ichthyosporidium that caused very high mortality rates in all ages of trout, reported from the State of Washington.

Progressive Fish-Culturist↗
USGS1988

Residues of benzocaine in rainbow trout, largemouth bass, and fish meal

Residues of the anesthetic benzocaine in muscle tissue of rainbow trout ( Salmo gairdneri ) and largemouth bass ( Micropterus salmoides ) were determined after exposure of the fish to 50 mg benzocaine/L for 15 min and withdrawal times of 0–24 h. The mean concentration of benzocaine residues in fish sampled immediately after exposure was 14.0 μg/g in rainbow trout and 10.6 μg/g in largemouth bass. Residues were below the control value after 8 h of withdrawal in largemouth bass and near the control value after 4 h of withdrawal in rainbow trout. Although residues of benzocaine were high in fish immediately after exposure, the concentration declined rapidly when the fish were held in flowing fresh water. Fish meal prepared from Pacific salmon ( Oncorhynchus sp.) that had been anesthetized with benzocaine or trieaine (MS‐222) contained residues of 45.1 μg benzocaine/g or 47.7 μg trieaine/g.

Progressive Fish-Culturist↗
USGS1988

High calcium concentration in water increases mortality of salmon and trout eggs

Several experiments were conducted to investigate the effect of water chemistry during water hardening on survival of eggs of Atlantic salmon ( Salmo salar ), rainbow trout ( Salmo gairdneri ), and. brook trout (Salvelinus fontinalis). Results of these experiments showed that survival was very low when eggs were exposed to very hard water containing high concentrations of calcium (approximately 520 mg/L or greater) during the first few hours of water hardening. Such high concentrations of calcium were associated with gypsum (calcium sulfate) in the water supply. In contrast, survival of eggs significantly increased when they were initially water‐hardened (1–3 h) in softer water (Ca concentrations, 34–64 mg/L). Incubation of eggs in high‐calcium water after the initial water‐hardening period did not significantly affect survival. Results of another experiment on water hardening of rainbow trout eggs showed a significant increase in survival when eggs were initially water‐hardened in either low‐gypsum water or in high‐gypsum water softened by ion exchange to markedly reduce the calcium; but not the sulfate, content.

Progressive Fish-Culturist↗
USGS1934

Ulcer disease of trout

During the summer of 1933, lesions of a disease were noted among some fingerling brook, rainbow, blackspotted, and lake trout at the Cortland (New York) trout hatchery. Although these lesions bore a marked superficial resemblance to those of furunculosis, they were sufficiently atypical to warrant further investigation. A more detailed examination of the lesions proved them to be of a distinct disease, which for lack of a better name is herein called "ulcer disease," for the lesions closely resemble those described by Calkins (1899) under this name. Because of the marked resemblance to furunculosis, ulcer disease has not been generally recognized by trout culturists, and any ulcer appearing on fish has been ascribed by them to furunculosis without further question.

Transactions of the American Fisheries Society↗
USGS1940

An evaluation of trout culture

In an evaluation of the efficiency of trout culture, the author presents a detailed analysis of complete loss records from 288 individual lots of trout at twenty-two hatcheries in the western United States. Summarized data are given to show the percentage loss of eggs, fry, and fingerlings by progressive one-half inch size groups. The accumulative percentage loss is also included to indicate the losses, under average hatchery conditions, between the egg stage and each successive size-group. These data cover the individual species of trout commonly reared in hatcheries; summarized data are given also for all species combined. A brief discussion of hatchery losses, natural losses, and the cost of artificial propagation is included.

Transactions of the American Fisheries Society↗
USGS1951

Tissue levels of various sulfonamides in trout

Studies were made on the tissue levels of sulfonamides in trout. The tissue concentrations of sulfamerazine were determined in brook trout given various doses of this drug. It has been found also that there exists a relationship between the rate of feeding, depending on the size of trout, and the tissue concentration of sulfamerazine. The level of sulfamerazine rose much faster and higher in blood and liver than in kidney and muscle. However, after the treatment was discontinued sulfamerazine level in all tissues dropped within 3 days to about 1 milligram percent. From the tested sulfonamides, sulfanilamide was absorbed fastest and produced highest tissue concentration. Sulfamerazine and sulfamethazine gave similar tissue levels, but the tissue concentration rose faster with sulfamerazine. Sulfadiazine and sulfaguanidine reached lower tissue levels. The tissue level of sulfathiazole was less than 1 milligram percent and sulfathalidine and sulfaquinoxaline were not absorbed from the intestine at all.

Transactions of the American Fisheries Society↗
USGS1967

Growth of lake trout in Lake Superior before the maximum abundance of sea lampreys

The growth in length of lake trout (Salvelinus namaycush) from the inshore water of Lake Superior in 1953 increased with age from the 3rd to 9th year, and was nearly constant from the 9th to the 12th year. Growth was greatest in the 1st year (4.0 inches) and least in the 2nd and 3rd years (2.3 inches). Between the 4th and 9th years the increments increased from 2.6 to 3.5 inches. Growth was calculated from a curvilinear body‐scale relation. Intraseasonal growth in length extended from late April until well after October; most growth was in late summer and fall. The younger fish started growth earlier, and some mature fish did not increase in length until after the October spawning. Lake trout reached the minimum legal weight (1.5 pounds) in the 7th year of life and the average size taken in the commercial fishery (about 3 pounds) in the 8th year. The annual increase in weight in the 8th year of life was over 64%. Fish used in this study grew more slowly than those from Lakes Michigan and Huron taken during the period when sea lamprey abundance was increasing, but at about the same rate as lake trout of Lake Michigan before the sea lamprey appeared.

Lake Superior↗
USGS1969

A hematopoietic virus disease of rainbow trout and sockeye salmon

A previously undescribed virus disease epizootic of hatchery rainbow trout ( Salmo gairdneri ) in British Columbia, Canada is presented. In the same locality, a similar virus disease was experienced among hatchery sockeye salmon ( Oncorhynchus nerka ). Typical symptoms included flashing, fecal casts, hemorrhagic areas at the base of fins, and petechial hemorrhages on the visceral fat and membranes in the abdominal cavity. Histopathologic changes were typified by extensive degeneration and necrosis in the hematopoietic tissues of the kidney and spleen. A virus was isolated from both species of fish on tissue culture and the viruses showed cross-infectivity. Based upon the pathological changes in the hematopoietic tissue and the demonstration of a vital infection, a tentative descriptive name was designated Infectious Hematopoietic Necrosis. The isolated viruses were distinctly different from the infectious pancreatic necrosis or viral hemorrhagic septicemia viruses of trout, but did show similarities to the Oregon sockeye and Sacramento River chinook viruses. Positive identification awaits further tests. The significance of these observations is the reporting of a new viral disease of rainbow trout and the extension of the geographic range of sockeye salmon viruses.

Transactions of the American Fisheries Society↗
USGS1981

Substrate conditions and abundance of lake trout eggs in a traditional spawning area in southeastern Lake Michigan

Spawning by planted lake trout (Salvelinus namaycush) was documented by sampling with a diver-assisted pump in a traditional spawning area in southeastern Lake Michigan near Saugatuck, Michigan in mid-November in 1978 and 1979. Bottom depths at the 11 locations sampled ranged from 3 to 12 m and substrate size from boulders to sand. Periphyton (Cladophora and associated biota) was several millimeters thick at most stations but sparse at the shallowest. The most eggs recovered from a single sample occurred at the shallowest depth (3 m). In both years, some of the small numbers of eggs collected (9 in 1978, 14 in 1979) were alive and fertilized. Laboratory incubation of viable eggs resulted in successful hatching of larvae. When compared with egg densities measured at spawning sites used by self-sustaining populations of lake trout in other lakes, densities in the study are (0-13/m 2 ) appeared to be critically low. Insufficient numbers of eggs, combined with harsh incubation conditions (turbulence, ice scour, sedimentation), were implicated as prime causes for lake trout reproductive failure in the study area, although other factors, such as inappropriate spawning behavior (selection of suboptimal spawning location, depth, or substrate) also may have reduced survival of eggs and larvae.

Lake Michigan↗
USGS1984

First evidence of successful natural reproduction by planted lake trout in Lake Huron

Twenty-two lake trout (Salvelinus namaycush) swim-up fry, 24-27 mm long, were captured with emergent fry traps and a tow net in northwestern Lake Huron on a small nearshore reef off Alpena, Michigan, between May 10 and June 1, 1982. These catches represent the first evidence of successful production of swim-up fry by planted, hatchery-reared lake trout in Lake Huron since the lake trout rehabilitation program began in 1973.

North American Journal of Fisheries Management↗
USGS1986

Evaluation of coded wire tags for marking lake trout

Among hatchery-reared lake trout ( Salvelinus namaycush ) of the 1979-1982 year classes stocked in New York waters of Lake Ontario, more than 3 million fish were marked with a coded wire tag (CWT) plus an adipose fin clip, and 1.5 million with only conventional fin clips. Altogether, 7,640 tags were recovered from fish collected with bottom trawls and gill nets or caught by anglers during 1980-1983. One person was able to extract and decipher 200 or more CWTs per day with about a 1% error rate in reading and recording codes. Presence of the CWT did not affect growth. The adipose fin clip did not regenerate. The occurrence of fish with an adipose fin clip but no CWT resulted primarily from the regeneration of paired fins among fish marked with a combination of the adipose fin and a paired fin. Loss of CWTs between marking and stocking (generally 4-5 months for fish stocked in spring and 1-8 d for fish stocked in fall) declined from nearly 11% for the 1979 year class stocked as fall fingerlings to less than 3% for the 1981 and 1982 year classes - a difference that primarily reflected improvements in instrumentation and tagging technique. The rate of CWT loss after the marked fish were stocked was probably less than 1% per year. The CWT is a reliable method for marking hatchery-reared lake trout. A large number of experimental groups can be uniquely marked, and fish from each group can be accurately identified throughout their life. Use of this technique should greatly facilitate evaluations of genetic strain, hatchery experience, condition at time of stocking, season of stocking, size at stocking, method of stocking and other factors that affect poststocking survival and performance of lake trout stocked in the Great Lakes.

North American Journal of Fisheries Management↗
USGS1991

Seasonal changes in microhabitat selection by rainbow trout in a small stream

Shifts in microhabitat selection by rainbow trout Oncorhynchus mykiss were related to seasonal and ontogenetic factors in a small stream characterized by short riffles, small pools, and boulder substrate. Resource availability did not differ significantly between summer and November sampling dates for most variables related to water velocity, substrate, and cover, although depths were greater and temperatures were significantly lower in November. Ontogenetic shifts were found for total depth, focal elevation, mean water column velocity, focal velocity, surface velocity, and substrate, but not for relative depth or temperature. When microhabitat selection was adjusted for fish size, selection was significantly different between seasons, most notably for velocity. Ontogenetic shifts in microhabitat use by young-of-year rainbow trout were interrupted by cooling winter temperatures. These changes resulted in substantially different microhabitat requirements for all rainbow trout size-classes in different seasons.

Transactions of the American Fisheries Society↗
USGS1993

Gamete ripening and hormonal correlates in three strains of lake trout

In our 2-year laboratory study of hatchery-reared adult lake trout Salvelinus namaycush of the Seneca Lake, Marquette (Lake Superior Lean), and Jenny Lake strains, we compared gamete ripening times and changes in plasma concentrations of seven hormones. If interstrain differences in these traits were found, such differences might help explain the apparent failure of stocked fish of these strains to develop large, naturally reproducing populations in the Great Lakes. The complex temporal changes in plasma hormone levels that occur during sexual maturation in lake trout have not been previously described. We detected little evidence of temporal isolation that would prevent interbreeding among the three strains. Strain had no effect on ovulation date (OD) in either year. Strain did not affect spermiation onset date (SOD) in year 1 but did in year 2, when the mean SOD of Jenny Lake males was earlier than that of Seneca Lake males but not different from that of Marquette males. Hormonal data were normalized around ODs for individual females and SODs for individual males. In females, estradiol-17β (E2) was highest 8 weeks before the OD; the highest testosterone (T) level occurred 6 weeks before the OD, and the next highest level occurred simultaneously with the highest level of 11-ketotestosterone (11-KT) 2 weeks before the OD. Plasma levels of 17∝-hydroxy-20β-dihydroprogesterone (DHP) peaked 1 week before the OD, then abruptly declined immediately after. Cortisol (F), triiodothyronine (T 3 ), and thyroxine (T 4 ) were highly variable, but F was the only hormone that showed no trend with week in either year. In males, plasma E2 levels were highest 3 weeks before the SOD, highest levels of T and of 11-KT occurred simultaneously 2 weeks after the SOD, and DHP peaked 5 weeks after the SOD and 3 weeks after the highest levels of T and 11-KT. As in females, plasma levels of F, T 3 , and T 4 were highly variable, and F was the only hormone that showed no trend with week in either year. Strain had no effect on any hormones in females and only on T and F in males. The lack of pronounced interstrain differences in gamete ripening dates and reproductive endocrinology and the similarity of the temporal patterns and relative concentrations of hormones to those reported for other salmonids suggest nothing unusual or dysfunctional about these reproductive traits that would impede lake trout rehabilitation in the Great Lakes.

Transactions of the American Fisheries Society↗
USGS1996

Comparison of three nonlinear models to describe long-term tag shedding by lake trout

We estimated long-term tag-shedding rates for lake trout Salvelinus namaycush using two existing models and a model we developed to account for the observed permanence of some tags. Because tag design changed over the course of the study, we examined tag-shedding rates for three types of numbered anchor tags (Floy tags FD-67, FD-67C, and FD-68BC) and an unprinted anchor tag (FD-67F). Lake trout from the Gull Island Shoal region, Lake Superior, were double-tagged, and subsequent recaptures were monitored in annual surveys conducted from 1974 to 1992. We modeled tag-shedding rates, using time at liberty and probabilities of tag shedding estimated from fish released in 1974 and 1978–1983 and later recaptured. Long-term shedding of numbered anchor tags in lake trout was best described by a nonlinear model with two parameters: an instantaneous tag-shedding rate and a constant representing the proportion of tags that were never shed. Although our estimates of annual shedding rates varied with tag type (0.300 for FD-67, 0.441 for FD-67C, and 0.656 for FD-68BC), differences were not significant. About 36% of tags remained permanently affixed to the fish. Of the numbered tags that were shed (about 64%), two mechanisms contributed to tag loss: disintegration and dislodgment. Tags from about 11% of recaptured fish had disintegrated, but most tags were dislodged. Unprinted tags were shed at a significant but low rate immediately after release, but the long-term, annual shedding rate of these tags was only 0.013. Compared with unprinted tags, numbered tags dislodged at higher annual rates; we hypothesized that this was due to the greater frictional drag associated with the larger cross-sectional area of numbered tags.

Transactions of the American Fisheries Society↗
USGS2000

Effects of fall-to-winter changes in habitat and frazil ice on the movements and habitat use of juvenile rainbow trout in a Wyoming tailwater

Overwinter declines in the abundance of small rainbow trout Oncorhynchus mykiss have been observed in a section of the Big Horn River that lies downstream from Boysen Reservoir, where reservoir releases prevent surface ice formation. To provide insight into the possible causes of these declines in abundance, radiotelemetry was used to determine movement and microhabitat use of juvenile (20–25 cm total length) rainbow trout during the fall and winter of 1995–1996. Throughout the fall and winter, both stocked (hatchery) and naturally spawned (wild) fish were generally found in main-channel pools with cover that reduced current velocities to less than 2 cm/s near the bottom and with nearby (<2 m) water velocities that were greater than 15 cm/s. These locations provided refuges from the current, with adjacent flowing water that could deliver drifting aquatic invertebrates. The fish were generally associated with cover that was formed by aquatic vegetation early in the fall, but they shifted to cobble and boulder cover (in deeper water) as the aquatic vegetation decomposed and as winter progressed. Episodes of frazil ice in January and early February were associated with movements of wild fish in the upstream portion of the study area—from normal activity areas to refuges at the bottom of deep pools or under shelf ice in shallow water near shore. Frazil-ice episodes often initiated long-term movements among fish. Our results suggest that changing habitat features from fall to winter and frazil-ice episodes can cause juvenile rainbow trout to move and to modify their habitat use, depending on their location in a tailwater.

Wyoming↗
USGS2000

Acute toxicity of fire-control chemicals, nitrogenous chemicals, and surfactants to rainbow trout

Laboratory studies were conducted to determine the acute toxicity of three ammonia-based fire retardants (Fire-Trol LCA-F, Fire-Trol LCM-R, and Phos-Chek 259F), five surfactant-based fire-suppressant foams (FireFoam 103B, FireFoam 104, Fire Quench, ForExpan S, and Pyrocap B-136), three nitrogenous chemicals (ammonia, nitrate, and nitrite), and two anionic surfactants (linear alkylbenzene sulfonate [LAS] and sodium dodecyl sulfate [SDS]) to juvenile rainbow trout Oncorhynchus mykiss in soft water. The descending rank order of toxicity (96-h concentration lethal to 50% of test organisms [96-h LC50]) for the fire retardants was as follows: Phos-Chek 259F (168 mg/L) > Fire-Trol LCA-F (942 mg/L) = Fire-Trol LCM-R (1,141 mg/L). The descending rank order of toxicity for the foams was as follows: FireFoam 103B (12.2 mg/L) = FireFoam 104 (13.0 mg/L) > ForExpan S (21.8 mg/L) > Fire Quench (39.0 mg/L) > Pyrocap B-136 [156 mg/L). Except for Pyrocap B-136, the foams were more toxic than the fire retardants. Un-ionized ammonia (NH3; 0.125 mg/L as N) was about six times more toxic than nitrite (0.79 mg/L NO2-N) and about 13,300 times more toxic than nitrate (1,658 mg/L NO3-N). Linear alkylbenzene sulfonate (5.0 mg/L) was about five times more toxic than SDS (24.9 mg/L). Estimated total ammonia and NH3 concentrations at the 96-h LC50s of the fire retardants indicated that ammonia was the primary toxic component in these formulations. Based on estimated anionic surfactant concentrations at the 96-h LC50s of the foams and reference surfactants, LAS was intermediate in toxicity and SDS was less toxic to rainbow trout when compared with the foams. Comparisons of recommended application concentrations to the test results indicate that accidental inputs of these chemicals into streams require substantial dilutions (100-1,750-fold to reach concentrations nonlethal to rainbow trout.

Transactions of the American Fisheries Society↗
USGS2003

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

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

Transactions of the American Fisheries Society↗