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At least 1,243 records · Page 69Linked to original sources
USGS1991

Hatching, growth, ion accumulation, and skeletal ossification of brook trout (Salvelinus fontinalis) alevins in acidic soft waters

Brook trout eyed eggs and subsequent alevins were exposed to pH 5.0, 6.5, and 7.0 in soft reconstituted water and to pH 8.2 in hard well water for up to 72 d. Hatching was delayed and hatching success reduced (p < 0.05) in eyed eggs exposed to pH 5.0 and 6.5. Alevin growth was not affected. Fish in all treatments rapidly accumulated monovalent ions in a similar pattern and in the order of Na+ > K+ > Cl- during yolk absorption and early exogenous feeding. Whole-body monovalent ion concentrations were reduced for short periods during yolk absorption in alevins exposed to pH 6.5 and throughout most of the experiment for those exposed to pH 5.0. Whole-body Mg2+ concentrations were not affected by treatment pH and remained near their median hatch level throughout the exposure. The whole-body concentration of Ca2+ was reduced in fish exposed to pH 5.0, particularly near the end of the experiment. Calcium accumulation in fish was influenced by the interaction of pH and time at pH 5.0 but not at the other pH levels. Alevins exposed to pH 5.0 experienced delayed ossification of skeletal structures associated with feeding, respiration, and locomotion that usually persisted for up to 10 d. The detection of skeletal abnormalities early in life might aid in identifying fish populations at risk in acidified waters.

Canadian Journal of Zoology↗
USGS2007

Population response to habitat fragmentation in a stream-dwelling brook trout population

Fragmentation can strongly influence population persistence and expression of life-history strategies in spatially-structured populations. In this study, we directly estimated size-specific dispersal, growth, and survival of stream-dwelling brook trout in a stream network with connected and naturally-isolated tributaries. We used multiple-generation, individual-based data to develop and parameterize a size-class and location-based population projection model, allowing us to test effects of fragmentation on population dynamics at local (i.e., subpopulation) and system-wide (i.e., metapopulation) scales, and to identify demographic rates which influence the persistence of isolated and fragmented populations. In the naturally-isolated tributary, persistence was associated with higher early juvenile survival (-45% greater), shorter generation time (one-half) and strong selection against large body size compared to the open system, resulting in a stage-distribution skewed towards younger, smaller fish. Simulating barriers to upstream migration into two currently-connected tribuory populations caused rapid (2-6 generations) local extinction. These local extinctions in turn increased the likelihood of system-wide extinction, as tributaries could no longer function as population sources. Extinction could be prevented in the open system if sufficient immigrants from downstream areas were available, but the influx of individuals necessary to counteract fragmentation effects was high (7-46% of the total population annually). In the absence of sufficient immigration, a demographic change (higher early survival characteristic of the isolated tributary) was also sufficient to rescue the population from fragmentation, suggesting that the observed differences in size distributions between the naturally-isolated and open system may reflect an evolutionary response to isolation. Combined with strong genetic divergence between the isolated tributary and open system, these results suggest that local adaptation can 'rescue' isolated populations, particularly in one-dimensional stream networks where both natural and anthropegenically-mediated isolation is common. However, whether rescue will occur before extinction depends critically on the race between adaptation and reduced survival in response to fragmentation.

PLoS ONE↗
USGS2018

Variation in angler distribution and catch rates of stocked rainbow trout in a small reservoir

We investigated the spatial and temporal relationship of catch rates and angler party location for two days following a publicly announced put-and-take stocking of rainbow trout ( Oncorhynchus mykiss ). Catch rates declined with time since stocking and distance from stocking. We hypothesized that opportunity for high catch rates would cause anglers to fish near the stocking location and disperse with time, however distance between angler parties and stocking was highly variable at any given time. Spatially explicit differences in catch rates can affect fishing quality. Further research could investigate the variation between angler distribution and fish distribution within a waterbody.

PLoS ONE↗
USGS1967

Comparison of three methods of sampling trout blood for measurements of hematocrit

Trout blood is frequently collected for hematocrit measurements by excising the caudal fin (Snieszko, 1960), but this technique is impractical if valuable fish are to be sampled or if repeated observations are desired. Schiffman (1959) and Snieszko (1960) collected blood from the dorsal aorta and the heart, but these methods are relatively slow and require the preparation of needles and syringes. The use of pointed capillary tubes for cardiac punctures increases the speed of sampling, but body fluids may dilute the blood (Perkins, 1957; Larsen and Snieszko, 1961; and Normandau, 1962). There is need for methods of sampling which are rapid and which neither influence hematological determinations nor harm the fish.

Progressive Fish-Culturist↗
USGS1970

An obscure disease of rainbow trout

An annul mortality among Rainbow Trout (Salmo gairdneri) has plagued the Shelton Hatchery of the Washington State Department of Game for the last several years. No infectious agent could be isolated from the moribund fish, but histopathologica1 changes in the liver of 1-month-old fish suggested the presence of a toxic substance. Scoliosis in 3-month-old fish suggested a possible deficiency in vitamin C. With this background in mind, we designed studies to determine the nature and source of possible toxicants and the role of vitamin C deficiency in the etiology of this disease.

Progressive Fish-Culturist↗
USGS1984

Determining fat digestibility in trout using a metabolic chamber

Fat digestibilities were determined in rainbow trout utilizing a metabolism chamber. Separate and quantitative fecal extracts were freeze dried and total lipids were extracted. Lipid digestibilities were comparable to those obtained by other methods (85‐91%). This method avoids problems due to leaching and the variable of accelerated passage through the gut encountered in other methods.

Progressive Fish-Culturist↗
USGS1990

Performance of rainbow trout fry fed supplemental soy lecithin and choline

Three feeding experiments were conducted with early‐feeding fry of rainbow trout ( Oncorhynchus mykiss ; initial mean weight, 0.10–0.12 g) to determine their need for lecithin contained in soy lecithin (SL), with and without supplemental choline. The source of assay protein was an isoelectric form (RP 100) of isolated soy protein (ISP) in experiment 1, a sodium protein ISP (RP 101) in experiment 2, and an ether‐extracted herring meal in expenment 3. Duration of the feeding trials was 20 weeks for experiment 1 and 16 weeks for experiments 2 and 3. Analysis of variance showed that supplemental SL and choline each increased body weight gain, survival, and body fat, and improved feed conversion (amount fed/weight gain). The extent of beneficial effects varied with type of diet fed. Fish fed either of the ISPs needed at least 4% supplemental SL, either with or without 0.3% choline, for highest survival, but survival of all fish fed extracted herring meal was high. Although choline alone enhanced growth, at least 4% SL, either with or without choline, was necessary for maximum growth.

Progressive Fish-Culturist↗
USGS1991

Choline requirement of swim-up rainbow trout fry

Triplicate 150‐fish lots of first‐feeding fry of rainbow trout ( Oncorhynchus mykiss ; initial mean weight, 0. 12 g) were fed casein–gelatin‐based diets containing 0, 200, 400, 800, 1,000, 2,000, 4,000, or 8,000 mg choline/kg of feed for 12 weeks to determine their need for dietary choline. Although the growth rates of fry were suboptimal, results showed that fry needed no more than 4,000 mg choline/kg casein–gelatin diet for maximum growth and 2,000 mg/kg for maximum body fat and minimum protein. Survival was significantly lower for fish fed 800 mg choline/kg of diet than for those fed greater amounts of the nutrient. These results suggest that the dietary choline requirement of early feeding salmonids is greater than that previously reported for older salmonids. The amount of choline needed by fishes apparently decreases with age or size.

Progressive Fish-Culturist↗
USGS1993

Eye abnormalities of lake trout exposed to gas supersaturation

Lake trout ( Salvelinus namaycush ) reared for 1 year at six levels of differential (excess) gas pressure (▵P 4, 17, 33, 43, 58, and 75 mm Hg above equilibrium) were examined for incidences of eye abnormalities including nuclear cataracts, hemorrhages, corneal swelling, cloudiness, rupture, and loss of eyes. Frequencies of nuclear cataracts, eye hemorrhages, cloudy corneas, and bilateral anomalies were not directly related to increasing dissolved gas pressures. However, incidences of corneal swelling and of all abnormalities combined increased with gas supersaturation above ▵P 4.

Progressive Fish-Culturist↗
USGS1994

Evaluation of the effects of an oxygen injection system on the growth, hematology, and immunity of lake trout

Fingerling lake trout ( Salvelinus namaycush ) were reared for 64 d at three pressures of dissolved gases, expressed in relation to saturation values (▵P)–untreated (control) water, ▵P = 10 mm Hg; water treated by column degassing with air, ▵P = 9 mm Hg; and water treated with an oxygen injection system, ▵P = −20 mm Hg. Dissolved oxygen concentration for experimental groups was increased with column degassing by 7.8% and with oxygen injection by 8.7%. Nitrogen level was reduced 2.2% with columns receiving air and 7.4% with the oxygen injection system. There were no differences in production, mean lengths, or mean weights among fish reared in the three treatments. Hematocrit, plasma protein levels, and mean antibody microtiters to injected Salmonella H antigen were not different among fish from the three water treatments.

Progressive Fish-Culturist↗
USGS1994

Duration of protection against Aeromonas salmonicida brook trout immunostimulated with glucan or chitosan by injection or immersion

Brook trout ( Salvelinus fontinalis ) were given the immunostimulants glucan or chitosan by single injections or by a 30‐min immersion to induce protection against the fish disease furunculosis. At 1, 2, 3, 7, 14, 21, and 28 d after immunostimulation, sublots from these groups were challenged by a 1‐min bath exposure to a 48‐h culture of Aeromonas salmonicida . All four groups showed high levels of protection against challenges given 1, 2, and 3 d after immunostimulants were administered. The groups injected with the immunostimulants showed a higher degree of protection than the immersed fish. They also retained a higher degree of protection against the pathogen challenge. However, by 14 d after immunostimulation, protection in both groups was greatly reduced. No significant differences in protection levels were noted between the glucan and chitosan immunostimulants. The effective short‐term protection induced by these immunostimulants demonstrates the importance of nonspecific defenses in fish and how, under certain conditions, these immunostimulants could be used for the prevention of diseases in fish culture.

Progressive Fish-Culturist↗
USGS1933

The chemical disinfection of trout ponds

The need for knowledge concerning the prevention and control of fish diseases has never been greater than it is in this present era of economy when two fish must be raised in the same water which once supported but one. Fish pathologists have contributed a great deal to our knowledge of fish diseases, but there is still much to be learned, particularly concerning better methods of preventing and eliminating diseases among our trout. In this era of circular pools and raceways, our disease elimination is way back in the early days of standard troughs.

Transactions of the American Fisheries Society↗
USGS1940

A new fungus disease of trout

A new species of fungus, for which time name Saprolegnia invaderis is proposed, was found in fingerling trout at the Leetown (West Virginia) hatchery. Infection occurs through the alimentary tract from which the fungus grows out through the body cavity and the abdominal wall to the exterior, where zoospores and chlamydospores are formed. Growth of the hyphae through the abdominal wall occurs only after the death of the host. A short technical description of the parasite is included.

West Virginia↗
USGS1948

The value of certain drugs, especially sulfa drugs, in the treatment of furunculosis in brook trout, Salvelinus fontinalis

Furunculosis of salmonoid fishes is a dread epizootic disease caused by a general infection by Bacterium salmonicida. In this experiment, treatment was tried with sulfonamides and another drug, “furacin” or “2–20–99” (new drug). The four treatments first used were: (1) sulfamerazine, (2) sulfathiazole, and (3) furacin, each administered by being mixed with the food; and (4) furacin added to the water of the troughs. For assignment of treatments, the troughs containing fingerling brook trout, approximately 8 months old and running 30 to the pound, were grouped in four blocks of five troughs–three blocks of fingerlings with furunculosis, and one block of fingerlings of similar age and size but free from this disease. In each block, one trough received no medication. The various treatments were assigned to troughs by random selection. The block of healthy fish was to test for possible serious ill effects from any of the treatments, and was located some distance from the infected fish. Treatments were begun August 30, 1945, and those involving sulfamerazine and sulfathiazole were continued through 25 days. The furacin treatments, less promising than the sulfonamide treatments, were replaced by sulfanilamide and sulfadiazine, each in the food, on the sixteenth day. Furacin in the water was not beneficial but furacin in the food had some helpful effect. Results with sulfanilamide and sulfadiazine were not encouraging. Sulfathiazole seems to have been more beneficial than furacin, but decidedly less effective than sulfamerazine. The improvement with sulfamerazine was impressive. Mortality dropped rapidly within a few days, generally was light after a week, and within 2 weeks almost completely stopped. Through 25 days, the loss was 17 percent, as compared with 50 percent among the infected lots not receiving medication. The data indicate that 8 grams of sulfamerazine per day per 100 pounds of fish is sufficient, and that a considerably lower dose is at least beneficial. Until further information is available, 8 grams of sulfamerazine per day per 100 pounds of fish, to be continued for at least 6 days after mortality stops, is recommended.

Transactions of the American Fisheries Society↗
USGS1949

Dosage of sulfamerazine in the treatment of furunculosis in brook trout, Salvelinus fontinalis

To determine the most effective dosage of sulfamerazine in the treatment of furunculosis in brook trout, two experiments were run. In the first experiment, yearlings were used and the daily dosage rates were 4, 8, and 12 grams of sulfamerazine per 100 pounds of fish. In the lots treated with sulfamerazine, mortality was brought under control within 15 days and was less than a quarter as high as in the controls. Results with the 4‐gram rate were nearly as good as with the higher rates. Treatment was continued for 10 days or more after mortality dropped to zero, and recurrences were few. A large number of the dead were checked bacteriologically for furunculosis. In the second experiment fingerlings in an early stage of a furunculosis epizootic were used and the daily dosage rates were 2, 4 and 6 grams per 100 pounds of fish. Losses in the controls were extremely heavy, with only 6‐percent survival. Losses were heavy in all lots, but in those treated at the 4‐gram and 6‐gram rates, survival was 10 times as high as in the controls. Mortality declined sooner with the 6‐gram than with the 4‐gram rate, and recurrence was almost eliminated by treatment, at the higher rate, for 10 days after mortality dropped to zero. Discontinuance of treatment as late as 4 days after the discontinuance of mortality was followed by resumption of mortality at a considerable rate. In the treated lots, late dead were small thin fish which evidently had received little food and drug. Dead fish were “spot‐checked” for furunculosis. The recommended daily dosage rate is 6 grams per 100 pounds of fish, to be continued for 10 days after mortality stops and for a total of at least 3 weeks. Other recommendations include: the early elimination of undersized fish; the prompt removal of dead and dying fish; the maintenance of clean troughs and pools; and strict observation of all sanitary measures practiced in the control of infectious diseases.

Transactions of the American Fisheries Society↗
USGS1954

Sulfonamide toxicity in brook trout

Sterility was observed in female brook trout that were treated with sulfamerazine at frequent intervals for 2 years to control endemic furunculosis. Feeding sulfamerazine for a period of 8 months caused massive kidney damage similar to that observed in humans who develop allergies to &ldquo;sulfa&rdquo; drugs. Kidney damage of the type observed would probably cause renal insufficiency which would handicap any physiological function including reproduction. Feeding sulfonamides for periods up to 13 weeks did not produce kidney damage.

Transactions of the American Fisheries Society↗
USGS1956

Histopathology of fish. IV. A granuloma of brook trout

In the summer of 1952, Snieszko and Griffin (1955) diagnosed kidney disease in brook trout from the Fish and Wildlife Service's station at Berlin, New Hampshire. During the examination of these fish, a peculiar lesion was observed in the vicinity of the gastric caeca. In very advanced cases, hard, glistening, white masses of tissue bearing a striking resemblance to mature testes often filled the abdominal cavity. In the initial examinations, the material was actually mistaken for normal testicular tissue. Subsequently, it was recognized as an entirely aberrant, proliferating tumor-like mass.

Progressive Fish-Culturist↗
USGS1959

Test of 34 therapeutic agents for control of kidney disease in trout

Sixteen strains of fish kidney disease bacterium were tested in vitro to determine their reaction to 34 therapeutic agents. On the basis of the results obtained ten of the drugs were employed in experimental therapy of kidney disease in eastern brook trout (Salvelinus fontinalis). Erythromycin at the rate of 100 milligrams per kilogram of fish per day (4.5 grams per 100 pounds of fish) for 21 days gave the best results. Other drugs gave only temporary benefit if any.

Transactions of the American Fisheries Society↗