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At least 1,261 records · Page 70Linked to original sources
USGS1961

Modification of the microhematocrit technique with trout blood

Commercial and laboratory‐prepared capillary tubes for hematocrit were tested. A 10 percent solution of heparin was found to be best for the preparation of treated capillary tubes. For examination of trout blood laboratory‐prepared capillary tubes were found to be superior to commercial tubes which are designed for human blood. Sharp, pointed heparinized capillary tubes were used with good results for collecting blood from the heart without killing the examined fish. Hematocrits determined directly in such tubes were found to have the same value as those prepared in other ways.

Transactions of the American Fisheries Society↗
USGS1963

The embronic and larval development of the rainbow trout

Photographs of the developing rainbow trout, Salmo gairdneri Richardson, are presented in sequence from the initial cleavage through hatching. Approximately 3,000 eggs were incubated in standard hatchery troughs supplied with spring water at a constant temperature of 54° F. Accepted fish cultural methods were followed to insure normal developmental patterns. Samples of these eggs were taken for study at 1‐hour intervals from the 5th to the 24th hour after fertilization; then once every 6 hours until they were 72 hours old; then at 1‐day intervals through the peak of hatching on the 23rd day. The embryos were fixed in 5 percent neutral formalin containing 0.95 percent sodium chloride, stained in Harrisˈ hematoxylin, and photographed with a vertically mounted camera.

Transactions of the American Fisheries Society↗
USGS1969

Some factors influencing susceptibility of rainbow trout to the acute toxicity of an ethyl mercury phosphate formulation (Timsan)

This study determined the influence of water temperature (55–68° F), dissolved oxygen (4–12 ppm), water hardness as CaCO 3 (20–256 ppm), and chloride ions (to 2 mM) on the susceptibility of rainbow trout ( Salmo gairdneri ) to the acute toxicity of ethyl mercury phosphate (EMP). The fish were exposed for one hour to 0.125 ppm EMP, the active ingredient of Timsan, a commercial EMP formulation. The death rate because of the exposure to EMP increased with an increase in water temperature, a decrease in dissolved oxygen, and an increase in chloride ions; calcium appeared to have no effect. The effect of water temperature and dissolved oxygen was ascribed to changes in the respiration rate of the fish, and a chemical explanation is presented for the effect of chloride ions.

Transactions of the American Fisheries Society↗
USGS1974

Comparative toxicity of two Iodophors to rainbow trout eggs

Toxicity of Wescodyne (R) and Betadine (R) to eyed eggs was not adversely affected by water hardness (as calcium and magnesium) or by exposure periods up to 60 min. Both iodophors were much more toxic below pH 6.0 than at pH 8.0. In general Wescodyne was slightly more toxic than Betadine. Significant egg loss occurred if freshly fertilized eggs were water-hardened in either iodophor at 100 ppm of iodine, but egg loss at 25 ppm of iodine or at 100 ppm if the eggs were disinfected 30 min after water hardening was comparable to the control. Also, there was no effect on the egg mortality or fry development following single or multiple exposures after eggs were water hardened. At pH 6.0 and above, Wescodyne and Betadine at 100 ppm iodine in a 15-min dip would be safe to use on rainbow trout eggs at any stage of development after water hardening. Recommendations and precautions for hatchery use are given.

Transactions of the American Fisheries Society↗
USGS1976

Effects of inbreeding on rainbow trout populations

An approach for measuring inbreeding depression on the basis of differences between inbred and outbred half‐sib family groups is described. Using this method, estimates of inbreeding depression in populations of rainbow trout (Salmo gairdneri) following one generation of brother‐sister mating was calculated for three production traits–percent egg hatchability, percent fry survival from swim‐up to 150 days, and weight at 150 days. The inbreeding depression estimates obtained from male and female half‐sib families were 1.7 and 4.4% for percent egg hatchability, 22.2 and 16.1% for percent fry survival, and 12.0 and 9.8% for weight at 150 days, respectively. Estimates for fry survival and weight at 150 days were significant at P < 0.01 while egg hatchability estimates were nonsignificant. Following one generation of full‐sib mating, the calculated effect of inbreeding on the number of live fish and total weight of fish at 150 days of age showed a reduction of 16.1 and 24.4% in female families and 22.1 and 31.4% in male families, respectively. The difference between inbreeding depression estimates derived from male and female half‐sib groups provide a measure of the maternal influence. Generalized trends of increasing depression with increasing levels of inbreeding from F = 0.125 to F = 0.50 were significant for weight at all ages from 77 to 150 days, but were nonsignificant for percent hatchability or percent fry survival. Inbreeding depression estimates for weight are considered to be minimum estimates because higher mortality rates in the inbred families resulted in lower fish density during the rearing period and, therefore, compensatory growth which reduced the weight difference between inbred and outbred families.

Transactions of the American Fisheries Society↗
USGS1977

Three generations of selection for growth rate in fall-spawning rainbow trout

A selection program to improve the growth rate of rainbow trout (Salmo gairdneri) was begun in 1967 with random samples of fall‐spawning fish from the Manchester and Wytheville National Fish Hatcheries. All matings were made as one male to one female, and selection was based on family mean fish weight of the progeny at 147 days post‐fertilization. The selected families in each year class were mated in all combinations at 2 years of age (age II) and 3 years of age (age III). Selection was applied only to the age II progeny. A control group was established in 1971 from the base population and carried through the remaining portion of the study. All families were reared under standardized rearing conditions. During the three cycles of selection studied, mean 147‐day weight of progeny from age II parents increased from 2.02 g in the first generation to 5.28 g in the fourth generation, a gain of 161%. Of the 3.26‐g total gain during the study, net genetic gain in weight from selection was 0.98 g or 30.1%. The rest of the gain (69.9%) resulted from improved rearing conditions. Gains in percentage hatch and percentage fry survival to 147 days were not significant. Differences in the performance of progeny from the age III parents, as compared to that of progeny of age II parents from 1970 to 1974 showed an advantage for the age III parents in all three traits; 6.4% for percentage hatch, 25.0% for percent fry survival, and 22.3% for 147‐day weight.

Transactions of the American Fisheries Society↗
USGS1977

Rotational line crossing: An approach to the reduction of inbreeding accumulation in trout brood stocks

A system is presented for maintaining trout brood stocks for long periods with levels of inbreeding accumulation lower than that experienced in random mating populations of equal size. The system requires the formation of three or more distinct breeding lines. Brood stock generations are advanced by a systematic mating scheme in which females of each line are mated to males of a different line. Eggs for hatchery production may be obtained from matings either within a single line or between lines. An opportunity for improving the breeding population is provided through selection of individual fish to be used in the production of the next brood stock generation. The requirement for increased handling of brood stock is not considered to be serious.

Progressive Fish-Culturist↗
USGS1979

Histochemistry of leucine aminoaphthylamidase (LAN) in rainbow trout (Salmo gairdneri)

The histochemistry of leucine aminonaphthylamidase (LAN) was studied in frozen tissue sections of rainbow trout both in yearling and adult fish. Age of fish had relatively little effect upon the results. The most intense LAN color production was in epithelial cells of midgut, pyloric ceca, hindgut, and in some segments of kidney tubules. Lower levels of LAN were evident in liver cells of Kupffer, and still lower or slight levels of LAN activity were found in blood cells, muscle, nerve, connective tissue, gonad, and pancreas. The results indicate that LAN might be useful in assessing histotoxicity to LAN‐rich areas of the body.

Transactions of the American Fisheries Society↗
USGS1981

Riboflavin requirement of fingerling rainbow trout

Fingerling rainbow trout (Salmo gairdneri) were fed purified diets containing graded levels (0, 3, 6, 12, 18, 24, and 54 mg/kg) of supplemental riboflavin for 20 weeks. The cellular riboflavin supply of the fingerlings was estimated on the basis of the activity of the FAD‐dependent enzyme, erythrocyte glutathione reductase (EGR). The dietary riboflavin level that produced the fastest growth, an efficient feed: gain ratio, and normal values for the EGR activity coefficient was about 3 mg of supplemental riboflavin per kilogram of diet.

Progressive Fish-Culturist↗
USGS1981

Dairy-processing wastes as a replacement protein source in diets of rainbow trout

Dairy‐processing wastes, not previously used in domestic animal and fish feeds, were evaluated as a replacement protein source in the diet of rainbow trout (Salmo gairdneri). Dairy residue replaced 10% dried whey without reducing growth or feed efficiency, and feed costs were reduced. Growth and feeding efficiency were somewhat reduced when dairy‐processing wastes in the diet were 15 or 20%.

Progressive Fish-Culturist↗
USGS1982

Comparative hatching success of lake trout eggs in Lake Michigan water and well water

A study was undertaken to examine the influence of water from southern Lake Michigan on the survival of lake trout (Salvelinus namaycush) eggs by comparing the hatching success of eggs from the same source incubated in water from Lake Michigan, or from the laboratory well. It is concluded that the observed differences in hatching are probably attributable to chemical constituents of water from the lake (eg, chlorinated hydrocarbons, metals and other industrial and agricultural chemicals).

Progressive Fish-Culturist↗
USGS1986

Infectious pancreatic necrosis virus: Protocol for a standard challenge to brook trout

A protocol for experimental challenge with infectious pancreatic necrosis (IPN) virus was defined with brook trout Salvelinus fontinalis as the model species. Fish were exposed by immersion for 5 h in water containing IPN virus at a concentration of 10 5 plaque‐forming units per milliliter. We propose the protocol as a standard challenge based on our studies of exposure methods and host response to virulent virus. Immersion challenge induced higher and more consistent mortality than did challenge by hyperosmotic infiltration. Challenge virus should be sequentially transferred no more than five times in cell culture because further transfers reduced the virulence of the virus. At 12°C, mortalities due to primary infection occurred 6–12 d after immersion challenge and were highest (≥70%) in fish 27–56 d old. Susceptibility to lethal infection was enhanced by nutritional stress.

Transactions of the American Fisheries Society↗
USGS1987

Comparative efficacy of 16 anesthetic chemicals on rainbow trout

Presently there are no legally registered fish anesthetics that allow for the release of fish or use of the fish for food soon after they have been anesthetized. MS-222 (tricaine), the only anesthetic registered for use on fish in the United States, cannot be used within 21 d of harvesting the fish for food. As the start in a search for an anesthetic that can be used with little or no withdrawal period, we tested the efficacy of 16 chemicals as anesthetics on rainbow trout Salmo gairdneri. Efficacy was defined by the fish (1) becoming handleable (quiet enough to be manipulated and handled readily) in 3 min or less, (2) recovering in 10 min or less, and (3) showing no mortality after 15 min in the anesthetic solution. Four chemicals--MS-222, quinaldine sulfate, benzocaine, and 2-phenoxyethanol--met these criteria for efficacy. Chemicals that yielded excessive induction or recovery times or caused excessive mortality were methylpentynol, chlorobutanol, etomidate, metomidate, Piscaine, propanidid, carbon dioxide, nicotine, salt, Halothane, Metofane, and Biotal. Because carbon dioxide leaves no residues and requires no withdrawal period, it may be an acceptable alternative for fishery workers who can tolerate somewhat shallower anesthesia and longer induction and recovery times.

North American Journal of Fisheries Management↗
USGS1991

Variation in feeding, aggression, and position choice between hatchery and wild cutthroat trout in an artificial stream

I compared feeding, aggressive behavior, and spatial distribution of differently ranked individuals of hatchery and wild coastal cutthroat trout Oncorhynchus clarki clarki in an artificial stream. Both hatchery and wild groups established stable dominance hierarchies that seemed to be based on size differences. Hatchery and wild fish within a hierarchical rank fed at similar rates. Hatchery fish were more aggressive than their wild conspecifics, irrespective of rank. Dominant hatchery fish were evenly distributed in pools and riffles, whereas dominant wild fish were three times more often in pools than in riffles. In both groups, socially intermediate fish were almost evenly distributed between pools and riffles, and subordinate fish spent most of their time in pools. On average, hatchery fish spent 57% of their time in pools and 43% in riffles, whereas wild fish spent 71% of their time in pools and 29% in riffles. These results support the hypothesis that excessive expenditure of energy for unnecessary aggression, use of fast-flowing water, or other purposes contributes to poor survival of hatchery fish after they are stocked in streams. Poor survival would reduce the efficacy of using hatchery stocks to supplement wild production.

Transactions of the American Fisheries Society↗
USGS1992

Performance of nine external tags on hatchery-reared rainbow trout

We evaluated nine commercially available tags to determine their suitability for marking yearling rainbow trout Oncorhynchus mykiss reared in raceways and circular tanks. The tags tested were Floy vinyl tubing tags FD‐67 anchor, FT‐2 dart, FT‐4 cinch‐up, and FT‐4 lock‐on; modified Carlin; modified Petersen disk; Monel strap 4‐1005; Monel butt end 4‐1242; and Stoffel fish seal. After 9 months, tag losses from raceway fish were lowest (8%) for the FT‐4 lock‐on tag; in tanks, none of the FT‐2 dart, FT‐4 cinch‐up, FT‐4 lock‐on, or the Monel butt end tags were lost. At 90 d after tagging, raceway fish marked with the Monel strap or the modified Carlin tags showed significantly less growth than did fish marked with the FD‐67 anchor tag; the converse was true for fish in tanks. After 9 months, raceway fish marked with the Monel butt end tag and tank fish marked with the FD‐67 anchor tag were least injured. Injury was greater in raceways than in tanks for all tag types. Judged by overall performance, the FD‐67 anchor was the most effective tag for fish maintained in raceways and the FT‐4 cinch‐up was a suitable alternative; the FT‐2 dart, FT‐4 cinch‐up, and Monel butt end tags were equally suitable for fish in tank culture.

Transactions of the American Fisheries Society↗
USGS1999

Dietary effects of metals-contaminated invertebrates from the Coeur d'Alene River, Idaho, on cutthroat trout

Benthic macroinvertebrates with elevated concentrations of metals were collected from the Coeur d'Alene (CDA) River, Idaho, pasteurized, and fed to cutthroat trout Oncorhynchus clarki in the laboratory from start of feeding until 90 d posthatch. Invertebrates were collected from two sites known to contain elevated concentrations of metals: near Pinehurst in the South Fork of the CDA River and at Cataldo, approximately 5 km below the confluence of the South Fork and the North Fork. Invertebrates collected from a relatively clean site in the North Fork were used as a reference diet. We performed measurements of fish health that indicate reduced fitness of fish fed the South Fork and Cataldo diets. Effects measured were reduced feeding activity, increased number of macrophage aggregates and hyperplasia of cells in the kidney, degeneration of mucosal epithelium in the pyloric caecae, and metallothionein induction. These effects would likely reduce growth and survival of fish in the wild. Vacuolization of glial cells were also observed in fish fed the Cataldo diet. Metals in the water often exacerbated the histological effects observed. Although the invertebrates collected near Cataldo had lower concentrations of arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) than the invertebrates from the South Fork, fish fed the Cataldo diet had equally high or higher concentrations of all metals except as by day 44. The Cataldo diet also caused the most deleterious effects on survival and growth. These findings are especially important for early life stage fish, whose diet consists wholly of benthic macroinvertebrates. Therefore, fish feeding on invertebrates in the CDA River below the Bunker Hill smelting complex are at risk of reduced fitness.

Transactions of the American Fisheries Society↗
USGS1989

Suppression of antibody-producing cells in rainbow trout spleen sections exposed to copper in vitro

Immunosuppression was demonstrated in sections of rainbow trout Oncorhynchus mykiss (formerly Salmo gairdneri ) spleens immunized in vitro and exposed in culture to different concentrations of copper chloride. The sections were immunized with dinitrophenyl-Ficoll and cultured in Eagle's minimum essential medium with 2% fetal calf serum; half of the medium was withdrawn and replaced every other day. The passive hemolytic plaque assay was used to determine the number of antibody-producing cells 10 d after injection. In the sections cultured with the high copper concentration (100 μg/mL), all cells died; at copper concentrations of 0.1–10 μg/mL, leukocytes remained viable, but fewer antibody-producing cells were present than in organ sections cultured in medium without copper. This in vitro method reduces the number of animals needed and the length of time required to determine toxicity and immunosuppression, and it provides information on the effects of certain environmental pollutants on fish.

Journal of Aquatic Animal Health↗
USGS1990

Multiplication of infectious hematopoietic necrosis virus in rainbow trout following immersion infection: whole-body assay and immunohistochemistry

The sites of replication of infectious hematopoietic necrosis virus (IHNV) in infected tissues were detected in fingerling rainbow trout Oncorhynchus mykiss by in situ histologic techniques following immersion infection. Virus antigens in tissues were detected by a neutralizing mouse monoclonal antibody and a one-step anti-mouse biotin-streptavidin conjugated to horseradish peroxidase. The efficiency of infection and virulence of the virus determined by mortality rates showed high virulence of the selected IHNV isolates, and viral replication in individual fish showed that virus content of the fish increased rapidly from the second day to the seventh day postinfection. The earliest viral lesions following infection were detected in the epidermis of the pectoral fins, opercula, and ventral surface of the body. Virus lesions became evident in kidneys on the third day. By the fifth day, when there was a significant increase in virus titer, foci of viral replication were detected in gill tissue and in the anterior internal tissues below the epidermis. Subsequently, extensive virus replication and tissue destruction were observed in the spleen, dorsal adipose tissues, ventricle, and pseudobranch. Replication in the liver, the muscularis layers of the digestive tract, and the general body musculature followed later. These infection experiments indicated that the epidermis and gills of fish constitute important sites of early IHNV replication.

Journal of Aquatic Animal Health↗