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Results for “Progressive Fish-Culturist”

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At least 199 records · Page 11Linked to original sources
USGS1980

Inhibition of nitrite-induced toxicity in channel catfish by calcium chloride and sodium chloride

Environmental chloride has been shown to inhibit methemoglobin formation in fish, thereby offering a protective effect against nitrite toxicity. Channel catfish (Ictalurus punctatus) were simultaneously exposed to various environmental nitrite and chloride levels (as either CaCl 2 or NaCl) in dechlorinated tap water (40 mg/L total hardness, 47 mg/L alkalinity, 4 mg/L chloride, pH = 6.9-7.1, and temperature 21-24°C). Methemoglobin levels in fish simultaneously exposed to 2.5 mg/L nitrite and up to 30 mg/L chloride as either CaCl 2 or NaCl were similar but significantly lower than in unprotected fish. Exposure to 10 mg/L nitrite and 60 mg/L chloride resulted in methemoglobin levels similar to those of the controls; most unprotected fish died. Fish exposed to 10 mg/L nitrite had significantly lower methemoglobin levels when protected with 15.0 mg/L chloride as CaCl 2 than with NaCl. Fish exposed to nitrite in the presence of 60 mg/L chloride (as either CaCl 2 or NaCl) had similar 24-h LC50 values that were significantly elevated above those obtained in the absence of chloride. Calcium had little effect on tolerance to nitrite toxicity in channel catfish in contrast to its large effect reported in steelhead trout (Salmo gairdneri).

Progressive Fish-Culturist↗
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↗
USGS1980

Development and survival of embryos of lake herring at different constant oxygen concentrations and temperatures

Eggs of lake herring (Coregonus artedii) were incubated in a continuous-flow system at four constant water temperatures (2-8&deg;C) and five dissolved oxygen (DO) concentrations (1-12 mg/L). In comparison with incubation time at 12 mg/L DO, time to median hatch was significantly longer (P<0.05) at 2 mg/L at 6&deg;C (no hatch at 1 mg/L), at 3 mg/L or less at 4&deg;C, and at 4 mg/L or less at 2&deg;C. The time between hatching of the first and last eggs varied inversely with temperature. Mean total lengths of newly hatched fry were significantly shortened (P < 0.05) at 1 and 2 mg/L DO. At 6 and 8&deg;C, percent survival through hatching was greater than at 2 and 4&deg;C at DO of 4 mg/L or more, but fell to zero at 1 mg/L. The percentage of normal fry produced decreased noticeably below 4 mg/L DO. The optimum temperature for highest percentage survival of normal fry decreased directly with the level of dissolved oxygen. The temperatures at which the highest percentages of normal fry hatched from eggs incubated at DO concentrations of 4 or 8, 2, and 1 mg/L, were 6, 4, and 2&deg;C, respectively-indicating a decreasing DO demand by embryos incubated at the lower temperatures. Our findings supported a previously published hypothesis that DO concentrations below 4 mg/L can be adverse to survival and development of coregonid embryos in nature.

Progressive Fish-Culturist↗
USGS1981

Depletion sampling in stream ecosystems: assumptions and techniques

Reliable fish and invertebrate population estimates depend on meeting the assumptions of the methods used for organism capture and data analysis. A review of several population estimation studies has indicated that assumptions of the removal method for population estimation are often violated. This paper outlines (1) procedures to assist in meeting the removal method assumptions (2) an economical procedure to obtain reliable invertebrate population estimates by the removal method and (3) a computer program (CAPTURE) designed to test the adequacy of study design and to analyze capture data where variable probability of removal exists.

Progressive Fish-Culturist↗
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

Growth and survival of Atlantic salmon fed various starter diets

Growth and survival were compared for groups of first‐feeding fry of Atlantic salmon (Salmo salar) fed various commercially available and experimental starter diets. In two separate 8‐ to 9‐week studies, survival was highest (more than 90%) in fish fed a semimoist closed‐formula commercial diet (BioDiet). In one study, fish grew fastest on BioDiet, whereas in the second study they grew fastest on a liver‐supplemented diet. Some diets were not eaten by the fish, resulting in little growth and less than 40% survival.

Progressive Fish-Culturist↗
USGS1981

Culture, feeding, and growth of alewives hatched in the laboratory

Alewives (Alosa pseudoharengus) were reared from the egg to the early juvenile life stage. The major obstacle to rearing alewives from the egg — providing an acceptable food that facilitates first feeding — was overcome by presenting a mixture of wild Zooplankton to the larvae twice daily, beginning on the day of hatching. Initial feeding by larvae held at 20°C was observed 2 days after hatching, when the yolk was nearly absorbed. Comparison of stomach contents and the wild Zooplankton composition suggested that the diet of larvae during the first 15 days of life shifted with changes in the availability of food but remained within a fairly narrow range of food sizes. Larvae hatched at a mean total length of 3.8 mm and grew at an average rate of 0.62 mm per day, to a mean of 35.5 mm after 50 days. At 50 days most fish had transformed into juveniles. The daily instantaneous mortality coefficient was 0.018. About half of the mortality occurred during the first 13 days after hatching.

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

Use of ozone in a water reuse system for salmonids

A water reuse system is described in which ozone is used in addition to biological filters to remove toxic metabolic wastes from the water. The system functions at a higher rate of efficiency than has been reported for other reuse systems and supports excellent growth of rainbow trout (Salmo gairdneri).

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↗
USGS1982

Immersion and injection vaccination of salmonids against furunculosis with an avirulent strain of Aeromonas salmonicida

Replicate groups of brook trout (Salvelinus fontinalis) immunized by intraperitoneal injection of graded dilutions of an avirulent strain of Aeromonas salmonicida were protected from a virulent challenge. Mean mortality after challenge was 88% in control trout, 66% in trout immunized with 3 × 10 6 or 3 × 10 5 cells, and 39% in trout immunized with 3 × 10 4 to 3 × 10¹ cells. In brook trout challenged after immersion for 60 s in a culture containing 2.3 × 10 9 avirulent cells of A. salmonicida per milliliter, mortality was 44%, compared with 94% in controls. In Atlantic salmon (Salmo salar), similarly vaccinated by immersion, mortality was 12.5% after challenge compared with 87.5% in controls. In additional studies, mean mortality of Atlantic salmon vaccinated by immersion was 14%, whereas that of control salmon was 92%.

Progressive Fish-Culturist↗
USGS1982

Plasma corticosteroids and chlorides in striped bass exposed to tricaine methanesulfonate, quinaldine, etomidate, and salt

Plasma chloride and corticosteroid concentrations were measured in yearling striped bass (Morone saxatilis) exposed to 25 mg/L tricaine methanesulfonate, 2.5 mg/L quinaldine, or 0.1 mg/L etomidate (an experimental drug), alone and in combination with 10 g/L salt (NaCl). Plasma chloride levels were unaffected in all treatments during a 15‐min exposure and during a 10‐min period of close confinement in a dipnet. Plasma corticosteroids increased in fish exposed to salt alone and in fish exposed to tricaine methanesulfonate or quinaldine, either alone or in combination with salt. Etomidate alone or combined with salt limited the increase in plasma corticosteroids during exposure and confinement. Etomidate appears to be a useful drug for suppressing physiological changes during the handling and transportation of striped bass.

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↗