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COHO SALMON (ONCORHYNCHUS KISUTCH) EXPOSED TO AN ACUTE, SUBLETHAL CONCENTRATION OF 3-TRIFLUOROMETHLY 1-4 NITROPHENOL (TFM) EXHIBITED AN INCREASED OUTPUT OF URINE WHEN COMPARED WITH CONTROLS, BUT THE URINARY EXCRETION OF NA, K, CA, MG AND C1 WAS NOT AFFECTED. ABOUT 35 TIMES MORE CONJUGATED TFM THAN FREE TFM WAS EXCRETED DURING THE 24-HOUR STUDY PERIOD.
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Experimental plantings of fin-clipped lake trout (Salvelinus namaycush) of various ages have been made in southern Lake Superior since 1952. The catch of planted lake trout by the commercial fishery was used to measure the success of stocking. Estimates of total returns were based on samples of 8.2 to 21.2% of the Wisconsin catches in 1955-62 and 36.4 to 46.8% of the Michigan catches in 1959-62. Marked lake trout were assigned to various plantings according to the fin mark, length of fish, readings of age from scales, and locations of capture. Estimated returns from Wisconsin plantings of 9-month-old lake trout varied from 2.1 to 6.4%. Wisconsin releases of 16-month-old fish yielded returns of 5.7 to 37.3%. Returns...
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Phoma herbarum, a fungal plant saprophyte, was isolated from diseased hatchery-reared coho salmon (Oncorhynchus kisutch), chinook salmon (O. tshawytscha), and rainbow trout (Salmo gairdneri). The disease was observed at 10 national fish hatcheries in Washington and Oregon, but the low incidence of experimental infections indicate that it is only weakly contagious. Histopathological examination suggests that the air bladder is one of the primary organs infected. The visceral organs are also affected in both natural and experimental infections.
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Scolecobasidium humicola, a previously undescribed fungal pathogen of fish was isolated from coho salmon (Oncorhynchus kisutch). In natural infections the kidney was the organ most affected. The disease was difficult to transmit experimentally and appeared to be only weakly contagious.
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Juvenile sockeye salmon (Oncorhynchus nerka) were injected with the infectious hematopoietic necrosis (IHN) virus, and tissue samples from the anterior kidney, spleen, liver, intestine, and pyloric caeca of moribund fish were prepared for electron microscopy. Bullet-shaped virus particles measuring 158 × 90 mμ were observed in the hematopoietic tissues of the anterior kidney and spleen. Virus particles were also observed in the outer connective tissues of the pancreas or pyloric caeca, or both. No virus was found in the intestine or liver. The healthy appearance of erythrocytes, reticular cells, and endothelial cells in necrotic areas of the spleen and anterior kidney, and the absence of lymphocytes in these areas,...
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Sockeye salmon (Oncorhynchus nerka) were immersion-vaccinated in suspensions containing 5 × 107, 5 × 106, 5 × 105, or 5 × 104 bacteria/mL of bivalent or monovalent, formalin-killed Vibrio anguillarum, Types I and II. The fish were split into two lots and held for 54 d. At that time one lot was challenged with living, virulent V. anguillarum, Type I, and one with living, virulent V. anguillarum, Type II. Immunization with bivalent bacterin effectively protected the fish from vibriosis, but monovalent vaccine was effective only against the homologous challenge. Immunization with the highest concentration of Type I monovalent bacterin resulted in 0% Type I and 58% Type II challenge mortality. Immunization with the...
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Commercial production of walleyes (Stizostedion vitreum vitreum) from western Lake Erie declined from 5.9 million pounds in 1956 to 140,000 pounds by 1969. Since 1956, marked irregularity in year-class success has developed. Only four year-classes were considered good during 1959–70. The rate and regularity of water warming during the spring spawning and incubation periods in 1960–70 had a positive effect on the density of egg deposits and the resulting year-class strength. Rates of warming were not themselves detrimental, but rather the extended length of the incubation period in cool springs increased the exposure of eggs to such negative influences as dislodgment from the spawning reefs by strong current action...
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The external metamorphosis of the sea lamprey was divided into four stages, based primarily on the condition of the mouth: mouth reduced, mouth fused, mouth enclosed, and mouth elongated. During metamorphosis, the eye enlarged greatly, the snout and mouth region changed from a fleshy hood enclosing a sieve apparatus to a large sucking disc, the nasopore membrane and the branchial area shrank, the branchiopores changed in shape, the general color changed from dark brown and yellow to an intense blue-black dorsally and white ventrally, and the total length increased. Metamorphosis began in early to mid-July and did not take place after August. The duration of external metamorphosis was about 3 months for lampreys...
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The effects of human population growth, industrialization, and the introduction of marine fishes have reduced the suitability of each of the Great Lakes for oligotrophic fish communities. The ultimate consequence has been a reduction of fishery productivity that has ranged from extreme in Lake Ontario to moderate in Lake Superior. If measures are not taken to alleviate the adverse effects of marine invaders and trends in environmental quality, a major reduction in fishery productivity can eventually be expected throughout the Great Lakes.Prospects for the next century will be improved if the lakes can be intensively managed. More stringent control of the sea lamprey (Petromyzon marinus), and subsequent reduction...
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Scenedesmus obliquus, Daphnia magna, and Poecilia reticulata accumulated dieldrin directly from water; average concentration factors (concentration in organism, dry weight, divided by concentration in water) were 1282 for the alga, 13,954 for D. magna, and 49,307 (estimated) for the guppy. The amount accumulated by each species at equilibrium (after about 1.5, 3-4, and 18 days, respectively) was directly proportional to the concentration of dieldrin in the water. Daphnia magna and guppies accumulated more dieldrin from water than from food that had been exposed to similar concentrations in water. When guppies were fed equal daily rations of D. magna containing different concentrations of insecticide, the amounts...
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In Puget Sound, Wash., the incidence of viral erythrocytic necrosis (VEN) varied geographically from 0 to 17% in chum salmon (Oncorhynchus keta) and from 4 to 59% in Pacific herring (Clupea harengus pallasi). The disease was experimentally transmitted by intraperitoneal injection to chum, pink (O. gorbuscha), coho (O. kisutch), chinook (O. tshawytscha), sockeye (O. nerka), and Atlantic (Salmo salar) salmon, and rainbow (S. gairdneri), brown (S. trutta), and brook (Salvelinus fontinalis) trout. The disease was transmitted to chum salmon and brook trout by waterborne virus. Virus obtained from herring was experimentally transmitted into chum salmon by intraperitoneal injection. Key words: viral erythrocytic necrosis,...
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The efficacy of mineral salts, pH, and tetramethylthianine (methylene blue) treatment in reducing the acute toxicity of nitrite to fingerling steelhead trout (Salmo gairdneri) was determined using a static bioassay system at 10 °C. The acute toxicity (96-h LC50) was reduced by a factor of about 24 for 5-g steelhead and 13 for 10-g fish when the total water hardness was increased from 25 to 300 mg/L (as CaCO3). NaCl or CaCl2 additions (0–200 mg/L) reduced toxicity by a factor of up to 3 for NaCl and 50 for CaCl2. Increasing the pH from 6.0 to 8.0 decreased toxicity by a factor of about 8 for the smaller and 3 for the larger fish. Methylene blue at 0.1 or 1.0 mg/L was effective in decreasing acute toxicity. For alleviating...