Critical velocities of 17 species of fish from the Mackenzie River have been determined from increasing velocity tests in both field and laboratory, and the effects on critical velocity of different acclimation temperatures and of temperature shock were examined. In five species the relation between fatigue time and swimming speed was investigated.Critical velocity data from 10 species were analyzed by solving the regression equation V = KLe (where V = critical velocity in cm/s, L = fork length, K = constant, e = exponent). Neither acclimation to different temperatures nor temperature shock over a range of ±7 C from acclimation temperature had a significant effect on critical velocity. Intraspecific variation was found to be unrelated to maturity, sex, or condition factor.From a graphical presentation of body length vs. maximum flow rate allowable in a 100-m culvert, it appears that culvert flow rates should be kept below 30–40 cm/s to allow successful passage of the majority of mature individuals of migratory species.
Atlantic salmon (Salmo salar) parr were exposed to a number of concentrations of either technical grade fenitrothion or an operational formulation of the pesticide for 7 d or to the operational formulation for two, 24 h periods separated by 7 d. Brain acetylcholinesterase (AChE) activity decreased as concentration, of fenitrothion increased. Recovery period was directly related to amount of depression, with recovery of AChE from exposure to 0.004 μL/L fenitrothion taking less than 1 wk. Samples must be taken soon after spray operations to detect exposure to such low levels of fenitrothion through AChE monitoring.
Experiments were conducted to ascertain the effects of crude oils at low concentrations on Atlantic cod (Gadus morhua) following long-term exposure (3–21 weeks) in a flow-through seawater system. Control and oil-treated fish were fed to satiation. Effects were assessed by comparing condition factor, organ indices, and hematological values with those of corresponding control animals. No mortality occurred but food consumption was significantly reduced in oil-treated cod, especially during summer–autumn. Condition factor and somatic indices of some organs were lower in oil-treated fish. Gall bladders were enlarged in oil-treated fish. Effects of oil exposure were less pronounced during winter, as food intake in both groups of fish was reduced considerably. The rate of gametogenesis was slower in male cod exposed to oil fractions in summer–autumn whereas spermeation was delayed in fish treated in winter–spring. These studies provide evidence that feeding, growth, and reproduction in male cod are biologically important variables that are affected following chronic exposure to petroleum.
To assess the long-term effect on the tissues of marine fish, Atlantic cod, Gadus morhua L., were exposed to water-soluble fractions of Venezuelan and Hibernia crude oils at concentrations of 50–300 ppb for 12–13 weeks in a flow-through seawater system. Histopathological changes in oil-exposed fish included increased numbers of mucus-producing epithelial cells, capillary dilation, lamellar hyperplasia, and fusion of adjacent filaments in gills, microvesicular formation in hepatocytes, delayed spermatogenesis with intratubular multinucleated giant cells, and an increase of melanomacrophage centers in the spleen and kidney. Lesions were more prevalent and severe in fish exposed to Hibernia crude than to Venezuelan crude at a similar concentration.
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