Diets containing tetracycline antibiotics were fed to hatchery populations of Pacific salmon. Subsequent examination of bone samples from these populations indicates that the tetracyclines are deposited permanently in the skeletal structure, are readily detectable after a period of rapid growth, and do not affect growth or survival. The most satisfactory and consistent marks were obtained by feeding 250 mg of tetracycline antibiotic per kilogram of body weight per day for 4 consecutive days.
Epizootiological analyses of field data on prevalances of hepatic neoplasms and other hepatic lesions in English sole (Parophrys vetulus) from Puget Sound suggest a link between these lesions and sediment-associated xenobiotics, particularly aromatic hydrocarbons (AHs). To further investigate this relationship, English sole from a minimally contaminated site were parenterally exposed at monthly intervals for 1 yr to an organic solvent extract of a contaminated urban sediment containing high levels of AHs (30 or 75 mg/kg body weight) or to the model carcinogen benzo[a]pyrene (BaP, 12 mg/kg body weight). Control groups included English sole exposed to an extract of a relatively uncontaminated reference sediment, sole exposed to the carrier only, and untreated sole. Eighteen months after the initial injections, examination of livers revealed a significantly different (increased, [Formula: see text]) incidence of a spectrum of hepatic lesions, including presumptive preneoplastic foci of cellular alteration, in sole exposed to the urban sediment extract or BaP. Sole in control groups did not develop any of these hepatic lesions. These results represent the first direct demonstration of the hepatotoxicity of sediment-associated chemical contaminants in English sole and strengthen the case for a cause-and-effect relationship between exposure to AHs and epizootic neoplastic hepatic lesions in this species.
General morphology of the lateral line of juvenile steelhead trout, Salmo gairdneri, is described. Through electrophysiological monitoring of individual nerve fibres, control patterns for spontaneous activity and reaction to sensory receptor stimulation were established. Spontaneous activity has a positive correlation with temperature and number of receptors innervated. Presence of directional sensitivity and response to near field water displacement at different frequencies is similar to that found in other fishes and amphibians.Normal lateral line response to a standardized set of stimuli was compared with the response of fish affected by gas-bubble disease. Results show that as gas emboli formed in the scale pockets of the trunk lateral line of stressed fish, the ability to respond to stimuli was either diminished or completely disappeared. Further testing demonstrated that this sensory loss was reversible and that upon return to equilibrated water gas emboli disappeared and normal function was regained. This sublethal effect of gas-bubble disease on the lateral line sensory system may be an important element contributing to indirect mortality.
A finclip and a chemical (tetracycline) mark were applied, in similar numbers, to hatchery-reared fingerling sockeye salmon (Oncorhynchus nerka). In mark-sampling of returning adults 3 and 4 years after release from the hatchery, numerical comparison of fish with the two marks showed that fewer finclipped fish returned than expected. It was demonstrated that the tetracycline mark did not affect survival and that the difference between returns of fish with the two marks originated in mortality caused by finclipping. The mortality attributed to finclipping was estimated as 39%.
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