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The freshwater snail Physa fontinalis was used as a bioindicator to study the effects of the herbicide Paraquat (PQ) in laboratory assays. The test solutions used, 0.125, 0.25, and 0.5 mg/l PQ, were in the range of the concentrations recommended for aquatic weed control. The study was carried out in
In a series of observations upon the thyroids of brook trout, extending from the time of hatching to fish of four or more years old, we have been able to follow step by step the development of thyroid hyperplasia. In these hatchery trout, thyroid overgrowth may be recognized anatomically at the end
Fry of brook trout, Salvelinus fontinalis (Mitchill), were infected under controlled conditions with Gyrodactylus salmonis (Yin and Sproston, 1948) and the course of infection followed for 22 days in four groups of 40 fish and for 60 days in a group of 200 fish. Between 15 and 44% mortality occurred