Atlantic salmon (Salmo salar) eggs and alevins were raised under conditions where the temperature was systematically varied either at fertilization, at the eyed egg stage, or at hatching. Mortality was more than 20% in eggs started immediately after fertilization at constant incubation temperatures < 4 °C as compared with 5% or less at temperatures > 4 °C. Alevins that eyed at 8 °C and higher were progressively smaller the higher the temperature. The optimum temperature from fertilization to eye pigmentation was near 6 °C. Eyed eggs reared at lower temperatures until hatching were larger than those hatched at higher temperatures. This size differential was maintained until the yolk was completely absorbed at all posthatching temperatures investigated. Sudden decreases in temperature at the eyed egg and hatching stages induced severe edema of the alevin yolk sac, resulting in slower growth and increased mortality.
Winter oxygen consumption was measured in 16 Ontario lakes. Whole lake respiration ranged from 0.08 to 0.39 g O2 m−2 day−1 and was positively correlated with mean depth, phosphorus m−2 at spring overturn, and summer chlorophyll a m−2. Morphological variables plus Secchi depth were explained over 80% of the variability in respiration rates.
Eleven hatchery facilities provided fry of Atlantic salmon (Salmo salar) for analysis just before food was introduced. These fry were analyzed for water content to determine degree of yolk utilization. Amount of yolk remaining at first feeding varied widely among hatcheries. Fry emerging from artificial substrates had very little yolk remaining at first feeding. A fry water content of 80% seems a good criterion to use for timing of first feeding.
Brook trout (Salvelinus fontinalis), white sucker (Catostomus commersonii) and yellow perch (Perca flavescens) from headwater lakes in New Brunswick and Nova Scotia (Canada) were analyzed for whole body concentrations of Pb, Cd, Hg, Cu and Zn. Fish from western New Brunswick generally had lowest concentrations of metals. Mercury concentrations were highest in fish from lakes close to urban centers on the leeward side. Only trout were collected from lakes in Cape Breton Island, and these were characterized by high Cd and Zn concentrations. The only consistently strong correlation between metal concentration and any lake chemistry parameter was a negative correlation between Pb concentration and lake pH. Copper and Zn were consistently positively correlated for all three species, perhaps due to their common existence in mineral deposits.
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