Temperature-induced changes in pentachlorophenol chronic toxicity to early ufe stages of rainbow trout

Temperature was a controlling factor in pentachlorophenol (PCP) toxiciiy to rainbow trout (Salmo gairdnen). Eggs of frout exposed to PCP from fertilization to hatch showed elevated mortality and reduced weight at hatch. The effects on hatch weight were greatest in the cold regime (6°C) compared to (the warm (10°C). Continued PCP exposure after hatch resulted in significantly elevated mortality, reduced growth rates and reduced yolk sac resorption efficiency, and these effects were again greatest in the cold regime (6°C) compared to the warm (15°C). In contrast, during 4 wk of feeding after yolk sac resorption, PCP-induced mortality was unaffected by temperature but growth rates were reduced to the greatest extent in the warm regime (20°C) compared to the cold (12°C). The potential biomass of 1000 newly fertilized eggs at hatch, after yolk sac resorption, and after 4 wk of feeding was calculated from observed mortality and wet weights. The overall production of fish in the warm regime was reduced relative to controls at estimated threshold PCP concentrations of about 10 μg/l. In contrast, final biomass of fish in a cold regime was higher than control biomass at 10 μg/l and the estimated threshold of adverse effect was 20 μg/l. Although fish in a warm regime appeared to be affected at a lower concentration of PCP than those in the cold regime, the overall response to; the highest PCP concentration was similar. Trout exposed to PCP during the egg stage were far more sensitive to PCP than were those exposed only after hatch.