The Toxicity of Zinc Sulphate to Rainbow Trout

Abstract

The toxicity of zinc sulphate to rainbow trout (Salmo gairdnerii Richardson) has been investigated in waters of different chemical and physical properties.Zinc sulphate was less toxic to rainbow trout in hard water than in soft water; when the log concentration of zinc was plotted against log median period of survival of the fish the dose response curve was linear in a very soft water, and curvilinear in a hard water, approaching an apparent threshold concentration. Solutions of zinc sulphate containing calcium chloride were less toxic than those containing an equivalent concentration of calcium as bicarbonate.An increase in temperature decreased the survival time of rainbow trout in solutions of zinc sulphate in a hard water, but the threshold concentration was not appreciably affected by changes in temperature.A reduction in the dissolved oxygen concentration of the water increased the toxicity of zinc sulphate, but the effect was reduced when the fish were previously acclimatized to the lower oxygen concentration of the test.The cause of death of fish in solutions of zinc sulphate was not by the precipitation of mucus on the gills but probably by damage to the gill epithelium.

Sublethal haematological effects of zinc on the freshwater fish, Heteroclarias sp. (Osteichthyes: Clariidae)

“…Jones (1983) demonstrated that Gasterosteus aculeralus survived longer in water containing zinc and calcium than when no calcium was present. Lloyd (1960) demonstrated that zinc was toxic to rainbow trout (S. gardnerii) in water of hardness 12 g CaCO 3 L…”

Environmental factors reducing the toxicity of zinc toStigeoclonium tenue

“…Among the factors which have been mentioned as reducing the toxicity of zinc, the one quoted the most often is the hardness of the water. For instance, it seems widely accepted that zinc is almost always less toxic to fish in hard than in soft waters (Lloyd, 1960;Skidmore, 1964;Mount, 1966). At any particular hardness an increase in pH over the range 6.0 to 8.0 leads to an increase in the toxicity of zinc to fathead minnows (Mount, 1966).…”

Influence of forest and rangeland management on anadromous fish habitat in Western North America: effects of mining.

“…Dissolved heavy metals, commonly found in waters polluted by mine drainage, are toxic to the aquatic biota (Cairns and Scheier 1957;Tarzwell and Henderson 1960;Lloyd 1960Lloyd , 1961aLloyd , 1961bLloyd and Herbert 1962;Mount and Stephan 1967). The actual metal concentration toxic to fish, however, is difficult t o determine.…”