Copper toxicity in fish

Liver from Atlantic salmon fingerling showing positive copper reaction in hepatocyte cytoplasm. Rhodamine stain. Note the intracytoplasmic granules (bright red or rust-red) that correspond to lysosomes with sequestered excess copper (arrow).

Copper is a significant trace element necessary for the normal growth and metabolism of living organisms. However, if there is overexposure, it can be toxic. Levels of dissolved copper are often increased from anthropogenic origins such as mine washings and direct applications of algicides, molluscicides or antifouling agents. The most toxic form of copper is the cupric ion (Cu2+). Fish and crustacea are 10 to 100 times more sensitive to the toxicity of copper than mammals. For salmonids, the upper recommended limit is < 0.03...