Protective Effect of Chloride on Nitrite Toxicity to Coho Salmon (<i>Oncorhynchus kisutch</i>)

Abstract

Tolerance of coho salmon (Oncorhynchus kisutch) to nitrite was increased when the concentration of chloride ion in the environment was high. The results of flow-through bioassays revealed that no mortality occurred when yearling coho salmon were subjected to nitrite-nitrogen (NO 2 − –N) of 29.8 mg/ℓ and chloride (Cl − ) of 261.3 mg/ℓ for 48 h. When yearling coho salmon were exposed to 3.8 mg/ℓ NO 2 − –N and 2.5 mg/ℓ Cl − for 12 h, the resultant mortality was 58.3%. Possibly, chloride competes with nitrite for transport across the gills and integumental tissues, thereby interfering with the onset of nitrite-induced methemoglobinemia.