Deleterious Effects of Cyanide on Early Life Stages of Atlantic Salmon (Salmo salar)

Abstract

Hydrocyanic acid, a common industrial pollutant, caused severe damage to developing embryos of Atlantic salmon (S. salar) when newly fertilized eggs were continually exposed to sublethal concentrations of the poison (0.01-0.10 mg/l HCN) up to the end of the sac-fry stage. Each test group was held in small flow-through basins with the toxicant metered through the entire experimental period. At 0.08 and 0.10 mg/l, cyanide delayed hatching by 6-9 days but all concentrations reduced hatching success by about 15-40%. During incubation conversion of yolk into body tissues was reduced at all concentrations above 0.01 mg/l. The most striking effect of cyanide was a high incidence of abnormalities ranging from about 6% at 0.01 mg/l to about 19% at 0.10 mg/l. During incubation cyanide had reduced development, but after hatching survival was not affected and growth of cyanide-exposed sac fry was either equal to or faster than that of the controls as a result of higher yolk conversion efficiency. The total metabolism of the sac fry was estimated to explain this phenomenon. To protect salmon streams during embryo-larval stages, the maximum acceptable toxicant concentration for cyanide should not exceed 0.005 mg/l HCN.