Tolerance of developing salmonid eggs and fry to [fertilizer] nitrate exposure

Flow-through systems were used with four nitrate concentrations tested in duplicate on eggs and fry of rainbow trout and steelhead trout, chinook salmon and coho salmon and five tested on Lahontan cutthroat trout. Standard bio-assay conditions were used. Nitrate at 5-10 mg per litre is shown to be mildly toxic to developing eggs and the early fry stages of rainbow and steelhead trout; chinook salmon were affected only at exposure levels of 20 mg per litre or higher. Coho salmon were sufficiently resistant so that nitrate exposure at the tested levels during incubation would not be significant.