Erythromycin levels within eggs and alevins derived from spawning broodstock chinook salmon Oncorhynchus tshawytscha injected with the drug

Abstract

This study was conducted as part of a field trial to evaluate procedures used for control of vertical transmission of Renibacterium salmoninarum in chinook salmon in a hatchery in British Columbia. Erythromycin levels in ovarian fluid, eggs and sac fry were measured following injection of the drug at a dose of 20 mg kg-' into the 'dorsal sinus' of female broodstock just before spawning. Significant drug levels were achieved in eggs following treatment as little as 9 d before spawning, and these persisted, in decreasing levels, until the external yolk sac had been completely resorbed by the developing alevin. Drug levels in ovarian fluid declined to below detectable limits within 20 d after injection.