Abstract

An epizootic in sockeye salmon Oncorhynchus nerka fry caused by infectious hematopoietic necrosis (IHN) virus occurred in 1987 in the Weaver Creek spawning channel, British Columbia, Canada. The prevalence of IHN virus in a sockeye fry was highest during the early part of fry migration from the spawning channel. Losses of migrating fry were estimated by holding fry for 4 d periods sequentially throughout the migration and observing mortalities. Of the 16.8 million fry migrating from the channel, an estimated 8.3 million likely died of IHN within days of leaving the spawning channel.