2.1

Central Valley late fall-run Chinook salmon were not recognized as a unique run until 1966, so little is known about their historical habitats or habits. They appear similar to other Central Valley Chinook salmon, but tend to be larger, reaching 75-100 cm (30-39 in.) and weighing 9-10 kg (20-22 lbs.) or more.

Historical abundance estimates are not available for Central Valley late fall-run Chinook salmon. While numbers have varied over time, the population in the Sacramento River and Battle Creek appears small but stable. Each year since 2002, less than 20,000 adults have returned to the Sacramento River, while about a thousand adults have returned to Battle Creek.

The late fall-run life strategy is much less well-known than those of other CV Chinook runs because of its recent recognition as a discrete run, its tendency to migrate and spawn when the Sacramento River is high, cold, and turbid, and limited historic capacity for genetic differentiation. Late fall-run Chinook adults begin their spawning migrations in mid-October to November, and spawn quickly after reaching spawning grounds in December to January. Unlike other Central Valley Chinook salmon, most late fall-run fish are four years old when they return to spawn. Fry emerge from the spawning gravel from April to June, and over- summer in the Sacramento River for 7-13 months before migrating out to sea. Juvenile migration to the ocean peaks in October; tagged juvenile late fall-run Chinook salmon moved downstream to the San Francisco Estuary from 14 to 23 km (about 9 to 14 mi.) per day.

Currently, late fall-run and fall-run are considered by NMFS to be two separate “races” under a single ESU.