Migration and Spawning of American Shad in the James River, Virginia

Abstract

Acoustic telemetry and ichthyoplankton surveys were used to characterize the migratory behavior and spawning grounds of American shad Alosa sapidissima in the James River, Virginia. Seven acoustic monitoring stations spanned a distance of 95 river kilometers extending downstream from just below the fall line in Richmond to the estuarine portion of the river at Hog Island. Ninety-three fish were tagged in the estuarine portion of the river near Hog Island on 21 March 2005. Eighty-six fish exhibited fallback behavior, and 45 of these fish eventually abandoned the migration. Forty-six fish were eventually detected upstream at the mouths of the two major James River tributaries (Appomattox and Chickahominy rivers), within the main-stem James River up to the fall line, or both. Upstream movements detected by stationary hydrophones during the prespawning migration were significantly related to flooding tides, and movements downstream during the postspawning emigration were significantly related to ebbing tides. However, there was no significant relationship between time of day and movements during the prespawning or postspawning migration phase. Movement patterns suggested three primary areas of residency located within the 65-km reach below the fall line downstream to Upper Brandon Plantation, although some fish exhibited behaviors that were inconsistent with a specific residence area. Ichthyoplankton collections of eggs and yolk sac larvae indicated that the principal spawning grounds were located in a 33.5-km reach extending downstream from the fall line, a finding consistent with repeated detection of a majority of the tagged cohort within this reach.