Estuarine retention and production of striped bass larvae: a mark-recapture experiment

Mark-recapture experiments were conducted in the tidal Nanticoke River (Chesapeake Bay) to determine how the salt front retains striped bass larvae and controls nursery production. During two spring spawning seasons, 25.1 million hatchery-produced, first-feeding larvae (5–12 days post-hatch) were released with chemically marked otoliths at selected locations and times. Surveys tracked the spatial and demographic fates of released and naturally spawned larvae. Released larvae dispersed rapidly within the freshwater tidal portion of the estuary and were retained above the salt front. Their distributions overlapped with natural larvae. Growth and mortality rates did not differ with respect to release location, but did vary with day of release, influenced by storm events and seasonal changes in temperature. In 1993, a group released during a storm event did not yield any recaptured larvae. Zooplankton concentrations in both years were likely sufficient for successful larval feeding. In spring 1993, a season of relatively high freshwater flow, nursery volume was 2.1-fold larger and juvenile production from larval releases was fourfold higher than in 1992. We propose that increased nursery volume reduces variance in water quality, enhances retention of larvae within the nursery, thus increasing production of larval striped bass.