A mark-release experiment on larval striped bass Morone saxatilis in a Chesapeake Bay tributary

A larval mark-recapture experiment was undertaken to compare dispersal patterns and vital rates of hatchery-produced and wild larvae. The potential of larval stocking to enhance recruitment in an estuarine tributary was also evaluated. Approximately 6.5 million striped bass Morone saxatilis larvae (5–7 mm, SL) were marked by immersion in 25 mg l−1 alizarin complexone, which was deposited in their otoliths. Following release on two dates, the dispersal of marked larvae from release sites was rapid and their distribution 4 days after release resembled that of wild larvae. Growth rates of four release groups ranged from 0.20 to 0.25 mm day−1 and mortality rates ranged from 0.09 to 0.19 day−1. The rates were similar to those of wild larvae. More than 70% mortality of released groups occurred from 0 to 3 days after release and larvae stocked at one down-river site apparently suffered complete mortality due to advective down-estuary loss. Hatchery-produced larvae were released during a period when temperatures were favorable for growth and survival. Survivors of released larvae were estimated to account for 10 to 35% of the age 0+ juvenile striped bass in the Patuxent River in 1991. The success of this experiment indicated that marked larvae can serve as “probes” to examine environmental and habitat factors that affect recruitment of striped bass and other anadromous species. In the case of striped bass, large-scale stocking of larvae could contribute significantly to recruitment in Chesapeake Bay tributaries.