Atlantic croakersMicropogonias undulatusundergo a transition from a coastal, pelagic, planktonic stage to an estuarine, demersal stage. Atlantic croaker larvae were collected at five descrete depths (0 m, 1 m, 6 m, and bottom) at stations along three transects north, south, and inside the mouth of the Chesapeake Bay in September 1980. Vertical distribution of the larvae was compared with salinity and temperature at the collection sites. Distribution patterns on the larvae were not uniform with depth but were related to hydrography. In vertically homogeneous water, larvae were found throughout the water column. In stratified water, they were found in the inward-flowing, lower layer, though not necessarily on the bottom. The distribution of Atlantic croaker larvae at the mouth of the Chesapeake can be accounted for by both passive and active transport mechanisms.