Investigations of inner continental shelf waters off lower Chesapeake Bay

Abstract

A series of monthly exploratory cruises into the neritic waters of the Atlantic Ocean adjacent to lower Chesapeake Bay were initiated late in1959 to: (a) locate the eggs and larvae of fishes spawning in the area; and (b) to trace the transport of these stages by surface and subsurface currents into the Chesapeake Bay system. This paper will serve as an introduction to a proposed series describing the results of the cruises.

The survey area, which covers 50 nautical miles offshore and 60 miles in a north-south direction, is the neritic zone lying within the 20 fathom contour and extending from False Cape on the south to Wachapreague Inlet at the northern limit. Twenty-two offshore stations in addition to three stations in lower Chesapeake Bay were sampled monthly with surface and bottom plankton nets. Routine hydrographic data were taken at each station.

Surface and bottom water samples from the cruises of December through May indicated these preliminary points: From December through March the water column was essentially homogeneous with respect to temperature. Vernal warming began in April and thermal stratification progressed through May. The distribution of salinities was generally coastal in character with isohalines parallel to the coastline. The discharge of effluent from Chesapeake Bay produces frequent deviations from the normal coastal pattern. In general, the major component of the discharge from Chesapeake Bay passes out around Cape Henry and proceeds southward.

Drift bottle returns indicated that the survey area is crossed by a southerly drift having a velocity of 10 to 14 miles per day.