SHORT-TERM VARIABILITY IN SURFACE CATCHES OF ICHTHYOPLANKTON IN THE UPPER CHESAPEAKE BAY

Four series of replicate tows with a 505 μm mesh plankton net were made at a single location in the upper Chesapeake Bay during the spring spawning period for anadromous fishes. The majority of the eggs and larvae collected were striped bass. Variation in egg and larval densities at the single sampling location and as associated with tidal stage and water mass sampled was as great or greater than that found to occur between locations in geographic surveys of spawning success conducted in the upper Bay by ourselves and others. Mean striped bass egg densities ranged from 4.13/m3 in the first replicate series to 17.25/m3 in the fourth. Mean striped bass larval densities followed an opposite trend and ranged from 15.90/m3 in the first series to 0.94/m3 in the fourth. Differences in developmental stage of striped bass eggs and in the abundance of other spring-spawning anadromous and resident species were also observed between series. The results are discussed in terms of the confidence which can be assigned to differences in egg and larval densities noted between locations in such geographic surveys. © 1979.