In Chesapeake Bay in June, the predatory lobate ctenophore Mnemiopsis leidyi and the eggs of the bay anchovy Anchoa mitchilli typically reach seasonal and localized abundance together. When examined at small vertical (1-3m), horizontal (10-50m), and temporal (6-hour) scales, the co-occurrence of M. leidyi and fish eggs (32.3-74.2% of which were A. mitchilli) was greatest in the northern reaches of the mouth of Chesapeake Bay, where the water column was stratified. Stratification to the south was effected by the Chesapeake Bay plume. With estimates of ctenophore clearance rate reported elsewhere and observed densities of ctenophores and fish eggs, potential predation was judged to be greatest in the northern reaches of the Bay mouth. The observation that co-occurrence and potential predation are greatest in areas where Chesapeake Bay water mixes with coastal shelf water implies that those fishes that spawn in low-salinity surface waters of well-stratified water columns may afford protection of their eggs from ctenophore predation
