Salinity Effects on Fertilization Success and Larval Mortality of Fundulus heteroclitus

Abstract

The effects of salinity on fertilization success and larval mortality of four populations of Fundulus heteroclitus were determined. These populations were representative of different salinity regimes, i.e., coastal vs Chesapeake Bay populations, and different subspecies, F. h. heteroclitus and F. h. macrolepidotus. Fertilization did not occur in freshwater for any of the populations nor did fertilization occur in 5 parts per thousand for the two populations representative of F. h. heteroclitus (Tuckerton, New Jersey and York River, Virginia) and only achieved 11-27% successful fertilization in the F. h. macrolepidotus populations (Woods Hole, Massachusetts and Sassafras River, Maryland) at the latter salinity. Differences in fertilization among populations could be due to genetically based subspecific differences, the fishes' acclimation salinity, or a combination of both factors. Larval mortality, independent of salinity during embryonic incubation, varied between the two coastal populations. The Tuckerton population exhibited higher larval mortality in freshwater than the Woods Hole population. The reduced ability to tolerate low salinity may prevent the heteroclitus populations from inhabiting low salinity environments and thus help to explain their absence in low salinity portions of Delaware and Chesapeake bays. For all populations, abrupt reductions in salinity during the reproductive season may have a significant but previously unrecognized, negative impact.