PETERSEN, C.W.; SALINAS, S.*; KIDDER, G.W. III; PRESTON, R.L.; College of the Atlantic, Bar Harbor, ME; College of the Atlantic, Bar Harbor, ME; Mount Desert Island Biological Laboratory, Salisbury Cove, ME; Illinois State University, Normal: Reproductive ecology of Fundulus heteroclitus in a New England salt marsh

The mummichog, Fundulus heteroclitus, is a widely distributed fish that has been extensively researched in the southern portion of its range (south of Cape Cod, MA). Those studies indicate that the southern F. heteroclitus exhibits a strong semilunar reproductive cycle, as measured by the presence of ovulated eggs in ovaries, direct observations of spawning, and the relative size of male and female gonads. This endogenous rhythm allows this species to spawn during the spring tides, positioning the fertilized eggs in the upper intertidal zone, where they can develop aerially and possibly avoid aquatic predators. During the summers of 2003 and 2004, we studied the reproductive ecology of F. heteroclitus in a Maine creek. Our direct observations show that, unlike more southern populations, northern F. heteroclitus spawns daily during its two-month spawning season. Although higher high tides were preferred on a daily basis to consecutive lower high tides, spawning was observed uninterrupted throughout the reproductive season. At a second site with less tidal influence, spawning became decoupled from times of high tide during less extreme neap tides. These temporal and spatial patterns of oviposition led eggs to be deposited in a much broader range of habitats than in southern populations of this species. In addition to differences in the timing of spawning, we documented patterns of reproductive behavior and oviposition-site use that differ from other published reports. These data add to the large body of information on clinal variation in this widely distributed fish.