Fundulus diaphanus (banded killifish) were the most abundant fish collected in the shallow water areas of Presque Isle Bay, making up 86% of fish collected. Peak spawning dates based on gonadosomatic index and ovary observations were July 9, 2003 and July 18, 2004. Females became sexually mature at age 1. During 2004, the majority of spawning occurred over a 20-day period between July 9 and July 29. Total fecundity increased with both size and age, and the mean total number of eggs produced was 526 ± 37 at age 1 (67 mm ± 1.8), 744 ± 38 at age 2 (79 mm ± 2.4), and 1062 ± 43 at age 3 (93 mm ± 4.1). Based on comparison of the total number of eggs and number of eggs with yolk contained within ovaries, three clutches of eggs may be released during each spawning season. Diets were similar between summer and fall; banded killifish fed almost exclusively on cladocerans and benthic macroinvertebrates.