There are mayfly hatches all season long in Lake Erie, as well as other emergent aquatic insects. As soon as the water temperatures warm in the early spring (on the bottom) until they cool way down in the mid to late fall there are hatches going on. Since most of them are not anywhere near as big as the main June mayfly hatch, most of them tend to go unnoticed. Lots of species of mayflies and other aquatic insects with differing life cycle timing. That's what the perch and other fish species eat throughout the year. It changes week-to-week, month-to-month, along with zooplankton. The menu changes just like our seasonal harvest changes.