Three common Lake Michigan species (spottail shiner Notropis hudsonius, alewife Alosa pseudoharengus, and white sucker Catostomus commersoni) migrated into Little Pigeon Creek, a Lake Michigan tributary with a marsh upstream, to spawn during 1980. Spottail shiners, not previously documented as spawning in Lake Michigan tributaries, spawned when stream water temperatures reached approximately 18 C (7 C warmer than the 1-m depth contour in Lake Michigan), about 1 month earlier in this tributary than in Lake Michigan. Densities of spottail shiner larvae were higher in the stream than in the Lake Michigan beach zone, most likely due to high productivity of the stream and concentration of spawning adults in one area. Little Pigeon Creek produced an estimated 100,000 spottail shiner larvae per day at times of peak hatch, over a 12-day period. White sucker larvae were pelagic in surface waters of the marsh for 1#x2013;2 months, then drifted downstream into bottom waters of the stream. Alewife larvae occurred in the tributary 2#x2013;3 weeks before peak hatches in Lake Michigan, as stream water continued to be warmer than the lake. Little Pigeon Creek exemplified the importance of small stream systems for reproduction of some Lake Michigan fishes.
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