Timing and Demographic Characteristics of Redhorse Spawning Runs in Three Great Lakes Basin Rivers

Boat-electrofishing surveys and fishway monitoring were undertaken to describe the characteristics of redhorse (Moxostoma spp.) spawning runs in the Grand River, Muskegon River and Trent River. Spawning began in early May and was complete by mid-June. Timing of spawning varied among species, rivers, and years. Shorthead redhorse and silver redhorse spawned earlier and at lower water temperatures than black redhorse and river redhorse. Differences between rivers and years likely resulted from differences in the timing of suitable water temperatures and suitable flow levels, respectively. Spawning males were generally smaller, more numerous, and present in spawning areas earlier than females. While males reached sexual maturity at a younger age than females, there were no overall differences in the ages of spawning male and female redhorse.