JENNIFER JOHNSON

Reproductive Development of Selected Macrhybopsis Chubs in Relation to Environmental Variables in the Lower Missouri River

Advisor: Dr.David Galat

Alterations in water temperature, turbidity, channel morphology, and flow patterns resulted in major changes in fish habitat and fish assemblages along many large rivers, including the Missouri River. Sicklefin (Macrhybopsis meeki) and sturgeon chubs (M. gelida) are small-bodied, short-lived, turbid river Cyprinids that have experienced over a 50% reduction in their former distribution along the Missouri River mainstem. They are currently listed as imperiled by >2 mainstem states, although recent collections indicate numbers may be larger than previously reported. Our objective is to describe reproductive development of M. meeki, M. gelida, and the more common M. aestivalis (speckled chub) using histological analysis. We will relate reproductive development to four environmental variables: photoperiod, lunar cycle, water temperature, and river discharge, and also evaluate differences between two segments in the lower Missouri River, Missouri. Sampling will occur between February and November 2005 to ensure collection of chubs before and after reproduction. Characterizing reproductive development of the relatively common sicklefin chub may enable us to generalize about development of the less the common speckled chub, and even rarer sturgeon chub. Knowledge of spawning modes and patterns of reproductive development is essential for conservation and management of the Missouri River’s small-bodied, short-lived fishes, information on their reproductive requirements can aid design of flow and habitat modifications to benefit imperiled chubs along with the endangered pallid sturgeon (Scaphirhynchus albus).