Date of Award

12-2017

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Forestry and Natural Resources

Committee Chair

Tomas O. Hook

Committee Member 1

David G. Fielder

Committee Member 2

Paris D. Collingsworth

Abstract

Historically, Saginaw Bay, Lake Huron had a complex of rocky reefs that functioned as preferred spawning habitat for various fish species, including Walleye (Sander vitreus) and Lake Whitefish (Coregonus clupeaformis). This reef system likely acted as a source of protection from egg predation, as well as of increased spawning diversity. Shifts in land use from forest to primarily agriculture and industry resulted in elevated runoff and sedimentation, leading to the loss of nearly all reef structure in Saginaw Bay. Coupled with overfishing and additional habitat degradation, these shifts precipitated dramatic declines of many fish species in the bay, including Walleye. Until recently, stocking was necessary to maintain Walleye in Saginaw Bay. Today, Walleye abundance is high, but the majority of production comes from Walleye spawning in tributaries, with limited production in the bay itself. Lake Whitefish production may also remain impacted by degraded spawning habitat in the bay. In recent years, improved land use and potential decreased sedimentation, has led to momentum towards reef restoration in Saginaw Bay. The purpose of this study was to analyze spawning patterns of two key Great Lakes fish species, Walleye and Lake Whitefish, to determine whether current reproductive usage indicates potential for successful reef restoration. Additionally, we sought to analyze physical conditions in Saginaw Bay and their potential impact on restoration efforts. We evaluated four sites with varying levels of reef degradation; two sites contained remnant reef habitat, while two sites contained little to no rocky structure, but served as potential restoration locations. We analyzed water quality, substrate, sedimentation, reproductive usage, and egg deposition and predation. After completion of a two-year study, we have documented actively spawning Walleye and Lake Whitefish and egg deposition and predation at multiple sites. However, densities of spawners and deposited eggs were low, suggesting that target species are not utilizing study sites as major spawning locations. Additionally, predation of both Walleye and Lake Whitefish eggs was documented for multiple fish species. Larger-bodied fish species, such as Channel Catfish (Ictalurus punctatus), in particular were able to consume large numbers of deposited eggs. Water temperatures and dissolved oxygen concentration appeared appropriate during spawning seasons to allow for successful spawning, but low overwinter dissolved oxygen was documented at multiple sites. Sedimentation analyses also suggested high amounts of suspended sediment at study locations, and a need for further understanding of sedimentation dynamics. Overall, we suggest that there is potential for successful restoration from a biological standpoint, but that more information is needed before full-scale reef restoration can occur. Reefs may be able to attract additional fish to spawn and provide protection from egg predators, but it remains unclear how sedimentation and overwinter dissolved oxygen may affect quality of restored spawning habitat.

Download

Share

COinS