This project is intended to be the first step to restore rock reef spawning habitat within inner Saginaw Bay. In order to achieve this, a collaborative team will assess the current status of reef spawning habitat in inner Saginaw Bay. The assessment will target spring (walleye) and fall (lake whitefish) spawning at two remaining reef sites and two potential restoration sites within the inner Bay. Past studies have shown that critical fish spawning is primarily occurring in the tributaries of the Saginaw River system. Restoring rock reefs within the inner Bay will help to diversify spawning habitat, fish populations, and contribute to a more stable and resilient Saginaw Bay fishery.
This project will focus on three main objectives, which will help to inform future reef restoration efforts:
Determine the suitability of inner Saginaw Bay’s remnant reef habitat by assessing the condition of the substrate (e.g. hardness of the lakebed) and water quality — and by surveying the project sites for predators (e.g. crayfish, round goby, white perch) that feed on fish eggs. Substrate conditions will be evaluated by visual inspection (e.g. under water video or by scuba divers) and sophisticated sonar equipment. The use of sonar will allow the project team to create a three-dimensional image of the remnant reefs and gain information on the relative hardness of the bottom substrate. Visual inspections and sonar will also be used to evaluate sedimentation, mussel colonization (e.g. zebra and quagga mussels), and aquatic vegetation at the project sites.
During spring and fall sampling events, the project team will use water quality monitoring equipment to collect data on several parameters including dissolved oxygen, turbidity, conductivity and temperature. Water quality data will be collected at all four project sites and will provide important information on habitat suitability.
Predator-prey relationships are another important factor when evaluating potential sites for restoration. For this reason the project team will conduct egg predator surveys to assess and document potential egg predation threats that are present during spring and fall spawning events. During spawning events, the project team will set nets and traps to collect and document the presence and relative abundance of predators at the project sites.
Assess the reproductive usage of the inner Bay’s remnant reefs by walleye and lake whitefish. Reproductive usage will be assessed by setting nets and egg traps overnight at the remnant reef sites during the spring and fall spawning events. By evaluating the catch and egg traps, the project team will be able to assess the relative abundance (catch per unit of effort), spawning condition, and age and sex (i.e., size structure and demographics) of the spawning fish.
Assess the genetic diversity of Saginaw Bay’s walleye and lake whitefish populations and determine if a population of river- and reef-spawning walleye are present in Saginaw Bay. Any remnant reef spawning walleye and lake whitefish captured during spawning will be assessed for reproductive behavior and compared to populations found in other locations of the great lakes. This work will include an evaluation of the timing of egg deposition and a lab analysis to determine the characteristics of the walleye and lake whitefish eggs (e.g. median diameter, dry mass, etc.).
In addition, tissue samples (fin clips) will be taken from walleye and lake whitefish for genetic analysis and will be compared to known genotypes and historic samples from Saginaw Bay and Tittabawassee River. Tissue samples collected from any walleye spawning on the reefs will be genetically compared to known Tittabawassee River genotypes and to historical data sets.
The information generated by this project will be used in the design and implementation of future reef restoration efforts in inner Saginaw Bay and throughout the Great Lakes. In addition, this project will provide important information that will help fisheries managers increase the resilience of Saginaw Bay’s fishery.