Survey of juvenile yellow perch in nearshore waters of Lake Michigan, and nearshore zone conditions for perch growth and survival
Yellow Perch Population Dynamics
Yellow perch (Perca flavescens) is an extremely important attribute to the Lake Michigan ecosystem due to its importance as a prey fish, but also a significant sport fish for recreational anglers. During the spring, summer, and fall field season, we gather young-of-year (YOY) and juvenile yellow perch to gauge the health of the population using gill nets with mesh sizes that range from 6-19mm. During the winter months, the perch caught are dissected. Length, weight, and sex are determined. Stomachs are removed for diet analysis and otoliths are collected for aging.
Nearshore Prey Fish Community Dynamics
While sampling for yellow perch, we also investigate nearshore fish communities. These include alewife, round goby, sand shiner, spottail shiner, bloater, and rainbow smelt. While providing an idea of what prey fish are available for game fish (i.e. yellow perch, chinook salmon, coho salmon, brown trout, rainbow trout, and lake trout), the information we gather allows us to monitor long-term changes to the fish community along the IL shoreline and potentially detect new AIS (aquatic invasive species). These fish are also processed and dissected during the winter months for future diet and aging analysis, allowing us to understand community interactions.
Benthic Invertebrate and Zooplankton Community Survey
We sample the nearshore benthic invertebrates and zooplankton to monitor changes in food availability to yellow perch and the nearshore fish community while providing early detection of new AIS in southwestern Lake Michigan. Using the PONAR grab sampler, we collect benthic substrate from depths up to 7 meters. The sample is then filtered through 363 µm mesh screens to remove sand but keep the majority of the invertebrates. In the lab, we identify and measure what organisms are inside each sample giving us an idea about food quality and availability in the environment that fish also dwell. Some common things found in our samples include nematodes, midges, aquatic worms, scuds, quagga mussels, water mites, and many other organisms.
Zooplankton are heterotrophic plankton that can be found in the water column and are a valuable food source for developing fish. Monitoring zooplankton is also important to understand ecological changes in case bigheaded carp successfully invade Lake Michigan. We collect macrozooplankton, using a 64 µm plankton net pulled vertically through the water column. Food source organisms, such as cladocerans and copepods, are identified and measured. Also, exotic organisms, such as spiny and fish-hook water fleas, are important to keep track of, given they may be diminishing food sources for native species. Rotifers are an often understudied and under-represented group of microzooplankton that we collect using a Van Dorn sampling bottle and filter with a 20 µm mesh.
Rubble Ridges Shoreline Stabilization Project
The dynamic nature of the Great Lakes ecosystem requires management techniques with the potential to adapt to changing environmental conditions (lake levels, storm surges, etc.) so that people may continue to live near and recreate on the lakes. In the summer of 2021, a submerged shoreline stabilization structure was constructed in the Lake Michigan waters of Illinois Beach State Park in Zion, IL. The goal of this five-year project is to determine the effectiveness of submerged shoreline stabilization structures for both erosion mitigation and potential fish habitat. The structure is made of three ridges of limestone boulders that will provide shoreline protection but will also dynamically respond to changing lake levels, winter storms, and currents.
Researchers from the LMBS and the Illinois State Geological Survey will monitor the structure for changes in physical and biological characteristics. LMBS researchers are using a combination of SCUBA surveys, gill nets, beach seines, and benthic cores to monitor colonization by quantifying the fish and invertebrates present at the site. This research is also complementary and comparable to our nearshore community surveys where some of the same data is collected. LMBS researchers have already explored the site and conducted preliminary SCUBA surveys for fish.
Lake Michigan constitutes an important and valuable resource for Illinois anglers. Most recreational fishing in Illinois waters targets yellow perch (Perca flavescens) or salmonines (i.e., Chinook salmon, Oncorhynchus tshawytscha; Coho salmon, O. kisutch; rainbow trout, O. mykiss; brown trout Salmo trutta; and lake trout Salvelinus namaycush). Additional angling effort is directed at other species such as the black basses (especially smallmouth bass, Micropterus dolomieu) and freshwater drum (Aplodinotus grunniens).
Since 1985, we have conducted regular creel surveys of recreational shore and boat anglers along the Illinois shoreline. This is a great opportunity to interact with the public and see the quality and quantity of game fish in Lake Michigan. We ask anglers about the fish they are targeting, what they have already harvested, expenditures, and time spent fishing in a specific area. Helicopter surveys are done every few years to count anglers along the entire Illinois shoreline. Length and weight are taken from a subsample of harvested fish. Our creel survey provides valuable data about fishing effort, harvest, and distribution of important sport fish; these are important components of the multifaceted datasets used by the Illinois Department of Natural resources to cooperatively manage Lake Michigan’s fisheries alongside other state, tribal, and federal partners.
Surveys of lake trout spawning habitat at offshore reefs
In another collaborative project with the Illinois Department of Natural Resources, surveys are being conducted on preferred spawning habitats of lake trout (Salvelinus namaycush). A GPS and echo sounder are used to determine the depth and shape of the reef. A hydroacoustic towfish gives side-scan images which illustrates the types of substrate on that reef. This study can lead to a better understanding and conservation not only of lake trout, but eventually other essential fish living in Lake Michigan.