Scientists are taking big steps to better understand the population of one of Lake Erie’s most important sportfish: the smallmouth bass.

In an ongoing study funded by Ohio Sea Grant, researchers led by Zak Slagle, fisheries biologist for the Ohio Department of Natural Resources (ODNR) Division of Wildlife, are tracking movements of the fish in Lake Erie using a technique called acoustic telemetry. Two years into the project, the team has already yielded significant findings that will help ensure the fishery is sustainable.

Each year, anglers spend hundreds of thousands of hours fishing for smallmouth bass on Lake Erie, contributing to the lake’s $1 billion fishing industry. Notably, anglers usually catch and release smallmouth bass, Slagle explained; during popular bass tournaments, anglers will move caught fish to boat launches so they can weigh them in.

“In order to best maintain the excellent fishery we have, we need to understand the population,” he said. “However, we don’t know a lot about how much they move in large lake environments.”

Smallmouth bass are generally considered to be sedentary, spending their entire lives within a small area of less than five square miles, yet scientists have never confirmed this using modern technology. If this is true, then fish displaced by tournaments may never make it back to their capture locations, which could function as a form of harvest, Slagle said. Greater catch-and-release mortality at popular fishing sites and low gene flow could be concerns as well.

On the flip side, if some bass are making long-distance movements, they could help repopulate areas and mediate gene flow between different parts of the lake. These traveling fish may also be more vulnerable to angling.

“A better grasp of bass movements and possible migrations would also help management agencies like ODNR better design studies to capture these fish and collect important data to help us inform anglers of their seasonal movements,” Slagle said.

To study bass movements, Slagle’s team tagged smallmouth bass with electronic transmitters that emit unique, ultrasonic soundwaves into the water. These soundwaves are then picked up by an array of over 400 acoustic receivers, providing useful location data. Researchers work through the Great Lakes Acoustic Telemetry Observation System to share data across its network, allowing them to see where tagged fish go.

“We have had very successful tagging seasons,” Slagle said. “We do have to physically retrieve the receivers, so the data do take a while to come in, but they allow us to learn a lot about fish behavior in the end.”

In 2023, the team tagged 60 smallmouth bass in the Bass Islands and in Fairport Harbor. In the spring of 2024, researchers tagged a total of 156 bass around the Bass Islands, Kelleys Island, Lorain Harbor, and Ashtabula Harbor across eight days of field work. They captured the fish using a combination of electrofishing and volunteer angling.

So far, preliminary results show that smallmouth bass don’t move very far, with the majority of tagged fish sticking to the same small area near where they were captured. However, a handful of fish made surprising movements: one fish tagged in Fairport Harbor traveled to the north shore in Ontario, returning within a week, and another tagged near North Bass Island migrated up the Detroit River to Lake St. Clair and back — twice.

“This one fish has moved nearly 500 miles in the course of 18 months, which is way farther than any bass has been known to move,” Slagle said. “What we’re seeing is a phenomenon known as ‘partial migration,” where some individuals make long-distance movements and others do not.”

Initial findings also indicate that angling-tagged fish move nearly twice as far as electrofishing-tagged fish and that smallmouth bass tend to avoid deeper water in the Central Basin. They are most active when moving to spawning grounds in April or overwintering grounds in September through October, but don’t move much during the nesting season in May and June.

“Now that all the tags are out, we get to sit back and let the data roll in,” Slagle said. “The transmitter batteries are good for about three years, so we will continue to get more data through around 2027.”

The team will continue to annually download and refresh the batteries in their receivers, and partners around the lake will do the same with their receivers, Slagle said. Once the data is downloaded, Slagle can run it through scripts to generate maps, graphs, and even movement animation to better understand when, where, and why smallmouth bass move on Lake Erie.

“The project is going great, and I am very appreciative of the Sea Grant funding I received to get it going,” Slagle said. The project is expected to wrap up in 2027.

For more information about this research, contact Slagle at zachary.slagle@dnr.ohio.gov, watch his recent Freshwater Science webinar, or read a prior Ohio Sea Grant article.

Ohio Sea Grant is supported by The Ohio State University College of Food, Agricultural, and Environmental Sciences (CFAES) School of Environment and Natural Resources, Ohio State University Extension, and NOAA Sea Grant, a network of 34 Sea Grant programs nation-wide dedicated to the protection and sustainable use of marine and Great Lakes resources. Stone Laboratory is Ohio State’s island campus on Lake Erie and is the research, education, and outreach facility of Ohio Sea Grant and part of CFAES School of Environment and Natural Resources.