On a cold April morning, I’m greeted on a dock in Arnold’s Bay by three Upper Great Lakes Management Unit staff. The crew is dressed in bright orange floater suits and are busy preparing their boat and gear for another day on the water. By this point, the crew has been setting and checking nets daily in the Moon River basin for well over a week. Their days of practice are apparent as they fall into an easy rhythm of preparing for another day of Spring Walleye Index Netting. Minutes later we are pulling away from the dock and heading towards the first net to be checked.
The Upper Great Lakes Management Unit (UGLMU) is a branch of the Ontario Ministry of Natural Resources and Forestry that assesses and manages fisheries in Lake Huron and Lake Superior. The UGLMU team based in Owen Sound is focused specifically on the Ontario waters of Lake Huron.
The UGLMU conducts a variety of fisheries assessments from targeted surveys like Fall Lake Trout Index Netting and Spring Walleye Index Netting (SWIN), to more broad surveys such as End of Spring Trap Netting (ESTN), Broad-scale Monitoring (BsM), and creel surveys (related to recreational fishing). Due to the size of Lake Huron and the number of tributaries entering the lake, only a few locations, called Nearshore Assessment Zones or NAZs, can be assessed each year.
Over two years, 2024 and 2025, the Moon River NAZ is being assessed using several survey types including SWIN, Spring Walleye Electrofishing (SWEF), Spring Muskellunge Index Netting (SMIN), ESTN, and BsM. Collectively, these standardized surveys will give fisheries managers a comprehensive picture of the fish community in the Moon River NAZ and the ability to compare the data to past assessments. GBB staff were fortunate to join UGLMU staff for several of these surveys.
Spring Walleye Index Netting (SWIN)
SWIN is a live release spawning survey intended to monitor the status of spawning populations of walleye (Ogaa or Gaa in Anishinaabemowin), namely abundance and biological characteristics (e.g., age, sex, size). Walleye are captured in 6’ live capture trap nets during their spring spawning run and sampled for length, weight, sex, maturity, lymphocystis (a chronic disease of freshwater and marine fishes), lamprey marks, and aging structures (e.g., scales, dorsal spine). Species other than walleye are counted and released with minimal biological sampling. During a SWIN survey, walleye may also be marked for future population abundance estimation either with an external floy tag and/or an internal transmitter.
Spring Muskellunge Index Netting (SMIN)
The SMIN protocol was designed by UGLMU specifically to assess muskellunge (Maashkinoozhe in Anishinaabemowin) populations during the spawning run. SMIN surveys utilize live capture trap net gear in known or presumed muskellunge habitat. Captured muskellunge are biologically sampled for length, weight, girth, sex, and may be affixed either with an external floy tag or have an internal transmitter implanted to monitor future movements and survival. The protocol uses a roving design which involves moving nets regularly depending on muskellunge catches. This approach allows for a large number of sites and areas to be surveyed in a relatively short period of time, which is important given the relatively low abundance of adult muskellunge and their accessibility to nearshore assessment gear for a limited period of time during the spring spawning run.
Broad-scale Monitoring (BsM)
The BsM survey type to is intended to describe the broader fish community. The netting gear utilized in this survey includes both large and small mesh gillnets. Large mesh gillnets target fish larger than 20 cm in length, the size range of interest to anglers. Small mesh gillnets target smaller fish, the size range of interest to large predator fish. A variety of information is collected from the fish caught including weight, sex, maturity, ageing structures (scales and/or ear bone), contaminant sample from muscle, and stomach contents. In addition to describing the distribution, amount, and diversity of fishes in Ontario, the BsM program also collects information about physical and chemical water characteristics, aquatic invasive species, and fishing effort.
A great deal of information was collected by the UGLMU over many weeks of intensive surveying. These efforts, and additional surveys in 2025, will help management biologists better understand how fish communities in the Moon River NAZ are doing.
You can help too! If you catch a fish with an external floy tag or an internal transmitter, call the phone number on the tag and report the unique ID number.
The results from these latest survey efforts will be shared with the public in the next State of the Bay report.
Read the fish communities section of the State of the Bay report to learn more!
