Fish Communities

Fishing is a favourite pastime of many who spend time on Georgian Bay. But did you know that one of the best ways to study the health of the Bay is to look at the fish community? Fish are a useful indicator of aquatic ecosystem health because they reflect changes in nutrients, prey availability, water quality, and habitat.

Georgian Bay has undergone significant changes over the past century as a result of the overharvesting of fish, introduction of invasive species, deforestation in the watershed, and the more recent pressures of climate change. From primary producer to top predator, every part of the ecosystem has been, and continues to be, affected.

Indigenous people have observed changes in fish since time immemorial. More recently, fisheries biologists have conducted a variety of studies on the fisheries of Georgian Bay. Together, these sources of information tell us a lot about how conditions have changed over time. Below, we provide reports on six fish-community indicators—prey fish, smallmouth bass (shigan/noosa owesi), northern pike (gnoozhe), muskellunge (maashkinoozhe), walleye (ogaa/gaa), and lake trout (nmegos).

Prey Fish

Prey fish, also called baitfish or forage fish, are the small fish eaten by others for food. They make up the majority of fish in Georgian Bay and support key ecosystem functions by connecting the aquatic food web. Prey fish eat phytoplankton, zooplankton, and benthic (bottom-dwelling) invertebrates and, in turn, provide food for predators. 

Historically, prey fish in Lake Huron were quite diverse. In offshore waters, there was a mix of native prey species such as the deepwater cisco, sculpin, lake herring, ninespine stickleback, and trout-perch. In nearshore waters, species like the gizzard shad, spottail shiner, emerald shiner, young whitefish, and yellow perch were important in the diet of predators. Native prey were in balance with native predators. However, around the 1970s, the balance shifted to favour an abundance of the introduced, non-native alewife and rainbow smelt.

After peaking in the late 1980s, prey fish biomass in Lake Huron began a steady decline in the mid-1990s and reached a historic low in 2008, following the collapse of alewife populations in the early 2000s.

Changes in the prey fish community are believed to be the result of top-down and bottom-up pressures in the food web. At the top, introduced and abundant salmon species consumed an excess of alewives and other prey. At the bottom, a major decrease in offshore phosphorus and the spread of invasive zebra and quagga mussels caused declines in the production of phytoplankton, zooplankton, and benthic invertebrates. As a result, less food is available for young fish, which threatens their growth and survival. Given this combination of pressures, prey fish are “squeezed” in the middle.

Despite periodic increases of certain species, overall offshore prey fish biomass and diversity in Lake Huron remains low, although there is a higher representation of native species. A return to historic levels of prey fish biomass is unlikely due to several factors, including reduced nutrient inputs, high predation levels by recovering predator populations, and changes in food web dynamics that potentially favour nearshore bottom-dwelling species such as the round goby. This situation creates a potential food web imbalance, where there is less food energy in the system for predators.

Invasive Round Goby

The invasive round goby is believed to have become a significant prey item in Lake Huron that, until recently, has been very difficult to survey. Round gobies tend to concentrate in nearshore and rocky habitats, where they are harder to capture with traditional survey equipment. Fisheries managers are coming up with new technologies and piloting new strategies to better study round gobies and their habitat.

The United States Geological Survey Great Lakes Science Center has developed the “GobyBot,” an autonomous underwater vehicle that utilizes high-resolution video and images to identify and quantify fish species found on the lake bottom. Three hundred kilometres of GobyBot transects were collected in the Canadian waters of Lake Huron in the summer of 2022 and will undergo analysis.

The Upper Great Lakes Management Unit of the Ministry of Natural Resources and Forestry is testing out an electrofishing unit used alongside a high-resolution underwater camera to count round gobies. A recent survey in Owen Sound utilizing this survey equipment estimated 118 million round gobies (144 tonnes) during day surveys and 144 million (237 tonnes) during night surveys.

Improving understanding of the status and trends in the round goby population is important for several reasons. Round gobies compete with native bottom-dwelling species, prey on eggs and fry of native fish species, consume invasive dreissenid mussels and are now also an important food source for native predator species including walleye, yellow perch, smallmouth bass, lake trout, and lake whitefish.

Smallmouth Bass (Shigan/Noosa Owesi)

Warm-water predator
Habitat: Shoreline rocks and points, offshore shoals, deep water, associated with cover.
Trend: Unchanging

In eastern Georgian Bay, smallmouth bass are one of the more abundant predator species. Smallmouth bass were historically limited to the Great Lakes and have since been introduced to inland lakes. They have a broad diet and are highly sought after by anglers, making them both ecologically and recreationally valuable. The diet of young smallmouth bass begins at the bottom of the food web and expands to include almost all aquatic organisms as the fish mature. As a result, thriving smallmouth bass populations suggest productivity and good health in the lower food web.

Despite their abundance, they are affected by human activities, including harvesting, habitat disturbances, and shoreline development. Research looking specifically at smallmouth bass in eastern Georgian Bay is limited, however they are captured as part of broad fish community surveys, as well as surveys targeting other species, such as walleye. Although smallmouth bass populations in eastern Georgian Bay appear to be healthy, biologists cannot confirm a definitive trend for Georgian Bay.

There is some evidence to suggest that smallmouth bass are benefiting from increasing water temperatures as a result of climate change and the presence of the invasive round goby. Warming water temperatures may allow smallmouth bass to expand their range in the Great Lakes to areas that would have once been too cold. Smallmouth bass have also been found feeding on invasive round gobies, helping them maintain their status as one of the most abundant nearshore predators—if not the most abundant.

Northern Pike (Gnoozhe)

As a top predator in nearshore waters, northern pike can provide insights about the health of the nearshore food web and coastal wetlands, which are important spawning habitat for this species. Pike are also an important sport fish and face substantial fishing pressure, although harvest rates have dropped, likely due to less fishing effort, more restrictive harvest regulation, and more anglers practising catch and release.

Although northern pike are not considered threatened anywhere in Canada, they are as vulnerable to habitat loss as any other nearshore species. Periods of sustained low water levels, along with continued shoreline development, reduce the size of important coastal wetlands upon which northern pike rely. For example, the prolonged low water period from 1999 to 2013 contributed to declines in northern pike populations in Severn Sound and potentially other areas of eastern Georgian Bay. Further monitoring is needed to determine whether or not populations have rebounded since, as water levels have risen.

Muskellunge (Maashkinoozhe)

Known to many as “muskie,” these impressive fish are a native predator of nearshore environments and a highly sought-after trophy fish. In Ontario, the fisheries goal for muskellunge is for populations to be self-sustaining, and to maintain Georgian Bay’s world-class fishery. UGLMU surveys confirm the widespread distribution and presence of mature muskellunge throughout eastern Georgian Bay. Nevertheless, there is continued concern over the potential for high-quality spawning and nursery habitat to become degraded and subsequently impact the species’ natural reproduction.

Muskellunge have a low reproductive rate, grow rather slowly, and have had their spawning and nursery habitat affected by shoreline development and, at times, sustained low water levels. Good muskellunge nursery habitat requires a diverse community of submerged aquatic vegetation, but under persistent low water levels, wetland vegetation can shift to a more uniform, less diverse community.

Research has shown that muskellunge numbers in eastern Georgian Bay appear to be unchanging, indicating a naturally reproducing, sustainable population.

Lake Trout (Nmegos)

Lake trout are a useful indicator of the health of offshore waters. Assessing their populations can provide insights into food web productivity, the presence and effects of invasive species, and the availability and quality of fish habitat. In addition to their important ecological role, lake trout in Georgian Bay are caught commercially and recreationally.

Prior to 1940, numerous populations lived in Lake Huron–Georgian Bay’s deep offshore waters. An invasion of sea lamprey (an eel-like parasitic fish), overharvesting, and the decline of their major food source (the deepwater cisco) caused lake trout to collapse in all but two isolated locations: Iroquois Bay and Parry Sound.

In 1969, efforts began to rehabilitate lake trout. Sea lamprey controls were implemented across the Great Lakes. Using the same genetic strain of the Parry Sound lake trout population, fish were stocked across Lake Huron and Georgian Bay, and a fish sanctuary was established. The Parry Sound population of lake trout is one of the only populations to be considered fully rehabilitated outside of Lake Superior.

Unfortunately, lake trout populations have not re-established in most locations where they were found historically. The management goal for lake trout is to restore populations to the point where they are naturally reproducing. Recovery in Georgian Bay is slow, but indicators have recently been showing more positive trends than previously. However, the prospects for lake trout rehabilitation remain uncertain, due to reduced productivity in offshore waters and other ecosystem changes.

Walleye (Ogaa/Gaa)

Walleye, also called pickerel, are highly sought after in subsistence, recreational, and commercial fisheries.

Since the early 1900s, Georgian Bay walleye stocks have declined due to a combination of overexploitation, human alteration of rivers, and the introduction of invasive species. Dams can cut off access to spawning habitat and change the flow of water. High, fast-flowing water can threaten eggs by washing them away, while low water can cause them to dry out. In the Moon River, for example, where walleye spawning runs used to number over 30,000 fish, these numbers have dropped to only several hundred.

Since the early 1980s, efforts to rehabilitate walleye populations have included habitat restoration, stocking young fish, and imposing regulations that restrict harvest. These efforts have been met with limited success. To further walleye rehabilitation efforts, the Upper Great Lakes Management Unit is in the process of drafting a walleye management plan for the Ontario waters of Lake Huron.

In 2002, Shawanaga First Nation (SFN) opened a walleye hatchery to help offset pressures on walleye. The hatchery releases millions of walleye fry each year into the Shawanaga River. Reports have shown that SFN’s efforts are having a positive effect on the walleye population in this area.

Members of Shawanaga First Nation have been stewards of the lands and waterways for time immemorial, using the seven grandfather teachings to manage the resources that were given to the people from the creator. Education about, and conservation of, the walleye population within Shawanaga’s traditional territory is the main goal for the hatchery, so that all walks of life can enjoy the fishery for generations to come.

Shawanaga First Nation Fish Hatchery Brochure

A Story of Lake Sturgeon (Nme)

If you have been lucky enough to see a lake sturgeon (nme), you have had the privilege of laying eyes on Ontario’s largest and longest-lived freshwater fish. These gentle giants can live more than 100 years and were once abundant in the Great Lakes. Today, their populations are only a fraction of what they used to be. In fact, the Great Lakes–Upper St. Lawrence populations were declared threatened in 2006 by the Committee on the Status of Endangered Species in Canada (COSEWIC).

While lake sturgeon have long been valued by many First Nations, prior to the mid 1800s, commercial fishers considered them a nuisance because they tore their nets, as the fishermen were targeting other species, like lake whitefish and lake trout.

At that time, sturgeon meat had little value on the market, so captured fish were disposed of, left to spoil, or even used as fuel for steamboats. By mid-century, however, people began discovering profitable uses for lake sturgeon meat, eggs, and swim bladders, sending demand skyrocketing. In 1880, 3.4 million kilograms of sturgeon were harvested from the Ontario waters of the Great Lakes! By the early 1900s, the lake sturgeon harvest had declined to commercially insignificant levels, owing to steep population declines.

Sturgeon supply is in a critical state…. We think that some strong remedy should be adopted for the preservation of this fish, before it becomes entirely extinct in the waters of Georgian Bay.

Fisheries Commission Appointed to Enquire into the Fisheries of Georgian Bay and Adjacent Waters” for the Dominion of Canada, 1908.

Severely overfished lake sturgeon faced additional threats in the form of habitat alteration and water pollution. Dam construction cut off access to spawning habitat in rivers; activities such as farming and logging degraded habitat through sedimentation; and industrial pollution impaired reproductive success.

Adding to these stressors, the biological characteristics of lake sturgeon make them even more vulnerable. These fish are:

• Slow growing: They grow quickly during the first 10 years of life, then their growth slows.
• Slow to mature: Males first spawn at around 20 years of age, and females around 25 years.
• Only spawn periodically: Males spawn every two to three years and females every four to nine years.
• Have high site fidelity: Spawning adults typically return to the same spawning habitat each year.

Due to a combination of stressors and biological characteristics, the loss of spawning-age fish (through overfishing, for example) continues to have a big impact on the recovery of the lake sturgeon population. As evidence of this, most of the populations that were overexploited in the late 1800s and early 1900s still have not recovered. The lake sturgeon commercial fishery was closed in 2009 in the Ontario waters of Lake Huron, 100 years after its protection was first recommended.

Despite the fact that lake sturgeon have been around for millions of years, there are still many questions about the status of the population, as well as the species’ habitat preferences, movements, behaviour, and more. Report the lake sturgeon you see on the iNaturalist app!

Partner Profile: Shawanaga First Nation

In 2019, Shawanaga First Nation (SFN) and Georgian Bay Mnidoo Gamii Biosphere partnered on a multi-year project to study lake sturgeon (nme) in eastern Georgian Bay. Staff at SFN conducted interviews with elders and knowledge holders, commercial fishermen, and local residents to gain a better understanding of the species and their cultural significance. The Indigenous knowledge gained from the interviews, combined with existing science reports, helped identify potential lake sturgeon spawning sites. Several of these sites were monitored during the lake sturgeon spawning season in May and June.

While this project started down a path of bringing together different sources of knowledge to improve understanding, there is still much to be learned about lake sturgeon in eastern Georgian Bay. If lake sturgeon populations in this region are to recover over time, it will take a collaborative effort involving many dedicated partners on the coast.

Partner Profile: Upper Great Lakes Management Unit

The nearshore waters of eastern Georgian Bay and the North Channel support the largest contiguous distribution of muskellunge (maashkinoozhe) populations in the Great Lakes. Nearly 380 kilometres, stretching from the south end of Severn Sound, north to the mouth of the French River, and west to Sault Ste. Marie, represent prime nearshore muskellunge habitat.

Prior to 1996, very little was known about the population characteristics of this species, yet the area was perceived by anglers as supporting a world-class fishery. Since 1996, close to 30 targeted muskellunge spawning surveys at 10 different locations in eastern Georgian Bay and the North Channel have been completed by the Upper Great Lakes Management Unit (UGLMU) of the Ministry of Natural Resources and Forestry (MNRF).

During the UGLMU’s surveys, over 1,000 muskellunge have been captured, biologically sampled, and affixed with external identification tags. Subsequent recaptures of over 300 tagged fish have provided valuable insights into their movements. Some tagged muskellunge have been recaptured multiple times in both UGLMU surveys and by recreational anglers.

Fish scale samples collected during these surveys have been the source of genetic material that scientists at the Aquatic Research and Monitoring section of the MNRF have used to determine the genetic structure of muskellunge in Lake Huron. This work has revealed that muskellunge in Georgian Bay are made up of small populations with limited ranges and high site fidelity, meaning they return to the same areas to spawn year after year. These findings reinforce the importance of identifying and protecting these habitats in order to maintain self-reproducing populations of muskellunge in Georgian Bay.

Aquatic vegetation is a critical component of wetland nursery habitat for young-of-the-year muskellunge, or those born within the past year. A joint study with McMaster University and the UGLMU found that sustained low water levels and increased shoreline modifications may have contributed to the recent disappearance of young-of-the-year muskellunge at many sites in southeastern Georgian Bay.

Assessment and research efforts continue and will be necessary to address emerging challenges, including climate change, ongoing habitat loss, invasive species, and more interest among anglers in pursuing muskellunge.