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Illustration courtesy of Kate Schwartz

Yellow Perch Populations

Wa hia hé:ta (Yellow Perch) Populations

Illustration courtesy of Kate Schwartz

1. Indigenous perspectives

2. Overview

3. What we’ve learned

4. Implications

5. What can I do?

6. Related indicators

7. Related community stories



We turn our minds to all the Fish life in the water. They were instructed to cleanse and purify the water. They also give themselves to us as food. We are grateful that we can still find pure water. So, we turn now to the Fish and send our greetings and thanks.

Now our minds are one.

Yellow perch spawning in Cornwall, Ontario. Photos courtesy of Stephany Hildebrand

Yellow perch spawning in Cornwall, Ontario. Photos courtesy of Stephany Hildebrand


Yellow perch are important for the Upper St. Lawrence River’s ecology and communities across the region. This species is so important that the Great River Rapport team decided to start their research on ecosystem health with yellow perch.   

Many people who grew up along this stretch of the river have memories of perch being plentiful and large. They can remember returning from a morning fishing trip with four or five fish to a pound. Today, local community members observe that yellow perch seem to be scarcer and smaller than they used to be. Meanwhile, Lancaster perch rolls (a well-loved Eastern Ontario specialty) have become increasingly expensive. So, what’s happening to yellow perch populations? Are they declining everywhere? Why are they declining? These were important questions for the Great River Rapport team to try to answer when looking at this indicator.  

As part of the assessment, the team gathered information from different sources. They looked at data from fisheries, government monitoring programs and river sediment samples. They also talked to local people who had spent their lives on the water. 

Some of what the team found was expected, but other findings were surprising. Below is a summary of some of the key findings from the assessment.

What We’ve Learned

Yellow perch populations peaked in the 1970s and 1980s; recent trends vary by region

Looking at big picture population trends, we found that yellow perch populations in the Upper St. Lawrence River have declined. This is particularly the case since the late 1970s—a time when many people have memories of abundant yellow perch. But the assessment also showed other important trends.  

Yellow perch populations increased over the first half of the 20th century, peaked in the 1970’s and 1980’s, and started to decline in the late 1980’s.

Population trends also vary between different sections of the river. Since the early 2000s, yellow perch populations have either stabilized or improved in the Thousand Islands, Lake St. Lawrence, and the Quebec section of Lake St. Francis. However, in the Ontario section of Lake St. Francis, yellow perch populations began to drop in 2010 and, as of 2020, remained low.  

These data raise new questions. Why do we see different trends in different parts of the river and (in the case of Lake St. Francis) even in different parts of the same section of the river? Why do we see this peak in populations in the mid-20th century? Some of the factors that we discuss below help to shed light on these questions. 

This graph shows the ‘catch per unit effort’ (or CPUE) from government monitoring programs in different sections of the Upper St. Lawrence River. Graph adapted from OMNRF, NYSDEC, MFFP

Yellow perch are an iconic and important prey species  

Yellow perch are native to the St. Lawrence River and are important for ecological, cultural and economic reasons. The species plays an important role in the food web as both prey and predators. They spawn in the springtime, and in the summer months they prefer shallow, vegetated slow-moving waters. In the winter months, they move to deeper waters. When the fish are young, they eat zooplankton, tiny animals transported on water currents. As they get older, they start eating small fish and larger invertebrates, like snails, worms and leeches. Yellow perch is, in turn, an important food source for larger fish like walleye, bass and pike, and other wildlife like cormorants.  

Yellow perch are an iconic species for people living along the Upper St. Lawrence River. Today, they are still the most abundant fish species in the main channel of the river and make up between 40-75% of the total fish population. The species supports important fisheries in the Upper St. Lawrence River.  

This infographic shows the relative population of selected fish caught in government monitoring programs. OMNRF 2020 and NYSDEC 2020.

An increase in nutrient levels in the mid-20th century helped the river support more yellow perch

Nutrients, like phosphorus, feed plants, which are a food source for invertebrates. Plants and invertebrates, in turn, provide food and habitat for fish like yellow perch. From the late 1940s to the 1970s, human activities led to a large amount of nutrients entering the Great Lakes and St. Lawrence River. These included agricultural runoff, the use of detergents containing phosphates, and poorly managed sewer systems.   

Nutrients are important for the river ecosystem. But too many nutrients can lead to negative impacts, including algal blooms. In 1972, the governments of Canada and the United States signed the Great Lakes Water Quality Agreement to help restore and protect water quality. This agreement led to actions to reduce phosphorus pollution.  

Looking at the data for both fish and nutrients over time, yellow perch populations rise with the increase in nutrient levels. Yellow perch population then also decline as nutrient levels decline. Nutrients are only one factor influencing yellow perch population trends. But this data helps to answer our question about why yellow perch populations appear to peak in the 1970s. 

Chart showing how changes in the level of nutrients in the river contributed to changes in other parts of the food web, including plants, invertebrates, yellow perch, and larger predator fish species. Data adapted from Schelske 1991 

A growing cormorant population places pressure on yellow perch, round gobies may lessen this pressure

Cormorants are another potential reason yellow perch populations declined after the 1970s.   

In the 1950s and 1960s, the number of double-crested cormorants in the Great Lakes and St. Lawrence River plummeted. A major reason for this drop was high levels of toxic chemicals in the bird’s diets, including pesticides (e.g. DDT). These chemicals led to thinner eggshells and other health problems. In the 1970s, new regulations helped to reduce the use of such chemicals. Cormorant populations started recovering, and their numbers have increased rapidly.   

Up until the early 2000s, yellow perch were an important food source for cormorants in the Upper St. Lawrence River, making up about 46% of the bird’s diets. But over the 2000s, an increase of round gobies (an invasive species) has led to a shift in cormorant diets. By the late 2000s, cormorants were eating about 49% round goby and only 20% yellow perch.  

Chart showing the relative percentage of yellow perch and round gobies in cormorant diets over time. Data from Johnson et al. 2015 

Commercial and recreational fisheries also place pressure on yellow perch

Fishing can contribute to long-term declines in fish populations if it is not done in a way that is sustainable. And this may be the case for yellow perch in some areas of the Upper St. Lawrence River. 

The amount of yellow perch caught by recreational fishers in the Ontario section of Lake St. Francis peaked in 2009, with an estimated 110,000 lbs harvested. After 2009, the quantity of yellow perch caught per hour began to drop.  

When we look at commercial fishing in the same area, we find a spike starting in 2010. In the case of commercial fishing, this spike was due to a change in regulations. In 2010, data available at the time showed that perch populations were recovering. Based on this information, the Ontario government changed its fishing regulations to allow commercial fishers in the Ontario section of Lake St. Francis to harvest three times more yellow perch than before. This increased the total to 18,832 lbs, which is still well below the estimated catch of recreational fishers in the area.  

Differences in fishing regulations could help explain the contrasting population trends in different areas of the river. On the Quebec side of Lake St. Francis, for example, there is no commercial fishery and live bait isn’t allowed. These factors could have an impact on population trends.

Data from OMNRF


The Great River Rapport team’s assessment of yellow perch revealed important trends, as well as potential reasons for some of these trends. The findings also help us identify recommendations to better protect this iconic species.   

The changing nutrient levels in the Upper St. Lawrence River have impacted the number of yellow perch that the river can support. Today, phosphorus levels have returned to pre-industrial pollution levels and the yellow perch populations reflect this shift, with a decrease from  the 1960s and 1970s populations. We need to consider revising fishing regulations to adapt to the changing conditions in the river.   

Double-crested cormorants can also place pressure on yellow perch populations, so we should continue monitoring their populations.  

Finally, the team’s assessment highlighted some important gaps in the data that is currently available. A major gap is the lack of long-term monitoring programs in the Brockville and Cornwall/Massena/Akwesasne sections of the river. More information about trends in these sections will help us better understand yellow perch populations in the Upper St. Lawrence River as a whole.   

What can I do?


Get outside and use the power of image recognition technology to identify wildlife, plants and fungi, and learn about the many organisms all around you. Earn badges for observing different types of species and participating in challenges.


The next time you’re out fishing, why not take part in citizen science by using the MyCatch app to identify and track your catch? This app can be used recreationally or in angling tournaments, and the data collected can later be used to help protect these fish species!


Contribute to citizen science by sharing your species observations on iNaturalist. Simply upload a perch photo and the app will provide suggestions for identification, information on its traits and allow other naturalists to share their own suggestions and observations.

Blue Fish Radio

A podcast that features subjects and people of special interest to the future of fish and fishing. Includes interviews with lead researchers and local experts in the field of fish biology, aquatic habitat, and sustainable fishing.

Encyclopedia of Life

NatureServe is a source for information on rare and endangered species and ecosystems in the Americas. This online guide provides information on the 100,000 species and ecosystems that they track.


Species profile of Yellow Perch, including overview, distribution, conservation status, and classification

Fishing Regulations

Government of Ontario

Gouvernement du Québec

New York State Department of Environmental Conservation

Document with information on the New York fishing regulations.

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Kate Schwartz – The Naturalist

Kate is a young, knowledgeable naturalist, with a deep love and curiosity for the natural world. She has translated this passion into lifelong learning, a career, and through it, she is making a contribution to the Great River Rapport.

Norm Seymour – The Duck Hunter

Norm Seymour lives and breathes ecology. He’s spent a lifetime studying it, teaching it, and writing about it. Now he’s sharing everything he knows for the benefit of Great River Rapport.

Mackenzie Petrie – Know the River

There’s a new generation of avid anglers in our midst—and they’re filled with passion, generational knowledge, and a deep connection to the river. Meet one of them, Mackenzie Petrie.

Nancy Hildebrand – The Food Forager

We all connect to nature in different ways. For some, it’s through a walk, hike, snowshoe or cross country ski in the great outdoors. For others, it’s heading out to a river to paddle a kayak, canoe, or paddleboard. For foragers, that bond comes from collecting wild foods.

Ron Macdonald – Power of Water

With a connection to the great river dating all the way to the construction of the moses-saunders dam, Ron MacDonald is a man-in-the-know when it comes to changes to our local waterway.