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Yellow Perch Populations

Yellow Perch Populations

1. Indigenous knowledge

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 an important species for the Upper St. Lawrence River and its People. Their populations have varied in size over the past century. Notably, there was a peak in yellow perch abundance between the 1960s and 1980s that followed a period of nutrient enrichment in the Lake Ontario-Upper St. Lawrence basin. Yellow perch abundance has since decreased with the gradual reduction of nutrient inputs into the river dating back to the 1970s. Long-term monitoring programs initiated in the Thousand Islands (1977 & 1989), Lake St. Lawrence (1986), and Lake St. Francis (1984 & 1996) have shown a variation in yellow perch abundance over the past few decades, with populations generally stable in the Thousand Islands and Lake St. Lawrence.

Opposing trends are present in Lake St. Francis, however, with yellow perch abundance decreasing in the Ontario portion of the lake, and increasing in the Quebec portion—potentially reflecting differences in fisheries management between the provinces. Other factors, such as double-crested cormorant predation, also likely affect yellow perch populations but to a lesser degree than nutrient concentrations and fisheries. The river is changing and so is the carrying capacity for yellow perch. Fisheries regulations need to account for these changes to ensure that yellow perch populations are maintained in the future.

What We’ve Learned

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

Long-term fish biomonitoring programs were initiated in the late 1970s and 1980s in the Upper St. Lawrence River. If we look instead at historical trends from fisheries catches over the past century, we see that these monitoring programs began when yellow perch populations in the river were at a high peak. This peak was followed by a consistent decrease in the size of yellow perch populations from the late 1970s through to the early 2000s. Since the early 2000s, yellow perch populations have either stabilized or recovered in the Thousand Islands, Lake St. Lawrence, and the Quebec portion of Lake St. Francis. However, in the Ontario portion of Lake St. Francis, yellow perch relative populations began to drop in 2010 and have remained low. There are currently no long-term monitoring programs to assess fish populations in the Brockville and Cornwall/Massena/Akwesasne sections of the river. 

Graph addapted from OMNRF, NYSDEC, MFFP

Yellow perch are a key iconic prey species ecologically and culturally

The yellow perch holds ecological, cultural, and economic importance for the Upper St. Lawrence River. Yellow perch are native to the St. Lawrence River and spawn in the springtime. They prefer shallow, vegetated, slow-moving waters in the summer months, and move to deeper waters in the winter. Yellow perch occupy a key position in the food web, both as prey and predators. As they grow, their diets shift from zooplankton, to invertebrates and small fish. Yellow perch are also an important food source for larger fish, such as walleye, and other wildlife. They are also an iconic species for people living along the Upper St. Lawrence River and there is a rich history of human relations with yellow perch. As the most abundant fish species in the main body  of the river, making up between 40-75% of the fish community, yellow perch support important fisheries in the Upper St. Lawrence River. Yellow per make up over 90% of recreational harvests (in Lake St. Francis) and between 60-70% of commercial catch in the Upper St. Lawrence River as a whole.

Data from OMNRF 2020 and MFFP 2020

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

Nutrients, such as phosphorus, feed plants and invertebrates, which, in turn, provide food and habitat for yellow perch. From the late 1940s to the 1970s, the use of phosphate-based detergents, poorly managed domestic sewer systems, among other factors, led to a dramatic increase in nutrient levels in the Great Lakes and St. Lawrence River. While nutrients are important for the river ecosystem, too many nutrients can lead to negative impacts, including algal blooms. In order to restore and protect water quality, the governments of Canada and the United States signed the Great Lakes Water Quality Agreement in 1972, which led to actions to reduce phosphorus pollution. When looking at the historical data, we see that yellow perch populations rise along with the increase in nutrient levels, and then decline as nutrient levels decline. This suggests that the increase in nutrient levels in mid-20th century helped the river to support unusually large yellow perch populations.

Data adapted from Schelske 1991

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

Prior to the 1970s, double-crested cormorant populations in the Great Lakes and St. Lawrence River had declined significantly, in part due to the impacts of pesticides such as DDT. In the 1970s new pesticide regulations allowed cormorant populations to begin to recover, and they have now reached unprecedented numbers. Up until the early 2000s, yellow perch were an important food source for cormorants in the Upper St. Lawrence River, making up roughly 46% of their diet. Over the course of the 2000s, however, a steady increase of round gobies (an invasive species) has led to a shift in cormorant diets. By the late 2000s, cormorant diets were made up of 49% round goby and only 20% yellow perch. So, what we learn from this data is that the growing number of cormorants in the region may be putting pressures on yellow perch (contributing to declines in yellow perch populations). However, cormorants are also starting to rely more on round gobies, and this alternative food source may lessen their impact on yellow perch populations.

Data from Johnson et al. 2015

Commercial and recreational fisheries also place pressure on yellow perch

If it is not sustainably managed, commercial and recreational fishing can contribute to long-term declines in fish populations. This appears to be the case for yellow perch in some areas of the Upper St. Lawrence River. The quantity of yellow perch caught by recreational fishers in the Ontario portion of Lake St. Francis peaked in 2009, when over 110,000 lbs of yellow perch were harvested. After 2009 the quantity of yellow perch caught per hour began to drop. When we look at commercial fishing, we find a similar spike in 2010. In 2010, government regulations changed to allow three times more perch to be harvested by commercial fishers in the Ontario side of Lake St. Francis, raising the total to 18,832 lbs. The patterns documented by the monitoring and harvest data suggest that the combined pressure of recreational and commercial fishing activities on the yellow perch population in that area were not sustainable given the current conditions.

Data from OMNRF


The rise and fall of nutrient levels in the Upper St. Lawrence River have had an important impact on the number of yellow perch that the river can support at any given time. With the decline in nutrient levels—following efforts to reduce phosphorous pollution—the river cannot support as many yellow perch as it could in the 1960s and 1970s. To maintain current yellow perch populations in the Upper St. Lawrence River, fisheries regulations need to be adapted to accommodate the changes in nutrient levels, and therefore the number of yellow perch that the river can support. Monitoring of the population size of double-crested cormorants, a major predator, is recommended as the birds can place additional pressure on yellow perch populations. Data gaps identified in this report, including lack of long-term monitoring data in Brockville and Cornwall/Massena/Akwesasne sections, also need to be filled to provide a better picture of the yellow perch populations in the whole of the Upper St. Lawrence River.  

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.

Related Indicators

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Fish Index

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Norm Seymour – The Duck Hunter

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Mackenzie Petrie – Know the River

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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.