Believe it or not, Hamilton Harbour is home to a diverse fish community. It sustains at least 45 species, and perhaps more surprisingly to some, the fish choose to live there.


When most people think of fish migration, they think of salmon and trout that travel long distances to spawn in the places they were born. People see the large fish navigating the natural barriers and bouncing up creeks, like our nearby Grindstone and Spencer Creeks.

Lately, the science community has gained a lot of knowledge on the migration of important, but lesser-seen fish through a simple technology called acoustic telemetry.


Acoustic telemetry can be used to track where fishes are throughout the year. It involves the surgical implantation of a small transmitter (typically no larger than an AA battery) in a fish and deploying receivers throughout the bodies of water in the study. The transmitters ping every three to five minutes. When a pinging fish swims past a receiver, it records their presence. In this way, a fish can be “followed” with minimal effort after the initial set up of surgeries and receivers.

Setup for a telemetry project with the transmitter in a fish “pinging” to be detected by the receiver.
Photo credit: Fisheries and Oceans Canada

Fisheries and Oceans Canada, in collaboration with researchers at Carleton University, University of Toronto Scarborough, the Ontario Ministry of Natural Resources and Forestry (MNRF), Royal Botanical Gardens, and Conservation Halton, piloted this approach in Hamilton Harbour in 2015. This project has since evolved to cover much of the Harbour and many of the connecting rivers. The network of receivers has further expanded across Lake Ontario to connect other telemetry projects in Toronto Harbour, Bay of Quinte, and the Niagara River (among other areas). This expanded network is further linked into the Great Lakes Acoustic Telemetry Observation System (, which is a hub of data sharing for researchers in all of the Great Lakes.

There have so far been many interesting findings. An American Eel ventured all the way from the Bay of Quinte to Hamilton Harbour, and in the fall, Hamilton Harbour Walleye, Freshwater Drum, and Longnose Gar travelled to Toronto Harbour and the Niagara River.

The researchers are making discoveries all the time through this approach. More importantly for the Hamilton Harbour Remedial Action Plan, the acoustic tracking program is being used to monitor fish stocking efforts in the Harbour.

Tracking Walleye

  • Tagged Walleye being released Photo credit: Fisheries and Oceans Canada
  • Walleye core areas for winter 2015. Red areas are higher use while blue is lower use. Source: Fisheries and Oceans Canada
  • Walleye release to Hamilton Harbour. Photo Credit: Maria Pricop

The Remedial Action Plan has goals to bring back top predators and establish a more natural food chain – one that is less dominated by Carp, Brown Bullhead, and Goldfish.

In 2012, the MNRF stocked Walleye as a way to jump-start the restoration of the Harbour’s natural fish community. Approximately 100,000 summer fingerlings were released near Pier 4 in Hamilton, and are now well established in the Harbour. Since then, other stocking efforts have been undertaken including another release in 2018. Monitoring efforts and fishers alike report that the Walleye being caught from the Harbour are in top condition.

Telemetry efforts paired with studies of dissolved oxygen (fish need oxygen to breathe too) show preferred locations in the Harbour, how preferences change as oxygen levels decrease in the summer, and ultimately that the Walleye are staying in the Harbour for much of the year. If they leave to visit Lake Ontario, they also come back. This not only means that the stocking efforts are working, but that fish choose Hamilton Harbour as a home even though they may migrate in, out, and within the Harbour with the changing seasons.

Movement of Walleye within the Harbour depends on a lot of things, but the dominating factors are dissolved oxygen levels, temperature, and where their prey are.

This information is incredibly useful for managing habitat in the Harbour. It pinpoints areas to install fish habitat to ensure they can find and use it.

After all, what’s the use of creating habitat when you don’t know if fish will use it?

Resurgence of a Fishery

Anglers migrated to the Harbour, too. The Walleye stocking has been getting a lot of attention in the fishing community and has re-sparked a recreational fishery. Like clockwork, when the Harbour freezes over in the winter, out come the fishing huts. Some have said the Walleye fishery rivals that of the Bay of Quinte, but now you don’t have to drive as far. It’s reconnecting people to the nature in their backyard.

Importantly, Walleye of Hamilton Harbour have been tested for safe eating and are included in the Guide to Eating Ontario Fish found here.

Making Comebacks

Sadly, the Harbour and its fish community is nothing like what it used to be. It once flourished with cold water fishes like Cisco over a century ago and had dozens of inlets and wetlands on the south shores. Infilling of the Harbour and urbanization resulted in aquatic habitat losses and a fish community dominated by pollution tolerant species (e.g., Brown Bullhead) and non-native fishes (Common Carp, Goldfish, and more recently, Rudd). But thanks to recent stocking and trap-net monitoring efforts, Walleye are estimated to be the fifth most abundant fish in the Harbour!

Telemetry programs coupled with stocking efforts and dissolved oxygen studies are some of the tools needed for Hamilton Harbour to bounce back as a healthy ecosystem. Tagging more top-predators like Northern Pike, would be especially helpful, since habitat creation efforts in the Harbour have primarily focused on this species.

More and more it seems that the beauty of Hamilton Harbour lies below the waters, where there are stories to be heard of where the wild things go. We just need to be there to hear them.

Visit for more information about the Hamilton Harbour Remedial Action Plan and event listings.

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Last modified: October 18, 2018

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