If you hook a Hamilton Harbour walleye or largemouth bass with an antenna sprouting from its midsection, don’t be alarmed.

It’s not an alien species from another world or even an invasive species from another continent.

And if you see a bunch of Fisheries and Oceans workers scooping up vast quantities of fish with nets from a trolling boat, it’s not because they are planning a barbecue.

They’re actually stunning the fish by running an electric current through the water. After they land the fish in the boat, they take down some vital information about species and size before releasing them back in the harbour.

It’s all part of a major effort to better understand fish stocks and the behaviour of fish populations in the bay. Certain ones are being implanted with radio telemetry equipment so their movements can be monitored.

Scientists will take note of where walleye, bass, pike and other species spawn, if they spawn at all.

Fisheries and Oceans watch their movements throughout the year and see whether they venture into the lake.

It’s all information that can be used to devise plans to improve fish stocks of the future.

But for now they especially want to get the word out to anglers that if they catch a fish with an antenna, throw it back in, so the monitoring of the fish can continue. Or if the fish is kept, call the number on its tag and arrange a drop off of the telemetry device so it can be reused. The units cost up to $800 each.

Christine Boston, of Fisheries and Oceans Canada, the lead researcher in the monitoring project, says 50 fish last year were fitted with the acoustic telemetry and another 60 are planned for this summer. The monitored species include walleye, largemouth bass, northern pike, yellow perch and freshwater drum.

John Hall, longtime co-ordinator at Hamilton Harbour Remedial Action Plan, said, “This is brand new science that is available to us now that was not available when everybody began the harbour restoration (more than three decades ago).

"It gives us important feedback that will help in the future and will be of interest to scientists working on other restoration projects.

Since the ‘80s, shoreline habitat has been improved at several locations in Hamilton Harbour, most notably in Cootes Paradise, where a carp barrier and fishway has managed to keep destructive carp from the Cootes marsh.

But Hall says the harbour still has too much phosphorous from effluent from Woodward Avenue wastewater treatment plant. It is scheduled for an upgrade over the next several years. The Skyway wastewater treatment plant, on the Burlington side, recently went through an upgrade that has greatly reduced its phosphorus loadings in the harbour.

Phosphorus leads to algae growth that inhibits light to underwater plants that are a vital part of the food chain. As well, it all leads to less oxygen in the water, which negatively affects fish growth and reproduction.