Every fisherman has a story about the "one that got away." But Chet MacKenzie is dedicated to making sure that this particular species of fish in Lake Champlain doesn't get away – or disappear.
MacKenzie is a fisheries biologist with Vermont's Fish and Wildlife Department, and he's not trying to catch the sturgeon per se, but track them to learn more about where the fish go in Lake Champlain after spawning upriver.
Earlier this spring, MacKenzie and other biologists caught and tagged 10 sturgeon from the Winooski River, surgically implanting an acoustic tag into their abdomen.
“I thought it would take two or three years to catch enough fish, and then this spring we caught 16 sturgeon in the Winooski,” says MacKenzie. He says from 1998 to 2002 they only caught about seven fish.
Swimming with dinosaurs
Sturgeon are an ancient fish. They come from a family that’s around 133 million years old, when dinosaurs roamed the Earth. The fish have leathery skin instead of scales, and have big bony plates that protect them.
The fish can reach 200 pounds, and females can live to 150 years old. After they hatch out it could take a female sturgeon 25 years before she matures and spawns; once she spawns, she may only spawn once every four to eight years.
“So that's why adult mortality is important in terms of managing Lake Sturgeon because it takes a long time for those fish to mature and then they don't spawn every year,” says MacKenzie.
In Vermont and neighboring regions, sturgeon numbers are threatened by everything from over-fishing to attacks from sea lamprey to dams that limit their access to spawning grounds.
Listening for sturgeon
On a recent sweltering hot summer's day MacKenzie and Tyler Brown, also with Fish and Wildlife, headed out on Lake Champlain to listen for a distinctive "click" or "ping" that means a sturgeon is swimming within a mile from the boat.
“What we'd like to learn is you know where do they go on the lake, and other areas in the lake where we can actually sample for Lake Sturgeon,” says MacKenzie. He says then biologists can use this technology and find where fish congregate in the lake.
“Then we could measure over time and determine whether the populations are increasing or decreasing.”
MacKenzie motors the small boat out of the mouth of the Winooski River and toward the middle of the lake, looking for the edge of the shelf where the lake begins to get deep. Partway across the lake he kills the engine and turns on the acoustic receiver to see if he can pick up any fish.
“They send out a coded signal that can be picked up not only by a portable receiver like we're using today, but these stationary receivers set around the lake, so whenever a fish swims by it that tag will ping,” says MacKenzie.
About 28 stationary receivers are placed in strategic locations around Lake Champlain, such as in the mouths of rivers, allowing researchers can see any time fish go upstream or re-enter the lake. The acoustic tags embedded in the fish last about 10 years, significantly longer than the radio tags.
So far, says MacKenzie, he’s incredibly pleased that he’s been able to find all 10 fish that have been tagged with regularity.