alt Hacker NewsKayak fished the St. Croix river last year, on the border of Minnesota and Wisconsin, for smallmouth bass. Crystal clear water. Floated over several huge sturgeon, 4-6 feet long. The way they look, it feels like coming across a dinosaur. Thankfully they're bottom feeders.
Acipenser transmontanus are harmless sucker mouth fish, and lived in the local rivers long before our towns were even an idea.
They are usually strictly catch and release, but in a kayak could probably pull you a great distance. They are deceptively strong for their size, and a big part of local conservation efforts.
400 years is plausible, as they do live a long time when left alone. =3