https://oodmag.com/ask-a-co-are-public-waterbodies-with-private-access-restricted-for-use/
Q: What factors would cause a lake to be considered private and unavailable for fishing to the general public? For example, can access to a lake that is surrounded by multiple private properties, but is accessible through a tributary either by boat or on the ice, be restricted?
Dave Bradford, Caledon
Natural waterbodies
A: Generally speaking, natural waterbodies in Ontario are not private. If the lake is accessible by a navigable waterway, then it may be accessed for the purpose of fishing. However, if the bed of the lake is private, and entry is prohibited under the Trespass to Property Act or the Security from Trespass and Protecting Food Safety Act, 2020, you will require permission to disembark or anchor.
The Fish and Wildlife Conservation Act, 1997 prohibits individuals from fishing or hunting in contravention of the Trespass to Property Act, meaning that generally a person can only fish or hunt on private property with permission from an occupier of that property. The ownership of the bed of waterbodies in Ontario can vary significantly, both across the province and even within different stretches of an individual river or stream.
Complications
Complicating the matter, ownership of the bed of the waterbody may be different from the adjacent (riparian) lands that flank it. If the bed of the waterbody is owned by the Crown, then a person can walk up the watercourse and angle within it regardless of the ownership of the riparian lands. If the bed of the watercourse is privately owned, then a person cannot do this unless they have permission from the occupier.
Landowners or anglers with questions about the ownership of the bed of a specific waterbody are encouraged to contact their local MNRF district office.
Answers by: David Critchlow Provincial Enforcement Specialist, MNRF