Foul hooked is a term used to describe a fish that is hooked on the body other than its mouth. In British Columbia, when a fish is foul hooked, it must be released with care. It is illegal to keep a foul hooked fish. Attempting to foul hook or intentionally foul hooking a fish is also illegal, this is known as snagging.
Accidentally foul hooking a fish can be pretty common when fishing in a stream during the salmon season. There are not many ways to avoid foul hooking fish, such as making sure your hook is not dragged through a school of fish. If you are float fishing, adjust your float depth so your hook does not drift through the fish (see short floating). If it becomes impossible to avoid foul hooking fish, it would be a good idea to stop fishing that particular area.