Researchers say every fish in B.C.'s Emerald Lake may have to be "sacrificed" after the discovery of a rare parasite in the water. But first, more testing needs to be done.

A person is pictured canoeing across Emerald Lake, which is usually open year-round, in B.C.'s Yoho National Park. Parks Canada has closed the lake until at least March 2025 after confirming B.C ...