Willoughby is listed as a National Natural Landmark. Willoughby contains rainbow trout (wild and stocked), lake trout, landlocked Atlantic salmon (mainly stocked), rainbow smelt, burbot, yellow perch, longnose sucker, white sucker, lake chub, common shiner, and round whitefish which is a native species of extremely limited distribution in Vermont. Steelhead trout (rainbow trout) are not native to the region, but were imported to Lake Memphremagog from the Pacific Northwest. They migrate up the Barton River and Willoughby River to the lake to spawn.