Thousand Islands – Frontenac Arch is one of four ecoregions of the Mixedwood Plains. The Thousand Islands in the Saint Lawrence River have a distinctive flora and fauna and are a part of the biological corridor. The bedrock is mostly gneiss, granite and marble, more than a billion years old. The Frontenac terrain is the youngest of the Ontario portions of the arch, dated at 1.2 billion years old. These rocks were once part of a large mountain chain of the ancient supercontinent of Rodinia. There is also a meteor crater near Holleford, where the shield meets the limestone plains of southeastern Ontario. The area
North American river otter often than game fishes when both are equally available. Slow-moving species include suckers (Catostomidae), catfish, sunfish and bass (Centrarchidae); and daces, carp, and shiners (Cyprinidae). For instance, Catostomidae are the primary dietary component of North American river otters in Colorado's Upper Colorado River Basin. Likewise, the common carp ("Cyprinus carpio") is a preferred fish species for the North American river otter in other regions of Colorado. Fish species frequently found in the diets of the North American river otters include: Catostomidae, which consists of suckers ("Catostomus" spp.) and redhorses ("Moxostoma" spp.); Cyprinidae, made up of carp ("Cyprinus" spp.), chubs ("Semotilus"