The Arc project is designed to study how land forms in the Sacramento-San Joaquin Delta interact with freshwater inputs and tides to create habitat favored by native fishes. The investigation focuses on regions in the North Delta where fish surveys have shown relatively high populations of native fishes - regions including Suisun Marsh, the flooded Sherman Island and the Cache and Lindsey sloughs. The areas together form an arc, inspiring the project name "North Delta Arc of Native Fishes."