State Forest. The lower portions of the river pass through Mendocino Woodlands State Park and the Big River Unit of Mendocino Headlands State Park before reaching the mouth of the river at the Pacific Ocean just south of the town of Mendocino. The Big River Estuary is the longest undeveloped estuary in the state. From the mouth, ocean salinities reach upstream in the summer and in the winter, when freshwater flows are greatest. The estuary has long been of conservation interest for its beauty and natural resources. The U.S Fish and Wildlife Service nominated the estuary for protection in 1980 under the Unique and Nationally Significant Wildlife Ecosystem Program. Although the nomination did not garner the desired protections, the estuary did receive protection in 2002, when the Mendocino Land Trust purchased a 7,334 acre parcel from the Hawthorne Timber Company. The land was donated to California State Parks as part of the Mendocino Headlands State Park. In 2010, the estuary waters were designated as a State Marine Conservation Area under the Marine Life Protection Act. Habitat and ecology The Big River is fed by precipitation, 90 percent of which falls between October and April. Annual precipitation averages on the coast at Fort Bragg and inland at Willits. Winter weather is characterized by low intensity rain. The summers are dry and cool, with coastal fog. The river provides recreation and groundwater recharge for agricultural and industrial water use for the community of Mendocino, California. The Big River provides wetland habitat for wildlife and cold freshwater habitat for fish migration and spawning. The anadromous salmonid populations native to the Big River are all listed as endangered or threatened under the federal Endangered Species Act. These include: coho salmon (Oncorhynchus kisutch), chinook salmon (Oncorhynchus tshawytscha), and steelhead trout (Oncorhynchus mykiss). Other native fishes include the anadromous Pacific lamprey (Lampetra tridentata), sculpins (Cottus spp.), three-spined stickleback (Gasterosteus aculeatus), and the Sacramento sucker (Castomus occidentalis). The Big River Estuary provides essential wetland habitat and has potential to provide critical salmonid habitat. The strong marine influences in the Big River Estuary are tied to a diversity of fishes. Pacific Herring (Clupea pallasi) lay their eggs in the estuary, shiner surfperch (Cymatogaster aggregata) and Bay Pipefish (Syngnathus leptorhynchus) give birth in the estuary, and juvenile English Sole (Pleuronectes vetulus) and copper rockfish (Sebastes caurinus) migrate to the estuary to rear. Many marine fish species also enter the