Before entering the ocean, the river turns abruptly north near the triple junction of the Gorda, North American, and Pacific plates. This bend denotes the usual upper limit of the estuary, although brackish waters can extend as far upstream as Highway 101 during king tides. Although small, this estuary provides nursery habitat for juvenile rockfish (Sebastes melanops, S. rastrelliger) and several species of flatfish, including starry flounder (Platichthys stellatus), English sole (Pleuronectes vetulus), and speckled sanddab (Citharichthys stigmaeus). The estuary also serves as a migration corridor for salmonids and Pacific lamprey (Lampetra tridentata), and as a summer feeding ground for several marine species, including topsmelt (Atherinops affinis) and surf smelt (Hypomesus pretiosis). Pacific staghorn sculpin (Leptocottus armatus) prickly sculpin (Cottus asper), coast range sculpin (C. aleuticus), and Three-spine stickleback (Gasterosteous aculeatus) are present in the estuary year-round. Above the estuary, the Mad River is home to resident coastal cutthroat trout (O. clarki clarki), rainbow trout (O. mykiss irideus), Sacramento sucker (Catostomas occidentalis), and Humboldt sucker (Catostomas occidentalis humboldtianus). The Mad River Estuary is recognized for protection by the California Bays and Estuaries Policy. The Mad River watershed was described as at carrying capacity with 22 colonies of North American beaver (Castor canadensis) in 1954, from the river mouth to well upstream. These beaver were re-introduced into the North Fork Mad River in 1946, or possibly were migrants from the Little River (Humboldt County). North American river otter (Lontra canadensis) were also numerous. See also List of rivers in California Mad River, California - the small community near the western extent of Ruth Lake. South Fork Trinity River, which parallels much of the river References External links Friends of the Mad River Hatchery The Trust for Public Land (PDF) California Department of Water Resources Humboldt County Rivers of Humboldt County, California Rivers of Trinity County, California Six Rivers National Forest Rivers of Northern California