The river provides recreational opportunities and important habitat to fish and wildlife. Flora of the area includes the Mad River fleabane ("Erigeron maniopotamicus"), a wildflower which was named for the river. Key fish species include coho salmon ("Oncorhynchus kisutch"), Chinook salmon ("O. tshawytscha"), and steelhead ("O. mykiss"), which were federally-listed as threatened in the Mad River in 1997, 1999, and 2000, respectively. Two threatened osmerid species - longfin smelt ("Spirinchus thaleichthy") and eulachon ("Thaleichthys pacificus") - are also listed as present in the estuarine portion of the Mad River, but have not been observed in recent years.