Publication Date

March 2023

The Los Angeles River is a highly modified urban system. Upper tributaries of the watershed are located in Angeles National Forest and are in a relatively natural state, but below the forest boundary the tributaries and the mainstem consist of a series of completely channelized sections with a concrete bottom that includes a low-flow channel and vertical walls, sections where there are graded berms and a substrate that was either not stabilized with a concrete substrate, or where enough sediment has accumulated to provide a “soft-bottom” with vegetation, boulders, and variation in flow, and off-channel impoundments. Here we provide the results of fish surveys and both professional and community-contributed citizen science observations collected from 2007-2020 that document the presence of 29 species, of which six, found either in upper reaches (sections of the river with similar habitat and hydrologic characteristics) or in the estuary, are native to the river. To accompany these data, we also provide a novel classification schema identifying the unique reaches of the LA River.