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The flood-controlled LA River supports fish life

Long before European settlers arrived in America, the Los Angeles River was an important source of food and water for native peoples. Europeans settled the Los Angeles area in part because of the river and the fertile alluvial soils it provided. The river and its tributaries frequently flooded and changed course, forming wide alluvial floodplains that extended across southern Los Angeles from modern day Santa Monica to Long Beach. When Los Angeles began its transition to teeming metropolis and settled these flat floodplains, the river's natural characteristics led to disastrous flooding.

In the interest of saving lives and property, civil engineers sloped the banks and encased them in more than 30 miles of concrete, a move that completely altered the fishery. Recently completed UC Cooperative Extension research indicates that, despite the concrete and influx of pollutants from LA storm drains and sewage treatment plants, the Los Angeles River is still capable of sustaining life.

Working with Friends of the Los Angeles River, an organization interested in restoring the LA River to a more natural state, UCCE natural resources advisor Sabrina Drill surveyed the fish population in the river's eight-mile Glendale Narrows area, a section that, because of its underlying geology, was left with a natural bottom. The researchers discovered a diverse and bountiful fish population in this stretch of the river.

"To our surprise and delight, toxicity reports show the small number of fish we tested to be free of mercury and have extremely low levels of PCBs," Drill said. "This may not be true for the rest of the river. Glendale Narrows is one of the cleanest sections, probably because the natural river bottom cleans itself and because of the high quality effluent coming out of upstream water reclamation plants."

The survey identified eight species of fishes, none of them native, plus tadpoles and red swamp crayfish in the river. The eight fish species are: fathead minnow, carp, black bullhead, Amazon sailfin catfish, mosquito fish, green sunfish, largemouth bass and tilapia. They hail from Africa, South America, Eastern North America and Asia.

Whether reestablishment of native species to the river is possible remains to be seen, and may not be the most important factor in river restoration.

"Difficult though it may be, you can't make the LA River what it used to be simply by digging up the concrete," Drill said. "Because of all the development, the water we import, and changes in hydrology, temperature, and water quality, it’s not the same system it was before people settled here."

But restoration can still take place, and Drill believes that in the next 10 to 20 years, large-scale habitat restoration and restoration of some historical floodplains will dramatically enhance the ecological function and natural beauty of the Los Angeles River.


LA River Fishing
USC film maker Megan McCarty created a seven-minute documentary on fishing the Los Angeles River, which includes an interview with UCCE's Sabrina Drill. See the video here:

L.A. River Fishing from Meghan Mccarty on Vimeo.

Click the link below for the complete 21-page report on the Los Angeles River fish survey.

The Los Angeles River winds through urban metropolis.
The Los Angeles River winds through urban metropolis.

Photo: Wikimedia Commons

Posted on Tuesday, October 19, 2010 at 11:35 AM
Tags: fish (6), Los Angeles River (5), Sabrina Drill (12)

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