The city of Los Angeles is preparing to remove parts of the LA River's concrete lining, but that may not be enough to bring back native fish, reported Zoie Matthew in Los Angeles Magazine.
"It's hard to do piece-by-piece restoration projects for things adapted to river and stream systems. And it's impossible for steelhead," said Sabrina Drill, UC Cooperative Extension natural resources advisor in Los Angeles and Ventura counties.
Steelhead need a continuous, rapidly flowing channel to complete their life cycle. Other native fish, such as the Arroyo chub, will need gravel, plants, sediment and pools to be restored.
"Ecological heterogeneity is really important," Drill said. "Fish tend to need different kinds of habitat."
Warmer water temperature is another concern. The river lacks trees and plants to shade the water and concrete soaks up the sun's warmth, creating a habitat unsuitable for natives.
Drill said some of the new fish in the river have favorable characteristics. Mosquito fish help with pest control and carp make for good fishing.
"Part of (the river's) role is to provide low-income, underserved communities with a place to access nature, see native birds, and increase public health by having a safe area to walk and fish," Drill said. "I think there's value there too."