Releasing aquarium fish into local waterways — or down the toilet — can damage aquatic ecosystems in a number of ways. The fish themselves can become an invasive species, they can disrupt habitats for other fish and aquatic species, and they may introduce secondary problems such as harmful pathogens or other aquarium species (seaweed, snails) into the waterways.

At least 13 of the 102 aquarium species that are imported into California have been introduced into California marine waters, according to a recent report by Susan Williams, professor in the...

The competition between farmers and fish for precious water in California is intensifying in wine country, say biologists at the University of California, Berkeley.

A recently published study links higher death rates for threatened juvenile steelhead trout with low water levels in the summer and the amount of vineyard acreage upstream. Like salmon, steelhead trout migrate from freshwater streams to the ocean before returning to their birthplace to spawn. Steelhead trout in Southern California and the upper Columbia River are endangered, and several other populations, including those in Northern California, are...

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...