The composition of fish populations in streams and rivers across the U.S. has been severely altered as a result of changing water temperatures and human-driven introductions of fish, according to new research. Cold-water streams have experienced disproportionate impacts, experiencing more than a 50% decrease in fish abundance over the last three decades, according to a study published Wednesday in Nature. Some of the largest threats include climate change and fish introductions — both by invasive species or game fish stocking, scientists say.

Related article:

• NPR: Warming waters are shifting the diversity of American river fish