Steve Lindley is with NOAA - the National Oceanic and Atmospheric Administration.

He says salmon returning to spawn in 2007 and 2008 had to contend with warmer ocean temperatures that produced little food.

“So the fish were hungry and we think many of them may have starved or in a weakened state and eaten by predators.” 

That means fewer of them made it back up the river.

Lindley also says river habitat has been declining…from Gold Rush era hydraulic mining to agricultural water exports in the Delta. The NOAA study suggests authorities take long-term steps to rebuild habitat in rivers. 

It also says fish hatcheries should look at restoring the salmon’s genetic diversity…which has allowed the fish to survive a changing environment for thousands of years.