Withering Syndrome (WS) was very significant in reducing black abalone populations in Southern California during the 1980s-1990s. The rickettisal bacterium that causes WS can infect all California abalone species but each reacts differently to infection. Green abalone appear to be more resistant to the disease than red or black abalone. CDFW biologists found that WS is much more pronounced at higher temperatures such as those experienced in Southern California during the summer. The agent of WS is now present as far north as southern Sonoma County, but the disease has not occurred there because cold water temperatures keep the bacterium in check. Elevated water temperatures associated with global climate change could make WS a threat for northern California red abalone in the future.The CDFW pathology laboratory has determined that all the shrunken northern California red abalone examined were not affected by WS and the shrinkage was due to starvation and the lack of food.