"The (herring) bubbles are released through the anal duct when the air expands as the fish ascend," explained Malene Simon, who worked on the research. "We do not know if the fish release air when staying at one depth as a reaction when meeting a predator. However, it is very likely that the bubble will confuse or scare the predator in such a way that the herring will have a better chance of escaping."
So, er, the story is that herring farts confuse whales. The whales slap the sea with their tails to stun the fish. Actually, the story does live up to the headline.