Mary Anna (27 Jan 2012)
"Fish die-offs more frequent in past 10 years"

While the direct cause of die-offs can be hard to determine, Gonder said there are some common elements. Thermal stress, the effect of changing temperatures on the fish, plays some part, and Gonder said storm events or spawning activity have also been associated with die-offs. However, those are only a handful of potential causes, he cautioned.

"Often, it's really difficult to determine why this sort of stuff happens," he said.