I lost a horse to a lightning strike close to 20 years ago. At the time it seemed really bad, but after all this time it's the best way I've seen for a horse to go.
Had a barn struck about 5 years ago; I found more damage from that as recent as last December.
I wonder if a lightning strike would necessarily be noticed in every pond? It seems it would be most obvious in small/shallow, heavily stocked ponds which get frequent attention (like at a fish farm). In a big, deep, body of water visited infrequently, fish kills from lightning might not be as severe (if the heat is the biggest problem), or at least would be missed more easily.