FWIW, I talked to a dirt guy today at a pond consult and he said that he noticed quite a number of ponds in this area this Spring (about 3 weeks ago) had dead fish floating. Not all large fish, not all small fish.

He didn't think it was from anyone spraying for aquatic vegetation, so I'm grasping at straws here.

www.hoosierpondpros.com

[Linked Image from lh6.ggpht.com]
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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).