Even if you don't throw lead/steel projectilis at them, there's other ways. Bottle rockets, etc.

A clients 7/8 ac pond had 5 of them that would visit almost daily. When I did a fish survey, I'd say around 70% of the fish showed that they had escaped from a cormorant. They had scratches/missing scales on their sides, or tears in their fins.

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).