Welcome to the forum. If the concrete dam would utilize the natural rocks at each side, I would drill and epoxy rebar into those rocks and use a bonding agent on those rocks right before the concrete was coming out of the chute, and any other place where the concrete will be touching natural rock. You don't want the water finding a way around the concrete between the rocks and washing out a hole over time.

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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).