I started with the 22lr - no luck. I then moved to a .410 with target loads - no luck. I was beginning to doubt by shooting skills. I figured it was time not to mess around. My heaviest load with my 12ga was buckshot, and I figured the cause and effect (my shooting the fish dead and the resulting pain in my shoulder) was a little too much, so I opted for the turkey loads. I will say that I don't believe there was any penetration in the fish, but rather the concussion killed it.
