I read lots of posts on PB with people complaining about herons and cormorants EATING their fish. I had no idea that birds were the main vector for parasites and diseases.
Obviously a little extra initial work in shaping the slopes on forage ponds will have a bigger pay off long term - for multiple reasons.
I have observed various species of herons take fish. Despite seeing lots of cormorants, I have never observed one taking a fish.
How do cormorants take fish? What needs to be added to an "anti-heron" pond design to also discourage the cormorants?
There is no such thing as a bird proof pond probably. Things a person can do are already mentioned but in addition to this reducing the time between harvests can do a lot to help. Few lepomis of the millions that swim up reach 1" in length in the destination pond that is loaded with other lepomis and LMB. RES and BG can attain 1" in 4 weeks from hatching under good growing conditions. In a forage pond the survival to this length is MUCH MUCH higher. If harvested every 6 weeks, one can get multiple crops of forage. The size at 1 to 1.5 " isn't very attractive to most wading birds (maybe the green heron as an exception). So simply by preventing the conditions that would attract them will help.
