Funny this topic has arisen. I was recently emailed this question from Dr. Robert Fulton, of Monroe, NC. He and I have established a friendship over the last few years and he tosses questions at me from time to time (and I do the same with him). Here's the answer I gave him. It will appear in Ask the Boss in July-August.
Geez, (He's known as the "River Geezer")
Well...I'll tell you. This is my 30th year as a professional fisheries biologist in the private sector. I have never seen, or otherwise been able to prove, that herons bring viable fish eggs to ponds to create a population of fish. I've not found any definitive studies which prove or disprove the theory, either. And, I've looked. I've wanted to simply believe this myth and go on with life, but my mind won't allow it. Too many times people make this statement to me as the truth. And since I'm in the bidness of knowing such things, I decided to put it to rest years ago, in my twenties. Still, though, I think about such things.
But, after years of wading in ponds, building them, draining them and studying things as fish eggs, fish behavior and fish recipes, I have grown to appreciate the fact that fish eggs are delicate, can't stand dry air, need oxygenated water, will suffocate in mud or silt and often need to be surrounded by siblings to enhance odds of survival. I can't believe that a bird can walk on a fish's nest, eggs stick to the leg, stay stuck to the leg as the bird flies, don't dry out and die along the flight, then the bird lands, the eggs unstick, find a hard substrate to continue their incubation and then hatch and create a population of fish. I would say the odds of all these things happening in favor of a fish are astronomical. If I were that egg, I would ask the bird to stop in and buy a lottery ticket as they fly over the local convenience store.
Do fish make their way into unstocked waters? Yep, they do. How? Beats me. I've seen sunfish in cattle hoofprints after a summer rain...500 yards from the nearest pond or stream...upstream or downstream. I have, once in my life, watched a great blue heron snatch a catfish fingerling out of one of my hatchery ponds, fly off with it, only to watch the six inch whiskerfish wriggle free and be dropped into the pond next to its home pond. I have seen herons catch my bluegill at Lusk Lodge, 2, some as long as 8 inches, take off and drop the fish in the dirt, yards from the pond, then circle, come back, land and eat it. I watch that process almost every week, with a cup of coffee from the patio as the fish feeder tosses its rich nuggets to our fish.
The only theory I truly believe, because I have seen it over and over, is that fish move when water moves...and usually the smallest fish take advantage of that opportunity. I've watched them move upstream from one pond to the next. What about ponds that sit alone in the watershed? Good thought, there, too. But, if that pond ever overflows, the water must go somewhere to another watershed...and when that happens, all a tiny, one inch sunfish needs is an inch of water depth and they will go...fast. Personally, I believe fish transfer themselves under their own power to stock a pond by swimming upstream in flowing water...unless someone's neighbor does them a "favor" and transfers a few fish into a new pond.
That's my story and I'm stickin' to it...unlike fish eggs to bird legs.
