rlk said:
You could call your fish supplier and ask him his throughts.
Bob
It would be in interesting test of his profit motive and integrity.
Assuming purchased fish to always be absolutely disease and parasite free (not always true) then there is less risk stocking with "store bought" fish. However if you have a resident population of fish that you have conducted significant sampling of (caught lots of them over a period of time) and they were always strong and healthy in appearance (fat, well colored, and put up a decent fight) then the risk may be judged to be acceptable.
Lets consider that you have a pond, we'll call it pond A. You stock it with store bought fish and they thrive for years. You have pond B and want to stock it. Do you buy from the hatchery or use some from pond A to stock B. Why are new fish from the hatchery so much better than the contents of pond A which are hatchery fish and their offspring?
How long can you have hatchery fish in a pond before they are inferior to new hatchery fish? If "used to be" hatchery fish in pond A are not "safe" to put in pond B then are they desirable to keep in pond A? If they aren't good enough for pond B maybe they aren't good enough for pond A either and should all be killed out with rotenone and replaced with new hatchery fish. Then we need to know how long we can "safely" keep fish in a pond before we kill them all and start over...
OK, I took this slightly to excess to make a point. Under good circumstances hatchery fish are probably parasite and disease free. After being placed in a pond they might get parasites and disease. For me, I'm willing to swap some fish between and among my 12 ponds if they seem to be good healthy specimens. I think the risk is acceptable. There is however some risk and probably more than getting disease or parasites in hatchery fish. Of course as soon as hatchery fish are planted they are subject to contamination and are soon little or no better than 2nd, 3rd, or nth generation fish.
My ponds are subject to overflow from one to another in the majority of cases. This tends to wash fry from one pond to another so even if I don't do it nature does. One of my isolated ponds overflowed and little 3/4 to 1 1/2 inch fish by the thousands were swimming out in a pasture in 1/2 to 3/4 of an inch of water over 100 feet from their home pond. Many of them made it 200 feet or so to a pond lower in elevation. I'm having to change my catfish feeding since my monoculture catfish pond got contaminated with perch.
I like to stock "Shell Crackers" (Redear Sunfish) as they preferentially eat snails, which figure into the life cycle of some of the parasitic worms, and then eat other things after they eat the snails. They interrupt the life cycle of the parasites which require the aquatic snails to complete their lifecycle. These parasitic worms are more of a real danger than other disease in my experience wlth these ponds. Fish with worms don't grow as fast, fill out as nice, or exhibit all the qualities of a nice healthy fish as much as those without. Did I mention shell crackers?
There is absolutely nothing wrong with stocking from a hatchery. It can be convenient, it isn't all that expensive (for small fish), and there is low risk of disease and parasites. Being selective and careful and stocking from your own sources is slightly more risky but enables you to select breeding stock with greater assurance and get way ahead in having a breeding population. It is much cheaper (if nothing goes wrong) and may be simpler and more fun.
In my case only 6 of my 12 ponds are safe from getting fish from upstream and the other 6 get stocked by upstream ponds during overflow events whether I intervene or not. This has been going on for decades in some of them as I only built 3 of the ponds myself and the rest have been around for varying lengths of time up to 25 years or more. So far there has been no problem with propagating diseases that I know of and get compliments on how big, fat, feisty, and well colored my fish are. Your mileage may vary! Risk assessment is often a topic of heated debate. I know there is risk but believe based on experience and analysis that it is acceptable and that the worst case event would still be tolerable and relatively easy to recover from in my situation.
Pat