Anyone familiar with VHS?
It started decades ago with salmon in the Northwest, and now is found in numerous species in the Great Lakes. It has been speculated that part of the spread of this viral disease has been caused by baitfish taken from the Great Lakes area, used as breeding stock in captivity, then later released elsewhere.
From the link above;
"Fish belonging to a large number of cyprinid and other species are collected from the Great Lakes and used as bait for sport fisheries around the U.S. Baitfish from Canada are routinely exported to the U.S. Additionally, some aquaculture producers collect baitfish broodstock from the Great Lakes to produce commercial baitfish in aquaculture facilities. The destinations and numbers of baitfish moved are not well documented, and regulation of this sector is inconsistent among States, or lacking entirely."
Native fish, going back to nature, can sometimes have serious consequences.
Outbreaks of infectious disease can occur when a pathogen is transferred to a new geographical area where it comes into contact with native fish which have no resistance to it. Seeing as there is no way for a hobbyist to state that their native fish is "pathogen free", after being exposed to captive conditions, it only makes good sense to never re-release a native fish back into the wild. There's no telling what it was packing when it arrived in your tank, and there's no real way in telling what it may be packing when it leaves your tank.
Hopefully we're all good on that now.