With storm management ponds sprouting out all over urban centers, and subdivisions, not only are we supposedly more safe from the threat of flooding, but by default, the promotion of nature around our urban centers has ensued. Most of it being natural, in the way of songbirds, frogs, herons,waterfowl, muskrat, mink, and native fishes, but also it looks like man has taken part in the act through more unnatural introduction methods.
Bring in the Gold rush, as many of these man-made ponds are full of goldfish, and at quite gargantuan sizes as well. With these ponds full of abundant food from algae, vegetation, to insects and various larvae, it’s no wonder how these small urban oasis’ can house such giants, making them live much more lavish lifestyles than life in the fishbowl.
As inoffensive and benign the practice of releasing your unwanted pet fish into the wild may seem, this can actually have drastic consequences for native species. Goldfish have no troubles surviving our winters, being native to northern areas of Asia, and they compete directly with our native fishes for food. In a storm pond, this may not be all to big a deal, but in our natural lakes and river systems is where this becomes more a concern. Keep in mind that they can easily spread from an otherwise seemingly confined water source, via flooding into a nearby stream, or by waterfowl spreading their adhesive eggs from one waterway to another.
As ethical as releasing your pet fish may be, refrain from this practice, and think about the ecosystem as a whole. Recently in Hamilton, the illegal dumping of goldfish into a local pond had devastating affects by drastically affecting Jefferson Salamanders, an endangered native species which frequently used that pond for breeding. Relegate the goldfish populations to your aquariums, or backyard ponds, not in our waterways!
That article can be read by clicking the link below.
http://news.nationalpost.com/2013/04/14/na0413-rr-salamanders/
Fishin envy 
Great Article John!! Thanks!