I thought i heard gobies as well. but we may have been misinformed. and as for fish being introduced by fisheries happened alot way back in the day. I know the common carp was introduced on purpose as another food source but they had no idea how they would adversly effect other fish populations. but they seem to at least around here have found an equallibrium. thats one case of none native fish being introduced. american native fish have been introduced into different parts of the country where they were not natively. such as walleyes in lakes like bulls shoals in arkansas. I know the illinois DNR are talking about introducing the alligator gar into the upper mississippi river. they think because they are such and awesome predator they may feed on the asian carp. this is the FAR northern edge of their natural range but they have not been here in a hundred years or longer. so it will be a reintroduction. but even so they will either die out or prey upon other game fish and may take time to get to a balance. but it is an example of introducing fish to combat invasive species. plants on the other hand there is no combating. u leave one piece and it can grow back, a piece gets stuck to a duck and gets transfered to another lake. get stuck on boats as well. which is one reason they now do wash stations at some boat ramps in places like minnisota. have to spray down your boat with boiling water to kill any plants or animals, can no longer transfer bait or fish in a livewell from one lake to another even if it's just a mile away and they are connected directly to eachother. to stop the spread of invasive species we have to do alot. problem is now that they are here they are here to stay. it's just down to controlling the spread. and up to nature to evolve or die out.