Some people on my team are thinking of running aquaculture and basically you cultivate a controlled enviornment for the sealife to breed them etc. and it helps improve water quality, create a more sustainable supply to the demand of seafood, there's an economic advantage providing jobs and helping fisheries get more revenue.
For ballast water (the inherency is really shaky) but every ship has a ballast tank where they fill it up with water and this tank with water helps the ship not fall over from tides. But with the water being put into the tank there are also organisms and fish in it. When the ship gets so many miles from shore of the country it is arriving to, it has to dump the tank which brings the fish into the new enviornment making them an invasive species. The solvency includes UV radiation killing the fish, switching out the water (I am not really sure on that option), or using biocides. I am not sure about this case though.