Well, that link sent me on a bit of a youtube journey and it's depressing...
This vid didn't fill me with joy either -
I lived on the QLD's Sunshine Coast for many years and there were several massive fish kills in the Maroochy river which were never officially traced but it's likely that someone decided to dump unwanted agricultural wastes into creeks or drains that flowed into it. (I don't doubt that the source was found, but it certainly wasn't publicised).
The Noosa river was once considered fairly pristine but it too had chemical pollution issues that caused dramatic and disturbing mutations in fish stocks, or at least in fry populations.
Really sucks that this is an ongoing issue. I hate to imagine what is leaching from the immaculate lawns of canal estates and from golf courses into tributaries and rivers.
It's looking more and more like the nearly impossible and time wasting farming of our own fish feed is the only way we can come close to avoiding this problem. But I doubt it is feasible for many of us on the scale we require. Really wish we could use tilapia in AP over here, that would make it a lot easier to source (hopefully) clean feed rations. I fear that natural sources of fish protein are tainted to some degree.
Do the commercial suppliers of AQ feed rations routinely test for contaminants and publish the results or claim maximum levels? (Mercury, PCB's, PBDEs, etc?)