it was determined that the fish inhabiting just 20% of the world's reefs could repopulate the entire world's reefs. (This was part of his argument to create the marine sanctuaries in the Florida keys as well as around the world.) This comment was made back in about 2000. So if this is true, how much damage did we really do during the 70s and 80s while we learned how to keep fish for longer periods of time? Yes, we know that some corals grow extremely slowly and over harvesting them back them has had a dramatic effect on many reefs around the world. But before they were totally gone, these areas closed to harvesting so that the reefs could rebound. HOWEVER, even if we took none of them back then, these corals would still be in jeopardy today as bleaching has been seen in many areas that once had flourishing colonies of corals. This is nature not hobbyists causing this. ( The debate of how mankind is effecting nature is another topic
) As learning hobbyists tho, we learned that doing what we did had dire consequences so other methods( i.e. fragging) needed to be developed, and were. Would fragging even exist if we hadn't killed those corals back then? I think of it as " Now that we know how to frag, no reef is in total jeopardy of being lost as it can be restarted with frags should the last resident polyp die."
But the aquarium hobby hasn't had nearly the effect on the ocean's inhabitants as other industries had. The oceans have been plundered for sponges for human use, shells and coral skeletons for decorations and been used as the biggest toilet bowl on earth for way longer than we have been keeping marine specimens in a tank. Maybe the creation of keeping marine life in a tank is/was the catalyst to stop these things or at least change the way they are now being done? Who's to say? We now have tank bred and raised fish that just 20 years ago were nothing but a thought or dream. All from "hobbyists" being unable to keep the wild specimens alive in a tank. Was it worth it?
As for the lionfish situation, more than just Lionfish have been found in the Caribbean. This was caused by misguided people thinking they were doing right or were too lazy to take proper care of their fish ( IMO). But what about the fish that were deliberately set loose in waters to have native populations to feed people. There are many Amazonian fish that have been set free in lakes and streams around the world that have adapted new ways of feeding and surviving. In our own country, striped bass can be found in lakes in the middle of the country. How did they swim there from the ocean? lol So you see, in my opinion, we hobbyists have had a minute effect compared to these other industries yet we are the ones doing the most to correct things.
Hope this adds some interesting content to your debate