Thanks for the wonderful presentation. However, I think we need to broadly review our scientific approach to research. As you've earlier mentioned, you'll have to innoculate a very high dose of the vibrio bacterium before getting the disease. Similar to my (phd) research work (- effect of Aeromonas hydrophilia, a normal aquatic flora said to be very pathogenic), most aqua-flora agents are not really pathogens but commensals / secondary pathogens.
Have you ever seen a fish / aqua-organism with very high dose of such microbes naturally? The answer is no! I infected fish seeds (eggs, fry and fingerlings) with varied doses of life A. hydrophilia per os (orally) at high stocking densities but observed that the microbe rather promoted the fish survival rather than resulting in disease condition - as commonly seen when innoculating fish with high doses of such (A.h.). I quite agree with most of your suggestions on probable solutions, but don't be too sure about the aetiology unless adequately proven - remember that some of these bacteria are natural inhabitants of water and fish gut.
Some publications are likewise seen on vibrio species as probiotics (you can verify online). Importantly, farmers should ensure:
* A good production system and it's adequate management for positive results. Water quality is very important!
* Use of probiotics/gut stabilizer in areas of high larval mortality. Plant oil extracts... may likewise do the job.
* Close attention should be paid to feed and method of feeding. When changing your fish / aqua-organism feed (from one type to another e.g. natural foods to fish concentrate/feed), it should be gradually done. A lot of hatcheries suffer huge loss due to this reason, though they often ascribe such to "disease".
* Observe your "fish" and "culture water" to give you the needful.