Yeah I can see your point Bill.
BRUV's (Baited remote underwater video) are being used in research now in Queensland. I can see something like this being a very good method for getting data on the number of fish at certain places at certain times of the year. So, for example, you might want to check for the number of snapper at Hutchies on the full moon in October - do that yearly and you can get an idea of numbers over time in that area at that time of year. But to get an idea about the actual number of snapper in south-east Queensland would be impossible. Snapper are found from the border up to Mackay and anywhere from 1m depth to over 150m. Thats a large area in which to place cameras, and to get a snapshot of the number of snapper present in one month (for example) over the entire fishery would require 1000's of cameras, millions even.
Another thing about that sort of data is that it is time consuming - somebody's got to watch all those 100's of hours of video, not to mention the logistics of a survey that complicated and extensive. It would require alot of people/resources.