Putting things into perspective helps.
Ever eating king prawns? Then you've been personally responsible for the deaths of literally hundreds of fishes including eels, flounders, gobies and all kinds of other benthic fish, not to mention other bottom living invertebrates. Trawling for large marine prawns results in 90% of everything caught in the net being thrown back, dead. In other words, for every large prawn you ate, nine fish/crabs/starfish/whatever died.
In fact most wild-caught seafood is more or less destructive of wildlife. Farmed seafood like salmon is marginally better, but the impact of parasites and ammonia from salmon farms is incredibly harmful on a local scale. Farmed freshwater prawns (the big prawns in Chinese food) do enormous harm to freshwater habitats because these prawns require brackish water, and the salt kills off freshwater fish as it leaks out.
If you've ever stayed at beachfront property like a hotel in Florida or really anywhere, you've contributed to the destruction of mangroves, salt marshes and other essential habitats for marine fish, particularly juvenile fish.
The impact of the hobby on fish populations is actually very small, probably negligible except in a very few cases such as Banggai cardinals and Galaxy rasboras where the wild populations were extremely small to begin with. In fact a properly maintained ornamental fish fishery provides native people with an incentive to keep their local waters in good condition.
Cheers, Neale
Sorry about being so pessimistic. I hate how in order to have such a great hobby so many fish have to die. Think about it, 6 freshwater morays are shipped in to any lfs every week. Saying 1 in 100 lives would be ridiculously optimistic. If we love our fish so much. Why must so many die?