The very title of this thread kinda annoyed me. Why don't we MAKE more fish
? While I am sure it was not intended and I am being thin skinned the way the question is phrased implies a misunderstanding of natural systems.
In my simple curmudgeonly way I would say a more realistic question would be: Why don't we MAKE fewer humans?" if you see my point.
Well, it turns out there are a lot of really good reasons. Probably the best way to make more fish
is to do nothing, leave 'em alone. The oceans were full of fish before we came around. But back as far as the 1400's there was some degree of fish stock depletion. There is serious thought that Columbus did not "discover" America but found out about it from fishermen who were working the Grand Banks
. The thought was it's existence was secret known only to a few who didn't want competition. As soon as Banks were widely known they were fought over and exploited. They continued to support a large fishery until large trawls were introduced in my lifetime. This wiped out the fishery (95%+ bio mass depletion) and destroyed the economy of Newfoundland
. Take away - modern man's techniques can be very destructive and counter productive in the long run.
Fish farming is a bit like meat production, it IS meat production. For cows we feed them corn and grow them and kill them. In the process we are taking a low level food
stock (corn) and using a critter (cow) to produce a different food
stuff (protein.) There is massive energy loss in the system, something like a 10:1 ratio. By eating lower on the food chain (vegetarian) you 'save' food (energy) by using it more efficiently. Very roughly speaking you could feed 10 people with the energy that goes into feeding one with beef.
The same math works if you 'MAKE more fish', you have to feed them. Where does the feed come from? Either by growing it and feeding it in pellets to pond raised fish or by harvesting critters lower on the food chain than the fish you want to eat. So you feed pellets to cat fish in ponds and menhaden to salmon in nets. But, in either case, you are not really solving any problem because the energy input into the system is still the same, or perhaps worse. We are not adapted to eating plankton directly, we eat it only once the energy has passed through some number of processing systems: little fish, bigger fish, salmon/tuna.
I hope that made some sense. I'm not an expert on this and make no claim. It's just that there is no free lunch, no perpetual motion machine. It is really just budgeting energy instead of dollars.
Below is a good Wiki article from which I have cherry picked a couple of quotes:
In recent years, menhaden are the primary source of fishmeal and fish oil, used as food for livestock and aquaculture, such as salmon. Atlantic menhaden are an important link between plankton and upper level predators.
There is increasing concern, especially from recreational fisherman and conservationists, that the Chesapeake Bay’s population is declining significantly.