It is difficult not to be a pessimist about the future of the world's fish population. Global marine catches, which had increased rapidly since World War II, stalled in the late 1980s and have been declining ever since. That decline will be difficult to halt.
The rapid depletion of fish stocks is the inevitable outcome of sophisticated industrial technology being thrown at dwindling marine populations as demand rises, fueled by growth in human population and incomes. The decline has so far been masked in the developed world by seafood products that were not previously available, such as farmed salmon, and by massive fish imports from developing countries.
But over-fishing has become a severe problem in the developing world as well. So fisheries worldwide are due for wrenching changes in the near future. A clear indication of the problem is "fishing down the marine food web" -- the increasing tendency to land fish and shellfish from the bottom of marine food chains, often the prey of the larger fish that were previously targeted.
This trend provides low-quality substitutes for the high-quality fish that we were once accustomed to, and will inexorably lead us toward catching plankton, especially jellyfish. Yes, jellyfish, which were once a specialty consumed around East Asia, are now a product caught in the Atlantic as well, and exported across continents.
The fishing industry is, on its own, incapable of reversing the "fishing down" trend, notwithstanding arguments by commentators who should know better. In his recent book The Skeptical Environmentalist, for example, the Danish public-policy analyst Bjorn Lomborg cited data reported by the UN Food and Agriculture Organization (FAO) that showed increasing figures for global fish catches. Lomborg used the figures to argue that if catches are up, then the underlying ecosystems must be in good shape, despite all the warnings from experts.
But Lomborg is wrong, and the experts are right. We now know that the apparent increases in global fish catches in the 1990s were due to massive over-reporting to the FAO by China. We also know that fish catches can remain high (and in fact usually do) even as stocks collapse, as illustrated by cod off Eastern Canada, which yielded good catches until the fishery had to be closed because there were literally no fish left.
But excessive catches are not even the whole story. Many fishing techniques now in use -- bottom trawls foremost among them -- literally tear up the habitat upon which fish depend. As a result, some fish stocks exploited in this manner do not seem to recover, regardless of quotas or other regulations on catches.
Aquaculture, the farming of fish and other aquatic organisms, could in principle ameliorate the coming shortfall. However, aquaculture refers to two fundamentally different kinds of operations.
One type of aquaculture is devoted to the farming of bivalves such as oysters and mussels, or to freshwater fish such as carp and tilapia. It relies on plants (plankton sometimes supplemented by agricultural by-products in the case of freshwater fish) to generate a net addition to the fish food supply available to consumers. Moreover, because this type of aquaculture is based predominantly in developing countries (mainly in China, but also in countries such as the Philippines and Bangladesh), it supplies cheap animal protein right where it is needed.