Look out, Hawaii! Open ocean aquaculture (OOA), also known as sea-cage farming, has many problems.

OOA of carnivorous fish is worse than over-fishing. Production of one pound of farmed tuna requires the oil from over 10 pounds of wild-caught fish, usually anchovies, menhaden and sardines, which are an important source of protein in Third World countries and an important source of omega-3 fatty acids in developed countries. Farmers use as much soy as they can, but tuna can’t survive without fish oil.

Anchovy, menhaden and sardines are important "cleaners" of the ocean. When these plankton-eating fish are over-harvested, jellyfish are released from competition for food, and they proliferate.

Farmed carnivores have higher levels of organic pollutants than wild-caught fish of the same species, and they have lower levels of omega-3 fatty acids because farmers use as much soy as possible in their feed.

Sewage from sea-cage fish is like human sewage in its effects on the ocean. OOA supporters say that dilution is the solution, but this only pushes the problem somewhere else.

OOA promotes disease in wild populations by acting as a reservoir of infection. When a wild fish falls ill, it starves or is eaten by predators, but sea-cage fish are fed and protected from predators, so when they fall ill they remain alive, shedding pathogen into the water. Pathogens are carried for miles by currents, and the rise in pathogen level causes wild fish to decline. Disease promotion by OOA goes unnoticed at low densities, and farmers ritually deny it, even where the evidence is overwhelming.

The Oahu moi-farming operation started by Randy Cates and Virginia Enos is exceptional because they chose a schooling fish with large scales and raised it outside of its customary surf-zone environment, away from wild moi. The UH scientists who helped Cates and Enos frankly admit that they lucked out in their choice of a fish. Kona Blue Water was less fortunate, and regular disease problems now have it on the road to drugs.

Escaped farm fish interbreed with wild fish, producing young with lowered rates of survival. Experienced OOA companies assume that 5 to 10 percent of their fish will escape by accident or by passing through the mesh of the cage when they are small.

Hawaiian aquaculture avoided such problems by using what is now called ecological engineering. Ocean ponds were situated in areas with edible seaweeds attractive to juvenile fish and upwelling fresh water in which fish could rid themselves of parasites. Cultured fish were as wild as juveniles, so escapes did no harm to wild stocks. Most of the cultured species were herbivorous, but a few barracuda were tolerated because Hawaiians understood their importance in disease control. Predators are not disease-specific, unlike the drugs used in OOA.

It is surprising that would-be OOA farmers like Bill Spencer ("Isle fish farming good for environment and economy," Star-Advertiser, Island Voices, Nov. 21) refuse to learn from Hawaiian wisdom. Bill and his friends suffer from what scientists refer to as techno-arrogance — the belief that modern technology makes ecology irrelevant. They remind me of the Norwegian salmon farmers who took the coast of British Columbia away from its aboriginal peoples. It’ll be different here, they promised us. But it wasn’t.