HOBART, AUSTRALIA — KRILL. Whales eat them, penguins gorge on them, and now man is munching them.Krill, crustaceans the size of small shrimp, are the key animal in the Southern Ocean. Without krill, most life there would die. "In Antarctica 50 percent of the [food] energy comes through krill," says Stephen Nicol, a senior research scientist at the Australian Antarctic Division. Krill are the major food source for penguins, seals, and some whales, and most fish include krill in their diet. Krill are high in protein, which is 40 to 60 percent of their dry weight. Krill thrive in the cold antarctic water, where they feed on plankton. Dr. Nicol estimates there may be around 500 million tons of krill worldwide. All of that protein has attracted the world's two largest fishing nations, the Soviet Union and Japan. The Soviets harvest 80 percent of the krill caught in the Southern Ocean, mainly around South Georgia Island in the winter and the South Orkney Islands in the summer. The Russians sell most of their krill to other nations, since it is too expensive for most Russian tables. The krill are shelled mechanically aboard huge fish-processing vessels. But the equipment is still too slow to keep up with the hauls. "You can catch 10-15 tons in a matter of minutes," says Nicol. "If you don't process them within three hours they are not fit for human consumption." Consumers are rarely aware they are eating krill. In Australia, for example, I&J Foods Ltd. markets krill under the label "Sea Shanty," described as a breaded seafood and vegetable mix. At the moment, Nicol says the amount of krill harvested poses no problem to the environment. But he worries that the krill fishing is expanding too fast. "If a country sends 100 ships for krill, we're in trouble," he says. Because of the potential threat of uncontrolled krill fishing, the nations active in the Antarctic in 1982 formed the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), based in Hobart. Nicol says some scientists are unhappy with the slow pace at CCAMLR: "We need a management plan to regulate the krill fishery." But Darry Powell, executive secretary for CCAMLR, says research on krill is just becoming available. This August, CCAMLR will meet in Tenerife, Canary Islands, to discuss the need for limits on krill fishing. Since the fishing companies maintain there is no evidence of any adverse impact, they are opposed to regulation. "It should be quite an intense debate," says Dr. Powell.