WHALES ARE among the most mysterious and exciting species alive. Their brains are in some respects more complex than man's. They display a range of emotions. They communicate with each other, show individual personalities and have long memories. Someday it may actually be possible to communicate with them and to gain unimaginable insights into life of the sea. But for that, not to put too fine a point on it, there will have to be some whales around.

The whales are endangered. Only one country-- Japan--is thwarting the ban on commercial killing that could save the great whales. Though other nations--Norway, Iceland, the Soviet Union and a few others--own whaling ships, all of them sell their catch to Japan. And only Japan is willing to take the lead in fighting the decisions of the International Whaling Commission, which are leading toward a moratorium on commercial whaling.

Whaling is a dying industry. It is dying because there are now economic alternatives to all uses of whale products and because greed and senseless exploitation have so reduced the numbers of whales that nearly all types are now too rare to be worth hunting. The decimation started with the largest whales, the great blue, of which 30,000 were killed in the peak year. When they were gone, the hunters turned to smaller types--the humpback, then the right whale, the bowhead, then the fin and sei whales. All were hunted near or into "commercial extinction." For many of them, so few individuals were left when the hunting stopped that the species appears unable to recover even after years of belated protection.

Of the large whales, only the sperm whale is still being hunted, and it too is endangered. Two decisions by the IWC last summer--one of them to ban sperm whaling, the other a requirement for a more humane weapon to shorten the hour or more it takes whales to die--provoked the current dispute. The IWC has a strange charter that allows members who object to a decision simply to file a formal objection and then ignore the rule. A few weeks ago, Japan filed objections to both decisions. Norway and Iceland also objected to the requirement for a new type of harpoon, and the Soviet Union is expected to join them.

With this flimsy structure, what has held the IWC together has been the force of international public opinion and the threat of sanctions by the United States. These laws allow the president to embargo fish imports from a country that violates IWC rules, and also to restrict the country's fishing rights in U.S. waters. President Ford's readiness to apply the sanctions in an earlier crisis when Japan and the Soviet Union defied IWC quotas kept the two violators in line until now. The current situation calls for an equally determined response if the IWC is not to fall apart and the goal of stopping commercial whaling is not to disappear. Last summer President Reagan eloquently called on the IWC to pass a whaling moratorium. He should show that he was in earnest now.