WHEN angry fishermen dumped tons of rotting fish outside the European Community headquarters here last year, EC officials charged with regulating the Community's struggling fishing industry took it as a good sign. "It was a recognition that the industry is indeed in the midst of a crisis that threatens its very existence," says Manuel Marin, a spokesman for the EC Fisheries Commissioner. With fish stocks in much of Europe's waters plunging to alarmingly low levels, and independent experts saying the fishing fleet is 40 percent larger than Community waters and their commercial species can support, signs are growing that fishermen and fisheries ministers from Copenhagen to Lisbon are beginning to take the threat to European fishing seriously. That hardly means that tensions over EC regulation have vanished, however. The protests may grow louder as the EC presents a package of measures designed to halt the destruction of European fish stocks by the end of October. Beyond that, Commissioner Marin plans to outline a new EC fisheries policy before the end of the year with species conservation at its heart. Until now, instead of setting each EC country's fish quotas according to the catch a species could withstand, national quotas have been set "by taking the number of fishermen and multiplying by the amount of fish a fisherman must take to survive," says the spokesman. "Now, we want to reverse that logic." According to EC sources, Marin senses the time is right politically, and extremely pressing environmentally, to push through a new fishing policy before the dawn of the Community's single market at the end of 1992. The European Commission, the EC's executive arm, "doesn't want to hear in three or four years, 'You allowed our waters to be fished fishless, says one EC source. "Either Marin gets some initial measures towards species conservation before the end of this year, or he'll wash his hands of the whole thing." The predicament of European fishing, or what is called "Blue Europe," is reminiscent in some ways of the problems besetting "Green Europe," or EC agriculture. Just as technological advances have allowed too many farmers to pile up expensive surpluses, radar and ever-longer nets have permitted fishing to become increasingly systematic. The economic stakes are hardly comparable, however. The EC has more than 9 million farmers and more than 60 percent of its budget is dedicated to agriculture. But the Community's 300,000 fishermen produce less than 1 percent of its GNP. Yet with fishing and related activities heavily concentrated in certain countries and regions, the future of Europe's fishing industry continues to carry political and social significance that neither member countries nor the EC Commission can ignore. A study released by independent experts earlier this year says more than 30 species, including almost all of those that are the most commercially valuable, are being overfished. For eight of those, the catch is four times higher than what would allow their natural replenishment. It is in North Sea waters that the fishing crisis is particularly devastating. For cod and haddock, two mainstay species, stocks are 10 percent to 15 percent of what they were 20 years ago. Remaining stocks are made up of younger and smaller fish. "In the North Sea they've reached the disastrous situation where they're taking fish before they've reached reproductive age," says the EC spokesman. To begin reversing the depletion of fish stocks, Marin prodded EC fishing ministers last year to accept mandatory days in port for boats operating in the most heavily fished waters. Also approved was a plan to compensate fishermen who decommission older vessels. Next month, however, Marin wants approval of more controversial measures: a ban on drift nets and an increase in size and redesign of fishnets from a 90-millimeter (3.6 inches) diamond-shaped mesh, to a 120-millimeter (4.8) square mesh. Under accelerated trawling, diamond-shaped mesh extends so that virtually nothing gets through, Marin says. Larger square mesh would allow smaller fish to escape and grow larger. Also on Marin's list for October are better means of enforcing fishing regulations. Fishermen and officials alike agree that quotas are widely disregarded. In addition to conservation, Marin wants a redrawn EC fishing policy to include economic assistance for fishermen who quit the business as well as for regions hit by shrinking fishing fleets. Emphasis will be placed on bilateral accords granting European fishermen access to other nations' territorial waters. Opinions on prospects for such ambitious measures remain divided. Too many fishermen still blame neighboring countries' fleets for the lack of fish, some observers say. Others recall past quota negotiations - with ministers haggling long hours over a few hundred tons of fish - to support fears that governments still are not ready to take the big steps required to save fish stocks. Yet EC officials are optimistic on one point: If humans involved will limit themselves, the sea can reverse the fishing industry's plight. Unlike the tropical forests, Marin is fond of pointing out, the recovery period for fish stocks can still be quite brief.