Every boy should have a pet, and mine is named Ralph. Or Amanda. I cannot be sure. I have never met the creature and, even if I had, I know nothing of the delicacy required to ascertain the sex of a striped bass.

Maryland, where a striped bass is called a rockfish and is the official state fish, has a program whereby for $5 you can adopt a bass. The proceeds help finance studies of the decline of one of America's most precious sport and commercial marine resources.

The striped bass has been called "the aquatic equivalent of the American bald eagle." It was the subject of the first conservation law in North America: in 1639, the Massachusetts Bay Colony forbade the use of these fish as fertilizer. In 1670, the first public school on this continent was financed in Plymouth Colony by profits from striped bass, herring and mackerel. Captain John Smith wrote of seeing the Chesapeake Bay so teeming with bass that a man could almost walk on their backs.

But today the bass population is on the verge of collapse -- of spawning failure. In 1973, 14.7 million pounds of bass were harvested from Atlantic Coast waters. In 1983, the catch was just 1.7 million pounds. The decline could become irreversible before scientific evidence even establishes the role of various causes, which may include overfishing but certainly and primarily include many forms of pollution.

At some point, economic forces become perverse: as striped bass have become scarce, the price they fetch has soared, increasing the incentive to catch them. And even the small amount of good news is a scientific puzzle. Why is the striped bass population in the Hudson River expanding? One delightful explanation is that the river's limestone bed acts like Alka-Seltzer and counters the acidity of acid rain.

Of the 12 coastal states along the bass migration range from Maine to North Carolina, Maryland is immeasurably the most important. Ninety percent of the striped bass are spawned in the rivers running into the Chesapeake Bay, and 75 percent of the bass caught are taken in waters under Maryland jurisdiction. Thus it is no empty gesture that Maryland has made in banning the taking of the bass, beginning next year and continuing until the decline is reversed.

The Chesapeake Bay has been called the nation's finest protein factory. But its productivity is now jeopardized by industrial pollution, chlorine from sewage treatment, runoffs of agricultural chemicals and acid rain. Maryland has grave responsibility for protection of the bay, but this is a national asset and hence a national problem. The president acknowledged as much when, in this year's State of the Union address, he mentioned protecting the bay.

Another Great Communicator, the Psalmist, celebrated "the great and wide sea with its living things too many to number." But those things are not too many to become endangered. Overharvesting is responsible for today's sharp decline in lobster stocks. The decline is so serious that perhaps 90 percent of each year's generation of one-pound lobsters is being taken, many of them before they have reproduced even once.

Last year William Warner, who won a Pulitzer Prize for his book "Beautiful Swimmers: Watermen, Crabs and the Chesapeake Bay," published a splendid, instructive book, "Distant Water." It tells how "factory trawlers" -- giant fishing boats -- almost destroyed commercial fishing in the North Atlantic, and how timely government limits enabled the sea to come alive again.

Regarding striped bass, the federal government has been relucant to intrude into coastal fishing regulation, traditionally a matter of states' rights. But bass are careless about crossing state jurisdictions, as is pollution. So Congress has passed legislation that would impose a moratorium on striped-bass fishing in any coastal state that does not comply with whatever plan is developed by the Atlantic States Marine Fisheries Commission.

This is utterly inadequate. The stakes are great and the threatened asset is a national asset, so Maryland's moratorium should be national policy.

Maryland's action to protect an endangered species injures another great American species -- the watermen, those fiercely independent and admirable men who for centuries have done the hard work of pulling protein from the productive waters. What we have here is a test of national stewardship. It is profoundly unjust for Maryland's watermen or other citizens to pay the price of conserving a national asset.

If the watermen's loss is to be temporary, national action must be timely, and should be generous toward a breed of men who did not create the problem they are bearing the burden of solving.