For a moment, consider the palate.

The platter on your left is ringed with hush puppies, a dollop of cole slaw and a nicely browned slab of catfish. It comes from a farmer's backyard in Alabama.

The dish in the middle is different. A little potato salad, a fresh green vegetable and, gently sauteed in butter, a collection of scallops and shrimp. They come from a seafood farm in South Carolina.

On your right, just out of the poaching dish, is a banquet-sized steak of salmon. It came from a salmon ranch along the coast of the state of Washington.

What makes this cornucopia of high-protein foodstuffs different is that it all came from a man-made, man-controlled setting, not a muddy creek bottom, an estuary or the open sea.

This is part of aquaculture, the subject of a series of bills pending before Congress that would get the federal government fully behind the business of fish farming.

There's nothing particulary new about aquaculture - it has been conducted on a large scale for centuries in some countries - but it accounts for only about 3 percent of the fish and shellfish consumed in the United States.

Judging by the interest on Capitol Hill, aquaculture seems to be an idea whose time has come for a hungry nation that now spends slightly more than $2 billion a year to buy fish and seafood from other countries.

One bill, passed by the House in February, directs federal agencies to step up their support of programs to increase production of aquatic species with research loans and guarantees for the industry.

Two Senate committees - Commerce and Agriculture - are considering a variety of proposals, each different, but each with the aim of boosting U.S. production of edible fish and shellfish in these controlled environments.

Almost everyone, from catfish farmers to legislators to federal bureaucrats, applauds the idea. But that is where the agreement ends and the waters become troubled.

There is an argument over which federal agency should control the action; there is a dispute over how much aid the legislation should provide and to whom. And there is the Carter administration, which doesn't want a bill.

Rep. Robert L. Leggett (D-Calif.) prime sponsor of the House legisalation and chairman of the subcommittee that generated the bill, believes the United States has fallen far behind other countries in boosting aquaculture.

And, so he told a Senate committee recently, the $15 million now being spent by the government is scattered through a number of agencies, each of which goes its own way in dealing with fish and shellfish production.

Most of the money goes to the Department of Commerce, which specializes in marine fish. Lesser amounts go to Interior, for research and hatcheries, and to Agriculture, which deals with fresh-water aquaculture - mainly catfish, which are "farmed" extensively.

The result is that one agency does one thing, the next agency does something else. James P. Walsh, deputy chief of Commerce's National Oceanic and Atmospheric Administration, told the Senate at least 16 agencies are involved somehow in aquaculture.

"We concur that there is a need for better coordination of the federal aquacultural efforts through an inter-agency process which recognizes the expertise of each agency and overall trade-offs with food production efforts," Walsh said.

But Walsh and Lynn Greenwalt, director of Interior's Fish and Wildlife Service, both stressed the White House opposition to aquacutlure legislation.

They said the administration opposes the bills because it is against new financing and loan programs contemplated by the bills and because President Carter's reorganization studies are considering aquaculture.

That is only part of the picture. The House-passed bill, while allowing each agency to continue its present work, gives Commerce the role as the biggest fisherman of them all.

In the world of bureaucracy and special interests the important thing is who holds the tiller. Fresh-water aquaculturists, led by the catfish and trout farmers associations, oppose Commerce because of a fear that it would emphasize marine species at the expense of fresh-water types.

They would rather see the power in the hands of USDA, which handles fresh-water matters, but the Shellfish Institute of America, with members in all 22 coastal states, is wary of USDA.

"Historically, the financial assistance programs of USDA and their administration gives little hope for funding new and imaginative ventures," the institute's Richard H. Loring told the Senate.

"The ultraconservative loan policy of USDA precludes loans to much of the aquaculture community . . . In a word, the aquaculture industry is looking for a little cooperation and consideration, not a series of energy and resource absorbing constraints."

The same jurisdictional problems that grip the industry also are lurking aroung the Senate. The Agriculture and Commerce committees, each with an interest in keeping a hand on the legislative tiller, held hearings independent of each other earlier this month.

The discussions center on how best to coordinate current federal aquaculture activity; which agency will become the "lead" outfit; how much federal money should be added to the kitty, and whether and how much loan guarantees and disaster-loan assistance should be provided.

The bill passed by the House would authorize about $800 million in federal spending over the next three years on aquaculture programs, plus additional unspecified cost that might come from loan guarantees and disaster insurance.

Senate committee members are shooting for completion of action on a final bill, possibly by blending the Agriculture and Commerce versions if they can settly the "lead" agency issue, sometime this year.

All of which is not unlike tossing hook and a bobber into your neighborhood stream and waiting for a bite. It may take awhile, but you may yet see more catfish and salmon on the platter than you believed possible.