AS the days get warmer and schools of mackerel end their spring run up the New Jersey coast, state officials are hopeful that new laws and programs put in place since last year to reduce coastal pollution will make this summer a better one than the last three. But researchers and environmentalists remain cautious about how to address the long-term underlying causes of coastal pollution.
Starting tomorrow, for the first time, helicopters will hover daily over the harbors and ocean waters to catch illegal dumpers or detect slicks of garbage drifting toward shore.
Also, special vessels are poised to scoop up large garbage slicks before they reach the surf waters of Monmouth County, and about $11 million more is being spent to keep beaches clean and promote tourism.
''We want to bring back the public's perception of the Shore to where it was in 1985 before all the bad publicity hit,'' said John Penn, a spokesman for the State Division of Travel and Tourism, adding that ''all we can do is try.''
Mr. Penn's note of guarded optimism was repeatedly echoed in interviews with Federal and state environmental officials, marine scientists and environmentalists as they anticipated the summer.
Beach closings and major pollution incidents between 1986 and 1988 were attributed to medical or household wastes from New York Harbor and Raritan Bay that washed up on beaches along the 127-mile coastline. Malfunctioning sewage treatment plants were also cited as factors in raising the bacteria levels in bathing waters.
Shore tourism, which generated $8.4 billion in 1987, declined by $780 million last year, to about $7.7 billion, according to the Division of Travel and Tourism. And individual communities and merchants have indicated that the losses were greater, up to 60 percent in such places as Asbury Park.
Scientists said it would take 10 years or more before the tide of contamination that lurks offshore can be substantially abated. But they said that this last year had represented the first time since coastal pollution began taking its toll at the end of the 19th century that long-term solutions began to be formulated.
Larry Schmidt, programs coordinator for the State Department of Environmental Protection, and others said that state and Federal agencies and the State Legislature had taken steps to make for a better summer this year, including these:
* In Operation Clean Shores, state prison inmates removed about three million pounds of debris from northern New Jersey piers and shorelines as of May 1. The debris, consisting of medical wastes and plastics, would have re-entered the water during storms and high tides. The program's cost is $3.5 million annually.
* In Operation Clean Sweep, some $4 million in Federal funds is being spent to have vessels from the Army Corps of Engineers on call to skim floatable wastes flushing out of New York Harbor and Raritan Bay. The boats are docked in the Arthur Kill, near Woodbridge, and adjacent to the Verrazano-Narrows Bridge.
* The Division of Travel and Tourism has allocated $2.8 million to promote the Shore through newspaper and broadcast advertising and public relations campaigns.
* Individual coastal counties are spending from $125,000 to $250,000 each on tourism promotions this year, state tourism officials said.
* The Department of Environmental Protection has added $500,000 to its water resources budget to monitor the 14 coastal sewage treatment plants more closely. The plants are in Atlantic, Cape May, Cumberland, Monmouth and Ocean Counties.
* Although only $50,000 will be spent on an existing ''New Jersey Shore - Keep It Perfect'' campaign against littering, Assembly Speaker Charles L. Hardwick, Republican of Westfield, has designated tomorrow as Clean New Jersey Day and said he would introduce four new anti-littering bills.
While encouraged by these efforts, officials, environmentalists and researchers remain cautious in their predictions for the summer, citing the difficulty of identifying and attacking the key sources of coastal pollution.
Earlier this year, for example, the House Fisheries Subcommittee, reporting on a two-year study on coastal pollution nationally, said that if current pollution trends continued, ''what is now a serious widespread collection of problems may coalesce into a national crisis by the next century.''
Commenting on the report, the May newsletter of the Boat Owners Association of the United States, which has more than 10,000 New Jersey members, said, ''Americans who go boating, fishing or just enjoying the beach may soon find declining sports fish and shellfish populations, more beach closings and a loss of recreation such as swimming, boating and fishing.''
Water-dependent industries, like tourism and commercial fishing, can expect ''significant economic losses,'' the newsletter said.
Another report, this one made to Congress concerning the New York Bight, which is the section of the Atlantic between the tip of Long Island and Cape May, has identified five major categories of problems in coastal waters, according to Eric Evenson, a biologist and deputy director of water resources for the Department of Environmental Protection, who helped compile the report. The categories mentioned in the report are floating wastes, pathogens, nutrients, toxics and habitat loss.
Mr. Evenson is one of 14 members of a work group on the Bight Restoration Plan, which in the last year has estimated the kinds and amounts of pollutants that are befouling the bight.