Mexico's new policy of using some of its oil revenues to build up a fishing industry led the government today to abrogate all agreements allowing U.S. commercial fishermen to operate in Mexican waters.

The U.S. State Department today was informed of Mexico's unilateral decision, which followed many months of bilateral haggling over fishing rights. d

Although the move in itself will affect a relatively small number of American fishermen, it is likely to have long-term consequences for the multimillion dollar U.S. tuna industry, which had hoped to be able to fish in Mexican waters.

Because Ronald Reagan has made the defense of U.S. business interests abroad a strong theme of his campaign, Mexican officials believe their decision may lead to a new chapter in this summer's chapter of the Mexican-American "tuna war."

A few weeks ago, "the American negotiators told us we were better off dealing with the Carter administration," one Mexican official here recalled. "They said Reagan is indebted to the tuna industry because [it] made important contributions to his campaign."

In the now-stalemated fisheries talks, both governments have been acting as proxies for private fishing interests, although the Mexican government has started making heavy investments in new boats, fishing ports, freezing and canning factories and outlets to make Mexico a major fishing power.

The fisheries department here has argued that the need for cheap fish is greater than ever as the rising cost of living puts other sources of protein increasingly out of reach of poor Mexicans.

Over the last few years Mexico has been phasing out traditional fishing rights for foreigners in Mexican waters. It ended shrimping rights for U.S. and Cuban boats in the Gulf of Mexico last year and for three years has argued with the United States over tuna fishing on the Pacific Coast.

Acting on the basis of a new law, Mexico made the initial running in the "tuna war" last July when it seized and finded six American tuna boats for unlicensed fishing within its 200-mile economic zone. Washington immediately retaliated by banning the $20 million worth of tuna the United States annually imports from Mexico.

Explaining why Mexico will not renew the 47 current tuna permits, Ambassador Andres Rozenthal, head of the Mexican negotiating team, said, "For many years the Eastern Pacific has been the bastion of the American tuna fleet. We are expanding our own capacity. We will not allow ourselves to be condemned to underdevelopment in fishing just becaue the U.S. has always fished here."

Today's renunciation of the two outstanding fishing agreements with the United States, Mexico claimed, is a tit-for-tat measure because the United States refused to renew Mexico's allocation to catch squid and hake off the New England coast.

One of the treaties, signed in 1976, granted U.S. fishermen the right to catch a quota of snapper and grouper in the Gulf of Mexico. On the Pacific side, 140 boats were allowed to operate within Mexico's 12-mile territorial waters. This number has now dwindled to 76 boats.

A second treaty, signed in 1977, gave Mexico the right to supply for squid and hake fishing off the New England coast.But last year, Mexican officials said, Washington, annoyed over Mexico's tuna restrictions, began to hold back on the squid quota and this year cut Mexico's request for 30,000 tons back to 1,000 tons of the cheapest kind.