Despite a strong performance in March, the E.I. Du Pont de Nemours & Co. recorded lower net income in the first quarter than in the year-ago period. The earnings, however, were much higher than in the peak fourth-quarter 1976 and marked the return to profitability of Du Pont's log-depressed textile-fiber operations.

Speaking to about 1,200 shareholders at the annual meeting, chairman Irving S. Shapiro said the firm earned about $2.40 a share in the first quarter and $1.87 a share in the fourth quarter. The first-period 1977 results included about 20 cents a share in gains from foreign-currency transactions. Shapiro said. Net earnings were not announced.

Sales for the quarter, according to Shapiro, were a recor $2.3 billion compared with $2.10 billionin first quarter 1976 and $2.06 billionin the fourth quarter.

Textile fibers, which account for about a third of Du Pont's annual sales, earned approximately 10 cents a share in the first quarter, after an $8 million writeoff for shutdown of acetate fiber operations. Shapiro said. Du Pont earned 70 cents a share on fibers in last year's first quarter but had posted losses on the operations in both the third and fourth quarters of 1976.

Shapiro said that the strongest performers for the company in this year's first quarter were electronic products, printing systems, finishes and several plastics. Du Pont's physical volume of sales, he said, was about 8 per cent above the year ago level.

The physical volume of fiber shipments from the firm's U.S. and European plants set a record for a first quarter, according to Shapiro. Recovery in European fiber markets, however, continue to lag that in the United States.

Du Pont's domestic selling-price index, which had declined because of fiber-industry problems last year, started to pick up in the first quarter, Shapiro said. He added that many of those price hikes came in fibers and that continued strong market demand should permit additional boosts during the rest of 1977.

Profit results were hampered in the first quarter, he said, by the sevreely cold weather in much of the United States during January and February.

Also at the meeting, shareholders defeated, 98.2 per cent to 1.8 per cent, a proposal which which have required Du Pont to report to stockholders on what steps it is taking to prevent company compliance with alleged Arab efforts to impose an economic boycott on Israel.

Will Maslow, general counsel of the American Jewish Congress, accused Du Pont at the meeting of surrendering to Arab pressures by furnishing ot Arab customers certificates stating that goods sold to them did not originate in Israel. Since Du Pont said its volume of Arab-related business is insignificant, "why does the company meekly accede to the Arab demands?" Maslow asked.

Shapiro, who has urged Congress to adopt anti-boycott legislation and who has been active in Jewish groups himself, defended Du Pont's policies. He said that such certificates are simply statements of fact and that Israel itself requires companies dealing with it to furnish certificates of non-Arab origin of products.

Such "negative certificates" should be banned by U.S. law, Shapiro said. Until such a legal prohibtion is adopted, though, he asserted. Du Pont will furnish these statements because "we live in a real world." The company has to compete for business with some firms which do not share Du Pont's distaste for the negative certificates, he added.