Catholic University announced yesterday that the Rev. William James Byron, an economist and Jesuit priest, will become the university's 13th president.

Byron, currently the president of the University of Scranton in Pennsylvania, said his chief responsibility at Catholic, the national university of the Catholic Church in the United States, will be spearheading the university's ambitious and long-range $50 million fund-raising drive. He assumes his new duties from the outgoing president, Dr. Edmund D. Pellegrino, on Sept. 1.

"It was made very clear to me by the board of trustees and the search committee that the financial development of this institution is of primary concern," Byron, 54, said at a news conference. He said raising money would require him to be "on the road" quite a bit, something his predecessor, who is leaving to join the faculty of Georgetown University, felt he did not want to do at the expense of his scholarly interests.

The university's money worries were underscored yesterday by the Most Rev. Philip M. Hannan, archbishop of New Orleans and chairman of the school's board of trustees. In announcing Byron's selection, Hannan noted that Catholic University's motto, "God Is My Light," will be fitting for his new office.

"We know that as an economist he realizes the increasing cost of energy and light for a university," Hannan said.

The choice of Byron, the first Jesuit president in Catholic University's 95-year history, marks a return of cleric leadership in that post. Pellegrino and his predecessor, Clarence C. Walton, were laymen.

A Pittsburgh native, Byron has been president and a professor of economics at the University of Scranton since 1975. He is a former dean and an associate professor at Loyola University in New Orleans and earlier held teaching positions at the Union Theological Seminary in New York City, Loyola College in Baltimore and the University of Maryland.

Byron, who served as a paratrooper in 1945-46, holds degrees in philosophy, economics and sacred theology and has written and lectured extensively in those fields. He was ordained to the Roman Catholic priesthood as a member of the Society of Jesus in 1961.

At his news conference, attended by some students and faculty members, Byron displayed the sense of humor and personal appeal for which friends say he is noted. He said he would be living on campus, would be accessible through liturgy and dormitory meetings and expected--despite his fund-raising travels--to be attending athletic events and student plays.

"I was about to say I'll be eating your food, but I'll have to read the fine print on that one first," he teased.

On the fund-raising itself, Byron declined to be specific. "You have to do friend-raising before you can do fund-raising," he said.

But Byron, a founding director of Bread for the World, did say he hoped to involve the university and its students in working to combat world hunger and racism, the latter of which he called "the poison at the bottom of the well for American cities."

For those who believe in the Gospel and in serving the Church, "It seems to me the world of public policy is always open to influence," he said.

Discussing the challenges facing Catholic University, Byron said he was distressed at the drop in enrollment at private colleges such as the one he is about to head. When he attended school in the 1950s, he recalled, 50 percent of the nation's students enrolled in private colleges or universities. Now, that figure has declined to 22 percent.

Catholic University, whose campus in Northeast includes law, nursing, social service, engineering, religious studies and five other schools, has an enrollment of 8,000 students. Chartered by Pope Leo XIII in 1887, it is the only American university that can grant pontifical degrees in theology, philosophy and canon law.