Jimmy Carter this week published his first written work since leaving the White House a year ago, and it wasn't a weighty tome in The Nation or The New Republic.

Carter's "Spruce Creek Diary," a reminiscence of a successful fishing trip to Pennsylvania last spring, is tucked away without fanfare in the January/February issue of Fly Fisherman magazine.

The low-key, 4,000-word essay recounts his and wife Rosalynn's one-week visit to Wayne Harpster's farm near State College, a foray capped by the former president's capture and release of a 17-inch brown trout.

Carter, in a phone interview from his home in Plains, Ga., yesterday, said there was no particular significance to the fact that his first post-presidential musings were on fishing. "It just kind of happened that way," he said, adding that he still is working on a book of political memoirs.

He said he rediscovered fly fishing during his tenure as president, having made his first experiments in Atlanta's Chattahoochie River when he was governor of Georgia. He began fly fishing again at Hunting Creek near Camp David, then moved on to more fertile Pennsylvania waters just before the Begin-Sadat summit meetings.

"I kind of live and breathe fly fishing," he said, adding that it and woodworking are his two hobbies. Carter said, "When we went to Spruce Creek I took notes for what I figured to be a chapter in a book on fishing" he plans to write some day.

He finished the chapter last June and got the inspiration to send it along to Fly Fisherman when he was leafing through the magazine. He called publisher Don Zahner "and he was enthusiastic," Carter said.

The article is notable for its lack of politics. Carter said he intended it that way and the only editing Zahner did was to remove one vaguely political reference.

Carter wrote that two prized, hand-made fly rods were stolen from his baggage in the move from Washington to Plains, and commented that their loss, and not the loss of the presidency, "seemed to be the more serious to all of us as we discussed important matters by the tumbling waters of the Pennsylvania creek." Zahner changed the mention of the presidency to "the election campaign," which he considered less political.

Other than that, Carter said, the article ran as written. As an outdoors story it covers all bases, including an explanation of how Spruce Creek came to be an extraordinary fishing hole (careful farming in the adjoining fields). Carter's easygoing style works well in describing the gentle, green landscape and the dainty sipping tactics of trout on the feed.

His hosts included some of the top Pennsylvania fly fishermen, who are among the best in the nation, and Carter shows them great respect.

He concludes with a description of his final night at Spruce Creek: "That night Rosalynn and I talked about how Wayne, George, Lloyd, Don and Joe all seemed very close to us, part of a large but close-knit fraternity of sportsmen who love God's world with its changing faces and seasons and want to preserve its beauty and its challenge and its excitement.

"After my week on Spruce Creek, I could see very clearly how far I still have to go to realize one of my goals in life: to become a good fly fisherman. But I look forward to the challenge--and to the excitement it brings."

Carter said he and his wife ride bicycles out to fly fish in the bream and bass ponds in Plains two or three evenings a week in the season, and have four or five major fishing excursions planned this spring. One of those, he expects, will be back to Spruce Creek.