Former congressman and avid outdoorsman Joseph L. Fisher (D-Va.) has found a job whose description reads as if it were created for him.

Fisher, defeated in November for a fourth term, will head a unit of the Wilderness Society, a conservation organization, that will try to provide economic arguments for preserving public lands targeted for development.

The program will be financed by a $620,000 grant from the Richard King Mellon Foundation that calls for a team to be headed by "a Ph.D. resource economist." The Arlington Democrat has a doctorate in economics from Harvard, and before being elected to Congress in 1974 was for 15 years president of Resources for the Future Inc., a private foundation that conducted research on problems of conservation and the environment.

At the Wilderness Society, Fisher, who was defeated for the 10th Congressional District seat by Republican Frank Wolfe, will join former Wisconsin Sen. Gaylord Nelson, another liberal Democratic politician who was rejected by the voters in last November's conservative tide. Nelson, who is regarded by many as the father of the modern environmental movement, was named chairman of the conservation lobbying group last month.

William A. Turnage, executive director of the 45,000-member, Washington-based group, said "we are delighted that Joe Fisher wants to continue working for those issues to which he has devoted untold time and energy throughout his life." Turnage predicted that Fisher will "shape and direct what will undoubtedly become a model for the movement."

The program will "for the first time allow conservationists to have equal footing with development interests in the debate over the wisest use of our natural resources," Turnage said.

The Mellon-financed program will focus primarily on conflicts over the hundreds of millions of acres managed by various agencies of the Interior Department, including the National Park Service, Forest Service, Fish and Wildlife Service and the Bureau of Land Management.

The Wilderness Society was a leader in the fight during the 96th Congress to preserve Alaska's wilderness. An example of what Fisher's unit might do, as envisioned by the Mellon Foundation, would be to "make the case" in an Alaska-type legislative battle, by quantifying the actual effects preserving wilderness acres would have on employment and inflation, and the housing and timber industries, compared to the benefits to tourism, recreation, fishing and hunting.

Fisher said "the values we conservationists think important should stand and will stand the scrutiny of economic anaylsis." He added that findings of his group, which also will include an economist, forester and ecologist, should "enable us to work constructively in resolving land and resource policy conflicts by engaging in professional dialogue with industry and with government, thus reducing the need for legislation or litigation."

In the recently ended 96th Congress, Fisher was chairman of the Environmental Study Conference. Fisher, who is a canoeist, hiker and tennis player, called the half-time appointment "a labor of love."

The 66-year-old Fisher also will be a consultant on a public policy program at George Washington University, where he "undoubtedly will end up teaching a class." He has taught economics at a number of schools, including Harvard, Berkeley and GW, and also served as an economist for the State Department and President Truman's Council on Economic Advisers.