GRAYLING (API—A 512 foot, 120-pound shark ) found dead on a beach at nearby Lake Mar grethe during the weekend. Russell Wright, conservation of ficer at Grayling, identified iit as a young thrasher shark. Such shark, he said, would measure about 20 feet and weigh 1,000 pounds at mator Wright theorized that the shark's getting into We lake was the result of a complicated and expensive practical joke on the part of National Guardsman. He said thrasher sha norm ally are found in the worm waiters of the Pacific and south Atlantic oceans. He noted that the National Guard Association recently held its convention in Hawaii. Wright said some guardsman apparently had the shark shipped alive from Honolulu to Grasling, where he released it in t o said it is possible for such shark fall in fresh water, but Ret probs