Muscle Motion Like all fish, the salmon relies on its muscles for much of its swimming and jumping power. Fish muscles, up to 80% of the body, are arranged in multiple directions that allow the fish to move in any direction. The fins provide a platform to exert the thrust from the muscles onto the water. Anadromous salmon, feeding heavily in ocean waters and swimming thousands of kilometres, develop strong, hard, richly vascularized muscles in preparation for their upstream spawning run.