Even the dead kept watch. They sat upright in their graves, men and women, and faced the river, waiting, it seemed, for the waters to roil again with massive, steel-grey fish. The sturgeon, barbeled giants with rows of bony scutes down their backs, appeared each spring in Serbia’s Danube Gorge, after battling the current all the way from the Black Sea. The largest of these fish weighed more than a dozen men. The oldest of these Beluga sturgeon survived more than a century.