geographic advantage has helped make Killybegs the largest fishing port in Ireland. Last year, its trawlermen landed almost 200,000 tonnes of fish, helping to feed a burgeoning national export market for seafood. A large part of this catch is found around 420 kilometers north in the Rockall Trough, a remote stretch of the Atlantic between Ireland, Scotland, and Iceland. Here, the fish gather in vast schools, especially near the region’s namesake pinnacle: Rockall, a tiny, uninhabited, jet-black outcrop of granite crowned by a pointillist splattering of guano.