It’s frightening enough that 87% of the world’s assessed fisheries are fully or over-exploited. But it is even scarier to consider how little we know about the condition of most of the world’s fisheries, because four-fifths of them have never been scientifically assessed. A recent study in the journal Science is providing fresh insights into thousands of fisheries where data has not been previously available. These “data poor” fisheries make up 80% of the world’s catch — and many are on the brink of collapse.