When salps moved alone, they went unnoticed. When they moved in swarms, they posed no great threat, it seemed, only inconvenience. For centuries, only one thing seemed clear: the salps, wherever they went, were unwanted. So there is almost no long-term historical record of the salps in any ocean. Few data sets go back more than twenty years, and the ones that do record salps only in these ephemeral explosions of abundance. Scientists only took notice of them when they gathered in such great masses that they made themselves impossible to ignore.
