Like sea turtles during their aforementioned "dark years," many young fish have long been regarded as passive creatures, floating where time and tide might carry them. And as with the turtles, researchers have begun to question that received wisdom. For example, when scientists involved in the Great Barrier Reef study we just mentioned tracked the movements of larval coral trout, they found that the baby fish could swim against the current and navigate by sun and smell back to their coral home [source: ABC]. Other fish larvae can control their vertical position in the water and find beneficial places to flap their fins [source: Milius].
Moreover, a study in the October 2014 issue of Biology Letters has revealed for the first time that one-month-old gray snappers (Lutjanus griseus) can make growls and knocking vocalizations that might aid them in schooling in the dark. A similar mechanism has been proposed for aiding adult fish in schooling [source: Milius]. Unfortunately, the discovery also demonstrates yet another aspect of life in the big briny that might be perturbed or even damaged by human activities, such as the sounds produced by boat motors.