Reef fish larvae are only millimeters-long when they hatch, but can smell the presence of coral reefs from several kilometers offshore, and use this odor to navigate home. The results are reported August 28 in the open access journal PLOS ONE by Claire Paris from the University of Miami and colleagues from other institutions.
The researchers used a novel drifting behavioral arena to find that larvae of two families, damselfish and cardinalfish, changed swimming speed and direction in response to the smell of reef water, but water from the open ocean did not evoke a similar behavior from the larvae. Water temperature and current directions, factors normally important to navigation in the ocean, did not appear to influence the orientation of larvae in this study. The study states that reef odor could act as a wake-up call that signals settlement fish larvae to modify their activity for directions towards the reef. Other fish such as sharks and freshwater salmon are known to navigate using olfactory signals, but this is the first study to report that reef fish larvae use similar odor cues. Paris elaborates, "Unlike most animals that migrate as adults on a seasonal basis, coral reef fish undertake their longest voyage early in their life history. Here we find that coral reef fish larvae smell the reef kilometers away and then switch to a proximal cue which allows them to navigate with a landscape frame of reference."
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