In the vast open oceans, how do fish larvae manage to find their way around? Or do they simply drift along with the currents?
In this study, researchers discovered that fish larvae around the world used external cues like the sun, Earth’s magnetic field and sounds to find their way around in the open ocean.
The fish larvae were able to control their destination and migrate by keeping a bearing.
“This study highlights the importance of a deeper understanding of larval orientation mechanisms and suggests the concept of vector-navigation in the early life history of fish,” said the study’s senior author Claire Paris, a professor of ocean sciences at the University of Miami's Rosenstiel School.
With this new knowledge, scientists can better predict fish larvae's dispersal, the connectivity of marine protected areas, as well as the structure of marine fish populations.
In the study, the researchers and their collaborators from various institutions analysed nearly two decades of studies using two methods of data collection. The first method involved a Drifting In Situ Chamber instrument that consisted of an underwater chamber with an imaging system to record the larval fish's swimming behaviour.
The second method was the Following method, in which two scuba divers follow late-stage larvae while recording the bearing and swimming speed.
The movement patterns recorded by the two methods were compared to the theoretical movement patterns expected under strict use of internal cues.
"Our study is the first to show that this is achieved using external directional cues, providing a systematic and global indication for a robust use of external cues by fish larvae for orientation,” said lead author Igal Berenshtein, a postdoctoral researcher in the Department of Ocean Sciences at the Rosenstiel School.
Having a better understanding of the larval stages of fish can lead to better management and conservation of marine populations, he added.
“It’s extraordinary that these tiny fish larvae find their way in a vast ocean” said Paris.
These findings were published in the journal Communications Biology last December.
“We can learn from them to fundamentally advance fisheries models and the science of underwater navigation,” said Claire Paris, a professor of ocean sciences at the University of Miami's Rosenstiel School