The researchers observed that larvae produced "knocks" and "growls"
in the range of 200-800 Hz, which is within the hearing range of most adult fish
. The fish larvae produced these sounds during 70%
of the nighttime trials , and none of the daytime trials . The
gray snapper larvae used in the study arrived in a large group over the
span of a few hours , suggesting that these acoustic signals may
provide a mechanism for these larvae to maintain group
cohesion during their pelagic journey