Hearing The Way Home

Date: 1/6/2005

How Fish Find Reefs The symphony of underwater clicks, pops and clacks is a powerful navigation tool for juvenile reef fish to find their way home, according to new research conducted by New Zealand scientists from the National Institute of Water and Atmospheric (NIWA) and the University of Auckland.  Andrew Jeffs of NIWA and Professor John Montgomery, director of the Leigh Marine Laboratory in the University of Auckland’s Faculty of Science, say the picture of reef fish larvae as passive passengers on ocean currents has collapsed in recent years under evidence of their enviable swimming capabilities. ‘Most reef fish spawn on the reef, and the larvae are swept out to sea where they live in the plankton for weeks to months.  The problem is, how do they return to the reefs when it is time to settle? ‘Although only millimetres long, we have shown that reef fish larvae can consistently swim faster than the currents they float in and in some cases we recorded them swimming for as far as 200 kilometres.  They are exceptional swimmers for their size, but the problem then becomes – how do they know which way to go?’ The research team built 24 patch reefs near Lizard Island on the Great Barrier reef. They used an innovative submersible speaker system for broadcasting imitation reef noises, which included the sounds of snapping shrimps and fish calls, on half of the patch reefs.  The other patch reefs did not have pre-recorded sound. Larvae settled in greater numbers on noisy patch reefs than on silent reefs. The study provides direct field evidence that settling reef fish use sounds to orientate towards and reefs, and indicates that some fish groups may also be ively using specific components on the reef sound to guide their settlement behaviour.

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