Skip to main content

Article Category

News

Article available in the folowing languages:

EU research reveals fish use senses to navigate

Scientists from the Netherlands and the United Kingdom have discovered how young coral reef fish use sounds, smells and sights to navigate from the high seas to find their shoal mates hidden among the roots of mangrove trees or blades of seagrass. Dr Ivan Nagelkerken, formerl...

Scientists from the Netherlands and the United Kingdom have discovered how young coral reef fish use sounds, smells and sights to navigate from the high seas to find their shoal mates hidden among the roots of mangrove trees or blades of seagrass. Dr Ivan Nagelkerken, formerly at the Radboud University Nijmegen, Netherlands, and now based at the School of Earth and Environmental Sciences at the University of Adelaide, Australia, noted that the findings are of particular importance. Published in the journal Ecology, the research 'highlights the importance of maintaining a mosaic of different habitats and healthy local populations in order for the French grunt, and many fish like it, to complete their life cycle'. The health of the sea and its inhabitants are under threat globally from a variety of sources including litter, industrial pollution and overfishing. According to the European Commission, in Europe, where marine species and habitat types have been assessed, 'the majority were found to be in unfavourable or unknown condition' with 'only 10% of habitats and 2% of species ... in good condition'. To discover how young fish find their way about, researchers from the Radboud University Nijmegen in the Netherlands together with colleagues from the University of Bristol in the United Kingdom studied the responses of young French grunts - a common species in the Caribbean - to local sounds, smells and visual cues. The team first tested which habitat noises the fish were attracted to, using auditory choice chambers. They found that newly settled fish, namely those that had just returned to the coast after developing in plankton for several weeks, were most attracted to recordings of coral reefs. However, they do not set up home on the coral reefs, which can be dangerous places for a young fish. Instead they seek the relative safety of nursery grounds in the mangroves and seagrass beds, where they grow for the first few months. The second experiment tested which habitat smells the fish were attracted to, using olfactory mazes shaped like a 'Y'. In contrast to the hearing study, the fish were attracted not to the smells of coral reefs, but rather to the smells of the muddy soft-sediment habitats of seagrass and mangroves. 'It seems that to find the shore the fish use coral reef noise, which is the loudest habitat noise and can be heard by fish from 100s to 1 000s of metres,' said Dr Chantal Huijbers from the Radboud University Nijmegen. 'Once in the right proximity, they can then sniff out their preferred nursery habitats.' In the third experiment, the team tested whether fish were attracted to the sight of a suitable habitat or to potential shoal mates. Observing their behaviour in a square arena, they found that fish couldn't pick apart different types of habitat, but were highly attracted to the sight of a familiar-looking fish. The fourth and final test examined the strength of this attraction to other fish. The team used the olfactory Y-maze and let fish identify their preferred scent, before opening a window that let the study fish see other individuals. They then switched the smells, but found that the fish ignored the loss of their preferred scent and opted to stay in sight of their new shoal mates. 'This suggests that once visual contact has been made, other cues become less important,' said the researchers. 'Their mission has been accomplished.' 'This study is the first to look at the hierarchy of different sensory cues that allow young fish to complete a life-or-death navigational task,' concluded Dr Steve Simpson, marine biologist and fish ecologist at the University of Bristol. 'Hearing then smell guides fish at the macro scale, but at the fine scale, vision takes over as the fish locate their new shoal mates.'For more information, please visit: Radboud University Nijmegen:http://www.ru.nl/english/ University of Bristol:http://www.bristol.ac.uk/news/2012/8305.html