Smell of leaves brings reef fishes back to islands


Coral reef fish rely on the smell of leaves to find their way home, according to research published in the most recent issue of the Proceedings of the Royal Society B: Biological Sciences.

Danielle Dixson and coworkers studied the clownfish Amphiprion percula in the coral reefs surrounding offshore islands in Papua New Guinea, noting from their survey results that host anemones and the clownfish are particularly abundant in shallow water beneath overhanging rainforest vegetation.

Basing their work in the island of New Britain, the authors carried out a series of experiments using paired-choice flumes (in chambers) to evaluate the potential role of water-borne olfactory cues in finding islands.

Newly settled juvenile clownfish were used in the experiments and in each experiment, a single individual was placed into the centre of the downstream end of the choice flume.

The fish were allowed to acclimate for five minutes before the researchers recorded the position of the fish on each side of the chamber at five-second intervals for a period of two minutes.

The procedure was then repeated with the position of the flumes within the chambers reversed.

Testing the effects of: (i) water samples from reefs with and without islands; (ii) water samples from island reefs at three different distances (one metre off shoreline, at reef crest and one kilometer offshore) and (iii) untreated offshore water and offshore water treated with either anemones or rainforest leaves, the authors found that juvenile clownfish exhibited a strong preference for: (i) water samples taken from reefs with islands; (ii) beach water (water taken one metre offshore) and (iii) water treated with anemones or rainforest leaves.

An experiment using laboratory-reared (instead of wild caught) clownfish larvae yielded similar results.

The authors concluded that clownfish larvae are able to use olfactory cues from rainforest vegetation for finding suitable settlement sites (island reefs).

For more information, see the paper: Dixson, DL, GP Jones, PL Munday, S Planes, MS Pratchett, M Srinivasan, C Syms and SR Thorrold (2008) Coral reef fish smell leaves to find island homes. Proceedings of the Royal Society B: Biological Sciences 275, pp. 2831"2839.