How young reef fish find a home

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Young coral reef fish pull out all the stops when it comes to locating a home, according to research published in a recent issue of the journal Ecology.

In this study, Chantal Huijbers and coauthors found that young French grunts (Haemulon flavolineatum) use sounds, smells and sight to locate their nursery grounds, providing insights as to how juvenile fish find their way to nursery grounds.

In the first set of experiments, the authors tested the affinity of young fish to sounds of different habitats using auditory choice chambers. They found that very young fish were most attracted to coral reef sounds.

Since the nursery grounds of the grunts were located in the mangroves and seagrass beds, but not coral reefs, it is likely that the very young fish were using the coral reef noises (which were the loudest) to help them locate coastal habitats by other means.

The second set of experiments used Y-shaped olfactory mazes to test the preference of the grunts to different habitat smells. The fish were found to significantly prefer the smells of the soft-bottom habitats of seagrass and mangroves.

In the third set of experiments, the authors tested the visual preference of the grunts by placing test fish in a square cage from which they were visually presented with either four different habitat types or a choice of different fish types (no fish, heterospecifics and conspecifics).

The grunts did not show a visual preference for habitat types, but were strongly attracted to conspecifics.

Finally, the authors tested the effect of multiple cues and found that the grunts preferred to use visual cues even when the "wrong" olfactory cues were presented. This suggests that other cues become less important once visual contact has been made.

According to co-author Ivan Nagelkerken: "This study demonstrates the complex behaviour employed by young juvenile coral reef fish, and 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."

For more information, see the paper: Huijbers, CM, I Nagelkerken, PAC Lössbroek, IE Schulten, A Siegenthaler, MW Holderied, and SD Simpson (2012) A test of the senses: Fish select novel habitats by responding to multiple cues. Ecology 93, pp. 46–55.

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