Orientation and settlement of coral reef fish larvae

A team of divers deploying the Drifting In Situ Chamber in Belize.

Coral reef fish have a complex life cycle with 4 distinct stages: egg, larva, juvenile, and adult. The larval stage is for many species the only possibility to connect distant populations on other reefs. It is necessary to exchange genes and individuals, and it is essential to replenish fish stocks.

Coral reef fish larvae start their journey on the reef where they are born. Currents disperse them offshore where they will grow protected from the predators living on the reefs. When they are ready to transform into juvenile fish, they need to find the way back to the reef. To better understand how larvae are able to find the reefs, we study their swimming and orientation behaviors during dispersal.

Studying fish larvae in their environment is complicated and necessitate the development of specific scientific tools and experiments. One of them is the Drifting In Situ Chamber, a behavioral area that we used to study the behavior of Elacatinus lori, an endemic goby living in Belize. Observing how larvae react within the chamber tell us more about their orientation and ultimately about the mechanisms they use to come back to the reefs.

We also test larvae in laboratory experiments. We try to recreate conditions that would lead larvae to make a choice. For example we ask the larvae to choose between different patches of corals. By studying their preferences in the experimental setting we can infer their preferences during settlement. These experiments help us understand how larvae select a suitable habitat.