An experiment reported in the journal Science has revealed that some coral reef fishes appear to have notable homing instincts.
The scientists involved in the project tagged two species of reef fish larvae in an effort to investigate where they end up after drifting around in the open sea for a period of weeks as they mature. The tagging was made possible by collecting female fish from a small reef in Kimbe Bay, Papua New Guinea, and injecting them with a rare, stable barium isotope. This isotope was passed on to the developing larvae where it accumulated in their bones, resulting in a unique detectable marker.
Some weeks after the “tagging” the team involved in the study returned to Kimbe Bay to collect juvenile fishes and find out how many of them, if any, had returned to their place of birth. The unexpected result was that approximately 60% had found their way back home
The two species investigated were the Common Clownfish and the Vagabond Butterflyfish. Although the study only involved two species, it’s likely to apply to other reef fish too, and if so it might have important implications for reef conservation. It demonstrates that small no-take marine reserves could well be a good way to protect species vulnerable to over fishing, as there should be enough juveniles returning to the area to sustain numbers over time.
Previously the question of where do the larvae go has been something of a mystery. Most marine fishes produce small eggs, which result in small larvae that then go on to live a pelagic existence before metamorphosis into a juvenile and settling onto a home reef. Given the small size of the larvae it’s been difficult until now to find an easy way of tagging them.
It remains uncertain how the juveniles manage to find their way home, leaving room for further speculation on the subject and for future research.
For me this raises the question of, “where is the other 40% ending up?” Apart from the implications on fishing stocks and species preservation it makes me speculate on whether populations of reef fishes can successfully relocate in response to changing climate.
Science 4 May 2007:
Local Replenishment of Coral Reef Fish Populations in a Marine Reserve.
Glenn R. Almany, Michael L. Berumen, Simon R. Thorrold, Serge Planes, Geoffrey P. Jones.