Feeding in the moonlight

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Acoustic data from the Malaspina research expedition, which circumnavigated the earth’s oceans between December 2010 and July 2011, shows that a full moon causes fish to stay at deeper levels.

Data analyzed by KAUST doctoral student Perdana Prihartato showed that the effect was consistent around the globe despite changes in environmental conditions and varying types of species in different parts of each ocean.

Previous research indicated that fish that occupy the mesopelagic zone (between 200 to 1000 meters) will avoid feeding on plankton available in relatively shallower waters on moonlit nights, possibly to avoid being eaten themselves by larger marine animals. Yet the effect was not a linear one, explained KAUST Marine Scientist Stein Kaartvedt. Contrary to their initial expectations, the team did not find the shallowest distribution of mesopelagic fish during the darkest night at new moon.

The researchers identified a threshold. “The distribution of organisms is unaffected by moonlight until a critical value is reached—about 70 percent full moon—after which they dive so as not to be seen by predators,” explained Kaartvedt.

The study illustrates the benefits of interdisciplinary research between statisticians and, in this case, marine scientists, said Marc Genton, KAUST professor of statistics. “Statisticians get access to very unique datasets that may trigger the development of new statistical methodologies, and the marine scientists get more robust and reliable results from the data they collect,” he explained.

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