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Moonlight enhances growth in larval fish

Shima, Jeffrey S., Swearer, Stephen E.
Ecology 2019 v.100 no.1 pp. e02563
cloud cover, fish larvae, foraging, larval development, life history, lighting, otoliths, predators, temperature
Moonlight mediates trophic interactions and shapes the evolution of life‐history strategies for nocturnal organisms. Reproductive cycles and important life‐history transitions for many marine organisms coincide with moon phases, but few studies consider the effects of moonlight on pelagic larvae at sea. We evaluated effects of moonlight on growth of pelagic larvae of a temperate reef fish using “master chronologies” of larval growth constructed from age‐independent daily increment widths recorded in otoliths of 321 individuals. We found that daily growth rates of fish larvae were enhanced by lunar illumination after controlling for the positive influence of temperature and the negative influence of cloud cover. Collectively, these results indicate that moonlight enhances growth rates of larval fish. This pattern is likely the result of moonlight's combined effects on foraging efficiency and suppression of diel migrations of mesopelagic predators, and has the potential to drive evolution of marine life histories.