Lunar rhythms in growth of larval fish

Abstract

Growth and survival of larval fishes is highly variable and unpredictable. Our limited understanding of this variation constrains our ability to forecast population dynamics and effectively manage fisheries. Here we show that daily growth rates of a coral reef fish (the sixbar wrasse, Thalassoma hardwicke ) are strongly lunar-periodic and predicted by the timing of nocturnal brightness: growth was maximized when the first half of the night was dark and the second half of the night was bright. Cloud cover that obscured moonlight facilitated a ‘natural experiment’, and confirmed the effect of moonlight on growth. We suggest that lunar-periodic growth may be attributable to light-mediated suppression of diel vertical migrations of predators and prey. Accounting for such effects will improve our capacity to predict the future dynamics of marine populations, especially in response to climate-driven changes in nocturnal cloud cover and intensification of artificial light, which could lead to population declines by reducing larval survival and growth.

Long-term exposure to artificial light at night in the wild decreases survival and growth of a coral reef fish

“…Contrary to our predictions, as well as the findings from a laboratory study on coral reef fish larvae, A. triostegus [ 57 ], we observed a negative, rather than a positive, impact of ALAN on growth which was 15%, 21%, and 51% lower in terms of height, length, and weight, respectively. Growth is a complex process influenced by many interacting physiological and ecological factors and their trade-offs [ 55 , 59 ] and the observed lower growth may be due to negative effects on growth-related physiology. One such effect may be the requirement of a period of inactivity for optimal growth.…”

The relative influence of environmental cues on reproductive allocation of a highly iteroparous coral reef fish

“…So why then do they spawn disproportionately around the new moon? One possible explanation is that spawning on a new moon results in a growth advantage to larvae that survive to settlement (Shima et al 2021). The mechanisms underlying this pattern remain untested, but may be related to interactions with a community of organisms that migrate vertically in the water column (see Shima et al 2021Shima et al , 2022 for the full hypothesis).…”

“…One possible explanation is that spawning on a new moon results in a growth advantage to larvae that survive to settlement (Shima et al 2021). The mechanisms underlying this pattern remain untested, but may be related to interactions with a community of organisms that migrate vertically in the water column (see Shima et al 2021Shima et al , 2022 for the full hypothesis). The growth advantage associated with spawning on the new moon may improve fitness of subsequent life stages, because fish that settle at a larger size may have a future competitive advantage (Forrester 1991;Sogard 1997;Shima and Findlay 2002).…”

Artificial light at night reverses monthly foraging pattern under simulated moonlight

“…Lunar-driven phenological life-history events such as reproduction and migration are found across the animal kingdom in marine [8][9][10][11], terrestrial [12,13] and freshwater [14,15] habitats across the globe. Lunar rhythms influence organisms' growth [16] and activity patterns [12]. Moonlight intensity affects communication [13], orientation [17] and risk-reward trade-offs [18,19].…”