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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. [ABSTRACT FROM AUTHOR]

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BSTRACT [ABSTRACT FROM AUTHOR]

The article discusses a study which investigated the relationship between regional variation in larval retention and dispersal drives recruitment patterns in a temperate reef fish Forsterygion lapillum in Wellington Harbour and the North Island in New Zealand. In the study, the harbour was predicted as an important source of recruitment for both regions as it is productive with many F. lapillum adults. Embryonic and larval otolith chemistry was used to estimate larval origins and dispersal histories. It was observed that recruitment in the harbour was greatest when locally spawned larvae were retained. Frequent dispersal of larvae from the harbour was also reported, but in low numbers.

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. [ABSTRACT FROM AUTHOR]

Abstract: An increasing number of studies are uncovering considerable flexibility in migration patterns of diadromous fishes. The development of otolith microchemical techniques has largely driven this research and led to an appreciation of the significance of facultative diadromy in the life history of numerous species. However, validation experiments need to be undertaken for each species and life stage of interest before diadromous migrations can be confidently reconstructed. These validation experiments are required to establish a salinity calibration series against which the otolith microchemistry of unknown individuals can be compared. To facilitate research on facultative amphidromy in galaxiids, we reared the larvae of two species, Galaxias maculatus and G. argenteus, in five different salinities (2, 5, 10, 20, 34). We tested whether trace element signatures of fish reflected their salinity treatment, and hence whether otolith microchemistry could reconstruct diadromous migrations. Distinguishing low salinity (2 and 5) from high salinity (20 and 34) treatments was straightforward using otolith Sr:Ca alone. The five salinity treatments resulted in five distinct multi-trace element signatures for both species (DFA classification success of 85% and 92% for G. maculatus and G. argenteus, respectively). Otolith lithium showed a similar trend to otolith Sr:Ca (ie. higher in saltwater), and otolith Rb:Ca showed a surprising negative trend with salinity despite higher ambient Rb concentrations in saltwater. Our results suggest otolith Li:Ca and Rb:Ca should be considered as part of a multi-trace element approach when investigating diadromous migrations, particularly when non-marine Sr levels may be high. [ABSTRACT FROM AUTHOR]

Survival of larval fish is often linked to production of preferred prey such as copepods, both inter- and intra-annually. In turn, copepod production depends not only the quantity of food, but also on the nutritional quality, edibility and/or toxicity of their micro-algal food. Hence, larval fish survival can become de-coupled from levels of nutrient input depending on the resulting composition of the plankton. Here we use a plankton dynamics model to study nutrient input, phytoplankton composition and copepod, Paracalanus , production in relation to interannual variation in recruitment of snapper, Chrysophrys auratus , in Port Phillip Bay, Australia. The model was able to simulate the ratio of diatoms to flagellates in the plume of the main river entering Port Phillip Bay. Interannual variability in the copepod, Paracalanus , abundance during the C. auratus spawning period over 5 years was accurately predicted. The seasonal peak in Paracalanus production depended on the timing and magnitude (match-mismatch) of nutrient inputs and how these were reflected in temporal change in the diatom:flagellate ratio. In turn, the model-predicted Paracalanus abundance was strongly related to inter-annaul variability in abundance of snapper, C. auratus , larvae over 7 years. Years of highest larval C. auratus abundance coincided with a matching of the spawning period with the peak in Paracalanus abundance. High freshwater flows and nutrient inputs led to an early seasonal dominance of diatoms, and consequently reduced abundances of copepods over the C. auratus spawning period with correspondingly low abundances of larvae. Conversely years of very low rainfall and nutrient input also led to low phytoplankton and copepod concentrations and larval C. auratus abundances. Highest abundances of larval C. auratus occurred in years of low to intermediate rainfall and nutrient inputs, particularly when pulses of nutrients occurred in the spring period, the latter supporting the match-mismatch hypothesis. [ABSTRACT FROM AUTHOR]