The Earth is getting brighter at night, as artificial light at night (ALAN) continues to increase and extend its reach. Despite recent recognition of the damaging impacts of ALAN on terrestrial ecosystems, research on ALAN in marine systems is comparatively lacking. To further our understanding of the impacts of ALAN on marine organisms, this study examines how the reproductive fitness of the common clownfish Amphiprion ocellaris is influenced by the presence of ALAN. We assessed how exposure to low levels of ALAN affects (i) frequency of spawning, (ii) egg fertilization success, and (iii) hatching success of A. ocellaris under control (12 : 12 day–night) and treatment (12 : 12 day–ALAN) light regimes. While we found exposure to ALAN had no impact on the frequency of spawning or fertilization success, ALAN had dramatic effects on hatching. Amphiprion ocellaris eggs incubated in the presence of ALAN simply did not hatch, resulting in zero survivorship of offspring. These findings suggest ALAN can significantly reduce reproductive fitness in a benthic-spawning reef fish. Further research in this field is necessary to fully understand the extent of this impact on population and community dynamics in the wild.

Infrastructure is increasingly being built in marine habitats, with extensive ecological consequences for benthic and fish assemblages alike. The practice of ecological engineering attempts to mitigate the negative impacts of infrastructure through the design of artificial structures that benefit both humans and nature. Although research has primarily focused on the benefits for invertebrates and algae, fish also respond to changes in habitat complexity and benthic biodiversity. We surveyed the scientific literature on natural and artificial reefs to identify key habitat features that fish respond to, and propose a decision tool for ecologists and managers to tailor the structural complexity of marine infrastructure for fish. Inevitably, natural habitats will increasingly be replaced with artificial ones, making ecologically sensitive designs essential for maintaining biodiversity and ecosystem services. Using lessons from natural and artificial reefs, we show that existing and new infrastructure could be designed not only to reduce negative impacts but also to foster positive effects on fish assemblages.