Large predators play important ecological roles, yet many are disproportionately imperiled. In marine systems, artificial reefs are often deployed to restore degraded reefs or supplement existing reefs, but it remains unknown whether these interventions benefit large predators. Comparative field surveys of thirty artificial and natural reefs across~200 km of the North Carolina, USA coast revealed large reef-associated predators were more dense on artificial than natural reefs. This pattern was associated with higher densities of transient predators (e.g. jacks, mackerel, barracuda, sharks) on artificial reefs, but not of resident predators (e.g., grouper, snapper). Further analyses revealed that this pattern of higher transient predator densities on artificial reefs related to reef morphology, as artificial reefs composed of ships hosted higher transient predator densities than concrete reefs. The strength of the positive association between artificial reefs and transient predators increased with a fundamental habitat trait-vertical extent. Taller artificial reefs had higher densities of transient predators, even when accounting for habitat area. A global literature review of high trophic level fishes on artificial and natural habitats suggests that the overall pattern of more predators on artificial habitats is generalizable. Together, these findings provide evidence that artificial habitats, especially those like sunken ships that provide high vertical structure, may support large predators.

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acoustic monitoring complements traditional methods for assessing marine habitat enhancement outcomes. Ecosphere 12(11):e03840.

Marine soundscapes often differ among habitats; however, relatively little is known about whether soundscapes on naturally occurring habitats differ from soundscapes on human-made structures. To address this knowledge gap, we investigated whether temporal and spectral characteristics of biological sound production differ between natural and artificial offshore reefs. Specifically, we analyzed recordings from 5 week-long hydrophone deployments on 2 natural rocky reefs and 2 artificial reefs on the North Carolina, USA, continental shelf. Analysis of sound pressure levels (SPLs) on hourly and seasonal scales revealed similar temporal patterns between the reef types. These patterns were largely driven by 4 dominant fish vocalizers with seasonal chorusing patterns, including a toadfish Opsanus sp. Despite similar temporal patterns within reef types, soundscape spectral content was more similar within than between reef types, especially during the April deployment, which had the most acoustic activity. Our findings suggest that the soundscapes of shipwreck artificial reefs may differ from the soundscapes of natural rocky reefs, possibly due to differing community composition. As sound plays an important role in the navigation and settlement of many marine species, soundscape differences between natural and artificial habitats could affect ecosystem function through species behavior and interactions.