Reef fish and their cryptobenthic larvae are a fundamental aspect of a productive and healthy coral reef ecosystem. Playbacks of ambient sound recorded from healthy shallow coral reefs, known as “acoustic enrichment” (AE), have been demonstrated to attract fish larvae and potentially coral larvae to degraded or artificial reefs. Initial AE studies relied on frequent diver surveys for evaluating performance, but these approaches are labor intensive and impractical for larger-scale and more remote studies. Here, we use autonomous cameras to assess AE efficacy on artificial structure deployments, conducted between July and September 2023 in Kāneʻohe Bay (O’ahu, Hawai’i). The deployments consisted of one control and one treatment site 65m apart, at 5m water depth. To document ecosystem responses, both sites used open-source burst-mode autonomous cameras, a directional vector sensor seafloor acoustic recorder, and hydrophones. A 3.8 kW-hr NiMh battery supply permitted treatment playbacks from sunset to sunrise for three weeks. Burst-mode images successfully documented fish larvae presence and movement. Image processing methods allowed automated estimates of numbers of larvae in a frame, when larvae were identified during a manual review. The resulting analysis demonstrates that the AE site attracted at least 23 times more larvae than the control site.

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