Healthy oceans are imperative to the wellbeing of mankind. Ocean health depends on biodiversity, which is threatened by global stressors. To restore ocean health, we need timely predictions of biodiversity change. Traditional biodiversity assessments are time-intensive and weather-dependent, leading to infrequent measurements. I will develop a new way to measure marine biodiversity at high resolution: by listening to it. Marine animals such as fish sing during vital parts of their life, allowing us to observe which species are thriving. Fish song will enable us to assess biodiversity change, and direct conservation efforts.