Using a passive acoustic-optical imaging system to monitor fish presence and behavior in marine protected areas

Marine protected areas have been established worldwide to protect coastal ecosystems and the species inhabiting them. However, it is difficult to quantify whether these areas are protecting targeted species. Passive acoustics allow for the monitoring of fish activities, diversity, and abundance. However, to date, sounds have been attributed to less than 5% of fish species. We describe Fish Optical and Acoustic Sensor Identification System (FishOASIS), a passive acoustic-optical imaging system that pairs a commercially available passive acoustic recorder with a custom-designed optical imaging system. FishOASIS is a cost-effective tool developed to facilitate linking the components of the soundscape likely coming from fish with the knowledge of the species producing the sounds. This diver-deployed system can also be used to make behavioral observations of fishes and collect time series of occurrences of animals. From our deployments in the kelp forest, we found that FishOASIS can record passive acoustic data continuously and capture over 1,500 high quality images per day for 14 days. Deployments revealed sound production for a species previously not know to make sound, Barred Sand Bass (Paralabrax nebulifer), various fish species exhibiting biologically important behaviors such as spawning and territorial defense, and daily patterns of presence/absence. FishOASIS addresses many of the limitations of previous passive acoustic-optical imaging systems enabling the implementation of passive acoustic monitoring in marine protected areas.