Long-term passive acoustic monitoring of parrotfishes (Scaridae) in the Hawaiian Archipelago

Parrotfishes (family Scaridae) are an important component of coral reef ecosystems, and this key functional group plays a major role in algae removal and bioerosion of reef substrate. They are also heavily fished in many locations, which may lead to ecosystem-wide impacts such as increased algal cover. In the State of Hawaii, parrotfish management is a priority for marine resource managers, with an ongoing need for accurate population monitoring that is currently addressed by diver-based visual surveys. However, parrotfishes are highly mobile and somewhat skittish around SCUBA divers, particularly in areas where fishing pressure is high. Because parrotfishes produce frequent audible scraping and crunching sounds associated with feeding, passive acoustic monitoring (PAM) can provide information on parrotfish occurrence without requiring the invasive presence of divers. Here, we present results from analyses of parrotfish foraging sounds in long-term acoustic recordings from 10 shallow reef locations throughout the Hawaiian Archipelago dating back to 2006. Parrotfish sounds are compared spatially across a fishing pressure gradient, from heavily fished areas in the main Hawaiian Islands to protected waters within the Papahānaumokuākea Marine National Monument (Northwestern Hawaiian Islands). Results from PAM are compared when possible with data from adjacent visual censuses conducted by divers.