Network Analysis of Acoustic Telemetry Reveals Patterns in Habitat Use and Community Structure of Reef-Associated Sharks

Caribbean reef sharks are common throughout the tropical and sub-tropical waters of the western north Atlantic Ocean, and are known to be highly site-fidelic. Like many reef-associated shark species, Caribbean reef sharks may spend the majority of their life history at a one reef. However, it is unknown how individuals interact within a population and if community structure plays a role in their residency and movement patterns. Traditional analysis of acoustic telemetry detection frequency does not elucidate interactions among individuals and may be an inaccurate predictor of movement. Network analysis was undertaken to detect patterns in social structure of Caribbean reef sharks at a remote atoll in Belize, Central America. Sharks were tagged with five-year internal acoustic transmitters at an acoustic array and detections were recorded from 2007-2014. Network analysis showed high connectivity among sharks. Weak community structure was identified, though communities could not be distinguished by demographic characteristics. Analysis of receiver connectivity showed patterns in habitat use and movement overall and for individuals. Results indicate that proposed commercial development of the atoll could disrupt major movement corridors of the resident sharks. This represents the first long-term report of network analysis of multiple free-swimming sharks using passive acoustic telemetry.