Tidal–diel patterns of movement, activity and habitat use by juvenile mangrove whiprays using towed-float GPS telemetry

Abstract

Stingrays are a diverse and widespread group of elasmobranchs. Despite their ecological and economical importance, many aspects of stingray ecology remain poorly understood. Few studies have examined fine-scale movements of juvenile stingrays within nursery areas. This study aimed to examine diel movement patterns in juvenile mangrove whiprays (Urogymnus granulatus) by using towed-float GPS telemetry within a reef flat habitat of the Great Barrier Reef. Juvenile mangrove whiprays travelled distances from 394 to 2189m, moving at a rate (mean±s.e.) of 3.97m min–1±2.5 during tracking periods ranging from 1.35 to 9h. Movements of juvenile mangrove whiprays were influenced by tidal height and diel period. Individuals chose more direct paths during outgoing and incoming tides and their activity space was significantly larger during the day than at night-time. Individuals showed preference for mangrove areas during high tides, which was likely to reduce predation risk. Our findings have established the use of the towed-float GPS telemetry as an effective tool to assess short-term movement patterns and habitat use of juvenile stingrays, as well as highlighted how juvenile mangrove whiprays use reef-flat environments.