Pacific nurse sharks Ginglymostoma unami exhibit yearly patterns of site fidelity to a tropical embayment subjected to seasonal upwelling

Seasonal upwelling in tropical coastal regions can create dynamic oceanographic conditions similar to temperate systems, which are known to influence the distribution and movement of marine species. Mobile marine species may seek warmer environments (i.e. exhibit behavioral thermoregulation) in response to stronger winds during the upwelling season, which cause cold, nutrient-rich waters to rise and cool shallower environments. Pacific nurse sharks Ginglymostoma unami are present in the upwelling regions of the Eastern Tropical Pacific coastline, serving as an ideal model species to study the effects of changing water temperatures on movement behavior. In this study, we analyzed 4 yr of passive acoustic telemetry data to quantify the movement, residency, and habitat use of G. unami in Santa Elena Bay, north Pacific coast of Costa Rica, located within the Papagayo upwelling system. A total of 28 sharks (15 males and 13 females) ranging from 85 to 256 cm total length were monitored inside the bay. The mean (±SD) residency index (i.e. number of days detected relative to the number of days monitored) of individual sharks was 37 ± 28%. Generalized additive mixed models revealed seasonal and diel patterns of G. unami use of Santa Elena Bay that were associated with water temperature and wind speed changes during the upwelling season. G. unami likely uses the warmer waters of Santa Elena Bay as a thermal refuge during the upwelling season to avoid colder adjacent waters. This research will serve as a baseline to understand the movement behavior of this species as climate change alters upwelling patterns.