LB 10-97 - Residency and movement patterns of Oceanic manta ray (Mobula birostris) in Bahía de Banderas, México

Giant manta ray (Mobula birostris) is an endangered species commonly seen in oceanic islands and seamounts; however, some resident populations have been described in highly productive, coastal areas. Bahía de Banderas, Mexico, is home to one of the largest giant manta ray aggregations, which represents a unique opportunity to learn more about the residency and movement patterns of this species. Here, acoustic telemetry was used to investigate the influence of environmental parameters on the occurrence of 66 tagged giant manta rays over an eight-year period. Seasonal trends in giant manta rays occurrence showed a peak in detections from January to March, and another peak from June to early October. Environmental variables such as temperature, chlorophyll-a, tidal range, wind speed and wind direction had a significant effect on the presence of giant manta rays during each of the recorded season. Results also suggest that the El Niño Southern Oscillation (ENSO) had a strong effect on the giant manta ray presence in the bay. On a finer scale, the detections of giant manta rays in the south of the bay were greater in the morning hours, suggesting that during the night they may move to deeper waters similar to patterns reported in other studies. This study serves as a baseline for future management plans for the species to minimize impacts to the population from human activities carried out where the giant manta rays aggregate.