Spatiotemporal abundance of the whitespotted eagle ray and the giant manta ray (Chondrichthyes: Myliobatiformes) from aerial surveys in southeast Florida

Abstract

This study employed aerial surveys to quantify the spatial and temporal abundance of the whitespotted eagle ray, Aetobatus narinari, and the giant manta ray, Mobula birostris, in southeast Florida. Aetobatus narinari abundance did not differ along the north-south axis of the coast, whereas M. birostris was more abundant at lower latitudes. Similarly, A. narinari did not exhibit any seasonal difference in abundance, whereas M. birostris was more abundant during December and February. Neither species exhibited a clear trend in abundance over the study period (2014–2021). In addition, the abundance of both species failed to correlate with water temperature, chlorophyll-a concentration, or photoperiod. Both M. birostris and A. narinari are protected species in Florida state waters, and M. birostris is designated as threatened under the US Endangered Species Act. In addition, both species are classified by the IUCN as endangered worldwide. Insufficient data exist to establish critical habitat designations for M. birostris so that the provided information on their distribution and abundance is useful for the development of effective management.