Environmental factors involved in breaching behavior of manta rays in estuarine waters

Abstract

Improving our knowledge on the behavior of threatened species is essential for developing effective conservation actions. The Paranaguá Estuarine Complex (PEC), southern Brazil, is the only estuary in the world where manta rays have been observed performing breaches seasonally. The exact role of this breaching behavior and the environmental factors connected to it are unknown. Our goals were to determine the spatial distribution, and the temporal and environmental factors that influence the breaching behavior of this endangered group in a dynamic estuarine habitat for the first time. Manta rays were observed breaching in the PEC during austral summer and early autumn, when the sea surface temperature (SST) and precipitation were high. Generalized additive models revealed that the presence and frequency of the breaches were both influenced by the SST and hours of daily effort, while the breaching frequency was also influenced by the wind direction and speed, percentage of moon illumination, and year. The breaches were mainly concentrated near the mouth of a river. Likely these factors influenced not only the occurrence and behavior of manta rays, but also the distribution of their food source, potentially providing optimal conditions for foraging and reproduction. Based on the coloration pattern, it is possible that the observations were of Mobula cf. birostris. These results provide valuable insights into the breaching behavior of manta rays in estuarine waters that will assist future conservation initiatives and research on their behavioral ecology, to optimize fishery management and contribute to developing sustainable ecotourism in the PEC.

Opportunistic sightings of manta rays on Brazil's Amazon Coast

“…The manta rays stranded in tide pools reported here were apparently healthy and with no injuries observed. Medeiros et al (2015Medeiros et al ( , 2021 highlighted the occurrence of manta rays in estuaries in Southern…”

“…Pronounced seasonality in M. birostris occurrences is known for subtropical Brazil, particularly for the Laje de Santos Marine State Park (São Paulo State, southeast coast), with sightings concentrated in the austral winter (Luiz et al, 2009), and the Paranaguá estuary (Paraná State, south coast), where records are concentrated in austral summer (Medeiros et al, 2015, 2021). There are records of M .…”

“…The manta rays stranded in tide pools reported here were apparently healthy and with no injuries observed. Medeiros et al (2015, 2021) highlighted the occurrence of manta rays in estuaries in Southern Brazil; nevertheless, alive stranded individuals in tide pools were never reported in Brazil or elsewhere. Most individuals recorded here were released still alive, although the post‐release survival rate is unknown.…”

Occurrence, distribution and threats to mobulid rays in Brazil: A review and updated database

“…(as Manta ehrenbergii Müller & Henle, 1841) from Southeast Brazil; Gadig & Sampaio (2002) presented the first record of Mobula mobular (Bonnaterre, 1788) and Mobula tarapacana (Philippi, 1892) in the Brazilian coast; Gadig et al (2003) reported the first occurrence of Mobula thurstoni (Lloyd, 1908) in the Western Atlantic; Casas et al (2006) analysed a pregnant M. thurstoni from Southeast Brazil; Luiz et al (2009) showed that the occurrence of Mobula birostris (Walbaum, 1792) in Southeast Brazil is seasonal, with most individuals sighted during the austral winter; Mendonça et al (2012Mendonça et al ( , 2018Mendonça et al ( , 2020 carried out extensive ecological studies on M. tarapacana in the Saint Peter and Saint Paul Archipelago (SPSP), also providing the record of pregnant M. thurstoni and M. birostris in the same site; Cintra et al (2015) reported on the occurrence of M. birostris (possibly Mobula cf. birostris) in the North Brazilian coast; Medeiros et al (2015Medeiros et al ( , 2021Medeiros et al ( , 2022 analysed the seasonal occurrence of M. birostris in a Southern Brazil, particularly focusing on breaching behaviour; Domit et al (2017) recorded the interaction between M. birostris and the cetacean Sotalia guianensis; Bucair, Venables, et al (2021); Bucair et al (2022Bucair et al ( , 2023 reported on the occurrence of M. thurstoni and Mobula cf. birostris in the Fernando de Noronha Archipelago, as well as Mobula cf.…”

“…Initially, it had a supposed distribution restricted to the Caribbean Sea and the Gulf of Mexico (Hinojosa-Alvarez et al, 2016;Hosegood et al, 2020;Stevens et al, 2018;Stewart, Nuttall, et al, 2018;White et al, 2018). However, it is currently assumed to occur along the Brazilian coast, from the North (Amazon coast) to Southeastern Brazil (Bucair, Francini-Filho, et al, 2021;Bucair et al, 2023;Medeiros et al, 2021).…”