Stranding survey as a framework to investigate rare cetacean records of the north and north-eastern Brazilian coasts

Abstract

Marine mammal stranding events are used as an important tool for understanding cetacean biology worldwide. Nonetheless, there are vast gaps of knowledge to be filled in for a wide range of species. Reputable information is required regarding species from large baleen whales to sperm and beaked whales, as well as pelagic dolphins. This paper describes new cetacean records from north and north-eastern Brazil, which are both the least surveyed areas regarding aquatic mammals. Regular beach surveys were conducted to recover cetacean carcasses along the coast of Pará beginning November 2005. At the coasts of the Maranhão and Piauí states, the surveys were conducted between 2003 and 2013. From 2003 to 2014, 34 strandings of cetaceans were registered. The study provides four additional species records’ in the area based on strandings (Balaenoptera borealis, Balaenoptera physalus, Peponocephala electra, and Pseudorca crassidens). A mass stranding of Guiana dolphins (Sotalia guianensis, N = 12), the most common species for the region, was reported for the first time. The records presented herein are of special concern, since they expand the knowledge on cetaceans from the Brazilian coast. In addition, this study conducted an analysis to verify the similarity between cetacean compositions described for north and north-eastern Brazil and the southern Caribbean region. The results showed a high similarity between these regions, proving the connection with the Caribbean cetacean fauna.

Strandings of cetaceans on the Espírito Santo coast, southeast Brazil, 1975–2015

“…Strandings were diffusely distributed along the Espírito Santo coast, without well-defined hotspots. The number of strandings of this species in this study was relatively high compared to similar surveys conducted in other portions of the Brazilian coastline ( Prado et al 2016 , Vianna et al 2016 , Costa et al 2017 ), which is consistent with at-sea surveys showing that melon-headed whales are occasionally seen along the coast of Espírito Santo ( Wedekin et al 2009 , 2014 ). It is worth noting that there was one instance where a live individual stranded in the state, but it later died and its death was attributed to plastic ingestion ( Costa et al 2012 ), illustrating the impacts of plastic pollution can have on this species.…”

“…At-sea observations suggest that sperm whales tend to concentrate along the central coast of Bahia, especially at the Camamu-Almada Basin, and occur at much lower densities in Espírito Santo (Batista et al 2012). The number of strandings of this species in this study was relatively high compared to similar surveys conducted in other portions of the Brazilian coastline (Prado et al 2016, Vianna et al 2016, Costa et al 2017, which suggests this species probably forages along the Vitória-Trindade ridge and occasionally approaches the Espírito Santo coast. It is worth noting that previous studies suggested that the species might be most abundant in Espírito Santo waters in winter and spring, from July to November (Batista et al 2012), but this was not evident in the strandings recorded in this study.…”

“…Lastly, it is worth highlighting that strandings of sperm whales and melon-headed whales occurred with an unexpectedly high frequency in comparison to other similar surveys conducted in portions of the Brazilian coastline (Meirelles et al 2009, Prado et al 2016, Vianna et al 2016, Costa et al 2017, which suggests that these deep-oceanic species might aggregate off the southern coast of Espírito Santo. Additional studies employing aerial and boat transects, telemetry and acoustic surveys are therefore warranted to investigate this hypothesis and determine important areas for cetaceans in the region.…”

“…( Paglia et al 2012 ). The cetacean fauna of Espírito Santo is largely composed by small and medium-sized tropical coastal and oceanic species, similarly to that of the Northeastern coast of Brazil ( Meirelles et al 2009 , Batista et al 2012 ), however with fewer Caribbean species and species related to upwelling fronts such as pantropical and Atlantic spotted dolphins ( Stenella attenuata and Stenella frontalis , respectively) and Bryde’s whales ( Balaenoptera brydei ) ( Costa et al 2017 ). In certain respects, the cetacean community of Espírito Santo arguably bears similarity to that other pantropical oligotrophic regions such as the Western Tropical Indian Ocean, the Eastern Tropical Pacific and the Gulf of Mexico ( Ballance and Pitman 1998 ).…”

Cetacean movements in coastal waters of the southwestern Atlantic ocean

“…A large proportion of what is known about cetaceans in Brazilian waters comes from studies using dead individuals collected from stranding events (e.g. Zerbini et al 1997, Greig et al 2001Ramos et al 2001, Costa et al 2017 and/or incidental catches in fishing operations conducted since the end of the 1970s (e.g. Siciliano 1994).…”