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

Abstract

Espírito Santo state is located on the eastern margin of Brazil, in a transitional tropical-subtropical area (18°S–21°S) dominated by oligotrophic waters. With the exception of humpback whales (Megaptera novaeangliae), the cetacean community of Espírito Santo has been understudied. In addition to the chronic impacts from fisheries, marine pollution, urban development, and coastal habitat degradation, in November 2015 the cetacean communities of Espírito Santo were challenged by the greatest environmental disaster in Brazil’s history. The Mariana dam disaster caused 60 million cubic meters of mining waste to be washed into the Doce River, which ultimately flowed to the coastal waters of Espírito Santo, with a high concentration of heavy metals. This study reviews and updates information on cetacean strandings in the state of Espírito Santo (excluding humpback whales) prior to this disaster. From 1975 to September 2015, there were 461 recorded cetacean strandings, representing 20 species. An average 1.18 strandings per 100 km per month were recorded since a state-wide daily beach survey program was implemented in October 2010, contrasting with the 0.14 strandings per 100 km per month in previous years. Six species comprised the majority (94.7%) of stranding events: Guiana dolphin (Sotalia guianensis), Franciscana (Pontoporia blainvillei), rough-toothed dolphin (Steno bredanensis), bottlenose dolphin (Tursiops truncatus), sperm whale (Physeter macrocephalus), and melon-headed whale (Peponocephala electra). Oceanic cetaceans stranded most frequently on the southern portion of Espírito Santo, where the continental platform is narrower, whereas the strandings of coastal cetaceans such as Guiana dolphins and Franciscanas were concentrated near estuaries, especially the Doce River. This is particularly concerning in face of the Mariana dam disaster, which drastically altered the estuarine and coastal environment associated with the Doce River.

Carcass non-recovery rate of franciscana dolphin (Pontoporia blainvillei), calibrated with a drift mark-recapture study at FMA Ia, Brazil

“…Although the cold fronts are related to a significant change in strandings, the prevalence of stranding did not follow the seasonality when this condition prevailed, winter. The highest stranding rates occurred in summer conditions (52%), also observed by Mayorga et al (2020) and Marcondes et al (2020), probably due to significantly more gillnet fishing activity at this time of year and consequent higher incidence of impact. About 55% of the entanglements were also concentrated in summer.…”

“…This means some carcasses washed ashore in these areas may also come from places further south and closer to the Doce River, especially those in advanced decomposition stages. According to Mayorga et al (2020), the average number of recorded strandings in the region increased by 750% after the start of the BMP; the BMP was fundamental for obtaining the results related to the recovery rates of drifters and characterization of the observed hotspot.…”

“…The Beach Monitoring Program (BMP) from Campos and Espírito Santo basins has been implemented in the study area. The BMP arises from the environmental licensing of PETROBRAS, an energy company focusing on oil and gas exploration and production; the program has ensured daily monitoring along the coast with high efficiency for carcass detection and also drifters (Mayorga et al, 2020).…”

Climate change and cetacean health: impacts and future directions

“…For example, the abundance of Bryde's whales ( Balaenoptera edeni ) increased between 2000 and 2010 in the Southern California Bight (USA), which was probably driven by prey availability [45]. Similarly, unusual sightings of Clymene dolphins ( Stenella clymene ) have been recorded on the northern coast of Spain [46], the Patagonian Coast (Argentina) [47] and the Brazilian coast [48], outside their usual habitat in the tropical waters of the Atlantic Ocean, Caribbean Sea and the Gulf of Mexico. Range shifts are believed to correlate with habitat expansion, leading to a functional feeding response of cetacean species to changes in the marine environment [40].…”

A Visitor of Tropical Waters: First Record of a Clymene Dolphin (Stenella clymene) Off the Patagonian Coast of Argentina, With Comments on Diet and Metazoan Parasites

“…In the southwestern Atlantic, records of Clymene dolphins have been reported only off the coast of Brazil, where sightings and stranded dolphins have been reported up to 30 • S (Simões- Lopes et al, 1994;Fertl et al, 2003;Moreno et al, 2005). However, the occurrence of Clymene dolphins in the Brazilian coast may be considered as unusual (Prado et al, 2016;Costa et al, 2017;Mayorga et al, 2020). Information about the food habits of Clymene dolphin is scarce, with data obtained from very few individuals stranded or incidentally captured off the Gulf of Mexico, the northeaster coast of Brazil or the North Iberian Peninsula (Jefferson and Curry, 2003;Pis-Millán et al, 2019).…”