Humpback whales washed ashore in southeastern Brazil from 1981 to 2011: stranding patterns and microbial pathogens survey

Abstract

In the Southwest Atlantic Ocean the wintering breeding ground of Megaptera novaeangliae is located in northeastern coast of Brazil, mainly in the Abrolhos Bank (16°55′ S, 38°50′ W) and its surroundings. During migratory percussion, events of strandings are thought to occur. A total of 58 stranded humpback whales were recorded between 1981 and 2011 along the coast of the Rio de Janeiro state, Brazil. The number of strandings in 20 years (1992–2011) increased during the period of study, with a mean of 2.6 events per year. In 2010 a peak occurred with 13 records of strandings. Most of them occurred preferably in the southern half of the study area, or in the southeast area of Rio de Janeiro state. Three cases of entanglement were found, two of these involving calves with less than eight meters of body length. Stranding events were more frequent during winter and spring. No statistical differences were found between age categories, but 33% were classified as “dependent calf” (< 8 m length). Males stranded more often than females. Only one whale out of 16 specimens that had the stomach contents examined presented food remains, but comprising only two cephalopod beaks of the squid Doryteuthis sanpaulensis. Bacteriological survey of Vibrionaceae and Aeromonadaceae agents in three live stranded whales on the Brazilian coast indicated evidence of animal impairment that resulted or were associated with the cause of death and stranding event.