Presence of Franciscana Dolphin (Pontoporia blainvillei) Remains in the Stomach of a Tiger Shark (Galeocerdo cuvieri) Captured in Southeastern Brazil

Abstract: The franciscana dolphin, Pontoporia blainvillei, inhabits the coastal Atlantic waters of South America (~18º-42º S). This paper reports the presence of P. blainvillei in the stomach of a tiger shark, Galeocerdo cuvieri, captured in southeastern Brazil. On 15 March 2003, the shark specimen, 4.0 m and 400 kg male, was captured in a bottom-set gill net placed approximately 2.2 nautical miles from the coastline and 15 m deep. The caudal peduncle keels and fin were entangled in the lower frame line; however, the net mesh, as well as the frame line, were not damaged by this capture. Analysis of the tiger shark stomach contents revealed the presence of an entire head belonging to a franciscana dolphin and some fish species. The present record is the first report of interactions between this species of shark and franciscana dolphins in Brazilian waters. The tiger shark is a voracius predator and its capture characteristics, with lower frame line involvement without net mesh damage, and preys recovered from its stomach, may indicate an opportunistic feeding activity. The shark could have been held in the frame line while feeding upon the fishes and the franciscana that were enmeshed. Further reports are necessary to determine if shark predation on franciscana dolphin is an important factor in its natural mortality in southeastern Brazil, where this species also is affected by coastal fisheries.

Key Words: Pontoporia blainvillei, Galeocerdo cuvieri, predation, stomach content, southeastern Brazil, franciscana dolphin, tigershark

Document Type: Research article

DOI: 10.1578/AM.30.2.2004.311

Page Numbers: 311-314

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