Post-Mortem Investigations on Stranded Dolphins and Porpoises From Hong Kong Waters

Abstract

Stranded cetaceans reported from the territorial waters of Hong Kong during the period May 1993 to March 1998 were examined to establish factors that may have contributed to their death. During the current study, 28 Indo-Pacific hump-backed dolphins (Sousa chinensis), 32 finless porpoises (Neophocaena phocaenoides), and four bottlenose dolphins (Tursiops truncatus) were necropsied. Bacteria (15 species) were isolated from nine animals. Of these bacteria, 47% were of possible fecal origin reflecting the high level of sewage contamination in Hong Kong's waters. One finless porpoise displayed wounds caused by a shark attack, and two female finless porpoises presented prolapsed uteri. At least 10 finless porpoises showed evidence of moderate to heavy lungworm infections (Halocercus pingi), and this appears to have been a factor contributing to death in at least six animals. Evidence suggesting blunt traumatic injury (probably caused by boat collisions) was found in six cetaceans (three finless porpoises and three hump-backed dolphins). Signs of fishery-related mortality were detected in at least nine animals (six hump-backed dolphins, two finless porpoises, and one bottlenose dolphin). Of these two human-caused mortality types, pre-existing disease or bacterial infection were detected in 29% of cases. Results indicate that human factors may have played a significant role in the death of at least 15 animals (32% of hump-backed dolphins, 15% of finless porpoises, and 25% of bottlenose dolphins).

Anthropogenic impact on a pregnant Cuvier’s beaked whale (Ziphius cavirostris) stranded in Brazil

“…In the whale reported here, the obstruction caused by the fishing artefact in the digestive tract must have resulted in the inability of this animal to feed. In addition, the bronchial fibrosis probably compromised normal breathing, as respiratory parasites are already known to have affected the health of cetaceans in the North Sea and Eastern Pacific and Atlantic Oceans (Baker, 1992;Cornaglia et al, 2000;Parsons & Jefferson, 2000;Fauquier et al, 2009). Summed to all that, a higher metabolic demand, which mammals present during pregnancy (Schillo, 2009), should have aggravated the pathological condition of the animal.…”

Posterior Respiratory Apparatus of Inia geoffrensis and Sotalia fluviatilis: Structure and Ultrastructure

“…This inter-specific interaction between fishermen and cetaceans may lead to death (Parsons & Jefferson, 2000).…”

Dolphins, whales and porpoises : 2002-2010 conservation action plan for the world's cetaceans

“…Despite the fact that it is illegal, electric fishing has become widespread in the Yangtze system during the last decade, and it probably kills porpoises outright and contributes to the depletion of their prey . Vessel collisions, especially involving high-speed ferries, may be a particular problem for porpoises in Hong Kong (Parsons and Jefferson 2000). Finless porpoises in Japan have high concentrations of organochlorines, butyltins, and mercury in their tissues (Kannan et al 1989;Iwata et al 1994Iwata et al , 1995Jefferson et al 2002b), and DDT levels of porpoises in Hong Kong are among the highest recorded for cetaceans (Parsons and Chan 1998).…”

“…Photo: Thomas A. Jefferson. dolphins and finless porpoises in Hong Kong (Parsons and Jefferson 2000) (Figure 5), and probably many other species of small cetaceans around the world. A general problem in determining the causes of death is that floating carcasses or moribund animals can be struck by vessels, thus confounding interpretations of signs of trauma during necropsies.…”