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Small Cetaceans (small + cetacean)
Selected AbstractsDOES RADIO TAGGING AFFECT THE SURVIVAL OR REPRODUCTION OF SMALL CETACEANS?MARINE MAMMAL SCIENCE, Issue 1 2006A TEST Abstract A long-term study of botos (inia geoffrensis) in the Brazilian Amazon permitted the comparison of survival and reproduction between 51 adults fitted with radio transmitters and an equal number that were captured and handled in the same way but released without a transmitter. For both sexes combined, 47 radio tagged botos (92.2%) survived at least three years after release compared with 42 (82.4%) without radios, equating to annual survival of 97.3% and 93.6% respectively. The difference was not statistically significant. Eight of 15 closely monitored radio tagged females were lactating at capture, and all their calves weaned successfully. Two that were pregnant at capture subsequently gave birth. The mean number of calves per year born to these 15 females after first release was 0.172 (SD = 0.107) and to 17 non-tagged was 0.174 (SD = 0.095), again a non-significant difference. These results indicate that the anchoring of packages to the dorsal fin of dolphins can be accomplished with no measurable impact on their subsequent survival or reproductive output. However, botos may be unusually robust to handling, and this study should not be used to justify using similar techniques on other species without customary caution, diligence, and expert guidance. [source] Polychlorinated biphenyls, organochlorine pesticides, tris(4-chlorophenyl)methane, and tris(4-chlorophenyl)methanol in livers of small cetaceans stranded along Florida coastal waters, USAENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2000Mafumi Watanabe Abstract Concentrations of polychlorinated biphenyl congeners (PCBs) and organochlorine pesticides were determined in the livers of bottlenose dolphins, Atlantic spotted dolphins, and pygmy sperm whales found stranded along the coastal waters of Florida, USA, during 1989 to 1994. The PCBs were the most predominant contaminants followed in order by DDTs, chlordanes, tris(4-chlorophenyl)methane (TCPMe), tris(4-chlorophenyl)methanol (TCPMOH), hexachlorobenzene, and hexachlorocyclohexane isomers. Among the cetaceans analyzed, organochlorine concentrations were greatest in bottlenose dolphins followed by Atlantic spotted dolphins and pygmy sperm whales. Hexa- and heptachlorobiphenyls were the predominant PCB congeners found in the livers of dolphins. Patterns of relative concentrations of PCB congeners varied among individual bottlenose dolphins. A few individuals contained predominant concentrations of octa- (CB-199, 196/201) and nonachlorobiphenyl (CB-206, 208) congeners, which suggested exposure to the highly chlorinated PCB formulation, Aroclor® 1268, a contaminant at a coastal site in Georgia bordering northern Florida. The estimated 2,3,7,8-tetrachlorodibenzo- p -dioxin toxic equivalents (TEQs) of coplanar PCBs in bottlenose dolphins were 170 to 18,000 pg/g, lipid weight (mean: 5,400 pg/g) with mono- ortho congeners 118, 105, and 156 contributing more than 80% of the TEQs. The ratios of CB-169 to CB-126 in cetacean livers were linearly related to total PCB concentrations, which suggested a strong induction of microsomal monooxygenase enzymes in the liver. The hepatic concentrations of TCPMe and TCPMOH in bottlenose dolphins and Atlantic spotted dolphins were greater than those in the blubber of marine mammals of various regions, which suggested the presence of sources for these chemicals along the Atlantic coast of Florida. [source] KILLER WHALE ATTACKS ON MINKE WHALES: PREY CAPTURE AND ANTIPREDATOR TACTICSMARINE MAMMAL SCIENCE, Issue 4 2005John K. B. Ford Abstract We describe nine incidents of predation or attempted predation of minke whales (Balaenoptera acutorostrata) by mammal-hunting "transient" killer whales (Orcinus orca) in coastal waters of British Columbia, Washington, and southeastern Alaska. Pursuits of minke whales were characterized by prolonged chases on a straight heading at velocities of 15,30 km/h. In four of the nine cases the adultsized minke whale gradually outdistanced the killer whales, which abandoned the high-speed pursuit after 0.5,1 h. In one case the minke beached itself and died. Four attacks were successful. In one instance a subadult minke was killed in open water following a chase. In two cases the fleeing minke entered a confined bay and was killed by the killer whales. One adult minke was taken after apparently attempting to seek cover beside a large sailboat. Minke whales made no attempt to physically defend themselves and were killed by repeated ramming or by asphyxiation. Although killer whales are capable of sprinting speeds greater than those of minke whales, it appears that adult minkes can maintain higher sustained speeds and evade capture if sufficient space for an extended escape trajectory is available. Successful predation of minke whales in coastal waters is rare compared to pinnipeds and small cetaceans, the main prey of transient killer whales. [source] GEOGRAPHIC GENETIC STRUCTURE IN THE FRANCISCANA DOLPHIN (PONTOPORIA BLAINVILLEI)MARINE MAMMAL SCIENCE, Issue 2 2004Marila Lázaro Abstract The franciscana, Pontoporia blainvillei, is endemic to the South Atlantic coast of South America. The species is of conservation concern because it suffers elevated mortality rates due to incidental captures in fishing nets, and perhaps it is one of the most threatened small cetaceans in this region. Previous morphological and genetic studies have suggested the existence of at least two distinct stocks to the north and south of Santa Catarina Island in Brazil. Fixed differences were found between a sample from Rio de Janeiro and one from Rio Grande do Sul, in southern Brazil. Using 94 sequences of the control region of mitochondrial DNA, we examined the genetic structure of the species. We found no shared haplotypes between Rio de Janeiro and samples from the southern range of the species distribution. However, a phylogenetic analysis suggests that the former population is diphyletic with respect to the southern samples. This suggests that the populations have not been isolated long enough to reach reciprocal monophyly. Furthermore, genetic differentiation is broadly consistent with a simple model of isolation by distance, that therefore appears as an alternative to a model of strict isolation of two stocks. The estimated levels of gene flow are higher among neighboring populations, and decrease as more distant localities are compared. Finally, the molecular data suggest that franciscanas have expanded in Rio de Janeiro. [source] GEOGRAPHICAL VARIATION OF THE PARASITE, PHYLLOBOTHRIUM DELPHINI (CESTODA), IN BALL'S PORPOISE, PHOCOENOIDES DALLI, IN THE NORTHERN NORTH PACIFIC, BERING SEA, AND SEA OF OKHOTSKMARINE MAMMAL SCIENCE, Issue 2 2001William A. Walker Abstract Prevalence of the larval cestode, Phyllobothrium delphini, was estimated from 2,445 Dall's porpoise, Phocoenoides dalli, from the incidental take of the Japanese high seas salmon drift-net fishery in the northwestern North Pacific Ocean, Bering Sea, and a local hand harpoon fishery in the southern Sea of Okhotsk. Prevalence of P. delphini was 22.7% in the northwestern North Pacific Ocean and 1.4% in the Bering Sea. This parasite was not found in the southern Sea of Okhotsk. Geographical differences in the prevalence of P. delphini may be due, at least in part, to regional differences in abundance of elasmobranchs known to feed on marine mammals and suspected as hosts of the parasite. Estimated intensity of infection of individual porpoises by P. delphini was low (estimated mean intensity of 3.5 plerocercoids per animal). This is a low intensity of infection compared to other species of small cetaceans studied and may be due to both differences in regional abundance of elasmobranchs and the comparatively short life span of P. dalli. [source] Averting the baiji syndrome: conserving habitat for critically endangered dolphins in Eastern Taiwan StraitAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2010Peter S. Ross Abstract 1.Numbering no more than 100 individuals and facing many threats, the geographically isolated Eastern Taiwan Strait population of Indo-Pacific humpback dolphins (Sousa chinensis) is in peril. The estuarine and coastal waters of central-western Taiwan have historically provided prime habitat for these dolphins, but environmental conditions today bear little resemblance to what they were in the past. 2.The humpback dolphins must share their habitat with thousands of fishing vessels and numerous factories built upon thousands of hectares of reclaimed land. 3.They are exposed to chemicals and sewage released from adjacent terrestrial activities. Noise and disturbance associated with construction, vessel traffic and military activities are features of everyday life for these animals. 4.Measures to slow the pace of habitat deterioration and reduce the many risks to the dolphins are urgently needed. As one practical step in this direction, this paper describes the habitat needs of these small cetaceans so that decision makers will be better equipped to define ,priority habitat' and implement much needed protection measures under the terms of local legislation. 5.The preferred habitat of these dolphins in Taiwan consists of shallow (<30,m), near-shore marine waters with regular freshwater inputs. 6.For such a small, isolated and threatened population, ,priority habitat' should not be limited to areas of particularly intensive dolphin use or high dolphin density, but rather it should encompass the entire area where the animals have been observed (their current ,habitat'), as well as additional coastal areas with similar bio-physical features (,suitable habitat'). Such a precautionary approach is warranted because the loss of only a few individuals could have serious population-level consequences. 7.While conventional socio-economic analysis might suggest that implementing protection measures over an area stretching ,350,km north,south along Taiwan's west coast and ,3,km out to sea would be too ,costly', the loss of this charismatic species from Taiwan's waters would send a troubling message regarding our collective ability to reconcile human activities with environmental sustainability. Copyright © 2010 John Wiley & Sons, Ltd. [source] | ||||||||||