Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): Thomas G. Muir, Steven R. Baker, Samuel H. Ridgway. Includes bibliographical references (p. 129-130). Also available online.

During long-term studies of dolphins, the number of individuals in the population being studied are constantly monitored using the technique of photo-identification. This constant monitoring makes use of different researchers over time. Therefore, measurement of photographic quality and individual distinctiveness for photo-identification analyses was incorporated in this dissertation to provide an additional data set for analysis. Researchers with differing levels of experiences did not obtain the same information from the same photograph and were unable to reliably quantify variables of photo quality and individual distinctiveness, but experienced researchers were found to be more adept than inexperienced researchers in counting notches on the dorsal fin of bottlenose dolphins. These results highlight the necessity for researchers to be trained in photo-identification techniques prior to carrying out their study. This study theodolite tracked dolphins off Durban from June 2004 to Feb 2005 to assess habitat utilization of bottlenose dolphins (Tursiops aduncus) in the Durban bay region. Dolphins were seen in all months surveyed and throughout the survey area. Temporal distribution of dolphins was skewed with 91% of dolphins seen before midday and 98% of sightings observed in water depths less than 30m. Six behavioural categories were recorded, including: social, fast travel, slow travel, feeding, resting and milling. The most dominant behaviour exhibited by dolphins was slow travel (46%) followed by feeding (27%). Resting was not observed at all. Of the feeding behaviour 88% occurred in the southern end of the bay whereas other behaviours occurred randomly throughout the survey area. Additional theodolite tracks were conducted during experimental boat approaches (before, during and after boat approaches) to determine potential short-term reactions of dolphins to dolphin watching boats. Two speeds of approach (slow ~ < 5 km/hr and fast ~ > 40 km/hr) and two distances of approach (20m and 80 m) were tested. The bottlenose dolphin groups did not change their behaviour in response to boat approaches during any of the periods of experimentation. Short-term changes in group speed, group size and spread were not statistically significant. Dolphin groups continued with their ‘normal’ behaviour and spent the same amount of time in the bay when compared to their distribution and behaviour in the absence of the experimental boat. These findings indicate that the experimental boat did not affect the behaviour of dolphins at either a slow or fast approach and even at a close distance. This is interpreted as being as a result of habituation of the dolphins due to their residency in a busy port. This work is crucial in developing guidelines for the development of a sustainable dolphin watching industry off Durban. / Thesis (M.Sc.) - University of KwaZulu-Natal, Durban, 2008.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1976. / Bibliography: leaves 113-121. / Microfiche. / vii, 121 leaves ill. 29 cm

Thesis (M.S.)--University of Hawaii at Manoa, 2007. / Includes bibliographical references (leaves 92-95). / ix, 95 leaves, bound ill. 29 cm

Thesis (Ph. D.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 208-255).

The by-catch of small cetaceans in fishing nets has been identified as a widespread problem, but attempts to reduce this require an understanding of the way these animals behave around the nets. One of the problems with assessing changes in behaviour between encounters is the difficulty of identifying individuals. Acoustic identification techniques overcome some of the problems associated with visual ID, and field research has shown that the presence of a sonobuoy and hydrophone have no effect on dolphin behaviour in the field. Dolphins produce whistles that can be used for identification, although current theory suggests these identify small groups rather than individuals. Novel algorithms have been developed to detect and process these tonal whistles, and their characteristic time-frequency-intensity contours extracted from the raw signals. Feature extraction techniques were developed for the contours based on timefrequency 'shape' of the contours, allowing a syntactic pattern recognition approach based around hidden Markov modelling to be employed for classification. The algorithms have enabled the whistles from concurrent whistles to be separated and analysed. Contours of 101 wild bottlenose dolphin whistles were successfully characterised. Analysis of the resulting classes indicated one group occurring only once and two other groups occurred twice but on different days. Another study was conducted of three groups of common dolphin, with a total of 49 recorded whistles analysed. The first group was found to contain whistles significantly different to either of the other two, although neither similarity nor dissimilarity could be inferred on the second and third. Further analysis suggested there were indeed two separate groups of dolphins for the last two groups, but that there was a period of overlap in their recording. A significant difference could be found between them once certain classes were re-assigned. It should be possible to apply these same techniques to a wider range of odontocete species, since most of those studied have been found to exhibit similar whistles. The tasks of whistle detection, isolation, and encoding can be applied automatically by computer with no loss of identity information, and these encoded contours can subsequently be quantitatively classified by their shape.

No description available.

Marine mammals are known for their low susceptibility to mercury toxicity, and it was hypothesized that selenium may play a role in protection against mercury toxicity. To gain insight into the mechanisms of the low susceptibility of cetaceans, we investigated the in vitro effects (1) of mercuric chloride (HgCl₂) on the ultrastructure and cell death of Atlantic spotted dolphin renal cells (Sp1K cells), (2) of HgCl₂ on the cell proliferation and cell cycle status of Sp1K and Rhesus monkey renal cells (MK2), and (3) of sodium selenite (Na₂SeO₃) on cell proliferation and cell death of control and HgCl₂-treated Sp1K cells. HgCl₂ affected multiple organelles and nuclei in Sp1K cells, and induced apoptosis in a time-and dose-dependent manner. Both ultrastructural changes and induction of apoptosis were milder than seen in other cell types in previous publications. In addition, Sp1K cells were able to proliferate at 25 µM HgCl₂ while MK2 cells were killed at 15 µM HgCl₂. An increase in percentage of cells in the G0/G1 phase in the cell cycle and a decrease in S, and G2/M phase cells were seen in Sp1K cells exposed to more than 10 uM HgCl₂ more than 72 hours. MK2 cells showed cell cycle changes only at 24 hours exposure, and may be due to a sensitive subgroup. These data suggested that Sp1K cells were less susceptible than other cell types in a cell-specific way, which was independent of selenium protection. Concurrent exposure to Na₂SeO₃ provided protection against the HgCl₂-induced decrease in cell proliferation of Sp1K. The protective effects were greater if Na₂SeO₃ and HgCl₂ were premixed, but disappeared if exposures did not overlap. Although pretreatments with Na₂SeO₃ alone did not provide protection, they increased the protection of selenium administered later. Furthermore, Na₂SeO₃ decreased HgCl₂-induced apoptosis. These data demonstrated the Na₂SeO₃ protection against HgCl₂ toxicity in Sp1K cells in terms of cell proliferation and apoptosis. This study is the first report that reveals the existence of mercury-selenium antagonism in cultured cetacean cells. The data supported the hypothesis that selenium protection against mercury toxicity is, at least partially, through competition of binding sites and formation of mercury-selenium complex. / Master of Science

No description available.

In the Eastern Tropical Pacific (ETP), the operation mode of purse-seine fishing can be divided into dolphin sets and non-dolphin sets. Dolphin sets can catch more yellowfin tuna, but cause a lot of dolphin deaths. On the contrary, non-dolphin sets can catch more skipjack tuna, but discard a lot of tuna. Therefore, the choice of the operation mode to the ETP purse-seine fishery is very influential. If the fishermen use more dolphin sets, they are able to catch high quantity and more valuable yellowfin tuna. Conversely, if the fishermen use more non-dolphin sets, they will not hurt dolphins. But the tuna fish caught by this operation mode is smaller in size and the discarding rate is extremely high which will affect the overall profits of the fishermen. The research will investigate how the fishermen make the choice of the operation mode in the dilemma between dolphin sets which cause dolphins-bycatch and non-dolphin sets which result in tuna-discarding, In addition, if managers can ban dolphin sets or non-dolphin sets to maximize the profit of the fishermen and maintain the ecological balance between tuna and dolphins.