Incidental mortality in fisheries, especially gillnets, is one of the most important causes of decline of many species of cetaceans around the globe. Local populations of franciscana, Pontoporia blainvillei, and Hector�s dolphins, Cephalorhynchus hectori, have been subject to high levels of mortality in gillnets for several decades. This is due to a combination of extensive overlap in distribution of these coastal dolphins and large numbers of fishing nets. Stage-specific population dynamic models (without environmental stochasticity) suggest that both species have a low potential for population growth of approximately 0.2% (95% CI: -3.7% to 4.2%) to 3.4% (95% CI: 1.6% to 6.4%) for franciscana and 0.85% (95% CI: -1.0% to 2.6%) for Hector�s dolphins. Although the two species have similar population growth rates, they result from different life history strategies. Franciscana has a relatively low adult survival rate (0.86; SD = 0.016) which is compensated by a relatively high reproductive potential. The latter is a combination of early reproduction and high fecundity. Hector�s dolphin has a low reproductive potential, which is a combination of late reproduction and low fecundity, which is probably compensated by a relatively high adult survival rate (0.92; SD = 0.02) Apparent differences in growth rate among franciscana populations are possibly due to a combination of varying population-specific reproductive potential and, in some populations, inaccuracy in parameter estimates. Inaccuracy in estimating natural survival rates is also a cause for the low growth rate of Hector�s dolphins. The estimated low population growth rates of these species are insufficient to compensate for current levels of fishing-related mortality in some local populations, especially when environmental and/or demographic stochasticity is considered. Under these circumstances Banks Peninsula population would have a negative mean population growth rate of 0.54% (95% CI: -2.2% to 0.9%) and would decrease below its initial size in approximately 74% of the simulations. Stochasticity alone would decrease considerably the probability of the Banks Peninsula population to grow and recover from past and current high bycatch levels. Effects of stochasticity were also high for one of the franciscana stocks (i.e. stock from Franciscana Management Area II). In other areas (e.g. West Coast of the South Island; franciscana stock from FMA I) fishing effort and bycatch mortality rate seem not to be impeding population growth. Even in a stochastic environment and under current levels of fishing effort, the West Coast population and the franciscana stock from FMA I would grow at a positive rate of 0.32% (95% CI: -1.2% to 1.8%) and 3.1% (95% CI: 2.2 to 7.2%), respectively. Parameter uncertainty does not change the conclusion that immediate and extreme limitations on fishing practice and effort are necessary to increase the chances of recovery for some local populations/stocks. Fishing effort in New Zealand is regulated by a quota system. The quota system, the low number of fishing boats and the relatively low overlap between fishing nets and dolphins are probably the reasons for the positive population growth of Hector�s dolphins from the West Coast of the South Island. On the other hand, not even the Marine Mammal Sanctuary is sufficient to avoid negative mean population growth rate of Hector�s dolphins under current levels of fishing effort off Banks Peninsula. In Brazil, Uruguay and Argentina, where franciscana occurs, gillnet fisheries are not regulated. In some areas, faced with a declining fish stocks, fishermen have increased fishing effort to compensate for reduced catches, and the bycatch of franciscana has increased as a consequence. Strategies aiming at the conservation of these two species are likely to benefit other components of the ecosystem. Especially in the case of franciscana, reducing fishing effort is likely to promote the recovery of depleted fish stocks.

Thesis (M.S.)--University of North Carolina at Wilmington, 2004. / Includes bibliographical references.

Incidental mortality in fisheries, especially gillnets, is one of the most important causes of decline of many species of cetaceans around the globe. Local populations of franciscana, Pontoporia blainvillei, and Hector�s dolphins, Cephalorhynchus hectori, have been subject to high levels of mortality in gillnets for several decades. This is due to a combination of extensive overlap in distribution of these coastal dolphins and large numbers of fishing nets. Stage-specific population dynamic models (without environmental stochasticity) suggest that both species have a low potential for population growth of approximately 0.2% (95% CI: -3.7% to 4.2%) to 3.4% (95% CI: 1.6% to 6.4%) for franciscana and 0.85% (95% CI: -1.0% to 2.6%) for Hector�s dolphins. Although the two species have similar population growth rates, they result from different life history strategies. Franciscana has a relatively low adult survival rate (0.86; SD = 0.016) which is compensated by a relatively high reproductive potential. The latter is a combination of early reproduction and high fecundity. Hector�s dolphin has a low reproductive potential, which is a combination of late reproduction and low fecundity, which is probably compensated by a relatively high adult survival rate (0.92; SD = 0.02) Apparent differences in growth rate among franciscana populations are possibly due to a combination of varying population-specific reproductive potential and, in some populations, inaccuracy in parameter estimates. Inaccuracy in estimating natural survival rates is also a cause for the low growth rate of Hector�s dolphins. The estimated low population growth rates of these species are insufficient to compensate for current levels of fishing-related mortality in some local populations, especially when environmental and/or demographic stochasticity is considered. Under these circumstances Banks Peninsula population would have a negative mean population growth rate of 0.54% (95% CI: -2.2% to 0.9%) and would decrease below its initial size in approximately 74% of the simulations. Stochasticity alone would decrease considerably the probability of the Banks Peninsula population to grow and recover from past and current high bycatch levels. Effects of stochasticity were also high for one of the franciscana stocks (i.e. stock from Franciscana Management Area II). In other areas (e.g. West Coast of the South Island; franciscana stock from FMA I) fishing effort and bycatch mortality rate seem not to be impeding population growth. Even in a stochastic environment and under current levels of fishing effort, the West Coast population and the franciscana stock from FMA I would grow at a positive rate of 0.32% (95% CI: -1.2% to 1.8%) and 3.1% (95% CI: 2.2 to 7.2%), respectively. Parameter uncertainty does not change the conclusion that immediate and extreme limitations on fishing practice and effort are necessary to increase the chances of recovery for some local populations/stocks. Fishing effort in New Zealand is regulated by a quota system. The quota system, the low number of fishing boats and the relatively low overlap between fishing nets and dolphins are probably the reasons for the positive population growth of Hector�s dolphins from the West Coast of the South Island. On the other hand, not even the Marine Mammal Sanctuary is sufficient to avoid negative mean population growth rate of Hector�s dolphins under current levels of fishing effort off Banks Peninsula. In Brazil, Uruguay and Argentina, where franciscana occurs, gillnet fisheries are not regulated. In some areas, faced with a declining fish stocks, fishermen have increased fishing effort to compensate for reduced catches, and the bycatch of franciscana has increased as a consequence. Strategies aiming at the conservation of these two species are likely to benefit other components of the ecosystem. Especially in the case of franciscana, reducing fishing effort is likely to promote the recovery of depleted fish stocks.

Thesis (Ph.D.)--Murdoch University, 2005. / Thesis submitted to the Division of Science and Engineering. Includes bibliography.

Thesis (Ph.D.)--Murdoch University, 2005. / Thesis submitted to the Division of Science and Engineering. Bibliography: leaves [168-198].

Thesis (M.S.)--University of North Carolina at Wilmington, 2005. / Includes bibliographical references (leaves: 65-59)

Synchrony between Atlantic spotted dolphins (Stenella frontalis) is crucial for successfully fending off bottlenose dolphins (Tursiops truncatus) during interspecies aggression. The present study examined synchrony in adult Atlantic spotted dolphins during aggressive encounters with bottlenose dolphins. Across group size, aggressive behavioral events increased preceding synchrony, peaked during synchrony, and decreased dramatically after synchrony. Although smaller groups (< 10 dolphins) became synchronous more frequently than larger groups (> 10 dolphins), larger groups remained synchronous longer; however, smaller groups exhibited more frequent aggressive behavioral events during synchrony, suggesting that additional aggressive behaviors may be necessary to compensate for the small group size, whereas larger groups may be able to rely on synchrony alone. Disorganized squawk bouts synchronized as physical synchrony began, but only if coupled with escalating aggressive behaviors. The synchrony during aggressive episodes observed in adult Atlantic spotted dolphins can be used as a baseline to determine the process of the development of this critical skill in juveniles. / Includes bibliography. / Thesis (M.A.)--Florida Atlantic University, 2015 / FAU Electronic Theses and Dissertations Collection

Long-term individual-based studies can be central to collecting data on aspects of individual and population biology and ecology. Photo-identification often underpins longterm individual based studies, particularly for cetaceans. Bottlenose dolphins (Tursiops truncatus) are long-lived with low reproductive rates and complex social structures, while showing plasticity in their behaviour, biology and ecology. As such long-term individual based studies are key to investigating the complexities of their population dynamics. My aim for this thesis was to synthesise over two decades of photo-identification data with the intention of exploring the value and contribution of a long-term individual based photo-identification study and answer key questions about the ecology and biology of bottlenose dolphins in Scottish waters. This thesis provides the first data on distribution and status of bottlenose dolphins around Scotland. Results highlighted the smaller population on the west coast split into two discrete communities with different ranging patterns and provided the first evidence that the highly mobile east coast population may be increasing. For the east coast of Scotland bottlenose dolphin population, laser photogrammetry identified morphological differences (larger size, no sexual dimorphism, no sex differences in growth) and highlighted fitness consequences to variation in early calf growth (calves that died over their first winter were significantly shorter). This thesis also identified differences in social structure over two decades at the two extremes of the population's range, potentially caused by or a consequence of, range expansion. Finally, this study provided empirical evidence of increasing trends in population abundance, reproductive rate and calf survival. This is a rare example of empirical evidence of a positive trend in demographic parameters of a cetacean population using a marine protected area. This work highlights the need for long-term individual based data to detect biologically meaningful change and suggests this small bottlenose dolphin population is a conservation success story.

Thesis (M. Sc.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 61-65).

Knowledge of the structuring of natural populations is important for understanding both evolutionary processes and population ecology, and for supporting management decisions. Conventional methods of direct observation often suffer from a lack of resolution, particularly when studying mobile animals in a marine environment. In this study, I combined direct observation with indirect molecular genetic approaches to infer the social and population structure of coastal (inshore) bottlenose dolphins, Tursiops truncatus. Genetic diversity and structure of bottlenose dolphins around the UK and Ireland was examined using tissue samples from stranded dolphins and incidental fisheries by-catch. Mitochondrial DNA (mtDNA) sequence data indicated significant subdivision among four main sample regions (NE Scotland, Wales, NW Scotland and Ireland). Genetic divergence between NE and NW Scotland populations, and low genetic diversity within the NE Scotland population, provide further support for the precautionary approach currently applied to the management of this population. Inference from both mtDNA and nuclear microsatellite genetic markers, and direct observational data were used to examine the social and population structure of bottlenose dolphins in the NE Bahamas. Novel strategies for collecting genetic samples (remote biopsy and faecal sampling) from free-ranging dolphins were developed and validated, enabling an individual-based analysis of population subdivision. Patterns of individual associations in two contrasting habitats indicated that environmental pressures affect dolphin grouping patterns; with a genetic basis for social affiliations occurring only where predation pressures are low. Nonetheless, a particularly notable feature of the social structure in both habitats was the persistence of stable alliances among maternally related males. At the population level, the significant degree of genetic structuring revealed among three sampled regions on Little Bahama Bank, supported the high degree of site fidelity suggested by individual-based photo-identification data. Contrary to the patterns of male dispersal and female philopatry common among both mammals and bottlenose dolphins, sex-specific patterns of genetic differentiation inferred from both mtDNA and microsatellite markers were indicative of female-mediated gene flow. This study provides novel insight into the factors governing the patterns of structuring within populations of highly mobile small cetaceans, and demonstrates the value of integrating both direct (field-based) and indirect (molecular genetic) data in the study of free-ranging animals.