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Date of Award
Master of Science (MS)
Department of Integrated Science and Technology
Documenting deformities in cetaceans can lead to understandings in the health of the populations, but also the state of ocean and human health in an area. Deformities like skin lesions can lead to information about local pollution levels or possible diseases, while physical impacts can give insight into vessel traffic or fishing gear entanglement information. Cetaceans encounter threats like vessel strikes and fishing gear entanglements worldwide, but less obvious activities like whale watching or pollution can also have impacts. Studies have been conducted worldwide and around the Madeira Archipelago to document deformities, but there are various descriptions for what is considered a deformity. This study aimed at producing a clear and unifying definition for the term deformity when dealing with the broad range of species that constitute cetacean marine mammals.
Methods involved the cataloging of deformities on identified individuals. Defining a deformity as “a condition, in which all or part of the body does not have the expected/typical/characteristic or normal species shape, color or appearance, which are congenital or acquired during the course of the individual’s life,” this study analyzed and documented 29 different types of deformities from 1,020 identified individual cetacean specimens covering 11 species found around the Madeira Archipelago. Analysis involved the use of photographs from a database at CIIMAR-Madeira.
Excluding rake marks and nicks, the main species that showed greatest numbers of deformities included Mesoplodon densirostris, Tursiops truncatus and Balaenoptera brydei. The percentage of the analyzed population for each of these species were 96.49%; 75.78%; and 87.88% respectively. It was discovered that 597 (58.53%) of the individuals have at least one deformity, while skin lesions were the most prominent category (50.44% of total deformities) and cuts (23.72% of deformities) were the most common deformity. Deformities from possible anthropogenic causes were observed in 80 individuals (7.84% of the total population). This research gives a baseline for the implications of the human impacts on the cetaceans’ deformities
Though the causes of certain deformities, such as skin lesions, are difficult to establish, pointing toward the need for further research to discover the full extent of the health hazards posed to cetaceans and marine life around the Madeira Archipelago.
Dietterle, Erich, "Assessing morphological deformities in cetaceans: Definition of patterns and quantification with a case study (Madeira Island, NE Atlantic)" (2017). Masters Theses. 530.