https://vital.seals.ac.za/vital/access/manager/Index ${session.getAttribute("locale")} 5 https://vital.seals.ac.za/vital/access/manager/Repository/vital:44170 Wed 18 Aug 2021 13:43:22 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5333 99%) better than presence (60%). Because coelacanths have a unique spot pattern it was possible to quickly and accurately identify specific individuals photographically using computer-aided identification software. Without any manual intervention by an operator the software accurately identified between 56 and 92% of the individuals. Identification success increased to 100% if the operator could also manually select from other potential matching photographs. It was also shown that fish exhibiting a yaw angle not exceeding 60° could be accurately identified in photographs. Each of the sections presented in this thesis represent a possible step towards analysing coelacanth-related habitats, locating and then analysing new habitats. Steps include first locating a population and then performing a habitat analysis. Coelacanth location within the different habitats can then be determined allowing the development of predictive models to potentially identify possible locations of new populations. The final step is to identify individual fish within the population for assessing demographic parameters and population monitoring.]]> Wed 12 May 2021 23:21:26 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:887 Wed 12 May 2021 23:18:43 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:11774 Wed 12 May 2021 23:16:11 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:10159 Wed 12 May 2021 22:53:50 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:10133 Wed 12 May 2021 22:35:03 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:9296 Wed 12 May 2021 22:31:28 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:29480 Wed 12 May 2021 22:22:16 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:8859 Wed 12 May 2021 22:17:25 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:4371 Wed 12 May 2021 20:52:26 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:38675 Wed 12 May 2021 20:22:18 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:9374 Wed 12 May 2021 20:18:31 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:38111 Wed 12 May 2021 20:12:29 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:4158 Wed 12 May 2021 19:51:40 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:8332 Wed 12 May 2021 19:51:40 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:9146 Wed 12 May 2021 19:50:19 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26421 Wed 12 May 2021 19:23:24 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5789 Wed 12 May 2021 19:18:34 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:1825 Wed 12 May 2021 19:18:30 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:8261 Wed 12 May 2021 19:15:12 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:1906 Wed 12 May 2021 19:10:38 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5331 Wed 12 May 2021 19:04:57 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:8821 Wed 12 May 2021 18:47:18 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:38073 Wed 12 May 2021 18:37:30 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:9012 Wed 12 May 2021 18:29:08 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:6391 Wed 12 May 2021 18:27:34 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:9903 Wed 12 May 2021 18:27:27 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:9044 Wed 12 May 2021 18:24:38 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:4130 Wed 12 May 2021 18:19:45 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:9127 Wed 12 May 2021 17:52:24 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:37971 Wed 12 May 2021 17:46:56 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5788 90% in the last 130 years), the cause(s)of which are unknown. There is a paucity of data on this species in the South Atlantic Ocean, therefore their trophic ecology at Tristan da Cunha was studied, specifically focusing on diet, using stomach content analysis and stable isotope analysis (SIA), in conjunction with an analysis of diving behaviour, assessed using temperature-depth recorders. In order to evaluate the influence of gender on foraging, a morphometric investigation of sexual dimorphism was confirmed using molecular analysis. Additionally, plasma corticosterone levels were measured to examine breeding stage and presence of blood parasites as potential sources of stress during the breeding season. Northern Rockhopper penguins at Tristan da Cunha displayed a high degree of foraging plasticity, and fed opportunistically on a wide variety of prey, probably reflecting local small-scale changes in prey distribution. Zooplankton dominated (by mass) the diet of guard stage females, whereas small meso-pelagic fish (predominantly Photichthyidae)dominated diet of adults of both sexes in the crèche stage, with cephalopods contributing equally in both stages. Adults consistently fed chicks on lower-trophic level prey (assessed using SIA), probably zooplankton, than they consumed themselves indicating that the increasing demands of growing chicks were not met by adults through provisioning of higher- quality prey. SIA also indicated that adults foraged in different oceanic water masses when feeding for self-maintenance and for chick provisioning, thus temporally segregating the prey consumed for different purposes. It is possible that adults ‘selected’ these higher quality prey for themselves, or this may be a reflection of opportunistic behaviour. At Tristan da Cunha sexual dimorphism was observed in culmen dimensions (length, depth, width), with males having larger beaks and feeding on larger individuals of squid and fish than females. No sexual segregation in terms of foraging habitat (i.e. different water masses, based on ð¹³N or trophic level ð¹⁵N) during the breeding season or pre-moult period was revealed through SIA, and stomach content analysis revealed no sexual differences in prey species targeted. The results of SIA of feathers indicate that during the pre-moult period birds foraged in different water masses than during the breeding period. The fact that throughout the breeding season birds foraged in similar habitats suggests no intra-specific competition, despite both sexes feeding on the same prey.Birds were generally diurnal, daily foragers (12 – 16 hr trips), with extended trips (maximum duration 35.5 hours) and nocturnal diving recorded in a few individuals. Birds dived well within their physiological limits, predominantly utilising the upper 20m of the water column, employing two different strategies to target different prey items. Long, deep (30 – 40 m), energetically costly dives were performed when targeting energy-rich prey (fish), and a greater number of shorter, shallower (5 – 20 m), energy-efficient dives were performed when targeting prey with a lower energy content (zooplankton). More than half of the sampled study population were infected with the intra-cellular blood parasite Babesia, but infection showed no relationship to body mass, corticosterone levels or breeding success. Fasting birds showed no signs of elevated corticosterone levels, suggesting they had acquired sufficient fat reserves prior to breeding. Failed breeders did not exhibit elevated corticosterone levels. Tristan skuas, Catharacta antarctica hamiltoni, were observed to be a significant cause of egg and chick mortality. The absence of sex-based differences in foraging, and the absence of any signs of stress in relation to body mass, presence of Babesia or breeding stage, suggest that there are no obvious signs of high levels of stress or food limitations during breeding at Tristan da Cunha.]]> Wed 12 May 2021 17:44:40 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:8474 Wed 12 May 2021 17:42:41 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5432 Wed 12 May 2021 17:38:32 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:10664 Wed 12 May 2021 17:11:51 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:11955 Wed 12 May 2021 17:05:13 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:9148 Wed 12 May 2021 16:46:59 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:3866 Wed 12 May 2021 16:33:12 SAST ]]> 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