Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499140
Title: Population Dynamics and Behaviour of Whale Shark (Rhincodon Typus, Smith 1828) in Costal Waters of The Seychelles
Author: Rowat, David Robert Lionel
Awarding Body: University of London
Current Institution: University of London
Date of Award: 2008
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Abstract:
Whale sharks (Rhincodon typus) are the world's largest living fish yet in 1980 Wolfson was able to document only 345 records of the species. The sharks have been recorded from around the Seychelles islands since 1768 and the area provides ideal opportunities for scientific investigation of the species. The distribution, abundance and movement of whale sharks were studied with a combination of aerial survey and in-water identification studies from 2001 to 2006. The temporal and spatial distribution of whale sharks was limited and patchy and was affected by physical and environmental parameters. These studies also showed that the population comprised mainly juvenile males with very few females or adult sized sharks. A large proportion of the sharks present bore scars due to either natural causes, anthropogenic causes, or a combination. Tagging and satellite tracking studies showed that the whale sharks migrate away from Seychelles, but that a large proportion, > 23%, are resighted around Seychelles in subsequent years. Digital photo-identification studies confirmed this high level of resighting and catch-markrecapture modelling estimated a population of 154-180 sharks during this period. Details of the sharks' behaviour revealed by Pop-up Archival Tags that showed the sharks spent a very large proportion of their time at water depths of less than 50 m, but made dives to depths in excess of 1000 m. These data also showed that the diel pattern of behaviour varied over time, probably in relation to bathymetry and other parameters. A two-year visual study of behaviour, based on aerial observations, indicated that the mean time spent swimming at the surface was significantly shorter when boats were in their direct vicinity (53 s c.f. 131 s). The implications of these findings are discussed with respect to the management and conservation of the species in both local and international contexts.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.499140  DOI: Not available
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