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Title: Status and conservation of the reef gastropod Trochus niloticus in the Philippines
Author: Dolorosa, Roger
ISNI:       0000 0004 2712 6375
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2011
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The most commercially important reef gastropod Trochus niloticus mainly harvested for the production of mother-of-pearl buttons, is highly susceptible to over- exploitation. Although conservation measures began shortly after the start of its commercial harvest in the early 1900s, their populations have been severely depleted prompting some countries like the Philippines to declare it as a threatened species. With the country's limited success in conserving trochus, this thesis explores the status of trochus in the wild, on-going conservation measures and some aspects of its biology in Palawan, Philippines. Field surveys show that abundance was very low in marine protected sites (MPAs) in mainland Palawan in spite of their proximity to law enforcing bodies. Natural recruits occurred in heavily exploited MP As, but the fates of released juveniles produced from a decade of artificial propagation are unknown. The breeders have high survival rates in intertidal tanks and were successfully induced to spawn after nearly a year of rearing. The growth rates of hatchery produced juveniles in cages on the reef were as fast as in the wild. Translocated wild trochus had high survival rates but growth rates varied among sites. Elasticity analyses of age-based matrix models revealed that survival of sub- and young adults has the greatest contribution to intrinsic population growth rate, so enhancing the survival of these age groups should be preferred over "head starting" when conserving trochus. Efforts to revive the trochus populations should focus on effective long term management/protection of MPAs. Captive rearing of broodstock in subtidal tanks could be a much cheaper alternative to hatchery propagation. Acclimation to predators of hatchery- produced trochus prior to release is hoped to increase their chances of survival. The translocations of wild trochus could be a more effective means of reviving a depleted population in areas having no sign of recruitment.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available