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Title: Stock enhancement of the mud crabs Scylla spp. in the mangroves of Naisud and Bugtong Bato, Ibajay, Aklan, Philippines
Author: Lebata, Ma. Junemie Hazel L.
Awarding Body: University of Wales, Bangor
Current Institution: Bangor University
Date of Award: 2006
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This study addressed the potential restoration of a population of mud crabs Scylla spp. in the mangroves of Naisud and Bugtong Bato, Ibajay, Aklan, Philippines. Survey of the study site showed that 50 of the 70 ha total mangrove area is still natural mangrove and represents suitable habitat for mud crabs. The dominance of Scylla olivacea in the mud crab catches, through all life stages, suggests fidelity of this species to the area. The absence of berried crabs in the samples may indicate offshore migration for spawning. The high percentage of immature crabs in all months with peaks in March or April may suggest year-round recruitment with peaks in the summer months. The negatively significant correlation of carapace width (CW) and body weight (BW) to time indicates growth overfishing. Results further revealed low yield and catch per unit effort (CPUE). Population estimates ranging from 14 to 34 crabs ha 1 were obtained through a mark-recapture study using coded microwire tag (CWT) and the Jolly-Seber method for open populations. Growth rates were 0.25 mm CW d"' and 1g BW d"1. Results of the stock enhancement trials showed that smallscale release can increase abundance of mud crabs in a partly isolated mangrove habitat. Growth and survival rates of released crabs suggest that S. olivacea is the best suited species for this particular area. The results further revealed that pondconditioned S. olivacea can have higher growth than those released directly from the hatchery and recovery rates equivalent to those of their wild conspecifics. The optimum size-at-release is 65.0-69.9 mm CW regardless of species or source. Both wild and hatchery-reared crabs also exhibited limited post-release movement, supporting the overall conclusion that stock enhancement can be an effective tool in addressing declining fisheries resources.
Supervisor: Le Vay, Lewis Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available