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    Some aspects of ecology, biology, and fishery of the horse mussel Modiolus metcalfei (Hanley, 1843) in Dumangas, Iloilo
    Uba, Kaent Immanuel N. (University of the Philippines Visayas, 2019-06)
    The exploitation of Modiolus metcalfei in Dumangas, Iloilo has been going on since the 1970s. It has undergone the cycle of resource depletion to recovery but its management remains hindered by the poor understanding of its ecology, biology, and fishery. The present study characterized the habitat, investigated the aspects of morphology, allometry, asymmetry, feeding biology, and analyzed the value chain of M. metcalfei fishery in the area. Monitoring of physicochemical parameters, sediment grain size and organic matter content, estimation of population density were conducted for six months. Morphology, allometry, and asymmetry were investigated using combined linear and geometric morphometric methods while pre-ingested food and plankton composition in the water were determined qualitatively. Moreover, interviews and observations were conducted to analyze the value chain of the horse mussel fishery. Although the physicochemical parameters were at optimal levels, results in the analysis of asymmetry indicated developmental instability and ecological stress. The primary factors influencing the variation in morphology were sex and environmental fluctuations. The horse mussel mainly relied on phytoplankton, primarily diatoms, for food. The lack of support from enablers, lack of adequate enforcement, and lack of post-harvest infrastructure hindered the full development of the fishery. Moreover, poverty dimensions were revealed in the analysis of the value chain. To craft better management policies, studies on the population dynamics and reproductive biology are recommended.
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    Influence of lunar cycle and tidal fluctuation of gonadal maturity of green mussel (Pema viridis) in Inner Malampaya Sound, Taytay, Palawan
    Baldevieso, Adzel Adrian G. (University of the Philippines Visayas, 2018-07)
    This study aims to identify the ideal period of harvesting cultured green mussel (Perna viridis) in order to attain larger flesh to shell ratio in inner Malampaya Sound, Taytay, Palawan by investigating the gonadal maturity in relationship to lunar cycle, tides, physicochemical and water productivity parameters. Twenty green mussel samples undergo histological analysis of gonad and 50 samples were measured for body indices weekly from October 2017 to March 2018. Results showed that the body and gonad indices have significant positive correlation with slight higher values during the first quarter weeks, and during a day before the low low tides. The peak of spawning was recorded during October. After which, partial spawning was observed and starts during the weeks of full moon until new moon with a duration of 1-3 week. Thus, the gonadal development/maturity of green mussel in the study is influenced by lunar cycle and tidal fluctuations. Among the water parameters monitored, salinity, pH, and temperature have a significant difference in the monthly, and lunar weeks levels. Furthermore, the drop in salinity might trigger the peak spawning. Diatoms (91%) dominate the plankton composition in the sampling area followed by small percentage of dinoflagellates (4%), zooplankton (2%), and cyanobacteria (2%) and ciliates (1%). The genus Coscinodiscus has the highest percentage (97.73%) among the diatom genera, this species could be one of the major algal diet of green mussels in the area. On the other hand, there was no significant correlation between the gonad index and body indices to the physicochemical parameters and water productivity parameters. Based on body indices and gonad index values, the ideal period to harvest green mussel is during the first quarter weeks. One out of 540 samples was found to be hermaphrodite.