No abstract

The status of the mud clam, Geloina expansa, an important bivalve in the artisanal fisheries of the Loay-Loboc River, was assessed using monthly shell length frequency data (October, 2012 to January, 2015 to estimate population parameters. Growth parameters derived were L ∞ = 91.35 mm, K = 0.75 yr -1 and t 0 = -0.16. Predicted L max was 90.39 mm. Estimated growth rates showed fast growth for the first two years. Longevity is approximately 6.1 years. Length-weight relationship showed a positive allometric growth (r 2 = 0.94). The estimated total mortality (Z) was 2.89 yr -1 . Natural (M) and fishing (F) mortalities estimates were 0.90 yr -1 and 1.99 yr -1 , respectively. Estimated exploitation rate (E = 0.69) was higher than the maximum sustainable exploitation (E max = 0.41). Two annual recruitment peaks occurred during the months of December to February and July to August. Monthly condition index (CI) suggested that spawning is year-round. It appeared that the variations in CI of G. expansa in the river was influenced by the water temperature and salinity (r² = 0.54; P < 0.0001). These biological information may be used for aquaculture technique development for G. expansa in central Philippines which will aid in the conservation and management of natural stocks.

P. erosa is an economically- and ecologically-important bivalve which thrives in brackishwater mangroves or Nypa zones. Unpredictable weather conditions and unregulated anthropogenic activities in mangrove area could lead to high turbidity conditions and possibly affect the filtering capacity of P. erosa. A laboratory experiment was conducted to determine the effects of turbidity concentration and body size on the filtration rate and pseudofaeces production of P. erosa. Filtration rates significantly increased with higher turbidity concentration up to 750 mg L-1 (P < 0.05). Pseudofaeces production also increased with increasing turbidity concentration (P < 0.05).  Body size did not affect the filtration and pseudofaeces production of P. erosa. Results suggest that P. erosa is resilient to highly disturbed, turbid environments and therefore could be a potential candidate species for aquaculture.