Application of water quality data to estimate the cultured oyster biomass in Hiroshima Bay: Estimation of the cultured oyster biomass

The cultured oyster biomass was estimated using biomass model, which was co mposed of the variables of growth, mortality, oyster fresh meat weight (FMW ) and oyster numbers. Oyster growth and mortality were estimated using mult iple linear equations composed of water quality variables. Results of the p resent study showed that actual growth was best modeled using an equation c omposed of difference values between two successive months of chlorophyll a , salinity and dissolved oxygen. The cumulative mortality estimated by the equation, which was composed of the variables FMW, annual minimum values of temperature, DO and chlorophyll a, also well simulated the observed mortal ity. The cultured biomass of oysters in different oyster culture areas (Ata da, Miyajima, Hiroshima and Ondo) were estimated according to the culture t echniques (Ikistu, Yokusei and Nokoshi). The results showed that the cultur ed biomass in all areas increased up to the maximum at the beginning of har vest season, and dropped sharply due to harvesting. The estimated growth an d cumulative mortality of oyster were not much different between areas, ind icating that a difference of oyster biomass In each culture area was signif icantly depended on the number of cultured oysters. Thus, this approach pro vides quantitative information of the cultured biomass of oysters in Hirosh ima Bay which has been difficult to monitor directly in the culture area.