Study on Evaluation Method of Shallow Sea Environment by Counting the pulse sound of Snapping Shrimps

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(1) Quantifying the relation between pulse counts and shrimp population ・ We developed the pulse location detection system using four hydrophones and a computer equipped with high speed analog-digital converted. By using the system, we conducted field surveys in several tidal marshes. ・ In the same time, we collect shrimps from the field and counted the number of nest holes. ・ From those surveys, we could develop a formula to calculate the shrimp population from pulse counts.(2) Making clear the environmental factors that affect pulse counts, and create a formula that quantify the relationship. ・ We showed that the hourly, daily, and weekly fluctuations are small and weather condition didn't affect them. ・ We created a formula which explains the relation between pulse counts and water temperature. ・We found a relation between pulse counts and hypoxia or red tide. ・ We found that the difference of pulse counts are not large among sandy silt bottom areas, thus, this method would be able to use to compare the condition of different locations.(3) Measuring the pulse counts in various areas in the world. ・ We conducted field surveys in Japan and foreign countries. The simple measuring equipments helped us to carry them to the distant locations. ・ So called polluted areas, such as Tokyo bay, Ise bay, Chita bay, etc., the pulse counts were smaller than that we predicted from the water temperature.(4) Evaluation as an index of environmental condition for bottom living organisms. ・ We described the calibration procedure to count the pulse with various different equipments. ・ We would be able to evaluate the environmental condition by comparing the observed pulse counts and predicted pulse counts from water temperature. If the observed pulse counts are smaller than the predicted ones, environmental deterioration might be happening. ・ At least, this method would be able to apply to a fixed point observation to detect environmental deterioration.