It has been considered that fishing areas for shrimp beam trawl have been in ruin because Korean local governments have permitted trawling into the areas limited by the fisheries local regulations from 1994. Physical and biological effects of the trawling were investigated in the study. Physical effects were investigated by optical methods such as trawling tracking by side scan sonar and comparing the gear both before and after trawling. Biological aspects were investigated by grab sampling of benthic animals, concentration of trace metals in sediment and a flux evaluation of NH4+, PO4-, and SiO2 by coring. The fishing activity had physical impacts on the seabed but these recovered naturally in less than fourty days naturally, which increased the benthic biodiversity, increases the trace metal concentration of and nutrient flux into the seawater, especially phosphate and silicate. This method and these results can help in further studies looking for disturbances by fishing.

In order to study basic information on the developed electro-magnetic compass, experiments were carried out on board M. S. KAYA at the pier of Dong Kuk Steel Mill in Pusan and the Korean southern sea using a three-axis magnetic sensor from Jan. 21, 1995 to Feb. 14, 1996. The obtained results were as follows : 1. The amount of old metal on the pier was about 27,290tons~57,440tons with an average of 40,560tons, the artificial local disturbance at the pier was min. 27.1μT, max. 66.5μT, ave. 433μT for the horizontal component and min. -27.0μT, max. 45.1μT, ave. 3.7μT for the vertical component. Its direction of horizontal component was 305˚ with the ship's head up bearing at 225˚. 2. The ship's magnetic distribution on the starboard side on berthing at the pier was 17.4μT for the horizontal component and -6.2μT for the vertical component. On the ship's port side, it was 19.8μT for the horizontal component and 4.1μT for the vertical component. On the ship's starboard side at sea, the ship's magnetic distribution was 19.2μT for the horizontal component and 3.2μT for the vertical component. On the ship's port side, the readings were 22.0μT for the horizontal component and -1.8μT for the vertical component. The directions of these readings were nearly starboard side. 3. On the pier, the secular change of the artificial local disturbance decreased 8.3μT from 61.0μT to 52.7μT for the horizontal component and decreased 7.1μT from 8.9μT M 1.8μT for the vertical component. On the starboard side from its berth, the ship, s magnetic distribution increased 2.6μT from 14.8μT to 17.4μT for the horizontal component and increased -0.1μT from -6.1μT to -6.2μT for the vertical component. On the ship's port side from its berth, it increased 7.1μT from 12.7μT to 19.8μT for the horizontal component and increased 10.2μT from -6.1μT to 4.1μT for the vertical component. 4. While at sea, on the ship's starboard side, the Secular change of the ship's magnetic distribution increased 3.9μT from 15.3μT to 19.2μT for the horizontal component and increased 2.0μT from -5.2μT to -3.2μT for the vertical component. On the port side, the changes increased 11.4μT from 10.6μT to 22.0μT for the horizontal component and increased 4.9μT from -6.7μT to -1.8μT for the vertical component. Upon berthing at the pier, the deviation of the secular change increased westerly 1 degree W~ 2.5˚ W from 3.5˚ W~ 5˚ W M 6W with the ship's head up bearing at 225˚. While at sea, these increased westerly 2˚ ~ 3˚ from the Northeast to the South and increased easterly 1˚ ~ 8˚ from the Southwest to the North. 5. While at port, within 1 mile between the ship and berth of the pier, as we approached the pier, the westerly deviation increased and when we departed the pier easterly deviation increased. When approaching the pier, the deviation was smaller than the deviation when the ship was departing from the pier. When approaching the bearing at 225˚ with the ship's head up bearing, the varies of deviation was smaller than the varies when the ship's head up bearing was departing from it.