Part 1 of 7. The Seto Inland Sea in Japan is located near Hiroshima. At one time, it had the highest catches of fish in the world. By 1990 it had the lowest. This was caused by massive industrialization and buildup of wastes in the water that eventually broke part of the food chain. The pollution also lead to red tide and fish kills. Canals from surrounding cities received wastewater from industry and homes,eventually making its way into the Seto Inland Sea. Currents from both the South and the North did not help the situation either as water currents flow into the sea instead of out so the sea does not get flushed out.