The Okinawa Deep Seawater Research Center on Kumejima has now been operating for more than 15 years with both surface and deep seawater pipes. The deep pipes are open-ended, while the intake for the surface pipe has bars to keep out larger fish.
In both surface and deep water cases, there are strainers prior to the pumps so that any fish large enough to have issues with a pump will be kept away from it. In the past, the ODRC pumps regularly turned off and on based on the demands of local industries and the center. Since 2013, however, the Okinawa OTEC facility now utilizes all remaining water for power production, and the pumps run 24/7, except in rare cases of maintenance at the ODRC.
Based on observations from maintenance personnel, it seems that only when the pumps stop do fish occasionally swim into the pipe intake. When the pumps are turned back on, the fish flow up to the strainer, where they can be safely removed for return to the ocean or for study. When the pumps run continuously, they seem to avoid the intake.
This month, during maintenance on the intake pit, we had a new visitor. This Fugu is quite large and a welcome visitor to the ODRC.