The LDEO trawl-resistant (TRM) ocean bottom seismometer was designed in 2012 for use on the heavily-fished continental shelf. The TRM comprises a heavy, low steel shield that is designed to deflect the lower leading line of bottom trawl nets. The TRM is lowered onto the seafloor from the ship and recovered using popup buoys or remotely-operated vehicles. Each OBS is equipped with a Trillium Compact seismometer, a Paroscientific absolute pressure gauge, and a hydrophone. Twenty TRMs were built for the Cascadia Initiative and were first deployed in 2011. There are currently 19 TRM OBS in the fleet.