With the potential of the United States expanding into the Exclusive Economic Zone, an increase risk exists where large marine mammals (i.e. whales) will encounter aquaculture farms. To create a situation that minimizes the risk, a combination of approaches will be necessary. The approaches include; (1) marine spatial planning efforts to site farms with low frequency whale passage; (2) deterring whales from entering the area where gear is deployed; (3) designing farms that will shed off the whale if interaction occurs; and (4) the installation of sensors that can detect and notify response personnel during a potential entanglement event.
With support from the World Wildlife Fund, a sensor system was designed, built and tested with the capability of measuring large mooring system deflections and communicating the information to a shoreside station. The design process first included examining datasets from physical and numerical model tests that described the response of a typical kelp line system to a simplified impact event. The results showed that this particular aquaculture configuration was more sensitive to deflections rather than component tensions. This assessment is consistent with observations of whales with fishing gear where entanglement movements are characterized by translations and rotations. Therefore, the instrumentation package was designed around an inertial measurement unit (IMU) having 9 degrees-of-freedom (DOF). The DOFs include a 3-axis accelerometer, to obtain movements in the x-, y- and z- directions (e.g. deflections), a 3-axis gyroscope to determine the corresponding rotations around the x-, y- and z- axes (e.g. spinning), and a 3-axis magnetometer for sensing the orientation of the 3 axes to the Earth’s magnetic field. The IMU is connected to a datalogger that can be configured for cellular, iridium or radio communications. A GPS unit is also connected to the datalogger to determine the location of the sensor. The system’s high flyer design serves as a gateway between in air communication and subsurface sensing. The instrument suite was built and attached to mooring gear for a series of impact tests with human powered surface vessels (i.e. students paddling canoes). The instrument successfully detected impact and transmitted the data. The next iteration of system design and ocean testing with aquaculture gear is now in the planning process.