Surveillance of Marine Resources by use of Stationary Platforms and Autonomous Underwater Vehicle (AUVS)

Abstract

In this thesis I investigate, describe and demonstrate new platform technology and its application in fisheries research. The first task was to prepare an Autonomous Underwater Vehicle (AUV) for payload integration (Paper 1). The instrument to be integrated into the AUV was a SIMRAD EK60 scientific echo sounder. Space limitations of the AUV demanded physical modifications. The EK60 software was designed for manual operation. To overcome the associated problem for remote control in accordance with the communication protocol of the AUV, a new version of the EK60 had to be designed and implemented (Paper 2). A field trial was performed to test the payload integration, including steered and autonomous runs; communication between the topside mother vessel and EK60 in the AUV, and the avoidance of the target species in the area (Paper 3).

The application of observation technology, with continuous recordings over time, gives a true representation of the temporal dynamics of density and vertical distribution without spatial resolution. This approach is complementary to snapshot research vessel surveying with area coverage assuming nil temporal effect. It may be particularly useful in areas of high dynamic activity, such as the Ofoten fjord area. An acoustic observatory was established in this area. Calibration of the main transducers needed special attention due to the expected depth effects on performance (Paper 4). The stationary transducers give the collected data an excellent temporal resolution at the sacrifice of spatial resolution. This makes it an ideal tool for studying vertical migration patterns. It is also important to compare these data with those collected from a moving research vessel (RV) (Paper 5). The lack of spatial resolution made it difficult to get any information about the fish school movements. Deploying an Acoustic Doppler Current Profiler (ADCP) as a unit of the observatory (Paper 6) gave this information including the potential of assessing biomass flux in and out of the fjord.