• Sherlock, Matthew
• Williams, Alan

Abstract

Oceanographers looking to obtain size-frequency information on fish species have traditionally used Baited Underwater Video Systems (BRUVS) to take still or video footage of feeding fish. Traditionally these BRUVS systems were very simple in construction. A small frame would hold a camera, while a boom with some fish bait would attract marine life in the surrounding area to the cameras field of view. These systems would typically be deployed in shallow water for short durations (on the order of days) with a surface float for recovery.In the study of gulper shark populations, it was necessary to design a BRUVS lander with enhanced capabilities. A lander was designed that allowed self contained deep water operation (up to 1000m), with an extended deployment period of up to six months. The lander was configured with stereo HD video with a pair of Panasonic HDC-HS700 cameras to allow for high quality stereo video of the attracted marine life. Lighting was provided using a single Deep Sea Power and Light LED Multi-SeaLite.A bait piston system was also designed to allow the controlled release of liquefied bait (10L total available volume) into the surrounding water. A boom allows for bait to be release in the field of view at a 1.5m distance from the cameras, while and attached binary LED clock allows for precise frame synchronisation during the post processing of the video data.The independent and deep operating capabilities of the system allow for monitoring of deep water species over extended periods. The resulting stereo video allows scientists to measure target dimensions and estimate volume (mass) of the target. A high power lighting system combined with very sensitive cameras, allow for extended target filming even at depth. A set of two ORE CART releases allow for release of ballast mass to get the system back to the surface, while a custom designed strobe unit provides visual and radio ranging for system recovery. A stainless recovery ring allows for easy shipside retrieval.The design of these deepwater BRUVS systems posed some very challenging engineering problems. Not only was operating at depth a challenge, but the systems needed to be small and light enough to be deployed using small vessels in coastal waters. In addition, the stereo video system required precision manufacturing to guarantee the mechanical stability of the assembly (and in turn the calibration) throughout the system deployment. Careful ballasting was also required such that the systems would fall upright through the water column during deployment. With three prototype system operational, it was necessary to determine the best operational program that would yield the most targets. A total of 24 hours of filming time, and 10L of bait is available in each deployment. It was necessary to consider the combination of bait and filming would provide the best results. It was decided that filming should begin soon after a bait deployment, and that bait dispensing should be evenly distributed across the recording time.Bait types and consistencies were also considered to maximise the attraction of marine life.These unique BRUVS systems have shown to be promising test beds for a variety of marine life observation studies. The flexibility of the systems in both software and hardware allow for expanded capabilities over time. In the future these systems will be equipped with acoustic doppler current profilers (ADCPs), temperature and salinity meters, to provide a link between marine life observations, and the surrounding sea conditions.Lighting type, intensity and colours are also being tested in order to find the optimal lighting settings to allow for maximum target observation while minimising intrusion into the marine habitats. This paper discusses the design, prototyping and deployment of these deepwater BRUVS systems, and presents preliminary results obtained from trial deployments.

Topics

• impedance spectroscopy
• surface