Although it’s a relatively recent marine research tool, video monitoring in marine environments is becoming more widespread as the technology becomes better and cheaper. Advantages of using video over traditional diver-based monitoring include:
- creating a permanent record of observations
- reducing observer bias
- allowing easy exchange of information between researchers and other stakeholders
- reducing in-water time for divers, lowering personal risk and increasing the number of sampling hours
- observing life in parts of the ocean out of reach of divers
- sampling in sensitive areas without impact (because they are non-extractive and harmless to fish and habitat).
AIMS uses two video monitoring techniques in tropical marine waters: towed video and baited remote underwater video stations.
Towed video cameras allow large areas of marine habitat to be surveyed in a systematic way in water depths up to 200 m. A video camera is towed behind a boat at a fixed speed along a survey line (transect) while scientists observe seabed habitat via video in real time and take high-resolution still images at regular intervals. This imagery is later analysed to describe habitats, analyse species distributions, and map seabed biodiversity over broad areas.
Towed video recordings have given AIMS scientists insight into the types of habitats that occur in many remote and previously unexplored locations from the inshore Kimberley coast to deep, offshore shoals far to the north and north-west of the mainland. Towed video is used extensively in the north-west of Australia where, as part of our commitment to the sustainable ecological development of marine resources. AIMS collects baseline data on offshore shoals to better understand and protect these habitats.
A towed video body waiting to be deployed from the back of a research vessel. Photo: M. Stowar, AIMS
Baited remote underwater video stations
First developed by AIMS, baited remote underwater video stations (BRUVS) have since become a common fish-surveying tool around the world. These stationary, seafloor camera stations use bait to attract the fish in their vicinity, recording species attracted to the bait or just swimming past the camera lens. They are particularly suitable for observing fish in hard-to-reach habitats in both shallow and deep waters, such as reefs and shoals, inter-reef areas and continental shelves. They are also used at night with lights.
BRUVS consist of small, inexpensive video cameras in simple underwater PVC–acrylic housings held in a steel frame with a mesh bag of minced pilchards on the end of a bait arm in the field of view. BRUVS are commonly deployed in fleets of 10 or more at a time across a large area, with each one attached to a separate rope and surface marker float to be picked up after one or two hours filming on the seabed. The footage is analysed in detail back in the laboratory where fish are identified by specialists and their abundance recorded.
A BRUVS sits on the lagoon floor at Scott Reef, WA. Note the bait bag held in front of the unit Photo: P. Tinkler, AIMS
As well as the benefits of video camera sampling mentioned above, BRUVS let us:
- make precise length and biomass estimates with analysis of paired images when cameras are used in stereo-pairs
- capture detailed images of habitat types, which can be incorporated into the analysis
- record large, mobile animals, such as sharks,rays and seasnakes, that normally avoid scuba divers or towed video cameras.
Baited remote underwater video stations are regularly used in a number of projects throughout AIMS. They have recently been used to explore fish communities and biodiversity patterns of offshore oceanic shoals north and north-west of the Australian mainland, including:
- monitoring iconic north-western reefs such as Rowley Shoals, Scott Reef and Ningaloo Reef
- monitoring effects of zoning (closure to fishing) on fish populations of the Great Barrier Reef Marine Park
- assessing the impacts of seismic surveys and the Montara oil spill on reef fish communities
- publishing maps of fish, shark and seasnake diversity throughout the Great Barrier Reef Marine Park.