Low cost remotely operated vehicles (ROV), 1.e costing under £ 100k, have become a relatively common tool for work in the marine environment. A survey conducted in 1992 identified over 800 such vehicles in use, however the vast majority are used for inspection/engineering tasks and only a few are known to be used for marine science (Michel, 1992).
Since 1993 Scottish Natural Heritage (SNH) has been using such an ROV as a component of its marine biological survey programme, a HyballTM from Hydrovision, Aberdeen, which has been modified to allow manual control of focusing the colour video camera. All dives are recorded on a S-VHS video recorder
The SNH survey programme with the ROV cornprises two broad categories Firstly, inventory surveys where the objective is to identify and describe the distribution of marine biotopes (i e. the habitat and associated assemblages of animals and plants). Secondly, surveys are carried out in relation to site-specific casework issues, for example, to allow SNH to advise on the location of aquaculture leases in relation to features of natural heritage interest.
The ROV has proved versatile in these applications, performing a variety of tasks including
Combined ROV/diver surveys-the ROV has been used alongside divers to extend the range of the survey in terms of both area covered and depth, and for the reconnaissance of sites in order to make the most efficient use of the divers' time
Survey of biotopes beyond diving depths
In situ observation of the behaviour of animals, especially those found beyond diving depth and previously known only from remote sampling
For ground-truthing during acoustic seabed survey In certain circumstances, for example, due to depth, terrain, where the ROV is preferable to drop-down video systems
To date the SNH ROV has been used in 20 surveys ranging from Orkney to St Kilda to Berwickshire, carrying out over 280 dives, with the deepest dive to 175m
All of the interpretation of data from our surveys has been undertaken using the semi quantitative abundance scale developed by the Marine Nature Conservation Review (MNCR), (Hiscock, 1996) During post-survey analysis of the video details of substrate, species and abundance are recorded on MNCR site and habitat forms for subsequent input to the MNCR database In addition, the ROV data are being made available within SNH via a GIs network. The use of the MNCR methodology for the interpretation of ROV video has proved to be successful in recording conspicuous epibiota The identification of species is obviously limited by the resolution of video and the constraints of remote viewing, however, this technique allows the reliable identification of marine biotopes (MNCR biotope classification, in prep), as reported by Holt at the 2nd SUT Underwater Science Symposium, 1995.
In the immediate future the ROV will be deployed in the monitoring of sites designated under the EU Habitats Directive (Directive 92/43/EEC). This aspect of the survey programme will require the collection of quantitative data The precise nature of the quantitative surveys will depend on the monitoring objectives, but a variety of techniques have been developed elsewhere and will be tested where appropriate