Improved methods for visual and photographic benthic surveys

As funding for field work becomes more competitive, it is increasingly important to produce cost effective quantitative results using calibrated methods. Much effort is devoted to visual and photographic surveys which are routinely employed to determine the density and distribution of animals or other organisms, the type and abundance of biological ground cover, and geological features near or on the ocean bottom. A number of techniques have been developed for estimating the scale of the study site and the size of individual specimens so that the observations can produce quantitative data for numerical analyses and comparative studies. This paper will review some of the more commonly employed methods and will present recently-developed, laser-based approaches to quantify visual and photographic images. The techniques to be discussed involve the projection of small light spots as fiducials onto the surface to be surveyed, so that the observer or camera can record absolute scale information. Demonstrated applications and proposed methods will be described.