Underwater measurements of fish

Brief description

Photography, stereo-photography, videography, and stereo-videography have become popular sub-tidal sampling techniques. These photographic or video sampling techniques have the advantage of being non-destructive, rapid and repeatable and can record information on the growth and competition of species without destroying the communities. They can also record data across broad spatial scales, which have proven useful in documenting large spatial scale differences between reefs, areas and regions. More recently underwater video has been widely used for recording epibenthic communities on temperate and coral reefs, in rocky shore intertidal areas, soft sediment and deep-sea environments.

The use of underwater photography and video to measure fish

Accurate and precise information on length, density and diversity of fish facilitates estimates of recruitment, fishing intensity and rates of recovery from fishing or other disturbances. Such information is vital for the process of planning management strategies, e.g. the design of Marine Protected Areas (MPA's), to protect vulnerable fish species and their associated habitat. The more accurate and precise the information is, the more easily changes in the populations can be detected leading to informed decisions on their management. When measuring a single fish’s length, accuracy is defined as the ‘closeness’ of the estimate to the actual length while precision is defined as the closeness of repeated measures to this fish’s length.

A review of techniques used for assessing changes in fish assemblages

by Dianne Watson, BSc (Hon's), PhD Candidate (Marine Science), School of Plant Biology,Faculty of Natural and Agricultural Sciences, The University of Western Australia. Contains a short review of current literature on the advantages and disadvantages of currently used sampling techniques and their ability to effectively measure changes in fish assemblages. Where relevant, suggestions for improvements in design and implementation are made.

Underwater video

Stereo camera fish measurements:
Quicktime video
(0.2 MB MOV)
(Apple QuickTime format)



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