Compensating for length biases in underwater visual census of fishes using stereo video measurements
Tom Davis A C , David Harasti B and Stephen D. A. Smith A
+ Author Affiliations
- Author Affiliations
A National Marine Science Centre, Southern Cross University, PO Box 4321, Coffs Harbour, NSW 2450, Australia.
B Fisheries Research, Marine Ecosystems, NSW Department of Primary Industries, Locked Bag 800, Nelson Bay, NSW 2315, Australia.
C Corresponding author. Email: davistn1@gmail.com
Marine and Freshwater Research 66(3) 286-291 https://doi.org/10.1071/MF14076
Submitted: 15 March 2014 Accepted: 31 July 2014 Published: 23 October 2014
Abstract
Underwater visual census (UVC) is a widely used technique for estimating species richness, abundance, and lengths of reef fishes. The technique has the advantage of being non-destructive, and can therefore be used for monitoring in marine protected areas. However, acquisition of robust data using UVC is reliant on the ability of individual divers to accurately identify fish, and estimate their lengths. Both of these variables can be affected by observer bias, which may also differ among observers. This study examines a technique with the potential to quantify and correct for observer bias in individual divers. We used simultaneous diver-operated stereo video and underwater visual census surveys, and compared the results to generate diver-specific correction factors. These correction factors were subsequently applied in additional estimates of fish length, with measurable improvement in the accuracy of the data.
Additional keywords: accuracy, observer bias, rocky reefs.
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