Sightability as an indicator of bias in manta tow surveys ofAcanthaster planci: comment on Fernandes, Marsh, Moran and Sinclair

✍ Scribed by G. De'ath

• Publisher: Springer
• Year: 1992
• Tongue: English
• Weight: 266 KB
• Volume: 11
• Category: Article
• ISSN: 0722-4028
• DOI: 10.1007/bf00357433

✦ Synopsis

The manta tow technique has been extensively used in broadscale surveys of A.planci on the Great Barrier Reef (Kenchington 1984;Moran et al. 1990). Frequently the unit of interest is an entire reef, or large part thereof, although Kenchington and Morton (1976) indicated that manta tow counts could be calibrated to give accurate estimates of scuba counts over smaller reef areas. This was experimentally tested by Fernandes et al. (1990) using the concept of sightability and they conclude that "The manta tow technique obviously cannot provide accurate estimates of the absolute number of starfish". The aims of this note are: (i) to indicate logical flaws in Fernandes et al. (1990) which invalidate the above conclusion; (ii) to provide a survey data set with similar characteristics to the data of Fernandes et aL (1990) which demonstrates that manta tow counts can provide accurate estimates of scuba counts; (iii) to suggest a more appropriate perspective than sightability to address questions of bias, precision and accuracy of survey data.