Unless you can quantify the area observed the data will always be less useful than transect data. Relative abundances can answer some questions too. However, the best may be timed swims when the observer is trained to maintain a constant speed throughout.

Thanks so much Christopher, any refrences on the method you describe?

Dear Stamatis:

Attached is a list of useful references dealing with visual census methods.

With best wishes,

Ron

Bellwood, D.R. 1988. On the use of visual survey methods for estimating reef fish standing stocks. Fishbyte 6 (1): 14-16.

Bohnsack, J.A. & Bannerot, S.P. 1986. A stationary visual census technique for quantitatively assessing community structure of coral reef fishes. NOAA Technical Report NMFS 41: 1-21.

Christensen, M.S. & Winterbottom, R. 1981. A correction factor for, and its application to, visual censuses of littoral fish. South African Journal of Zoology 16: 73-79.

Jennings, S. & Polunin, N.V.C. 1995. Biased underwater visual census biomass estimates for target-species in tropical reef fisheries. Journal of Fish Bology, 47: 733-736.

Kulbicki, M. & Wantiez, L. 1990. Comparison between fish bycatch from shrimp trawlnet and visual censuses in St. Vincent Bay, New Caledonia. Fishery Bulletin 88: 667-675.

Mallet, D. et al. 2014. Complementarity of rotating video and underwater visual census for assessing species richness, frequency and density of reef fish on coral reef slopes. PLoS ONE 9 (1) e84344: 1-12.

Rochet, M.-J. et al. 2006. Precision and accuracy of fish length measurements obtained with two visual underwater methods. Fishery Bulletin 104 (1): 1-9.

Sale, P.F. & Douglas, W.A. 1981. Precision and accuracy of visual census technique for fish assemblages on coral reef patches. Environmenal Biology of Fishes 6 (3-4): 333-339.

Samoilys, M.A. & Carlos, G. 2000. Determining methods of underwater visual census for estimating the abundance of coral reef fishes. Environmental Biology of Fishes 57: 289-304.

Thresher, R.E. & Gunn, J.S. 1986. Comparative analysis of visual census techniques for highly mobile, reef-associated piscivores (Carangidae). Environmental Biology of Fishes 17 (2): 93-116.

Try stationary visual census at

http://spo.nwr.noaa.gov/tr41.pdf

Thank you Dearest Ron for the refs!

Daniel Brotto thanks - we have tried this in Greece with a Croatian friend; I will think about it more now that you brought it up....

My best regards,

Stam

I used this method with some modifications in my doctorate project

on top of the swim or stay and look methods you can use video cameras. or baited video cameras. google BRUVS.

all methods have inherent biases. it all depends on the research question and the environmental conditions in your site.

the best quantitative methods will always be the ones you can get fish per area.

I agree with Christopher, you will need to quantify your area to get an idea of abundances. If you can count your fin strokes and only swim for a set time (timed swims) as you are counting fish you can get an approximation of the distance covered. Another idea is to drop a weight at the start and end of the survey and then measure the distance between weights. That will require you swimming rather straight though.

I would second Ronald Frickes references above...especially Bohnsack and Bonnererot 1986. That pub is the basis of NOAA NMFS (USA) fisheries-independent scuba diving visual survey and has resulted in a long term data set from which multiple publications have been derived. This visual "cylinder" method has been employed in the Florida Keys reef system and more recently in US states and territories throughout the Pacific.

For a relative abundance metric (without true densities), consider the "roving diver" survey such as that utilized by REEF organization. The quantitative nature of the data is poorer, but the overall quantity of data is much higher given the number of citizen-scientists contributing to the database. Contact Lad Atkins or Christine Semmons:

https://www.researchgate.net/profile/Christy_Pattengill-Semmens

Cheers,

Ian

Hi, some years ago i was involved in a programme where we did a kind of ecological status assessment of the coral reef . We measured fish diversity using a diversity index by recording fish presence and their relative abundance while we were diving (or snorkeling) .

Here are some monitoring protocols that may help you . Good luck ¡¡

http://reefcheck.org/rcca/monitoring_protocol.php

You might also find this paper useful:

Vianna et al (2014) Acoustic Telemetry Validates a Citizen Science Approach for Monitoring Sharks on Coral Reefs

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0095565#pone-0095565-g005

Sarah, Celia, Ian, Charlotte, Eran, Daniel,

Thanks so much - the idea was a citizen science method, the research question is relative abundances and species list with best possible standardization for repeatability. NOT easy I understand.

Lets keep at it.

Stam

There is a huge literature on underwater visual census, and techniques used go all the way from rapid appraisal to detailed, sometimes very focused work. The key thing to figure out is what you want to know: do you want just presence/absence, do you want body size data, do you need all individuals identified down to species level? etc