rugosity index for habitat complexity

[William Allison]

Hello Caroly and others,

The chain method is beguiling but consider that two very different habitat scales may 
produce the same index value. A section of reef with complex, small-scale topographic 
variation (e.g., a section of Synarea rus) might produce the same "rugosity" value as a 
section with a simpler pattern but larger scale variation (e.g., a few large Porites 
colonies sitting on hardground).

Another approach involves measuring the vertical distance from a horizontal line to 
substratum at intervals along the line - tie a weight to a tape measure. A sensitive 
depth gauge might do the trick too depending on your precision needs. This approach 
doesn't necessarily pick up complexity but might if you played with the intervals used.

You might find the following useful:

McCormick, M. (1994). “Comparison of field methods for measuring surface topography and 
their associations with a tropical reef fish assemblage.” MEPS 112: 87-96.

What you use will depend on your info needs and the time and effort you can or will 
expend.

Good luck, its not a simple question.

Bill
-- 
William (Bill) R. Allison
Coral Reef Research and Management
Ma. Maadheli
Majeedhee Magu
Male 20-03
MALDIVES

ph 960 32 9667 (direct)
fx 960 32 6884 (voice, fax)
e-mail: wallison at dhivehinet.net.mv