Sophie, since nobody seems to have answered you I will share my thoughts
which may spur others who are more expert than I to answer.
Many snails will be very likely to move up or down the rocks during the year
(winter may be different than summer) because of wave action, food
availability, predators, heat stress and many other factors. In the tropics
the snails may not move as much as in more temperate areas.
Sampling is pretty simple using standard sized squares or rings as long as
you record your methods. I'm a microbiologist so we usually use a 10 X 10
CM square. I watched last year as a clam survey was done on the Pacific
Coast and one meter rings were used. The important issue is to collect
enough data so that you have 100 to 200 observations for the species you are
looking at so that you are at the 90% or better confidence interval
statistically. Observing the other species of common algae and animals
(barnacles for example) that also inhabit the rocks and their vertical
location makes your observations more useful. Some questions: Are the
snails distributed differently on the front versus the back of rocks? Do
they like it better on flat surfaces or in cracks? Are there particular
species that eat them (this may limit lower levels of distribution)? Do the
snails like areas where fresh water seeps over the rocks? Do they like
direct sunny areas or shady spots?
I hope this helps. Bert Bartleson, Olympia, WA, USA
-----Original Message-----
From: Conchologists List [mailto:[log in to unmask]] On Behalf Of
Sophie Valtat
Sent: Monday, August 15, 2005 2:34 AM
To: [log in to unmask]
Subject: Technical help for zonation of a rocky shore
Hello,
First of all, un grand merci, to all those who have answered my previous
mail about Mozambique. Thanks to their advise we are now there for almost
two weeks.
I need a technical advise as I'm currently with no litterature.
There is here ba nice rocky shore with a succesion of Littorinidae,
Neritidae... species. I would like to describe the zonation of this
intertidal shore as precisely as possible.
It's rather easy to note the vertical distributin of each species but, if a
species is present from 3.5m to 2m most of the specimens are between 3.1 to
2.5 for example. So it's necessary to make a quantitative measurements.
It's where I need your help.
Could someone be kind enough to explain how technicaly I should do thqt ? I
imagine I have to define squares of 20x20cm for ex count the specimens for
each species in the squares... But how many square should I concider, how to
choose them, what size ?
I would be very grateful to anyone who could help me. Thank you very much in
advance,
Sophie
----------------------------------------------------------------------
[log in to unmask] - a forum for informal discussions on molluscs
To leave this list, click on the following web link:
http://listserv.uga.edu/cgi-bin/wa?SUBED1=conch-l&A=1
Type your email address and name in the appropriate box and
click leave the list.
----------------------------------------------------------------------
----------------------------------------------------------------------
[log in to unmask] - a forum for informal discussions on molluscs
To leave this list, click on the following web link:
http://listserv.uga.edu/cgi-bin/wa?SUBED1=conch-l&A=1
Type your email address and name in the appropriate box and
click leave the list.
----------------------------------------------------------------------
|
