Hi Sophie,

I find this topic fascinating and I must say that I am in agreement with
you.

So many factors need to be considered.
Does preferred habitat impose collecting limitations?
What about efficiency of the collecting method itself?
Rare species become common once a preferred habitat is discovered while
older literature cites it as rare.
Local populations may be scarce one year only to be followed by a
population blooms.
Common species may not be common at a particular location, or perhaps
become rare over time.
This list can go on!

To me, the term "frequency" implies statistical support.
I'd rather see general comments supporting a species "obtainability."
Perhaps I'm being nit-picky here?

I'd love to read more on this topic.

Cheers,

Bob Abela
Tamuning, Guam
http://www.guamcell.net/~babela/bobsguamshells/

-----Original Message-----
From: Conchologists of America List [mailto:[log in to unmask]] On
Behalf Of Sophie Valtat
Sent: Monday, June 16, 2003 2:18 AM
To: [log in to unmask]
Subject: How to evaluate the frequency of a species in an area


Hello,

In some papers I've read information about the frequency (rare, common,
abundant...) of species in an area, let say the infralittoral fringe of
a particular beach.

How is it possible to make such evaluations ? In some papers I've the
feeling it's done with no objective criteria, just the result of the
experience or so.

What would you suggest ?

Thank you in advance,

Sophie