Wonderful question. Lots of people should join in. There are many descriptions of frequency (locally common--rare in this habitat--moderately rare or common) None of these descriptions is scientifically based over time. O. porphyria, once relatively common, has become somewhat scarce. C. gloria-maris, once rare, only a dozen known specimens, now has had its hiding place revealed.
   This is one area where Tom Rice can help. That is: if it's expensive---it's rare and will show as such in "Rice's Prices". Of course---even that has limits. It may be so rare as not to be offered. Or it may be so common as not to rearn a listing.
   Hope this lights a small---but not always visible---candle in the dark.
   Art

>
> From: Sophie Valtat <[log in to unmask]>
> Date: 2003/06/15 Sun PM 12:17:50 EDT
> 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
>

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