Marlo Krisberg has some excellent points.
 
Yes, collectors can put pressure on populations. If the largest specimen is
removed from a tide pool every year, then the species will eventually
diminish because the survivors are all small. This is an example of
artificial selection. I would expect the effects to be especially severe
where the number of collectors is large, or single collectors take large
numbers of specimens. Also where populations are small to begin with, and
in areas that are readily accessible to collectors. In principle, the most
important areas can be surveyed by ecologists and made into preserves where
no one can collect anything. And people will have to content themselves
with photographs and dead shells more often.
 
It is absurd to think that scientists can make thorough surveys of
molluscan faunas without help from amateurs. At least up to a point, the
more eyes study an area, the more species are found. The typical, one-time
ecologic survey will tend to miss MOST of the rare species, and will miss
many species that live in the area only part of the year, or go through a
complex life cycle. The tools chosen by the scientists will affect what
they find: hand-picking, trawling, coring, and dredging all yield different
faunas. If they neglect to break open some rocks, they will find very few
rock-boring bivalves, for instance. The sample size makes a big difference;
two kilograms of sediment may yield more species of microgastropods than
one kilogram.
 
With the samples back in the lab, the scientists typically have a lot of
dead shells and a few live ones. How long have the dead shells been sitting
on the seafloor? Are they modern, did they die out 5 years ago in this
area, or are they a few thousand years old? Not easy to answer in one field
season.
 
Oops, the project funding is running out. The principal investigator
directs his staff to take no more than ten minutes to identify each
specimen. The species count goes down again, and especially the count of
rare and obscure species.
 
Suppose the specimens were held in formalin a bit too long before being
transferred to ethanol. No matter for most of the organisms, but all the
shells are etched, and the smallest ones break at a touch. Oops, no time to
collect another sample.
 
Lack of prior experience can be disastrous. "You mean those things that
looked like used cigarette papers were polychaete tubes? I threw them
out... Sorry. Was it very important?"
 
Well, enough ranting. To make a really thorough list of fauna in a given
area--an absolutely basic, "alpha" task for an ecologic study intended for
environmental management--takes time and many people. I remember when Doug
Shelton's list of Alabama marine shells had less than 500; it now has over
600. Amateurs can help a lot in this process, especially by locating and
identifying rare species and range extensions. Marlo Krisberg is absolutely
right about the problems of sustaining interest among amateurs in these
projects, and only a few amateurs will sustain a strong interest in
scientific problems in the long term. But if we all come out ahead, then so
what? If a club sponsors a solidly identified species list for a given area
and then makes it available for all to use, isn't that a fine contribution?
 
So... Thanks and a tip o' the hat to Marlo, for good work performed without
a thought of reward.
 
Andrew K. Rindsberg
Geological Survey of Alabama