For those of you interested in the dynamics of population fluctuations,
natural selection and related topics, I strongly recommend the following
extremely readable "fictional" narratives by Franklin Russell:
Watchers at the Pond
Searchers at the Gulf
Each is a fictional account of the many lives, their births, journeys,
deaths and rebirths involved in a pond or a gulf.  The books are very
readable (I found them to be riveting, like a good crime novel!).
Even though they are fictional, I think they are better at giving one a
sense of what is actually going on out there than many drier technical
articles.  I'm not saying that the books are filled with literal facts,
but they do give one an awesome sense of the natural dynamics going on
around us all the time.
I'm sure any of you have rad these booms will agree with me. (I notice
there are many available on bibliofind.com).

Nora
Calgary, Alberta
Canada


A Menez wrote:

> Hello
>
> This is an interesting topic with many ramifications. There are many
> reasons for fluctuations in populations. Some are well documented,
> others not. There are certainly numerous reasons that are not known.
> Although populations can be impacted upon, with resultant abundance
> and demographic changes resulting, these changes have to be considered
> on a larger scale.
>
> I would ask whether the populations affected are in limited
> localities, or whether there is a general trend in the species itself.
> Some very localized populations can be radically affected by
> stochastic events, man-made or otherwise (climate, pollution etc).
> Populations can decline over time as a result of an on-going
> perturbation, forcing individuals to 'cling' to an area with the
> available resources (which may now be sub optimal) changing.
> Individual fitness can decrease causing either local extinction or
> long term decrease in abundance.
>
> On a macro scale, is the species declining in all its localities? Are
> larger scale factors operating? These factors may not be evident if
> local populations are considered. Many population changes can be
> adequately described using metapopulation models which consider the
> larger scale effects.
>
> Of very great interest, and ecologically a field of intense recent
> debate, are chaotic models that may describe population changes. These
> require long time series data sets for analysis but there have been
> useful findings using these models.
>
> Remember that communities are not closed. They form parts of a larger
> system. This means that to fully understand communities (which are
> components of the larger system), and which no one purports to do
> anyway, you need to look at the system. And different scalar effects
> operate at these different levels, which is why I said that the scale
> is important.
>
> An interesting topic!
>
> Alex
>
> "Thomas E. Eichhorst" wrote:
>
>> James,
>>
>> "...look at Strombus gigas... look at the Tridacnids...  These
>> species were
>> (and still are) under such high predation..."
>>
>> I assume you mean collection pressures by man as "high predation."
>> Actually, if you really look at S. gigas I bet you will find
>> development and
>> the resultant polution had more to do with its demise than
>> collecting
>> pressures (whether for food, bait, or tourists).  This thread has
>> gone
>> around a number of times on Conch-L and someone always mentions the
>> tons
>> annually harvested in places like Haiti or the Bahamas -- where the
>> S. gigas
>> is still plentiful.  Yet in Florida, where collecting has been
>> banned, and
>> despite attempts to repopulate with "farmed" stock, the population
>> has not
>> come back.  The reasons are probably many and complex; but the
>> bottom line
>> is, a complete halt to collection has not meant a resurgent
>> population.
>>
>> Because large numbers of a shell are or were collected does not
>> equal the
>> reason for its scarcity.  Bob's example of the ubiquitus Cypraea
>> moneta is
>> the best example of this.  Tons of these small cowries were
>> collected in the
>> past and they are still sold by the pound for the tourist trade.
>> Yet this
>> remains a very common shell.  Extinction is far more complex than
>> most
>> people realize and it is often too easy to latch onto a single,
>> "sensible"
>> but unproven reason.
>>
>> I applaud your efforts to look at this issue, but as an old pysch
>> prof used
>> to say, "correlation is not causation."  Mankind (pun fully
>> intended) has
>> certainly developed harvest techniques for just about anything you
>> want to
>> name way beyond what is reasonable.  Left unchecked we can or soon
>> will be
>> able to clean out any given species.  This has only recently become
>> the case
>> with the seas, but ever-vigilant, we strive onward and continue to
>> improve
>> our methods.  I say this to balance off my earlier statements.  I
>> think it
>> would be tough to really point to a seashell species and say, "They
>> were
>> collected into oblivion."  But 50 years from now, that statement may
>> be
>> something like, "As went the passenger pigeon, so went the so-and-so
>>
>> seashell."  But today, I think we should look to the environment we
>> are
>> creating; the effects of which may make over-collecting irrelevant.
>> Yeah, I
>> know about dynamiting the reefs and all of that -- but pressures are
>> on in
>> those areas to halt this practice (effective or not), but who is
>> stopping
>> the sewage, chemicals, fertilizers, silt, garbage, etc from an ever
>> increasing population that either flows into the ocean or is hauled
>> out to
>> sea and dumped.
>>
>> Soapbox just cracked and before it breaks, I'm outta here.  Didn't
>> mean to
>> sound preachy (notice, that is not the same as saying I didn't mean
>> to
>> preach).  Any responses or arguements, please send them to Art Weil.
>>
>> Tom Eichhorst in New Mexico, USA
>