Mr. Yamaguchi makes a very good point: quite often, the remarkable
resiliance of fast-growing, widely-dispercing species such as C. moneta,
is used as a generalization to condone intensive "harvesting" of
molluscan populations (i've done this myself!!).  The truth is that some
populations are far more vulnerable to commercial pressures than others,
and we should be aware of this, and when asked, should advise whoever
asks our opinion, based upon this knowlege.

Cold and Damp in the Wet, but still great north,
Ross.
>
> I would like to point out that there are specific differences between different molluscs with regard to
> resilience against human exploitation. While weedy species like money cowry can withstand heavy
> losses due to predation by humans or any other agents, slow-growing and late-reproducing species
> like queen conch, giant clams, trochus and so on are vulnerable because their adults or breeding
> individuals are conspicuous and easy-to-be-wiped-out from their specific habitats. Though their
> juveniles are cryptic, if intensive harvesting pressure persisted for several years to remove those
> growing individuals before they could reproduce, the stock is doomed. Replenishment of populations
> by their enormous numbers of planktonic larvae is expected only when some significant abundance
> level of broodstock remained (or is maintained) in natural refugia or protected areas. In conclusion,
> specific and different ecology or life-history strategies would make different outcome for molluscs
> under human pressure.
>
> Masashi Yamaguchi

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