Dear Tom,

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