Heavy collecting, even if sustainable, can deplete local populations or, at least, change the population structure. Where harvesting is discriminate (e.g., selective of a particular size class, through imposition of size limits, nature of gear, or hand collecting), it acts as a form of selective pressure that may potentially alter the structure of the population. For example, recently fossilised Queen Conch shells in the West Indies were found by Stager and Chen (1996) to be significantly larger than those currently being harvested, and very large individuals were proportionately fewer in living populations, possibly due to recent overfishing.



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Department of Environment and Heritage