The effects of size-selective harvesting on a sex-changing limpet, Lottia gigantea.
Fenberg, Phillip*,1, Roy, Kaustuv *,2, 1 University of California, San Diego. Section Ecolgy, Behavior, Evolution, La Jolla, CA2 University of California, San Diego. Section Ecolgy, Behavior, Evolution, La Jolla, CA
ABSTRACT- Human harvesting of marine species is nearly always selective for the largest individuals in a population. Size-selective harvesting has been shown to affect the life histories of many fish species, but very little is known about the effect of such harvesting practices on marine invertebrates. The Owl limpet (Lottia gigantea) is a highly exploited intertidal gastropod, and illegal size selective harvesting of this species is rampant along the coast of southern and central California. L. gigantea is particularly susceptible to selective harvesting because it is a protandric hermaphrodite, sequentially changing sex from male to female, with the largest size classes being predominately female. Thus, frequently harvested sites are likely to be preferentially losing females over males. Life history theory predicts that such exploitation should lead males to change sex at smaller sizes and earlier ages. A comparison of sex ratios from frequently harvested sites versus well-protected reserves provides strong support for this hypothesis. Average size at which males of Lottia gigantea change to females is significantly larger within well-protected reserves compared to exploited populations (63 mm versus 45 mm in length). Thus, size-selective illegal harvesting is fundamentally altering aspects of the life history of Lottia gigantea throughout most of its geographic range.
Key words: size-selective harvesting, sex change, Lottia gigantea, gastropod
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