Effect of Exploitation on the Limpet Lottia gigantea: A Field Study in Baja California (Mexico) and California (U.S.A.)

Abstract

Specimens of Lottia gigantea (Sowerby) from intertidal populations,
\nartisanal catches, and shell middens were obtained from 1985 to 1988 at
\n11 sites along the Pacific coasts of Baja California (Mexico) and California
\n(U.S.A.). A scaled rating system of 0-4 was used to describe the amount of intertidal
\nexploitation associated with visiting patterns of gatherers, accessibility,
\nand site topography. Maximum and mean size of intertidal populations and
\nartisanal catches decreased along a gradient of increasing exploitation. Mean
\nsize was significantly different between catches and the corresponding intertidal
\npopulation. Mean size of specimens in older middens was significantly larger
\nthan in a recent midden. Measurements at the most inaccessible site inmediately
\nafter the exceptional extratropical winter storm that swept the California coast
\non 17-18 January 1988 showed that the storm had removed larger specimens
\napproximating exploitation measuring 1-2 on our scale. Intertidal gathering
\noccurs or has occurred unless it is physically prevented by topography, distance,
\nor some kind of restriction of access. Ecological implications of exploitation
\nwere explored utilizing the conceptual model proposed by Catterall and Poiner
\nfor assessing potential impact of traditional shell gathering on intertidal molluscs.
\nThe model suggests that size at maturity of this species and its pelagic
\nlarval stage may prevent depletion by harvesting.