Lepophidium microlepis ranges from Baja California to Peru, a distribution shared with L. negropinna and L. pardale. Unlike its more shallow-dwelling congeners, L. microlepis exhibits marked latitudinal variation in meristic and morphometric characters and
in certain features of pigmentation. Three well marked subspecies are defined, two of which, L. microlepis hubbsi and L. microlepis inca, are described as new. The isolating mechanisms involve the fact that adults of microlepis occur in cold waters of the deep shelf
and upper slope while the larvae require warm surface waters as do all species of Lepophidium. Unfavorable surface currents which move larvae offshore, surface temperature and its annual variation, poleward-flowing undercurrents, and physiographic features of the Continental Shelf itself
are all discussed as factors in maintaining stock isolation of one or all of the subspecies. Surface currents are judged to be most important in isolating microlepis from hubbsi. Reasons for the isolation of hubbsi and inca are less clear but probably involve
the marked difference in surface temperatures between the range of the two as well as surface currents and possibly the Peru-Chile Undercurrent.
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