Distribution patterns of Lutjanus fishes (Perciformes: Lutjanidae) in the Ryukyu Islands, Okinawa, Japan, were quantitatively investigated by fish market surveys in Okinawa Island (26° N, 127° E) and Ishigaki Island (24° N, 124° E). At Okinawa and Ishigaki, totals of 296 and 326 ports × days surveys recorded 8,866 and 8,246 individual Lutjanus fishes, respectively, of 19 species. Frequency of occurrence and number landed for some commercial Lutjanus species were different between the two islands during comparison within the same gear type. Five species (e.g., L. fulviflammus, L. gibbus) that were common (>1.0% in frequency of occurrence) at both islands were thought to have main distribution from south of the Ryukyu Islands to around Okinawa Island. Two species (L. decussatus, L. rivulatus) that were common at Ishigaki and not at Okinawa were thought to have main distribution from south of the Ryukyu Islands to around Ishigaki Island. Three species (e.g., L. bengalensis, L. stellatus) that were not common at both islands were thought to have main distribution outside the Ryukyu Islands. The remaining five species (e.g., L. malabaricus, L. vitta) were common at Okinawa but not at Ishigaki, despite the fact they are widely distributed in the area south of the Ryukyu Islands. This distribution pattern looks discontinuous and implies that the environments around Ishigaki Island are not preferable for nursery grounds or adult habitats of these species. Both qualitative (only presence or absence) and quantitative descriptions of the distribution will facilitate understanding of their biogeography.
Quantitative Analysis of Distribution of 
