ABSTRACT
To investigate the genetic structure of the purplish Washington clam population, Saxidomus purpuratus Sowerby, in Korea. A portion of mitochondrial COI gene sequences (605 bp) for phylogenetic comparison was determined. Sequence analysis of 62 individuals collected from six regions revealed 13 haplotypes. Phylogenetic analysis using Phylogeny Inference Package (PHYLIP) subdivided the purplish Washington clam into two clades (termed clade A and B), weak supported groups (<65 of bootstrap value). This haplotype subdivision was also in accordance with geographic separation; one each at Masan, Yeosu, Samcheonpo, Jubyeon and Geojedo, and the other at Sineju. Population genetic analysis subdivided these two population groups with a geographic distance (d=0.431, p=0.379). Furthermore, in the Sineju population, the maximum sequence divergence (2.67%) and minimum nucleotide diversity (0.0012426) were shown in which might be reflective of a relatively small population size and the geographical isolation of the population as compared with other populations. However, a very high migration rate (Nm=59.62-infinite) and a very low level of geographic distance (FST=-0.076-0.055) were noted to exist among the South and East Sea populations, suggesting that individuals between populations should show a significantly active genetic mixing and migration regardless of geography. These findings allowed us to conclude that the purplish Washington clam populations occurring in the South and East Sea were formed with randomly dispersed individuals.
ABSTRACT
Effects of ocean climate changes on the population structure and abundance of Pacific saury (Cololabis sira) were investigated on the basis of climate indices, sea surface temperature (SST) anomalies, catch and body size information from the Tsushima Warm Current (TWC) region (Yellow Sea, East China Sea and East/Japan Sea) during the period 1950-2010. It is suggested that oceanic regime shifts in the early 1970s, late 1980s and late 1990s occurred in the TWC region in winter, but the regime shifts in the mid-1970s and in the late 1980s were not evident in the spring SST anomaly series. The abundance and body size of Pacific saury fluctuated in association with the winter oceanic changes in the TWC region. The catch rates and abundance of large size saury were far bellow average during their northward migrations in the TWC region in the years with abnormally cool winters (e.g., 1963, 1970, 1977, 1981-1989 and 2006) and above average in the years with warm winters. These patterns demonstrate decadal-scale variations together with large inter-annual fluctuations in the structure and abundance of Pacific saury in association with the climatic-oceanic changes. These results, along with an alternation of dominant pelagic fish species, indicate the status of the saury population in the TWC region is in good condition, similar to that in the Kuroshio-Oyashio Current (KOC) region during the warm regime after the late 1980s climate regime shift.