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Eualus biunguis was found at depths of 500-900 m in the East Sea of Korea, with the highest percentage of occurrence (33%) at 800 m. A positive correlation was observed between the number of individuals and depth. The overall sex ratio with depth deviated significantly from the expected 1 : 1, with a predominance of females, ranging from 84.80% to 97.25%. On average, the large males occurred at 600 m, the large females and ovigerous females were found at 800 m. Only non-ovigerous female E. biunguis were parasitized by the bopyrid isopod, Hemiarthrus abdominalis on the abdominal sternum between the first and second pleopods. The number of infested females differed significantly with depth. The relationship between carapace length and body weight in the parasitized and non-parasitized shrimps differed significantly, and the intercept of the non-infested shrimps was higher than that of the infested shrimps. This finding indicates that the parasite H. abdominalis has a negative effect on the growth of E. biunguis. Not only were the ovigerous females observed in relatively shallow depth range of the water, but their distribution depth range was extended to 900 m. The ovary weight of ovigerous E. biunguis increased during the incubation period, suggesting that the females are consecutive breeders, capable of multiple spawning within a single reproductive period. The gonadosomatic indices of the non-ovigerous females and ovigerous females differed significantly with depth. Mean egg size was 0.71 ± 0.09 mm3 in the non-eyed stage and 0.89 ± 0.16 mm3 in the eyed stage. There was no significant relationship between carapace length and egg size in the deep-water dwelling species E. biunguis. [ABSTRACT FROM AUTHOR]

Species composition and abundance of decapod crustaceans were studied in the waters off Geoje Island, located off the southeastern coast of Korea, using a shrimp beam trawl from November 2000 to October 2001. Water temperature above the sea bottom was lowest (<13°C) in March and highest (>25°C) in August. A total of 196,149 individuals of 41 species from 17 families and 3 suborders was observed. Shrimps (Macrura Natantia) accounted for 23 species, hermit crabs (Anomura) and crabs (Brachyura) for 7 and 11 species, respectively. Crangon hakodatei was the most abundant species both in terms of overall number and biomass. Total biomass showed three peaks during the study period. The first peak in January was due to C. hakodatei and Charybdis bimaculata. The second and third peak were due to C. hakodatei and Palaemon gravieri. Cluster analysis, based on monthly abundance data of the 12 dominant species, showed that the species could be separated into three different groups: resident, seasonal, and temporary. The decapod community structure in the study area was predominantly affected by the resident group. [ABSTRACT FROM AUTHOR]