DISTRIBUTION AND REPRODUCTIVE PATTERN OF DEEP-WATER CRANGONID SHRIMPS IN THE EAST SEA OF KOREA

In this study, we investigated the distribution patterns of two crangonid shrimps in the East Sea of Korea. The distributions of the shrimps differed significantly with depth. Neocrangon communis (Rathbun, 1899) was found at depths of 300-900 m throughout the survey area, with the greatest number of individuals at 300 m depth in the total sampling period. Argis toyamaensis (Yokoya, 1933) occurred over the entire depth range (300-900 m), with the greatest numbers of individuals at 800 m depth in the total sampling period. On average, the large females and ovigerous females of N. communis and A. toyamaensis were mainly distributed in shallow waters (300-400 m depth). The ovigerous females of the shallow-dwelling species N. communis mainly occurred in shallow waters. The deep-dwelling species, A. toyamaensis, differed slightly from N. communis in terms of the distribution of its ovigerous females. The ovigerous females of A. toyamaensis were widely distributed at all depths, and the gonadosomatic index did not differ significantly with depth. However, the deep-dwelling species, A. toyamaensis, had larger eggs than had N. communis. We suggest that life-history strategies are determined by many environmental factors, including depth, in the deep-water environment. The optimal distribution depths of these two species were closely related to their reproductive strategies.