A short note on a euphausiid, Euphausia pacifica, an important food source to demersal fishes in Uljin area, the eastern coast of Korea.

Gut contents of two species of demersal fishes, Pleurogrammus azonus and Dasycottus steiger were examined to understand the importance of a euphausiid, Euphausia pacifica as prey of demersal fishes at coastal waters off Uljin, the eastem Korea where aggregations of large amounts of the euphausiids were found. Euphausiids were significantly important food source to the species of fishes examined. All of the stomachs of P. azonus examined contained euphausiids (% of a food item frequency occurred, F = 100%) in March and June 2003. Individual numbers of euphusiids in the guts ranged from 10 to 540 individuals per gut. Percents of individual number of food item were 99.60 and 99.96 for euphausiids in March and June 2003, respectively The guts of D. steiger also frequently contained euphausiids (F = 86.67 and 79.20% in October 2002 and June 2003, respectively), while amphipods (F = 36.67% and 16.17%,) and other fishes (F = 33.33% and 45.80%) were also often observed. Pleurogrammus azonus preferred larger euphausiids with size range 16.9-28.4 mm, while the range of euphausiids distributed in the ambient water column was much broader (from eggs to adults).

Distribution of a pelagic tunicate, Salpa fusiformis in warm surface current of the eastern Korean waters and its impingement on cooling water intakes of Uljin nuclear power plant.

Impingement of a large amount of gelatinous plankton, Salpa fusiformis on the seawater intake system-screens in a nuclear power plant at Uljin was firstly recorded on 18th June 2003. Whole amount of the clogged animals was estimated were presumptively at 295 tons and the shortage of cooling seawater supply by the animal clogging caused 38% of decrease in generation capability of the power plant. Zooplankton collection with a multiple towing net during the day and at night from 5 to 6 June 2003 included various gelatinous zooplanktons known to be warm water species such as salps and siphonophores. Comparatively larger species, Salpa fusiformis occupied 25.4% in individual density among the gelatinous plankton and showed surface distribution in the depth shallower than thermocline, performing little diel vertical migration. Temperature, salinity and satellite data also showed warm surface current predominated over the southern coastal region near the power plant in June. The results suggested that warm surface current occasionally extended into the neritic region may transfer S. fusiformis, to the waters off the power plant. The environmental factors and their relation to ecobiology of the large quantity of salpa population that are being sucked into the intake channel of the power plant are discussed.