THE PRESENT STATUS OF MARINE CULTURE IN KOREA

Jong Sick Kim *

I. Introduction

A. General information of the Korean peninsula

The Korean peninsula is located between latitudes 33° 6" - 43°N and longitudes 124 11' – 131 50' E. The total population of the Republic of Korea is 42 million and its population density is 423 persons/km².

The climate of ROK is continental rather than oceanic and is characterized by four distinct seasons. The coldest season in winter occurs between January and February when atmospheric temperatures drop to -7 °C, the hottest season occurs between July and August with the temperature rising to 29 °C.

* Junior Researcher on Finfish Culture, National Fisheries Research and Development Agency, 16 2-GA, Namhang-Dong, Yongdo-Gu, Pusan, ROK.

B. Environmental characteristics of the Korean coast

The Korean peninsula is surrounded by the sea on three sides except for the northern part. The surrounding waters can be divided into 3 regions by their environmental characteristics; East, West and South sea.

Information on the environmental characteristics of the sea on its three parts is of great important in order to run successful marine finfish culture. The local water currents is mixed with those of the Pacific ocean in the Korean coastal waters. The water currents and water masses in the Korean coast are mainly influenced by Tsushima warm current, a branch of the Kuroshio current. The characteristics of each coast are as follows:

a. Eastern coast

The water in this area is sharply deepened with rough waves and with submerged rocks and reefs in the bottom. The coastal line is monotonous without any distinct gradient.

In the central part of this coast, the upward Tsushima warm current mixes with the downward Liman cold current from north. This coast is unsuitable for marine finfish culture using floating netcage, except for stocking in tanks land based.

b. Southern coast

The waters have moderate wave action and are much shallower than the eastern coast. This area is archipelagic with many inner bays formed in the coastal area. The current is strongly influenced by the Tsushima current. This coast is therefore adequate for various kinds of aquaculture facilities. Most of the marine finfish culture by netcage is centered in this area.

In spite of this favorable condition overwintering is a major problem in most of this area due to thr considerable drop in water temperature in winter.

c. Western coast

The coast is characterized by numerous islands and complicated seashore. Tidal flats are long and wide due to the large tidal range. Sea water in this area is influenced by the influx of inland water. Therefore, this region is frequently exposed to lowering of salinity especially during rainy season, which makes finfish culture unstable.

The profiles in mean water temperature and currents in the Korean coast are shown in Figures 1 and 2.

B. Marine finfish culture production

With the increasing demand for finfish production and a consumption estimated at 2,676 tons in 1986, finfish culture has played an important role as one of the major protein sources for the Korean people. Total fisheries production from the coastal waters in 1987 was 3,331,825 mt including aquaculture production of 866,063 mt. Among the total aquaculture production of 866,063 mt, finfish culture production accounted for 1.773 mt in 1987.
The aquaculture productions by resource group from 1983 to 1987 are shown in Table 1. The production of finfish culture by main commercial species is shown in Table 2.

Table 1. Mariculture output of major resource groups from 1983 to 1987.

Figure 1. Distribution of mean water temperature over the Korean coastal waters in February and August.

Figure 2. Major water current systems affecting the Korean coastal waters.

Table 2. Mariculture production of major finfish species from 1983 to 1987.

II. Finfish culture in Korea

Marine finfish culture was initiated in 1964 with a pilot-scale netcage culture in of Pohang, Gampo and Samchuek which are located on the eastern coast of Korea.

Before 1975, marine finfish culture was small-scale and experimental. Since then, with the increasing interest in marine finfish culture, an industrial-scale netcage culture system was started in Chungmu area, now the centre for netcage culture of marine finfish in Korea.

Thanks to the high market demand and export price many coastal inhabitants living in this area have invested in netcage culture. At present, the main species of finfish cultured in Korea are: yellow tail, red seabream, rock fish, seabass and flat fish.

A. Site selection criteria

The success of aquaculture is directly dependent on the selection of a suitable location with good environmental conditions. Site selection criteria for finfish culture, though brief, is as follows:

a. Adequate water current velocity

Due to high stocking densities an adequate water velocity is required (10–20 cm/sec.) to wash away the metabolic wastes and residual feeds in order to avoid them to accumulate on the bottom of the culture grounds which would eventually cause it to deteriorate.

b. Long-term optimum temperature

Annual temperature range fluctuates from 2–29 °C in Korea. The optimum water temperature for the growth of fish is between 20°C and 28°C without rapid changes.

Yellow tail (Seriola quinqueradiata)
	Red seabream (Chrysophrys major)
Rock fish (Sebastes schelegeli)
	Sea bass (Lateolabrax japonicus)
Flat fish (Paralichthys olivaceus)

c. Environmental pollution

The suitable site should be located far from polluted areas around industrial complexes and far from red tide occurrences.

d. Avoidance of typhoon damage

Culture facilities should be constructed in areas which are not strongly affected by typhoons, which occur from the end of summer to early autumn.

e. Others

Easy access to the farming areas.

B. Culture facilities

In general, there are two widely used types of culture facilities in marine finfish culture in Korea. One is the netcage culture system, and the other a land based tank system.

a. Netcage culture system

The netcage culture system is divided into two kinds of facilities: the floating system and the sinking system, as shown in Figure 3 and Figure 4. The arrangement of floating net cages for yellowtail culture is shown in Figure 5. Floating netcages for yellowtail, red seabream, rock fish, and seabass are widely disseminated in the Korean southern coast. However, the sinking system is not yet widely adopted in Korea; it is still at the small-scale experimental stage.

b. Mariculture on land based system

Land based systems are used for overwintering and rearing the fingerlings and are also widely used for rearing flat fish.

C. Seedlings

a. Collection of natural seeds

The culture of most species of marine finfish still depends largely on natural seeds collected from the sea. Among the marine finfish species cultured in Korea, yellowtail is the main species. Provision of yellowtail seeds depends much on wild capture. The fry are harvested by fisherman with hand nets during early May to late June and their length is about 30–70 mm.

Figure 3. Floating netcage system.

Figure 4. Submerged netcage system.

Figure 5. Arrangement of floating netcages for yellowtail culture.

b. Artificial seed production

At present, the main species for artificial seed production are flat fish, red seabream, and rock fish. The production of flat fish seeds is more popular compared to the other species. The brief procedure of artificial seedling production of marine fish in Korea is as follows:

1. Mass culture of fry feeding organisms.

2. Breeding of broodstock.

3. Spawning and hatching.

4. Rearing of fry.

5. Rearing of fingerling.

D. Culture management

From the management point of view feeding, disease control, and culture facilities are very important. Optimum density and efficient feeding are the important factors in keeping the environment clean and securing high production levels.

a. Preparation of feeds

Most fishes cultured in Korea are fed with fresh fish meat. Marine fishes widely used for feeding are anchovy, jackmackerel, mackerel, sardine, sand lance, etc.

b. Disease prevention and environment pollution

As culture grounds becomes old, diseases are more likely to occur. Fish cultured at high densities can easly become infected. Fish farmers should concentrate their efforts on keeping fish healthy rather than on increasing culture densities in order to obtain higher productivity.