The crab Pugettia quadridens and the starfish Asterina pectinifera are the commonest predators of young sea urchin Strongylocentrotus nudus. The predation of urchins of two sizes (1 cm or 2 cm mean diameter) by these two species was investigated in relation to water temperature (5-20°C) . The crab predated predominantly on the smaller urchins, and the predation was strongly inhibited under low temperatures. The effect of temperature on starfish predation was unclear, but the starfish also preferred the smaller urchins. Thus, the suitable time to release the small urchins seems to be the low temperature season when the crabs become less active.

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The grouper, Epinephelus coioides, larvae were reared in outdoor tanks with nauplii of copepods and/or rotifers, Brachionus rotundiformis as food. Nauplii propagated in tanks consisted mainly of Pseudodiaptomus annandalei and Acartia tsuensis. Gut content was examined for a total of 953 larvae sampled from day 3 to day 10 (day of hatching being day 0) . Grouper larvae successfully started feeding on early stage nauplii even if their abundance was as low as ca. 100 ind./l and showed better survival and growth thereafter compared to those fed with rotifers only. Feeding incidence reached 100% on day 4 when nauplii were available and only on day 9 when rotifers were given alone. Selective feeding ability of larvae seemed to start from day 4 and the larvae thereafter preferred to feed on medium- and large-size nauplii than rotifers. Coastal calanoid copepods of the genera Pseudodiaptomus and Acartia could be reproduced in tanks and their nauplii can be used as food for marine fish larval rearing.

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In order to clarify the metabolic response of carbohydrate to starvation in Japanese pearl oyster, Pinctada fucata martensii, glycogen content and carbohydrate-metabolizing enzyme activities in adductor muscle and internal organ were compared between the fed and the starved shellfish cultured at 25°C for 45 days.
The weights of adductor muscle and internal organ of the fed shellfish negligibly changed, whereas those of the starved shellfish markedly decreased from the 15th day and 8th day of the starvation, respectively. On starvation, the glycogen content of the adductor muscle and internal organ decreased, and the activities of pyruvate kinase of the both tissues, the activities of phosphorylase and phosphofructokinase of adductor muscle also started to decrease from the 8th day and later they were all lower than those of the fed shellfish. However, the fructose-1, 6-bisphosphatase activities in both tissues obtained from either fed or starved shellfish showed no decrease during the experimental period.
These results indicated that starvation might decrease glycolysis and maintain gluconeogensis in the shellfish.

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The ability of bovine lactoferrin (LF) to suppress stress reactions of rainbow trout, Oncorhynchus mykiss, reared at high density was examined. Two test diets containing different amounts of LF (0.04% and 0.4%) were fed at 2% of fish body weight per day (LF at 8 and 80mg/kg body weight/day) to rainbow trout weighing about 30g for 14 days at 14°C. The control group received the same diet but no LF supplemented. The fishes were then kept at densities of 2, 5 and 10 individuals/10l for 2 days without feeding and the blood parameters were measured. The levels of plasma cortisol and glucose in 0.4% LF-supplemented group were lower than those in the control. Increases in the levels of plasma cortisol and glucose were density-dependent in both the control and the 0.04% LF-supplemented groups. The parameters also increased in the group supplemented with 0.4% LF kept at 10 individuals/10l. In case of the groups kept at high density (5 and 10 individuals/10l), changes of values for plasma cortisol and glucose became smaller with the increase of the amount of LF in the diet. The concentrations of K and Zn in plasma of rainbow trout kept at 10 individuals/10l were lower than those at 2 individuals/10l in the control and the LF-supplemented groups. In the fishes kept at high density, the parameters in the control group were lower than in the 0.4% LF-supplemented group. These results suggest that (i) rainbow trout kept at high density incurred considerable stress, and (ii) supplement of LF in the diet reduced the stress of rainbow trout.

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The effectiveness of a variety of fishing baits to attract aquatic animals was statistically estimated adopting the attraction indices a and gr as a preliminary approach to search for possible new attractants for fish feeds. The abalone Haliotis discus, the oriental weatherfish Misgurnus anguillicaudatus and the yellowtail Seriola quinqueradiata were used in the experiments. Water soluble extracts from twelve species of baits distributed over a variety of phyla were examined. Attractivity for abalone was stronger in extracts of limpet>Japanese pilchard>sea cucumber>others. For oriental weatherfish, the order of preference was earth worm>Japanese pilchard>barnacle followed by the others whereas yellowtail preferred Japanese pilchard>silkworm pupa>limpet>others. The efficiency of the extracts of these baits was clearly concentration-dependent. The effective baits common to the three test animals were Japanese pilchard, whiskered velvet shrimp, and sea cockroach although their attractivity varied to some extent depending on the test animals.

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This experiment was conducted to investigate the effect of the meal of a sterile mutant of Ulva pertusa as feed supplement on the growth and physiology of yellowtail, Seriola quinqueradiata. After investigating the adequate ratio of Ulva meal addition to the diet, the growth, feed efficiency, body color and tolerance to low oxygen were compared in yearling and 1-year-old yellowtail fed for a long period with diets containing 0 and 3% Ulva meal.
1) During short-term rearing, the fish fed diets with 3% Ulva meal showed maximum growth and feed efficiency and the performance decreased with further increaseases in the ratio of Ulva meal in the diet.
2) During long-term rearing of yearling yellowtail, the growth was slightly diminished byUlva meal addition, but the feed efficiency, protein efficiency ratio, energy efficiency, apparent protein retention and energy retention were improved, and the excess accumulation of fat was reduced. In addition, the brightness of body color and resistance to streptococcicosis were improved, though differences in tolerance to low oxygen were not found.
3) In the long-term experiment with 1-year-old yellowtail, such the marked improvement were not observed in fish fed the diet containingUlva meal probably as a result of the decreased feeding activity of the fish.

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The dietary value of the rotifer, Brachionus rotundiformis, and the brine shrimp, Artemia sauna, enriched with a blue-green alga, Synechocystis sp. SY-4, was evaluated by feeding them to the larvae of red sea bream, Pagrus major, devil stinger, Inimicus japonicus, and Japanese flounder, Paralichthys olivaceus. Results were compared to those of zooplankton enriched with Nannochloropsis oculata, Euglena gracilis and Chlorella vulgaris K-22, singly or in combination with Synechocystis sp. SY-4.
The survival rate and growth of devil stinger fed on zooplankton enriched with Synechocystis sp. SY-4 was better than those on other diet. The dietary value of rotifer enriched only with Synechocystis sp. SY-4 for the larvae of red sea bream and Japanese flounder was low, but was effectively improved by combination with N. oculata or E. gracilis.

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The nutritive value of a mysid, Arc haenomysis kokuboi for juvenile Japanese flounder, Paralichthys olivaceus was investigated by using two size-groups of juveniles weighing 0.14 (total length, 24mm) and 0.88g (total length, 36mm) . For comparison, fish were fed either live mysids, mysid meal diets or a commercial diet. The mysid meal diets were formulated by using this ingredient to replace fish meal at levels of 80%, 34.6% and 0%.
Juvenile flounder of both sizes showed the best growth when they were fed live mysids during the 14-day feeding period. However, in the smaller size group of fish the live food proved to be better utilized compared to the other diet types. On the other hand, among the three levels of mysid meal in diet, the 34.6% level produced the highest growth followed by the 0% level, indicating that the growth of juvenile flounder was influenced not only by the live mysid but also by the mysid meal diet. The lowest growth observed in fish fed the 80% mysid meal diet was probably due to excessive amount of NaCl contained in the dried meal.
In a corresponding experiment, the changes of DHA and monoene content and the relative taurine content of the whole body of juvenile Japanese flounder after transfer from the commercial diet to live mysids were also investigated. While DHA and taurine contents increased rapidly until the 5th day, monoene levels dropped. The three values approached those of fish fed live mysids for 14 days in the previous experiment.

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Two experiments were conducted to investigate the effect of full-fat soybean as an alternative protein source, and the effect of different feed types and feed additives on reduction of tolerance nitrogen and phosphorus (T-N, T-P) for carp, Cyprinus carpio culture. Two preparations of full-fat soybean feeds, steam and extruded pellets (SP and EP), and three kinds of feed additives, Bacillus toyoi, phytase, and sepiolite (magnesium silicate) were fed to carp. Carp fingerlings (initial body weight of 8.9 and 12.0g) were fed 5 and 7 kinds of experimental diets for 60 days at 23.5 and 23.7°C in Exps. I and II, respectively.
In Exp. I, fish fed the diet containing extruded full-fat soybean showed almost same feed performances as the control diet, suggesting that the test ingredient is a possible alternative protein source for carp, similar to defatted soybean meal. In Exp. II, a 57% reduction of TN was observed in the fish fed low protein EP containing full-fat soybean compared with a commercial diet. Phytase provided to be very effective in SP diet, achieving a drop of over 37% in T-P, compared to the values from usual commercial diets. Apart from this, it was found that sepiolite was an effective binder of the feed and feces as well, preventing leaching into the environmental water. On the other hand, the fish fed EP and B. toyoi supplemented SP enabled a cut in the fecalmass output. These results indicated that utilization of full-fat soybean, EP, and SP with feed additives such as B. toyoi, phytase, and sepiolite, are potential ways for reducing T-N and T-P in carp culture.

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Aquaculture of marine finfish in Korea has been developed very rapidly after establishment of the large-scale artificial seed production technology for flatfish (Paralichthys olivaceus) in 1985 and for black rockfish (Sebastes schlegeli) in 1990s. Recently, twelve hatcheries belonging to National Fisheries Research and Development Agency and 395 private fish farms are engaged in producing artificial seed production for mariculture industries and reinforcement of marine finfish resources. The number of artificial seeds of marine finfish produced by government-established hatcheries appeared to be 2, 810, 000 and those by private farms were 190, 450 in 1995. The produced seeds include several species such as flounder, black rockfish, tiger puffer, yellow puffer, gray mullet, red seabream, black porgy, and rock bream. On the other hand, some hatcheries and farmers also produce crustacean artificial seeds and the number of seeds from both blue crab and prawn reached to be 232, 750, 000 in 1995.
Considering only marine finfish seed production, seed production leans largely upon black rockfish and flatfish, which shows 51.82% and 44.99%, respectively, and thus summed to be 96.8% of total number of the artificially produced seeds. As the production of mariculture industry relies too much on a few species, farmers are confronted with some problems such as disorder of circulation and decline in the price and thus it is necessary to develop seed production technology for other kinds of economically important marine finfish.
The following strategies can be suggested to overcome such problems and to guide future directions for the artificial seed production.
First, as the coastal water temperature in Korea is usually fallen down to 7 to 8°C in winter which is lethal to the warm-water fish, wintering of such fish is a difficult matter in mariculture. Thus, the priority in the development of seed production technology would rather be on the low temperature tolerant species such as sea bass, black porgy, gray mullet, spotty belly greenling, etc.
Second, difficulties of wintering caused by low temperature in mariculture of the warm water fish such as orange spotted grouper, seven banded grouper, kelp grouper, rock bream, tiger puffer, and yellow puffer, can be solved by using warm discharged water from the atomic or steam power plant. The young fish reared up to 200 to 300 g in their body weight at such locations can reach marketable size within a year.
Third, Cheju island, locating at the southernmost region of Korea, has abundant ground water whose water temperature maintains 17°C and thus it can be used as a seed production base. The young fish can be cultivated using ground water until their body weight reaches to about 300 g and then they can be moved to the net-cages which are common in the southern coast of Korea. In this case, they can grow to be marketable size within a year.

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Lipids in muscle are important on factor for carcass quality, but excessive lipid accumulation is a nutritional loss and induces deterioration of carcass quality. Lipid synthesis and lipid mobilization should be wellbalanced. This paper examines the nature of adipose tissue and control of lipid accumulation by an appropriate feeding regime and environmental conditions. Feeding medium chain triglycerides, tea catechin and algae can control lipid levels in cultured fish. Lipid metabolism and the nature of adipose tissue could also be controlled by the daily feeding frequency and water velocity of rearing ponds.

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