• Fisheries and Aquatic Sciences
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• v.1 no.1
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• pp.82-93
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• 1998

Monthly changes of the gonad follicle index (GFI), reproductive cycle, egg-diameter composition, first sexual maturity of the Pacific oyster, Crassostrea gigas, were studied based on the samples which have been collected from the intertidal zone of Poryong west coast of Korea, from January to December, 1996. C. gigas, is dioecious, while a few individuals are alternatively hermaphroditic. Monthly variation of gonad follicle index (GFI) used for determination of spawning period, coincided with the reproductive cycle. GFI increased from April when seawater temperatures gradually increased and reached the maximum in May. And then, GFI sharply decreased from June to September due to spawning. Reproductive cycle of this species can be divided into five successive stages: in females, early active stage (March to April), late active stage (April to May), ripe stage (May to August), partially spawned stage (June to September) and spent/inactive stage (September to February); in males, early active stage (February to March), late active stage (April to May), ripe stage (May to September), partially spawned stage (June to September) and spent/ inactive stage (September to February). The diameter of fully mature eggs are approximately 50um. Spawning occurred from June to September, and two spawning peaks were observed in June and August when the seawater temperature was above $20^{\circ}C$. Percentages of the first sexual maturity of males of 20.1-25.0 mm in shell height were over $50\%$, while those of females of 25.1-30.0 mm in shell height were over $50\%$. All the males of > 30.1 mm and all the females of ^gt; 35.1 mm completed their first sexual maturity. The results suggest that C. gigas has a protandry phenomenon. Sex ratios of 919 oysters observed were 453 females $(49.29\%)$, 429 males $(46.68\%)$, 16 hermaphrodites $(1.74\%)$, and 21 indeterminate individuals $(2.29\%)$. In age class I, sex ratio of males were $64.00\%$, thus, a higher percentage than that of females. It was noted that $64.00\%$ of the young males (age class I) were more functional than females in age class I, but 2-3 year-old oysters showed higher percentage of females. Percentages of hemaphrodites in 2-3 year classes were relatively higher than those in other year classes. Histological pattern of hermaphrodites can be divided into two types: Type I (hermaphrodite having a number of newly formed developing oocytes on the oogenic tissues within a degenerating spermatogenic follicle after discharge of numerous spermatozoa) and Type II (hermaphrodite having two separate follicles in the same gonad).

• Korean journal of food and cookery science
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• v.12 no.3
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• pp.312-319
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• 1996

Oyster (Crassostrea virginica) and Weakfish (Cynoscion regalis) were stored at 6, 0, -4 and -20$^{\circ}C$ for up to 45 days and examined for changes in microflora. Aerobic plate counts (incubated at 21$^{\circ}C$) were performed at selected times during storage and 495 isolates (255 isolates from oyster and 240 isolates from Weakfish) were randomly selected from the plates during the storage. Before the storage of the fishes, viable counts of oyster were 4.9${\times}$10$\^$5/ CFU/g of meat and those of Weakfish were 1.5${\times}$10$^4$ CFU/cm$^2$of skin. Microflora of oyster before storage, the major isolates identified as Pseudomonas spp. (67%) and Vibrio spp. (20%). Pseudomonas ll1/1V-H and Flavobacterium/Cytophaga were predominant genus in the microflora of oyster during cold storage at 6, 0, -4 and -20$^{\circ}C$. The composition of the microflora of Weakfish before storage, Acinetobacter (40%) and Moraxella (33%) were the major species, with Pseudomonas and Vibrio constituting a small percentage of the total isolates. The microflora shifted to predominantly Pseudomonas spp. during storage at 6. 0 and -4$^{\circ}C$, making up from 60 to 100％ of isolated strains. During frozen storage, the percentage of isolates identified as Mnraxella increased to 40-60% of the total isolates. During cold storage, halophilic bacteria (Pseudomonas lII/IV-H and Vibrio) were predominant in oyster while nonhalophilic bacteria (Pseudomonas III/IV-NH and Moraxella) were predominant in Weakfish. Vibrio spp. were higher in oyster than in Weak fish. Listeria spp. were not isolated but unidentified ${\beta}$-hemolytic bacteria were islolated from both of the fishes during cold storage.

• Korean journal of food and cookery science
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• v.6 no.3 s.12
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• pp.43-50
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• 1990

Distribution of amino acids and related compounds in the muscle extract of seven species of right-eye flounder (spotted halibut, slime flounder, marbled sole, sand flounder, stone flounder, frog fleunder and bastard halibut) were studied. The effect of heat treatment on quantitative change in the composition of amino acids and related compounds in the extract of sand fleunder muscle was also investigated since the sand flounder has much Ex-nitrogen in the extract of the muscle. The content of crude protein and that of pure protein were in the range of $17.54{\sim}19.99%$ and $15.63{\sim}17.95%$, respectively. Among the extracts of the seven fish muscle, stone flounder showed the highest content of Ex-nitrogen(2.12%). In the muscle extracts of the seven fish taurine was abundantly contained $(29.4{\sim}56.9%)$, and followed alanine $(6.6{\sim}10.4%)$ and glycine $(1.6{\sim}16.7%)$. The compositions of amino acids and related compounds were characterized by the existence of phosphoethanolamine, ${\alpha}-aminoadipic\;acid$, DL-allocystathionine, ethanolamine and ornithine. The experiments on amino acids and related compounds of the muscle extract of sand flounder with reference to heating time and temperature were resulted in that the amount of taurine, tyrosine, leucine and alanine were increased with the heating time at $100^{\circ}C$, whereas that of lysine, histidine, ${\alpha}-aminoadipic\;acid$ and proline were decreased with prolonged heating time. When heating temperature was changed from $90^{\circ}C$ to $130^{\circ}C$ for 60 min, the contents of taurine, alanine and leucine were increased, while that of histidine, lysine and aspartic acid were decreased.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.2
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• pp.278-287
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• 1998

Carotenoids in integument of wild manchurian trout, Brachymystax lenok, and wild and cultured masu salmon Oncohynchus macrostomus, which are all the Korean native cold fresh water fish, were investigated by thin layer chromatography, column chromatography and HPLC. The total carotenoid contents of the wild manchurian trout were $3.72\;mg\%$ which is relatively higher compare to other species of salmonidae. The carotenoids were composed of $36.9\%$ zeaxanthin and $14.7\%$ $\beta-carotene$ as the major compounds, $7.8\%$ triol $7.3\%$ isocryptoxanthin, $5.7\%$ 4-hydroxy echinenone, $4.7\%$ lutein, $4.5\%$ salmoxanthin and $2.2\%$ astaxanthin as minor compounds, and other carotenoids such as canthaxanthin, tunaxanthin A, tunaxanthin B, tunaxanthin C, $\beta-cryptoxanthin$ and $\alpha-cryptoxanthin$ as minute carotenoids. Wild masu salmon contained more total carotenoids than cultured one and the contents were $0.82\;mg\%$ and $0.66\;mg\%$, respectively. The composition of the carotenoids from wild masu salmon were $20.7\%$ xeaxanthin, $17.0\%$ isocryptoxanthin and $15.8\%\;\beta-carotene$ as major compounds, and $6.2\%$ triol, $6.1\%$ 4-hydroxy echinenone, $6.1\%$ salmoxanthin, $5.9\%$ canthaxanthin, $5.8\%$ lutein, $4.9\%$ $\alpha-cryptoxanthin$ and $1.0\%$ astaxanthin as minor compounds. The composition of the carotenoids from cultured masu salmon were $19.7\%$ isocryptoxanthin, $18.0\%$ $\beta-carotene$ and $10.3\%$ zeaxanthin as the major compounds, and $8.9\%\;\beta-cryptoxanthin$, $8.5\%\;\alpha-cryptoxanthin$, $8.0\%$ lutein, $7.6\%$ canthaxanthin, $5.1\%$ triol and $2.0\%$ astaxanthin as minor carotenoids. Based on these data, wild masu salmon contained more zeaxanthin, salmoxanthin and 4-hydroxy echinenone while cultured masu salmon contained more $\alpha-cryptoxanthin$, indicating that carotenoid pigment of masu salmon depends on their living conditions. Unlike wild masu salmon, 4-hydroxy echinenone and salmoxanthin which are the characteristic carotenoids of salmons, were not found in the integument of cultured masu salmon. Unlike manchurian trout, both wild and cultured masu salmon did not contain tunaxanthin A, tunaxanthin B and tunaxanthin C.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.500-507
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• 2016

This study was undertaken to improve the survival and early life growth rates of cold-water fish by culturing rotifer (Brachionus plicatilis) with low-temperature tolerance. The enrichment experiment was carried out at different temperatures and over different time intervals. Cultivation of the rotifer at low temperatures was repeated, with the selected and cultured as the water temperature was gradually lowered from $20^{\circ}C$ to $10^{\circ}C$. Enrichment of the rotifer was completed using A, S, SCV and SCP. Enrichment was carried out after 6, 12 and 24 hours at three different temperatures (10, 15 and $20^{\circ}C$). In the growth experiments, the rotifer increased to approximately triple their original size, from $350{\pm}7.9ind./ml$ to $1,064{\pm}5.7ind./ml$ at $10^{\circ}C$ over 50 days. The fatty acid composition of the four enrichment materials was species-specific, with the highest ratios belonging to eicosapentaenoic acid (EPA, C20:5n-3) and docosahezaenoic acid (DHA, C22:6n-3) in SCP. The fatty acid composition of the rotifers was affected by the enrichment materials. The EPA (% of total fatty acid) was more than 2 % in SCP, which showed a higher ratio than the other enrichment materials. DHA was higher in S reaching 12.40 % at $15^{\circ}C$ for 24 hours. The highest levels of EPA (3.09 %) and DHA (11.65 %) were obtained after the rotifers were enriched with S at $20^{\circ}C$ for 12hours.

• Korean Journal of Veterinary Research
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• v.35 no.2
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• pp.327-336
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• 1995

This study was carried out to develop the animal protein(feed for fry) that was isolated, purified and lyophilized the rumen ciliates from the healthy rumen contents which have $10^5-10^6/g$ ciliates and were discarded in abattoirs. The rumen ciliates are non-pathogenic, anaerobic and the weight of this protozoa is 2% of rumen content. The rumen protozoan and bacterial proteins both have a biological value for rats of 80-81, which is higher than the 72 of brewer's yeasts. Furthermore, the true digestibility and net protein utility of the protozoan protein are 91 and 73, much higher than those of bacterial(74 and 60) or yeast(84 and 60) proteins. The amino acids of rumen protozoa is nutritionally superior than the others. The size of rumen ciliates is $30-200{\times}20-110{\mu}m$ and so we had isolated and purified the rumen ciliates from the rumen contents by the physical methods. The purified rumen protozoa was lyophilized with freezing dryer. The results of this experiment were as follows : 1. Population dynamics of protozoan ciliates in slaughtered rumens; % of samples which small ciliates were predominated was 82.5%(52/63) and that of large ciliates was 17.5%(11/63). 1) predominant species of small ciliates were Entodinium ovinum and E nanellum. 2) predominant species of large ciliates were Epidinium ecaudatum and Diploplastron affine. 2. The lyophilized rumen ciliates which were isolated and purified from 1 kg of rumen content at the pH 6.2-6.8 was about 7.0 gram. 3. The nutrient analysis of lyophilized rqmen ciliates(LRC) was as follows: 1) Proximate analysis of the LRC and the composition of fry feed; moisture 8.05%(below 10.0), protein 35.37%(45), fat 5.39%(4.5), fiber 1.23%(below 2.5), ash 2.25%(below 15.0), Ca 0.26%(below 2.0), P 0.14%(below 1.1), energy 4,608.11(fish meal 5000 cal/g) 2) Amino acids (% in crude protein) of the LRC and the rotifer(Brachionus plicatilis); Arg 5.19%(4.50), His 2.50%(1.55), Ile 5.29%(3.45), Leu 8.11%(5.85), Lys 10.34%(6.15), Met 2.25% (0.85), Phe 5.66%(3.80), Thr 5.14% (3.45), Val 4.18%(3.90), Ala 4.13%(3.35), Asp 13.26%(8.25), Glu 16.62%(9.20), Gly 4.23%(3.10), Pro 3.25%(5.05), Ser 4.85%(3.85), Tyr 5.04%(3.05) 3) Fatty acids(% in fat) of the LRC and the rotifer(biological feed ; Brachionus plicatilis); myristic acid(C14:0) 3.27%(0.3), myristoleic acid(C14:1) 0.83%(-), palmitic acid(C16:0) 39.11% (23.5), palmitoleic acid(C16:1) 2.81%(2.0), stearic acid(C18:0) 9.36%(5.6), oleic acid(C18:1) 25.54%(3.5), linoleic acid(C18:2) 15.05%(32.9), linolenic acid(C18:3) 1.74%(9.8). Judging from the above investigated results, the analytical data of proximate analysis, amino acids, fatty acids of the purified and lyophilized rumen protozoa are reasonable for the feed of freshwater fishes(fry and fingerling). But it was disappointed of our expectation that the crude protein of lyophilized rumen ciliates contains low percentage, it was thought that because of the small ciliates(starch digester) in beef cattle rumens which were administered the concentrated feed, is much difficult to isolate and purify than the large ciliates(fiber digester).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.6
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• pp.509-519
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• 1987

Annual reproductive cycle of the Damselfish, Chromis notatus collected monthly at the four coastal areas around Chejudo, Korea are studied on the bases of histological observations of gonadal tissue and various quantitative variables including gonadosomatic index (GSI), fatness, egg diameter composition and the first maturity. The ovary consisted of a pair of saccular structure with many ovarian sacs. Oogonia proliferated along the germinal epithelium of the ovarian sac. Young oocytes with basophilic cytoplasm showed several nucleoli along the nuclear membrane. When the oocytes reached about $450{\mu}m$ in diameter, nucleus migrate toward the animal pole, nuclear membrane disappeared and most of cytoplasm were filled with yolk materials and oil drops. After ovulation, residual follicle and growing oocytes remaining in the ovarian sacs degenerated. But early young oocytes without follicle layer were not degenerated, and growing continuously till the next year. The testis consisted of a pair of lobular structures in the right and left were united in the posterior seminal vesicle. Cortex of testis was composed of many sperm ducts connected with lobuli. GSI began to increase from March, starting season of longer day length and higher water temperature, and reached the maximum value between June and August. It began to decrease from September with the lowest value appearing between October and February without any evident variation. The annual reproductive cycle could be devided into five successive stage : growing(April to Many), mature(May to August), ripe and spent (June to August) and recovery and resting stage(September to March). The spawning peak occurred from June to August. According to the frequency distribution of egg diameter, Chromis notatus was a polycyclic species to spawn twice or more in a spawning season. Fatness, correlated with gonadal phases, was remarkably decreased by spawning. Percentage of the first maturity . in femate and male fish ranging from 7.0 to 7.9 cm were $50\%$ and from 9.0 to 9.9 cm in total length $100\%$.