• Journal of Aquaculture
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• v.20 no.3
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• pp.154-159
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• 2007

Manchurian trout (Brachymystax lenok) is an endangered fish species in East Asia including the Korean peninsula. To establish a method for artificial propagation and to improve our understanding of the reproduction in the species, we have produced recombinant gonadotropins, follicle-stimulating hormone (r-mtFSH) and luteinizing hormone (r-mtLH), which may play central roles in reproductive activities. In the present study, the biological activities of the recombinant hormones were analyzed by gonadosomatic index (GSI), ovarian follicle diameter, and sex steroid levels in mature rainbow trout (Oncorhynchus mykiss). In the 6th day post-injection, FSH-injected fish were slightly decreased in the GSI value, although there were no significant differences among those of control, r-mtFSH, and r-mtLH treatments. Injection of the r-mtFSH increased follicle diameters significantly as compared with those of control- and r-mtLH-injected fish. The plasma steroid levels showed wide differences in the groups at 1, 3, or 6th day post-injection. Despite the variable steroid levels, three individuals receiving either r-mtFSH or r-mtLH showed a great increase in a maturation-inducing steroid, $17{\alpha},20{beta}$-dihydroxy-4-pregnen-3-one, at 3 and 6 days. Taken together, these results suggest that biological efficacies of the recombinant FSH and LH should be further studied in the Manchurian trout.

• Korean Journal of Ichthyology
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• v.25 no.2
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• pp.90-105
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• 2013

This study was performed to find out stomach contents of cold water fish such as Manchurian trout (Brachymystax lenok tsinlingensis) and River salmon (Oncorhynchus masou masou) in the Odae mountain area. Field survey was carried out 3 times by each season from May to October 2012 along the Gyebang stream and the Yangyang-Namdae stream at north-west mountain slope and north-east mountain slope of the Odae mountain area respectively. The result of digestive track analysis showed that food species of Manchurian trout were total individuals of 645 including 5 orders, 23 families, 39 species of benthic macroinvertebrates and 11 taxa of terrestial insects. And each IRI (Index of Relative Importance, %) value of food species by Manchurian trout was terrestial insects 37.0%, Trichoptera 36.4%, Ephemeroptera 20.0%, Diptera 3.9%, Plecoptera 2.7%, and Gordea <0.1%. While the River salmon fed on 1,186 individuals covering 4 orders, 20 families, 33 species of benthic macroinvertebrates and 6 taxa of terrestial insects including arachnid. Also IRI values by River salmon were terrestial insects including arachnid 2.7%, Ephemeroptera 52.9%, Trichoptera 27.9%, Diptera 9.4%, and Plecoptera 7.0% respectively. With these results, we might say that both Manchurian trout and River salmon is carnivorous fish which display the feeding preference to terrestial insects and benthic macroinvertebrates. As a results we could find out that the two kinds of cold water fish preferred similar habitat types and liked same order of food species in same season, however the compositions of food species for Manchurian trout and River salmon were considerably different.

• Development and Reproduction
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• v.12 no.3
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• pp.261-266
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• 2008

In the present study, we investigated in vivo effects of Manchurian trout recombinant gonadotrophin hormone (mt-rGTH) on the induction of maturation in female eel, Anguilla japonica. The brood stock, female eel (450$\pm$50 g) were weekly injected intramuscularly with different doses of 0.1, 1, 10 ${\mu}g\m{\ell}$/fish (mt-rFSH or mt-rLH) for 10 week. The effects of r-mtGTH were analyzed by gonadosomatic index (GSI), ovarian follicle diameter and sex steroid levels. All groups did not exhibit significant differences in the GSI values. Whereas plasma testosterone (T) and estradiol-17$\beta$ (E2) levels did not change significantly in control group, plasma levels of T and E2 by injection of the r-mtFSH or r-mtLH were increased at 2 or 4 week after injection. In addition, injection of the mt-rFSH (1, 10 ${\mu}g/m{\ell}$/fish) or mt-rLH (0.1, 1, 10 ${\mu}g/m{\ell}$/fish) significantly increased follicle diameters comparing to the control group. These results demonstrate that the recombinant hormone may affect early ovary development and maturation in female eel. Taken together, these results suggest that the recombinant Manchurian trout FSH and LH are effective for reproductive activities in female eel.

• 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.

• Korean Journal of Ecology and Environment
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• v.42 no.1
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• pp.58-66
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• 2009

The telemetry of eight adult manchurian trouts (Brachymystax lenok tsinlingensis) in the upper part of the Nakdong River, which is the southern limit of distribution of manchurian trout on the Korean peninsula, was used to examine migration patterns and evaluate characteristics of over-wintering and the spawning season between December, 2007 and May, 2008. Based on the tracking data, the tagged fish showed a limited migration between adjacent pools, moving only up to $8.6m\;day^{-1}$ during the winter season (December to February). Hydraulic conditions of over-wintering pool areas were, ca. 1m depth, slow moving surface water with areas of sand and gravel. The migration of tagged individuals was successful, moving up to $96.2m\;day^{-1}$ during the spawning season. Two tagged individuals (BL4, BL6) exhibited upstream migration, whereas others showed downstream movements. The timing of upstream migration of the two individuals was consistent with an increasing phases of water level and discharge. The fishes migrating toward the down stream moved to the wide pool areas downstream, where they spent the summer season for the growth.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.652-663
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• 2019

The purpose of this study was to conduct ecological health assessments by using the fish communities in the Manchurian trout habitat. Sampling was conducted twice in July and September 2018. In the survey, 1,119 individuals belonging to 16 species and seven families were collected. The dominant species by number was Rhynchocypris kumgangensis and the subdominant species was Zacco koreanus. Korean endemic species represented 73.33% at Geybang Stream and 76.92% at Naerin Stream. Community analysis revealed that the structure of the fish community was unstable by the dominance index 0.63 (±0.09)-0.97 (±0.01), the diversity index 1.63 (±0.23)-0.33 (±0.09), the evenness index 0.79 (±0.06)-0.24 (±0.07) and the richness index 0.67 (±0.14)-1.80(±0.16). According to the analysis of the tolerance guilds, the total individual number of sensitive species was higher than the intermediate and tolerant species. The insectivore species accounted for 65.09-98.56% of the total trophic guilds, which was the highest observed. The value of the QHEI (Qualitative habitat evaluation index) in the Brachymystax lenok tsinlingensis habitat was 119.5 (±0.5)-153.5 (±0.5), indicating an optimal-suboptimal condition. The FAI (Fish assessment index) stream health value was A to B in the study sites. Correlation analysis with FAI and various factors was conducted and a high correlation in QHEI, Brachymystax lenok tsinlingensis individuals, species, individuals, diversity, richness, sensitive species, carnivorous species, insectivorous species, and omnivorous species was found. The similarity analysis was divided into three groups from A to C, based on 56.9%.

• Korean Journal of Environmental Biology
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• v.39 no.1
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• pp.108-118
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• 2021

The purpose of this study was to provide baseline ecological data for the conservation of the Manchurian trout habitat through the investigation of the growth status of Brachymystax lenok tsinlingensis, and Pearson's correlation analysis (PCA) between the B. lenok tsinlingensis population and the use of the land around Gyebangcheon stream. Sampling was conducted twice in July, September, and October 2018. During the July and September surveys, 882 individuals belonging to 13 species from six families were collected. The dominant species was Rhynchocypris kumgangensis and the subdominant species was Zacco koreanus. The total number of B. lenok tsinlingensis collected was 99. The results of the length-weight relationship in the B. lenok tsinlingensis population were analyzed with a regression coefficient b value of 3.1272 and a condition factor (k) value of 0.0006. Therefore, the growth condition of B. lenok tsinlingensis was regarded as fairly good. The QHEI(Qualitative habitat evaluation index) value in the B. lenok tsinlingensis habitat was 119.5(±0.5)-153.5(±0.5), indicating optimal-suboptimal conditions. As a result of the HIS (Habitat suitability index) analysis, it was confirmed that the optimal habitat for B. lenok tsinlingensis was 0.45-0.55m and >1 m in water depth, 0.55-0.65 m s^-1 in water velocity, and boulder in the substrate. The ratio of the land use in this study site was analyzed as 66.26-96.31% for forest and grassland areas, 0.00-23.79% for agricultural areas, 0.00-4.19% for urbanized areas, and 3.69-8.87% for others. Correlation analysis of the number of B. lenok tsinlingensis and various factors revealed statistically significant correlations between QHEI and forest and grassland areas, agricultural areas, and urbanized areas.