• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.47 no.5
• /
• pp.654-658
• /
• 2014

We report the first identification of a spawning ground of the blackfin flounder Glyptocephlaus stelleri near the Wangdol-cho sea mountains, located in the southern East Sea. Eggs and larval fish of G. stelleri were collected during April and June, 2014, when an abundance of eggs was found in the southern area of Wangdol-cho. Our findings suggest that G. stelleri prefers to spawn in the vicinity of the off-shore sea mountains, where the temperature is between 10 and $12^{\circ}C$ and the water depth is 100 m, rather than inshore.

• Korean Journal of Ichthyology
• /
• v.28 no.3
• /
• pp.164-174
• /
• 2016

Tanakius kitaharae and Glyptocephalus stelleri, belonging to the family Pleuronectidae, were very similar in external morphology not only during adult periods, but also during larval periods. In this study, we compared larval development and growth of the two pleuronectids species in detail. Fifty-eight specimens of T. kitaharae larvae and five specimens of G. stelleri larvae were collected from the East Sea, southern Korean Strait, and the adjacent waters of Jeju Island during 2014~2016, and were identified using morphological and molecular markers. Flexion larvae of T. kitaharae (10.23~16.77 mm total length, TL) and G. stelleri (14.33 mm TL) were similar in morphometrics, but can be distinguished by the melanophores in the fin membranes (present in the former vs. absent in the latter), and the melanophores at posterior margin of shoulder girdle (absent in the former vs. present in the latter). Postflexion larvae of T. kitaharae (17.12~24.92 mm TL) and G. stelleri (27.71~32.95 mm TL) differed in the number of melanophores on the mid-lateral caudal region (two in the former vs. five in the latter), and that on the dorsal and anal fin pterygiophores (five or six in the former vs. one row in the latter). Tanakius kitaharae and G. stelleri larvae differed in size at the beginning of metamorphosis. The left eye of T. kitaharae larvae between 23.13~24.92 mm TL reached the dorsal margin of the head while that of G. stelleri larvae between 38.66~42.67 mm TL did not reached yet.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.52 no.4
• /
• pp.430-436
• /
• 2019

The diet of Glyptocephalus stelleri was studied using 475 specimens collected in the coastal waters of the East Sea of Korea. The specimens ranged from 6.8 to 43.4 cm in total length (TL). G. stelleri was a crustacean feeder that consumed mainly euphausiids [percent index of relative importance (%IRI)=63.7%]. Polychaetes were the second largest prey component. The diet also included small quantities of bivalves, copepods, amphipods and shrimps. Individuals smaller than 15 cm TL fed mainly on euphausiids. The proportion of euphausiids decreased as body size increased, whereas the consumption of polychaetes increased gradually.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.48 no.4
• /
• pp.483-488
• /
• 2015

We studied oocyte steroidogenesis in the blackfin flounder Glyptocephalus stelleri as a region-specific species, in the East Sea of Korea during the spawning season. Maturing oocytes (0.76, 0.82, 0.88, and 0.91 mm in oocyte diameter) were incubated in vitro in the presence of [$^3H$] $17{\alpha}$-hydroxyprogesterone ($[^3H]17{\alpha}$-OHP) as a precursor. Steroid metabolites were extracted from the incubated medium and oocytes, and the extracts were separated and identified by thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC) and gas chromatographymass spectrometry (GC/MS). The major metabolites produced from $[^3H]17{\alpha}$-OHP were androgens [androstenedione (A4) and testosterone (T)] and estrogens [$17{\beta}$-estradiol (E2) and estrone (E1)] and progestins [$17{\alpha},20{\alpha}$-dihydroxy-4-pregen-3-one ($17{\alpha}20{\alpha}P$) and $17{\alpha}20{\beta}$-dihydroxy-4-pregnen-3-one ($17{\alpha}20{\beta}P$)] in maturing oocytes. The metabolic rate of $17{\alpha}20{\beta}$ was elevated (29.04%) in oocytes measuring 0.88 mm (nucleus migration stage following the induction of germinal vesicle breakdown), but was very low in oocytes measuring 0.76, 0.82, and 0.91 mm (0.42, 0.67, and 2.62%, respectively). From these results, we suggest that $17{\alpha}20{\beta}P$ acts as a maturation-inducing steroid in the blackfin flounder.

• Journal of Marine Life Science
• /
• v.7 no.1
• /
• pp.37-44
• /
• 2022

This study was performed to obtain information on the sex ratio, size at sexual group maturity, and main spawning period of Glyptocephalus stelleri. The sex ratio (female: male) was 1:0.54 (n=189:103, 64.7% female), and the frequency of females in the population tended to increase with total length. The oocyte development pattern was group synchronous development, in which oocyte groups at different stages were identified within the same ovary. The total length at 50% sexual group maturity was analyzed using a logistic regression model, and was determined to be 28.51 (female) and 30.49 cm (male). The gonadosomatic index (GSI) displayed the highest values in April (female) and March (male), and the main spawning period being in April to May.

• Korean Journal of Ichthyology
• /
• v.20 no.4
• /
• pp.263-271
• /
• 2008

The maturity and spawning of Korean flounder Glyptocephalus stelleri were investigated using samples randomly collected in the East Sea of Korea from May 2005 to September 2008. Gonadosomatic index began to increase in December and reached a maximum between March and May. After spawning it began to decrease from June. The spawning period was March to June, and the main spawning period was April to May. Annual reproductive cycles of this species can be divided into four successive stages; immature stage (July~November), maturing stage (December~February), mature stage (March~April) and spent stage (May~June). The fecundity ranged from 15,146 eggs at 24.1 cm (TL) to 101,491 eggs at 38.1 cm (TL). The relationship between total length (TL) and fecundity (F) can be expressed as $F=0.0004TL^{3.449}$ ($R^2=0.663$), with F increasing with TL. The TL at 50% group maturity ($TL_{50%}$) was estimated to be 25.6 cm.

• Fisheries and Aquatic Sciences
• /
• v.15 no.2
• /
• pp.169-176
• /
• 2012

Age and growth of Glyptocephalus stelleri in the East Sea of Korea were determined, from monthly samples of commercial catches, caught by the eastern sea Danish seine fishery in 2007. The annuli of G. stelleri are formed once a year, with the boundary between opaque and translucent zones forming in September. Relationships between total length (TL) and total weight (TW) were $TW=0.002TL^{3.392}$ ($r^2=0.970$) for females and $TW=0.002TL^{3.335}$ ($r^2=0.961$) for males. TLs at annuli formation in otoliths were back-calculated from the otolith-length relationship and were adjusted to von Bertalanffy growth curves to $L_t=39.71(1-{\exp}^{(-0.152(t+1.156))})$ for females and $L_t=32.16(1-{\exp}^{(-0.213(t+0.879))})$ for males. From the age of 3 years, females grew faster than males (P<0.05).

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.52 no.4
• /
• pp.394-402
• /
• 2016

In order to manage and rebuild fishery resources, the fishing effort should be controlled effectively. Especially in the setting up of the proper level of fishing efforts, economic standards as well as biological standards must be carefully considered to promote the sustainable and economically viable development of fisheries. This study aimed to analyze the optimal economic fishing effort ($E_{MEY}$) as the most economically efficient one for the Eastern Sea Danish seine fisheries. The results showed that the optimal economic fishing effort ($E_{MEY}$) of Eastern Sea Danish seine fisheries for blackfin flounder should be reduced by about 27%. That is, reducing fishing efforts up to the level of $E_{MEY}$ could lead to the reduction of fishing costs, thereby resulting in the increased fishing profits.

• Korean Journal of Ichthyology
• /
• v.23 no.3
• /
• pp.187-197
• /
• 2011

Fish species composition and size frequency distribution of major species were analyzed using seasonal samples collected by an otter trawl in the coastal water off Uljin and Hupo in 2002. Fish collected during the study were 20 species, 1,927 individuals and 53,969 g off Uljin, and 23 species, 2,762 individuals and 146,550 g off Hupo. Liparis tessellatus, Glyptocephalus stelleri and Cleisthenes pinetorum were predominated in abundance, and these 3 species were accounted for 70.9% in the number of individuals and 83.8% in biomass off Uljin, and 90.3% and 70.9% off Hupo, respectively. In the Korean coastal water of the East Sea, the migrating pelagic fish were predominated in catch by set net or gill net, and species composition varied greatly by season. Meanwhile, the fish collected by an otter trawl in the coastal water off Uljin and Hupo were dominated by the resident demersal fishes and did not show any clear seasonal trend in species composition. Collected G. stelleri and C. pinetorum were mainly composed of young fish, and size data as depth indicated that they moved into deeper shelf as they grew.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.48 no.4
• /
• pp.415-427
• /
• 2012

Seasonal variation in species composition and abundance of fish assemblage in the north coast (NC: Ayajin) and central coast (CC: Hupo) of the East Sea were calculated using samples collected by trammel net during 2011-2012. A total of 20 species from NC and 17 species from CC were collected. Of the fishes collected, the dominant fish species were Glyptocephalus stelleri and Careproctus rastrinus in the NC, and Dasycottus setiger and G. stelleri in the CC. These 2 fishes accounted for 71.7% and 81.0% of the total number of individuals collected in the NC and CC, respectively. The number of fish species, number of individuals, biomass and species diversity indices fluctuated with the seasons. The cluster analysis and non-metric multidimensional scaling (MDS) based on Bray-Curtis similarity revealed that the fish assemblages classified into north and central groups. Analysis of similarity percentages of species contributions (SIMPER) indicated that most individual of G. stelleri and Gadus macrocephalus contributed to north group, and D. setiger and G. stelleri in central group, whereas 15 species contributed to 90% of the dissimilarity.