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

• Journal of the korean society of oceanography
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• v.32 no.4
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• pp.202-207
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• 1997

Species composition and abundance of fish larvae were studied from May 1988 through August 1989 in the Han River Estuary and adjacent Kyunggi Bay, Korea. Of 23 taxa identified, Coilia nasus, llisha elongata, and Cyprinidae spp. were dominated. Maximum density (3,5771/1,000m)$^3$ occurred in August 1988 and minimum (3/1,m$^3$) in February 1989. O1igo- ormesohaline species dominated during ebb tides while polyhaline species during flood tides. Correspondence analysis revealed that three distinctive species groups; oligohaline species, Coilia nasus, Ilisha elongata and Cyprinidae spp., which dominated at both channels of Kwanghwa Island (stations 1, 2), mesohaline species, Sardinella zunasi and Gobiidae spp., at the mouth of Yeomha Channel (station 3), and polyhaline species, Engraulis japonicus and Syngnathus schlegeli, in the middle of Kyunggi Bay (station 4). Coilia nasus was the most abundant species and reported first time in the study area. Given the species composition and density of fish larvae, the Han River Estuary is considered to be a major spawning and nursery ground for brackish water species such as Coilia nasus, Ilisha elongata and some Cyprinidae spp.

• Journal of Fisheries and Marine Sciences Education
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• v.23 no.4
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• pp.763-771
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• 2011

Development and distribution of Japanese mantis shrimp, Oratosquilla oratoria (De Haan) larvae were investigated in the northwestern water off Incheon. O. oratoria larvae were monthly collected at 15 stations from early June to early October in 2007. Bongo net with 330 and 505 um mesh was deployed in a double once with an oblique tow way. Larval densities were relatively higher in southerner stations in July and in northerner stations in August and September. No larvae were discovered in June. Zoea I and II were not captured during the entire sampling period. Zoea III occurred in July for the first time and were found until September. Thereafter, the proportion of later stages increased. The number of zoeal stages decreased during the summer months and no larvae were found in October. Of zoeal stages, zoea IV was the most abundant in number. Zoeal densities were highest in July and August, particularly at the stations near the coast. O. oratoria larvae may be retained and grow within our study sites without advection to growing areas. Non-occurrence of zoea I and II indicate that they were retained near spawning grounds or near parental burrows. Pattern of larval occurrence was coincided with previous researches conducted in conspecific distribution ranges.

• Korean Journal of Ichthyology
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• v.22 no.1
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• pp.34-40
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• 2010

The reproductive ecology of the goldeye rockfish (Sebastes thompsoni) was examined using 421 specimens collected monthly from January to December 2005 in the coastal waters of Busan, Korea. Specimens ranged in standard length (SL) from 13.8 to 31.8 cm. The gonadosomatic index (GSI) of females was highest in March and decreased until June. In males the GSI was the highest in February after that the values declined. The spawning season lasted from January to June, and the ratio of female to male did not differ significantly ($x^2$-test, p>0.05). The length at first spawning was 16.8cm SL, and the size at 50% maturity was estimated at 20.11 cm SL. All females more than 25 cm SL were sexually mature and the egg diameters were from 0.60 to 1.75 mm. Fecundity (F) ranged from 23,881 to 44,509 eggs, with a mean of 30,937 eggs. The relationship between fecundity and standard length was estimated as F=9.3762 $SL^{1.1662}$ ($R^2$=0.81). The relationship between fecundity and body weight (BW) was estimated as F=184.37 Ln (BW) - 665.09 ($R^2$=0.87).

• Korean Journal of Ichthyology
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• v.10 no.2
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• pp.191-199
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• 1998

The ovary of the spotted flounder Verasper variegatus is a conical bag in shape and is bilateral structure develops lengthily from the posterior of the abdomen to the end of the anal fin. The testis also is bilateral in structure, usually located in small size in the abdomen. In females, the gonadosomatic index (GSI) showed very low from March to July, and then began to increase from August, thereafter reached the maximum in January through out the year. In males, the GSI reached the maximum (1.7) in January through out the year, as seen in females. Compared with the male GSI in other fishes, the maximum GSI of this species were very lower than those of other fishes. According to the distributions of egg diameter in the spawning season, it is assumed that the spotted flounder spawn four times or more in the spawning season. The total length of female and male reached 50% first sexual maturity were 42.0~44.0 and 28.0~30.0cm, respectively and total length of female and male reached 100% maturity were 44.0 and 32.0cm, respectively. The reproductive cycle could be classified into four successive developmental stages: growing stage (August~October), mature stage (November~December), ripe and spent stage (December~February), degenerative and resting stage (March~July).

• The Korean Journal of Malacology
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• v.29 no.4
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• pp.313-323
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• 2013

Gonad development, the reproductive cycle, first sexual maturty and size at 50% of group sexual maturity (the biological minimum size) of Gomphina (Macridiscus) veneriformis were investigated for clams collected from the coastal waters of Donghae City, the East Sea of Korea by histological, and morphometric analysis. Monthly variations of the gonad index showed a pattern similar to that of the reproductive cycle. The reproductive cycle with the gonad developmental stages in female and male G. (M.) veneriformis can be classified into five successive stages: early active stage (December to March), late active stage (March to June), ripe stage (June to July), partially spawned stage (June to August), and spent / inactive stage (September to December). The spawning period continued from June to August, with a peak between July and August when the seawater temperature exceeds $20^{\circ}C$. The percentages of first sexual maturities of female and male clams ranging from 25.1 to 30.0 mm were 56.3% in females and 61.1% in males, and for clams over 30.1 mm shell length, it was 100%. Shell lengths at 50% of group sexual maturity (biological minimum size, $RM_{50}$) were 27.71 mm in females and 26.31 mm in males. Because harvesting clams < 26.31 mm in shell length could potentially cause a drastic reduction in recruitment, a measure indicating a prohibitory fishing size should be taken for adequate fisheries management.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.6
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• pp.888-894
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• 2014

Seventeen specimens of leptocephali [9.8-44.5 mm total length (TL)], of the family Ophichthidae, were collected from southeastern waters off Jeju Island and the Korea-Japan intermediate zone, and identified by means of morphology and genetics. These specimens were identified as belonging to the subfamily Ophichthinae based on various combinations of morphological characters: 211-215 total myomeres; 7 gut swellings; 2 liver lobes connected with the gall bladder on the second lobe; 6-7 postanal pigments present from anus to caudal margin. An analysis of the partial 12S rRNA sequences (849 base pairs) of mitochondrial DNA showed that our specimens must be Ophisurus macrorhynchos because their sequences were concordant with those of the adult O. macrorhynchos (genetic distance = 0.000). Furthermore, their total myomeres were consistent with those of the O. macrorhynchos adult. This is the first time that the morphological characteristics of O. macrorhynchos leptocephali have been described for Korean waters, and we suggest diagnostic characteristics for the genus Ophisurus leptocephali. We hypothesize that one of the spawning grounds of O. macrorhynchos is located in the southeastern part of Jeju Island.

• Fisheries and Aquatic Sciences
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• v.26 no.6
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• pp.380-392
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• 2023

Groupers (Family Epinephelidae) are commonly caught in data-poor small-scale multi-species fisheries for sale on both export and domestic markets. This study presents data on the species composition and size/life-stage structure of Epinephelus spp. groupers caught by small-scale fishers and sold locally in the Indonesian province of South Sulawesi. Data were collected from fishing ports and local markets at 12 sites representing the three seaways around South Sulawesi (Makassar Strait, Flores Sea, Gulf of Bone). Each specimen (n = 3,398) was photographed alongside an object of known length, and total length (TL) was obtained using the Rapid Scaling on Object (RASIO). Of the 23 species identified, four (Epinephelus areolatus, Epinephelus ongus, Epinephelus quoyanus, and Epinephelus fasciatus) collectively comprised 69% of the catch, while the 13 least abundant species contributed less than 5%. The catch was dominated (67%) by the subadult life-stage, with just under 20% in the adult class. Juveniles dominated the catch of Epinephelus fuscoguttatus, a valuable export commodity. Observations of early maturity as well as the sizeable gap between length at first capture (Lc) and length at first maturity (Lm) indicate recruitment overfishing of most species, with the notable exception of Epinephelus rivulatus. The proportion of adult fish was low (≈5%-30%) for the twelve most abundant species (E. areolatus, E. ongus, Epinephelus quoyanus, E. fasciatus, Epinephelus coioides, Epinephelus faveatus, Epinephelus sexfasciatus, Epinephelus maculatus, Epinephelus bleekeri, Epinephelus corallicola, E. fuscoguttatus, Epinephelus polyphekadion). For two moderately abundant species (E. faveatus and E. malabaricus), TL < Lm for all specimens. The limited data available indicate spawning ratio is lower than reported from deep-water fisheries of E. areolatus and E. coioides. The results call for targeted research to fill knowledge gaps regarding the biology and ecology of groupers exploited mainly for domestic markets; highlight the need for species-level data to inform management policies such as minimum legal size regulations; and can contribute towards species-level status assessments.

• Korean Journal of Ichthyology
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• v.3 no.1
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• pp.1-10
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• 1991

Spawning behavior and development of eggs and larvae of Mugilogobius abei were observed in the laboratory at Pusan, Korea. The adult male of Mugilogobius abei was observed making nest-like spawning-bed to lay eggs and showing territorial and courtship behaviors. The eggs were transparent and spherical in shape, measuring 0.40~0.50 mm in diameter. They have a bundle of adhesive filaments at their basal end and a cluster of small oil globules. The eggs became ellipsoid shape after the insemination and measured about 0.93~0.96 mm on the long axis. Hatching began about 110 hours after fertilization at water temperature of $24.5{\sim}25.5^{\circ}C$. The newly hatched larvae were 2.04~2.10 mm in total length, with 24~25(8~9+16) myomeres. Many melanophore and guanophore are distributed on eye cups, gas bladder, optic vesicle and the caudal region. Four days after hatching the yolk and oil-globule were completely absorbed and the larvae attained a total length 2.20~2.35 mm. The larvae swam actively in the aquarium and start to practice feeding on the rotifer. Twelve days after hatching, the larvae averaged 3.20 mm in TL and the caudal notochord flex at $45^{\circ}$. Rudimental second dorsal, anal, caudal and ventral fins are also formed. The larvae attained 10.40~10.80 mm in TL, 35 days after hatching, are found to start the bottom-life after having completely formed first dorsal and ventral fins. The larvae reached the juvenile stage at 50~60 days after hatching and attained 15.37~20.25 mm in TL. At this period all scales appeared on the body.

• The Korean Journal of Malacology
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• v.21 no.2 s.34
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• pp.121-132
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• 2005

We investigated the reproductive cycle with gonad developmental phases of Sinonovacula constricta by histological observations, and seasonal changes in biochemical component of the adductor muscle, visceral mass, foot muscle and mantle were studied by biochemical analysis, from January to December, 2004. The reproductive cycle of this species can be classifed into five successive stages: early active stage (March to May), late active stage (May to July), ripe stage (July to September), partially spawned stage (August to October) and spentfinactive stage (October to March). Total protein content was the highest in the following order: adductor muscle, visceral mass, foot muscle, and mantle. Except for mantle, it was generally higher during the ripe and spawning stages, while lower during the spent/inactive stage. There were positive correlations in total protein contents among adductor muscle, foot muscle, and visceral mass. However, the correlations were not statistically significant. Total lipid content was the highest in the visceral mass; it was more than 5 or 6-fold higher than those in the adductor muscle, foot muscle, or mantle. The monthly change was also most dynamic in the visceral mass. It first Increased during the early active stage (March to May), decreased during late active stage (May to July), and then increased again rapidly during the spawning stage (September). There were a strong negative correlation in total lipid contents between foot muscle and adductor muscle (r = -0.634, p = 0.027), and a strong positive correlation between adductor muscle and mantle (r = 0.665, p = 0.018). Glycogen contents showed more or less similar pattern to total lipid contents in the adductor muscle, foot muscle, and visceral mass. It was higher during the early active and spawning stages, while lower during the late active and spent/inactive stages. There was no statistically significant correlation in glycogen contents among different tissues. Especially, total lipid content showed a negative correlationship between the foot muscle, adductor muscle, visceral mass and mantle. Therefore, these results indicate that the nutrient content of the foot muscle, adductor muscle, viseral mass and mantle changed in response to gonadal energy needs.