• Korean Journal of Ichthyology
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• v.8 no.2
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• pp.16-22
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• 1996

Age and growth of Epinephelus akaara were determined using samples collected from the south western sea of Korea. Thin - sectioned otoliths showed relatively well defined annuli when examined under dark - field microscope. Because the fish do not feed at the temperature under $10^{\circ}C$, the annuli in otoliths are considered to be formed during the period between December and April. Considering that the peak spawning season is July, the first annulus must have been formed in 0.5 year after birth. The oldest fish examined was 9 years old, and the largest one was 47cm. The body length(L, cm) was linearly related to the otolith radius (R, ${\mu}m$) : L= - 2.84+7.01 R. Back-calculated lengths for each age using the relationship between body and otolith size were well adjusted to the Von Bertalanffy growth curve : $L_t$=55.5[1-exp{-0.162(t+0.128)}]. Using relationship between length and weight ($W_t$=0.00608$L^{3.21}$), growth in weight was expressed by Wt=2409(1-exp{-0.162(t+0.128)}]$^{3.21}$.

• Korean Journal of Environment and Ecology
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• v.26 no.4
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• pp.475-483
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• 2012

Tribolodon hakonensis(Cypriniformes; Leuciscinae) is anadromous; they are born in freshwater, migrate back to the ocean, then return to their home stream for spawning from mid-March to early-June. Here, five microsatellites were used to assess the level of gene flow among T. hakonensis populations from the Samcheok-Oship Stream, South Korea. The frequencies of dominant alleles across several loci differed between down-and upstream populations divided by several weirs, and pairwise multilocus $F_{ST}$ estimate was significantly high(0.083). However, there were no signs of any loss of genetic variation in the upstream population. Assignment tests of individuals in admixture model(K=2) to a set of baseline samples showed fairly correct assignment to each cluster; all of upstream individuals sere included in the first cluster, while the majority of downstream individuals(65%) comprise the second cluster. These results indicate reduced gene flow between up- and downstream populations but allowing passive downstream drift. It is likely that man-made structures might at least partially be a factor for creating and consolidating the current distribution patterns of genetic variation among T. hakonensis populations in the Samcheok-Oship Stream. This information will assist governing agencies in making informed decisions regarding conservation of anadromous fishes in Korean drainage systems.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.5
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• pp.659-663
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• 1999

Gametogenesis, reproductive cycle, condition factor, and meat weight rate of the surf clam, Tresus Keenae were studied by histological observations and morphometric data based on the samples which have been collected from the south coast of Korea, from January 1995 to February 1996. The annual ranges of the mean seawater temperature and specific gravity in habitat of the surf clam were $4.9\~24.9^{\circ}C$ and 1.0210$\~$1.0266, respectively. Monthly changes in the condition factor showed in a wide range from 0.2381 to 0.2827, began to increase in January and reached the first maximum (0.2827) in April. And then the value rapidly decreased in June, thereafter, reached the second peak (0.2812) in August. The condition factor of this species showed the two peaks, and gonadal development reached sexually mature and ripe conditions during the period of these two peaks. The meat weight rate ranged from $38.0\%$ to $46.4\%$, and its change showed a similar tendency with the condition factor. The reproductive cycle of this species can be divided into five successive stages: in both sex, multiplicative (December to January, July to August), growing (January to February, September to October), mature (February to April, September to November), spawning (April to June, September to November), and degenerative and resting stage (May to July, November to January).

• The Korean Journal of Malacology
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• v.25 no.3
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• pp.189-196
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• 2009

Based on 1,260 samples, the age and growth of purple whelk, Rapana venosa (Valenciennes) (Gastropoda:Muricidae) have been investigated. The samples were collected monthly during one year time (from February, 2004 to January, 2005) from the West Sea of Korea. The age of R. venosa was determined by the ring of the operculum analysis. The relationship between whelk's shell height and ring radius in each ring group was expressed as an equation of linear regression and later a correspondence in each ring formation was determined. Based on the monthly variations in the marginal index (MI) of the operculum, it was assumed that the ring of this species has been formed once a year during the period from July to August. The relationship between shell height and shell width was expressed by the equation SW = 0.7867 SH - 6.3988 ($R^2$=0.8604); and between shell height and total weight by the equation $TW=0.0000626{\times}SH^{3.206}$ ($R^2$=0.8324). The purple whelk's spawning period was estimated through the fatness analysis and has occurred during the period from May to July. Obtained results suggests that the ring formation occurs once a year (in July) and the length of time period since the first ring has been formed on the operculum is approximately 13 months (1.08 year). The purple whelk's growth curves for shell height and total weight fitted to the von Bertalanffy's equation and were expressed as follows: $SH_t=199.653(1-e^{-0.104(t+2.478)}$ $TW_t=1484.105(1-e^{0.104(t+2.478)})^{3.206}$.

• Korean Journal of Ecology and Environment
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• v.54 no.2
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• pp.79-86
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• 2021

In this study, the distribution and habitat characteristics of Odontobutis obscura were investigated. It is a freshwater fish species which belongs to the Class I Endangered species as specified by the Ministry of Environment of South Korea. Sampling was conducted in the Sanyang Stream watershed between April and August of 2016. The Sanyang Stream watershed includes the Sanyang and Gucheon Streams, and their tributaries. Odontobutis obscura was caught at every sampling site, except sites 1~3, which are located in the lower part of the Sanyang Stream. Its habitat range extended from the headwaters to the lower parts of the stream that were not impacted by the South Sea. Salinity was the major factor limiting the distribution of O. obscura in the Sanyang Stream watershed. All individuals of O. obscura were caught in areas where the substrate composition was over 50% gravel. Furthermore, the substrate composition seems to be the most important habitat factor affecting spawning of O. obscura. Ecological studies of O. obscura are scarce, and this study is the first to report a detailed distribution for the species. Further studies on the physiology and ecology of O. obscura are essential for establishing preservation strategies for this endangered species.

• Korean Journal of Ichthyology
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• v.36 no.1
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• pp.1-9
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• 2024

This study investigated the early life history of the Boleophthalmus pectinirostris living in the southern coastal Yeoja-man and compared the results with the same Gobiidae fishes. The brood stork used in the study were captured with bare hands in the tidal flats of Beolgyo-eup, Jeollanam-do, in June 2015. The amount of spawning was 411~11,688, and the eggs were short oval and the size was 1.40×0.72 mm. The time of hatched took 91 hours and 35 minutes at a water temperature of 25~27℃. Newly hatching larvae, the yolk sac had a total length of 3.02~3.31 (average 3.17±0.08, n=30) mm and did not eat rotifer. 4 days after hatching, the total length was 3.31~3.52 (3.43±0.07, n=30) mm, and as the mouth and anus opened, the fish transitioned to the preflexion larvae and fed. 14 days after hatching, the total length was 5.06~5.25 (5.16±0.06, n=30) mm, and the distal end of the vertebra was completely bent at 45° and the transitioned to the postflexion larvae. 41 days after hatching, the total length was 14.3~16.8 (15.4±0.85 mm, n=30), and the number of fins reached an integer of 5 first dorsal fins, 26~27 second dorsal fins, 24~27 anal fins, and 6 ventral fins, and the transitioned to the juveniles. As a result of the study, star-shaped melanophore were deposited from the front of the pectoral fin to the base of the caudal fin, which distinguished them in form from other postflexion larvae of Gobiidae fishes.

• Korean Journal of Ichthyology
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• v.35 no.4
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• pp.253-262
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• 2023

This study compared the results of observing the early life history of Gymnogobius urotaenia, which lives in Hwangbocheon Stream, an inflow stream on the east coast, with the differences between fish of the same Gobiidae fishes. In May 2022 and 2023, fertilized eggs and brood stork scattered under rocks were captured twice in Hwangbocheon Stream. The spawning amount was 827~1,540 and the orchid was a elliptical in shape with a size of 3.21×1.07 mm. The stage of ovulation observed in the laboratory was 16 cells, and hatching began after 193 hours. The breeding water temperature range was 18.8~19.3℃. Newly after hatching larvae, the yolk sac with a total length of 3.84~4.33 (average 4.10±0.17, n=30) mm, and the anus was not open. 6 days after hatching of incubation, the total length was 5.32~6.11 (average 5.67±0.25, n=30) mm, absorbing all egg yolk and transitioning to the preflexion larvae, ingesting food, and developing a keynote on the tail fin. 15 days after hatching, the end of the urostyle end was completely bent at 45° with a total length of 7.33~8.52 (average 7.81±0.46, n=30) mm and transitioned to postflexion larvae, and melanophore developed throughout the body. 38 days after hatching, the total length is 22.1~26.1 (23.8±1.36, n=30) mm and the number of fins (6 first dorsal fins, 11 second dorsal fins, and 11 anal fins, 12 ventral fins) is all the number of fin base became integer and transferred to the juvenile. As a result of the study, it was possible to distinguish the melanophore of postflexion larvae of G. urotaenia from other postflexion larvae Gobiidae fish in that they were distributed throughout the body of half the body and tail.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.13 no.4
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• pp.179-183
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• 1980

The efficiency of energy transfer by a population of the farmed pacific oyster, Crassostrea gigas was studied during culture period of 10 months July 1979-April 1980, in Geoje-Hansan Bay near Chungmu City. Energy use by the farmed oyster population was calculated from estimates of half-a-month unit age specific natural mortality rate and data on growth, gonad output, shell organic matter production and respiration. Total mortality during the culture period was estimated approximate $36\%$ from data on survivor individual number per cluster. Growth may be dual consisted of a curved line during the first half culture period (July-November) and a linear line in the later half period (December-April). The first half growth was approximated by the von Bertalanffy growth model; shell height, $SH=6.33\;(1-e^{0.2421(t+0.54)})$, where t is age in half-a-month unit. In the later half growth period shell height was related to t by SH=4.44+0.14t. Dry meat weight (DW) was related to shell height by log $DW=-2.2907+2.589{\cdot}log\;SH,\;(2, and/or log $DW=-5.8153+7.208{\cdot}log\;SH,\;(5. Size specific gonad output (G) as calculated by condition index of before and after the spawning season, was related to shell height by $G=0.0145+(3.95\times10^{-3}{\times}SH^{2.9861})$. Shell organic matter production (SO) was related to shell height by log $SO=-3.1884+2.527{\cdot}1og\;SH$. Size and temperature specific respiration rate (R) as determined in biotron system with controlled temperature, was related to dry meat weight and temperature (T) by log $R=(0.386T-0.5381)+(0.6409-0.0083T){\cdot}log\;DW$. The energy used in metabolism was calculated from size, temperature specific respiration and data on body composition. The calorie contents of oyster meat were estimated by bomb calorimetry based on nitrogen correction. The assimilation efficiency of the oyster estimated directly by a insoluble crude silicate method gave $55.5\%$. From the information presently available by other workers, the assimilation efficiency ranges between $40\%\;and\;70\%$. Twenty seven point four percent of the filtered food material expressed by energy value for oyster population was estimated to have been rejected as pseudofaeces : $17.2\%$ was passed as faeces; $35.04\%$ was respired and lost as heat; $0.38\%$ was bounded up in shell organics; $2.74\%$ was released as gonad output, $2.06\%$ was fell as meat reducing by mortality. The remaining $15.28\%$ was used as meat production. The net efficiency of energy transfer from assimilation to meat production (yield/assimilation) of a farm population of the oyster was estimated to be $28\%$ during culture period July 1979-April 1980. The gross efficiency of energy transfer from ingestion to meat production (yield/food filtered) is probably between $11\%\;and\;20\%$.

• Korean Journal of Ichthyology
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• v.4 no.2
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• pp.1-25
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• 1992

Taxonomic study of the five species (Acanthogobius elongata, A. flavimanus, A. lactipes, A. luridus and Synechogobius) from Korea was carried out based on morphometric, cephalic sensory canal and ecological characters. Taxonomic revision and classificational keys are provided. Synechogobius hasta is easily distinguished from four species of the genus Acanthogobius in eleven characters, i. e., the number of dorsal and anal fin rays, the transverse scales, the vertebral numbers, the formula of interneural spine of the first dorsal fin, the number of interhemal spine anterior to the first hemal spine, the number of epipleural and pleurals, the ratio of caudal peduncle length, the ratio of caudal peduncle depth and the regular variations in the ratio of body parts with the body length. In the genus Acanthobobius, A. elongata is distinguished from other 3 congeneric species in the ratio of body parts and the oculoscapular sensory canal. Moreover, A. flavimanus differs from other 3 congeneric species in the lateral scales, the transverse scales, the number of predorsal scales, the vertebral number, the number of epipleural and pleurals. Sensory papillae rows of S. hasta is not similar that of the genus Acanthogobius in having a singular sensroy papillae rows. A. elongata has no oculoscapular sensory canal D and A. flavimanus has transverse sensory papillae in cheek, and these are one of the unique characters distinguished form other congeneric species. In the spawning period inferred from gonadosomatic index, A. elongata varied from late March to late June ; A. flavimanus, January to April ; A. lactipes, May to September ; A. luridus, early May to early July and S. hasta, early March to early May.

• The Korean Journal of Malacology
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• v.27 no.2
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• pp.107-114
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• 2011

The manila clam (Ruditapes philippinarum) is mainly distributed in the coastal area which consist of mud, sand and gravel, but they rarely live on the upper and down reaches of river. For a long time the manila clam has been inhabited in Taehwa river which has been exploited as a traditional earning resources and has become as a major object by neighborhood fishermen. This study was undertaken to evaluate stock assessment and to build management implications with the ecological parameters in Taehwa river from June 2009 to June 2010. The maximum age of manila clam was determined to 6 years old from observing ring radius of shell, the length and weight relationship was TW = $0.0002SL^{3.063}$ ($R^2$ = 0.925). K and $L_{\infty}$ were respectively estimated 46.64 mm and 0.341/year by von Bertalanffy growth. The instantaneous total mortality was estimated to be 1.171/year and the age at first capture was 1.37 years by the Pauly's method using shell length composition. The current total biomass of manila clam was calculated 1,483 mt over study area $1.46\;km^2$ by swept area method. ABC (Acceptable Biological Catch) estimates of manila clam showed 512 mt with using $F_{0.1}$. It's desirable to determine the optimum harvesting time as after main spawning season, as well as it's required to manage fisheries resources considering capture age and biomass through adjusting a first age at capture.