• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.4
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• pp.419-423
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• 2014

We consider changes in the fishing ground of the small yellow croaker Larimichthys polyactis and discuss their utility in predicting fishing conditions for this species. The fishing ground, which having been formed around Jeju Island since the 1970s, is dominated by the Yellow Sea Bottom Cold Water (YSBCW), and variation in its southward expansion from the Yellow Sea is the single most key environmental factor affecting the L. polyactis catch. When the YSBCW showed strong expansion and the fishing ground shifted to the west and southwest of Jeju Island, as occurred in the late 1980s, late 1990s, and early 2000s, the L. polyactis catch was low; conversely, when expansion was weak, as in the early 1990s and late 2000s, the L. polyactis catch was high. This relationship was statistically significant and should be useful in predicting fishing conditions for L. polyactis.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.4
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• pp.650-655
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• 2020

Chilsan-do Island, South Korea, has previously been identified as one of the biggest spawning sites of the small yellow croaker Larimichthys polyactis in the Yellow Sea. To determine whether Chilsan-do still serves as a spawning site for L. polyactis, three to five stations around Chilsan-do Island were surveyed for eggs from April to June (the main spawning season of L. polyactis) in 2019, using an RN80 net. For the first time, three L. polyactis eggs were identified at two stations, located just in front of Chilsan-do Island and between Chilsan-do and the coastline, only in May. The diameter of L. polyactis eggs (1.26-1.34 mm) was very similar to those of Collichthys niveatus (1.30-1.37 mm) and Setipinna tenuifilis (1.34-1.35 mm). During the survey period, the sea surface salinity remained constant (32.0-32.1 psu), but the sea surface temperature (SST) rapidly rose from 13.6-13.7℃ in April to 22.1℃ in May. Our findings suggest that L. polyactis still spawns near Chilsan-do Island today, but on a very small scale, and that changes in SST promote spawning of L. polyactis.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.3
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• pp.199-206
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• 2005

As the basic study about improvement of yellow croaker drift gill net fishing implement and development of the fishing system, this study drew problem after synthetically analyzing hauling system of yellow croaker drift gill net used in the coast of Chuja Island and tested several characters and analyzed in hauling process with 5 step net hauler model for improving the problem. The analysis results are as follows. When the angle between axises of drum centers was small, it showed the tendency that hauling time was fast. Hauling time was faster when drum was 5 step rather than 3 step. When drum was 5 step, slippery phenomenon was small and hauling was stable. Tension was larger when drum was 5 step rather than 3 step. When drum was 5 step, the range of change of the maximum and minimum value was small and hauling was stable. When drum was 3 step, there was following formula between hauling time ($Ht_3$) and angle between axises of drum centers ($A_g$) $Ht_3$ : ($7.15Hs^{-0.81}$) $A_g^{-0.81}$, when drum was 5 step there was following formula.$Ht_5$ : ($6.45Hs^{-0.75}$) $A_g0.10$, here, Hs is hauling speed. When drum was 3 step and hauling speed was 28cm/sec, tension was $T=0.08A_8^3-1.60A_g^3-0.49A_g+369.56(r=0.99)$, when drum was 5 step, tension was, $T=-0.01A_g^3+1.96A_g^2-34.05A_g+414.58$ (r-0.99), here, T was tension(g).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.52 no.3
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• pp.220-231
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• 2016

Yield-per-recruit (YPR) analysis is used to provide management guidance for the efficient use of a fish cohort. However, the individual fish price per unit weight of small yellow croaker (Larimichthys polyactis) or hairtail (Trichiurus lepturus) increases dramatically by size in Korea. Therefore, age-based production value-per-recruit (PPR) analysis has recently been developed (Zhang et al., 2014). Since age determination requires a substantial amount of money and time and it is even impossible for some fish species, it is difficult to obtain age information to apply the age-based PPR model. Thus, we attempted to develop an alternative method, which uses length data rather than age information, called the length-based PPR analysis. The results revealed that length-based PPR analysis was much more conservative for stock management than the YPR analysis. Furthermore, the PPR analysis was more economically beneficial than the YPR analysis, which can prevent the fish stock from the economic overfishing. In conclusion, the length-based PPR analysis could be a proper approach for stock assessment in the case that the individual fish price per unit weight increases dramatically by size, and this analysis is useful to obtain vital management parameters under data-deficient situation when traditional stock assessment methods are not applicable.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.2
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• pp.228-242
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• 2023

We examined the osteological development of the cranium, visceral skeleton, pectoral girdle, vertebral column, fins, and pterygiophore of small yellow croaker Larimichthys polyactis cultured at the Jeju Fisheries Research Institute. At 5.89 mm NL (notochord length), the larvae already had ossified frontal and basioccipital bones, parasphenoids, and vomer in the cranium. All elements of the visceral skeleton except the metapterygoid were ossified at 5.89 mm NL. Preorbital bone was ossified at 8.11 mm SL (standard length), and suborbital bones were ossified at 12.90 mm SL. In the vertebral column, ossification proceeded from the first to last centrum. The urostyle ossified at 7.41 mm SL. The caudal skeleton ossified at 6.78 mm NL, along with three hypural bones. In the pectoral girdle, the cleithrum, supracleithrum, postcleithrum, and post-temporal bones ossified at 5.89 mm NL. Caudal fin ossification began at 6.19 mm SL and was complete at 7.16 mm SL. Dorsal and anal fin ossification began at 7.16 mm SL and was complete at 8.62 mm and 8.11 mm SL, respectively. Anal and dorsal pterygiophore bone ossification was complete at 9.86 mm and 11.54 mm SL, respectively, and that of the supraneural bones was complete at 9.60 mm SL.

• Korean Journal of Ichthyology
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• v.18 no.1
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• pp.45-54
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• 2006

Age and growth of the small yellow croaker, Larimichthys polyactis were estimated using right sagittal otoliths of 506 fish specimens from March to December, 2002 and from January to February, 2005 in the South Sea, part of the East China Sea of Korea. Examination of outer margins of the otolith showed that the opaque zone was formed once a year. Marginal increment of the otolith formed annual rings from May and June at the beginning of spawning season. In the relationship between total length and body weight, a multiplicative error structure was assumed because variability in growth increased as a function of the length, and the estimated equation was $BW=0.0044TL^{3.2502}$ ($R^2=0.97$). The relative growth as body weight at total length has significant difference between females and males (P<0.05). For describing growth of the small yellow croaker, Larimichthys polyactis a von Bertalanffy growth model was adopted. The von Bertalanffy growth curve had an additive error structure and the growth parameters estimated from non-linear regression were $L_{\infty}=33.88cm$, K=0.20/year and $t_0=-2.39year$. Growth at age of males and females shows no significant difference (P>0.05). Most examined fish were 1, 2 and 3 years old, although the oldest fish were 7 old for males and 8 for females.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.1
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• pp.37-44
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• 1992

Annual biomasses of small yellow croaker, Pseudosciaena polyactis, were estimated by biomass-based cohort analysis (Zhang, 1987) , using data on annual catch in weight at age for 1970-88 in Korean waters. Annual biomass of croaker was highest in 1974 with about 100,000 mt, declining to a level of 20,000-30,000 mt after 1981. Adult biomass also showed a peak in 1974 with about 50,000 mt. Afterwards, however, it continuously dropped. According to the estimates of biomass at age obtained from this analysis, the age composition of small yellow croaker in the 1980's differed greatly from that in the 1970's. The proportions of older croakers (>5 years) were very low in the 1980's and even the biomasses of young croakers (1-4 years) were at a very low level in the 1980's. Year classes of 1968, 1972 and 1978 appeared to be relatively dominant. The mean value of instantaneous fishing mortality (F) in the 1980's was twice that of the 1970's. Recruitment of croaker exhibited an unusally linear relationship with adult stock biomass.

• Journal of Aquaculture
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• v.19 no.3
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• pp.188-196
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• 2006

Annual reproductive cycle of small yellow croaker, Larimichthys polyactis were histologically investigated based on samples captured nearby the coast around Chujado, Youngkwang and Kanghwa, South Korea from February $2004{\sim}February$,2005. By histological survey, the annual reproductive cycle was classified into the following successive stages: The primary growth stage from September to October, the second growth stage from October to December, the mature stage from January to April, the final mature, ovulation and spawning stage from May to June, the degeneration stage from June to July and the rest stage from August to September. Throughout anatomical observation of the ovary, it is found that the small yellow croaker, L. polyactis belongs to an asynchronous and multiple spawner from late spring to early summer.

• Journal of Life Science
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• v.31 no.3
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• pp.314-320
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• 2021

In the present study, we investigated the effect of photoperiod and water temperature on the gonadosomatic index (GSI), histological stage of the testes, and plasma levels of sex steroid (testosterone, T; 11-ketotestosterone, 11-KT) hormones in cultured male small yellow croakers (Larimichthys polyactis). In a photoperiod experiment, small yellow croakers were reared under a natural photoperiod (NP, 10L:14D-11L:13D), long photoperiod (LP, 14L:10D), and short photoperiod (SP, 10L:14D) at 17℃ for 90 days. The GSI was significantly higher in the LP group than in the other groups at 30 and 60 days. The plasma 11-KT levels were significantly higher in the LP group than in the other groups at 30 days. In a water temperature experiment, small yellow croakers were reared under natural water temperature (NT, 19.1-15.0℃), or at 17℃, 21℃, or 25℃ under a LP (14L:10D) for 60 days. The GSI was significantly lower for the 25℃ group than for the other groups at 30 and 60 days. The plasma 11-KT levels were significantly lower for the 25℃ group than for the other groups at 60 days. Therefore, the sexual maturation of cultured male yellow croakers was promoted by LP and inhibited at water temperatures above 25℃. These findings suggest that the sexual maturation of cultured male small yellow croakers is controlled by both the photoperiod and the water temperature.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.6
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• pp.478-484
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• 2004

On 11 June 1991, eggs from the brood stock of small yellow croaker (Larimichthys polyactis) were artificially fertilized using the standard dry method and were hatched. Each of the fertilized eggs (1.1-1.2 mm in diameter) had an oil globule and was transparent and buoyant. The fertilized eggs hatched in a range of water temperatures $(17.5-20.3^{\circ}C)$ 44 hrs after fertilization. The total lengths of the newly hatched larvae were 3.1-3.3 mm, and these hatchlings had 31 myotomes (10+21). Melanophores and yellow-brown chromatophores were concentrated on the head, at the ventral part of the yolk, and in the middle of the tail. Four days after hatching, the larvae completely absorbed the yolk and became flexions of 5.1-5.5 mm in total length. Fifteen days after hatching, one spine (the anterior tip of the maxillary) appeared in the upper jaw and three spines developed at the upper parts of the eyes and on the posterior part of the head. At this stage, the larvae were approximately 8.3 mm long. Thirty-nine days after hatching, juveniles (1.9-3.4 mm in total length) had a pointed tail fin. By 66 days after hatching, the juvenile fish (about 4.0-6.5 mm in total length) were similar to adult fish in body shape. The larvae of L. polyactis could be distinguished from those of L. croacea by two distinct characteristics: the large number of vertebrae (28-29), and a relatively small bony ridge on the occipital region of the head.