• Journal of Marine Life Science
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• v.8 no.1
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• pp.1-7
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• 2023

This study was performed to understand the reproductive ecology of cephalopods, described the microanatomical structure of the male reproductive organs and spermatophore in the common squid, Todarodes pacificus, a major cephalopods in Korea. The common squid was gonochorism and had sexual dimorphism, the color of the reproductive organs reflected on the mantle and the presence of the hectocotylus. Male reproductive organs were composed of testis, primary vas deferens, spermatophoric gland (seminal vesicle), spermatophoric sac (Needham's sac) and secondary vas deferens. The male has specialized reproductive organs such as the spermatophore forming organ, spermatophoric gland. Testis was histologically a seminiferous tubule type. The primary vas deferens was a thin and inverted triangular spring-like form that connected from the rear of the testis to the spermatophoric gland. Inside, it was filled with sperm of basophilic in H-E stain. The spermatophoric gland is an irregular oval connected to the primary vas deferens and spermatophoric sac, and there were a number of tubular glands. The spermatophoric sac is a tubular structure located between spermatophoric gland and secondary vas deferens, and a number of spermatophores have been identified in the lumen. The secondary vas deferens was connected to the posterior of the spermatophoric sac and had a spermatophore inside. The spermatophore was a long, transparent tube about 22 mm long, with a sperm mass inside.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 1997.06a
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• pp.300-301
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• 1997

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.18 no.3
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• pp.131-141
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• 2013

Stock identification of Todarodes pacificus collected in the East Sea, Yellow Sea and East China Sea during the period from September to December in 2011 was analyzed by morphometric characters and mitochondrial DNA (mtDNA) cytochrome oxidase subunit I (COI) gene nucleotide variations. Frequency distributions of mantle length was analyzed by morphological method with measuring size of T. pacificus. Then each stock was estimated to confirm their maturation for mean mantle length comparing with mean mature mantle length 20-22 cm. According to morphologic stock identification, it is estimated that the northern part of East Sea is categorized as summer stock and the rest parts, including mid /southern part of the East Sea, northern part of the East China Sea and northern part of the West Sea were autumn stock. For genetic analysis, a total 49 haplotypes were defined by 33 variable nucleotide sites. From the extensive haplotype diversity, limited nucleotide diversity and star-like shape of haplotype network, T. pacificus appears to have undergone rapid population expansion from an ancestral population with a small effective population size. Although pair-wise Fst estimates which represent genetic difference among groups were low, there are relatively remarkable difference of Fst between middle and southern part of the East Sea. Although middle part of the East Sea and southern part of the East Sea were situated at the East Sea, genetically separated groups were appeared.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.1
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• pp.59-61
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• 2014

We conducted eight surveys in the northern East China Sea (ECS) in winter (February - April), summer (July), and autumn (October) 2004-2009, to investigate the seasonal distribution of T. pacificus. A total of 482 paralarvae, ranging in mantle length (ML) from 1.0 - 17.0 mm, were collected at 73 out of 181 stations. There were higher numbers of paralarvae during the winter and summer months than in the autumn. There was significant seasonal variation in the paralarval mantle lengths; mantle lengths were longer in winter (April) than in summer (July). The position of oceanic fronts in the study area played an important role in restricting paralarval distribution along the inshore edge of the Tsushima Warm Current (TWC). When the TWC expanded to western Jeju Island in winter and autumn, the paralarval distribution range extended to include western Jeju Island. However, when the TWC was located southeast of Jeju Island in the summer, paralarvae were distributed along the frontal zone off southeast Jeju Island. Sites at which paralarval mantle length was <2.0 mm ML indicated that the spawning ground were likely to be within the northern ECS in winter and summer, but north of the study area in autumn.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.6
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• pp.685-695
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• 2019

To assess the state of Todarodes pacificus fisheries, we examined changes in major fishing and ecological characteristics by comparing jigging fishery data between high (HCLP, 1996-2000) and low (LCLP, 2013-2017) catch level periods. The peak catch occurred in October during the HCLP compared with December during the LCLP. The average catch per unit effort was higher during the HCLP (1.3 tons/jigging vessel) than LCLP (1.0 ton/jigging vessel). During the HCLP, fishing grounds were highly concentrated in the southwestern East Sea and Yamato bank, whereas during the LCLP, the distribution of grounds extended to the South Sea, West Sea, and northern East Sea (near Russian waters) at a low density. Water temperatures in the main fishing ground in the southwestern East Sea were higher at 0, 50, and 100 m depths during the LCLP than HCLP. Meanwhile, the average mantle length of catches decreased from 23.5 cm during the HCLP to 22.21 cm during the LCLP. The mantle length at 50% maturity also decreased between the two periods from 22.06 (HCLP) to 18.77 cm (LCLP). These findings will help guide future management strategies for T. pacificus.

• 한국수산학회:학술대회논문집
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• 2005.05a
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• pp.95-96
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• 2005

• Proceedings of the Malacological Society of Korea Conference
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• 2002.05a
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• pp.3-4
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• 2002

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 1995.06a
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• pp.209-210
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• 1995

• 한국전자현미경학회:학술대회논문집
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• 2001.11a
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• pp.51-53
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• 2001

• 한국전자현미경학회:학술대회논문집
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• 2001.11a
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• pp.46-48
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• 2001