• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.59 no.4
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• pp.362-376
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• 2023

The IUU Fishing Index is composed of 40 indicators. These indicators were grouped by state responsibilities (flag, coastal, port, and general including market) defined in the FAO IPOA-IUU (2001) and then by type into vulnerability, prevalence, and response. A total of 152 coastal nations was surveyed. Korea's total combined IUU Fishing Index was 2.49 in 2019 and 2.91 in 2021, indicating a drop in the ranking to the third worst out of 152 countries followed by China and Russia in 2021. The indicators that increased the IUU fishing risk in 2021 compared to 2019 included seven indicators of prevalence and two indicators of response while those reducing the risk included one prevalence and one response indicator. The IUU Fishing Index revealed that many fisheries observers and monitoring, control and surveillance (MCS) practitioners active in the waters of RFMOs jurisdiction where Korean distant water vessels operate have mentioned concerns about the compliance with RFMO conservation measures or fishing practices. It suggested that strengthening management intervention in the fishing sector is needed. The primary tool for management is the MCS system. Given the logistical difficulty of oversight from land, air and at-sea, there is a need to enhance MCS strategies through logbook data, at-sea observer and electronic monitoring program. It also suggested that MSC fisheries certification and fisheries improvement projects, which are widely used for improving fishing sector performance, could contribute to the eradication of IUU fishing and the promotion of sustainable distant water fisheries.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.1
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• pp.42-49
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• 2015

According to the catch condition of Scomberomorus niphonius in autumn season affected greatly, the catch price for the set net fishery. Catch production and the selling price were relatively even except 2009 showing a great big blooming jellyfish of Nemopliema nomurai in 2008~2011. The fishing cost of the set net fishery in Yeosu has increased gradually by the decrease of catch production and unexpected environmental change like as jelly fish blooming. The increase of fishing cost diminished net income and caused a negative impact in profitability. The lowest Fisheries ratio of gross profit to gross costs the set net fishery were appeared 60.2% in 2010, respectively. Bycatch was highest in 2008 and lowest in 2009. In general, the bycatch was occurred from May to July every year and when Scomber japonicus was most dominant in the catch price by bycatch had a advantage in the profit side. However, the catch increase of immature small fishes by the bycatch, which will bring about the decrease of fisheries resources. Finally, the present state in set net fisheries will act as a defect on the long-term management of fisheries resources.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.3
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• pp.262-270
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• 2018

We examined the characteristics of egg and larval distributions and catch changes of anchovy in relation to abnormally high sea temperature in the South Sea of Korea in summer 2015 and 2016. The densities of anchovy eggs and larvae in the southern coastal region were lower in July-August 2016 than in July-August 2015. In particular, anchovy eggs and larvae (approximately 5 mm TL) were rarely observed in the coastal region in August 2016 due to the abnormally high SST (up to $28^{\circ}C$), which was above the optimum spawning temperature of anchovy. The catch of non-swimming stage (< 2 cm TL) larval anchovy was lower in July-August 2016 than in July-August 2015. The decreased catch of larval anchovy in July-August 2016 could be attributed to decreased spawning density in June-July 2016. In contrast, the catch of swimming stage (> 2 cm TL) anchovy was increased in July-August 2016. In the summer of 2016, prominent sea temperature near the southern coast of Korea and sea temperature higher than $30^{\circ}C$ in the offshore region of the South Sea of Korea could greatly enhance the retention of swimming anchovies in the coastal fishing grounds.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.49 no.4
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• pp.449-458
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• 2013

This study investigated purplish Washington clam, Saxidomus purpuratus on its gonadal development, reproductive cycle and shell length (age) at 50% female group maturity from January to December 2011 in Jinhae Bay, Korea. This species is dioecious. The gonad index (GI) began to increase in January, reached the maximum value in May and to decrease in June, reached the minimum value in September then to increase slowly in October again. The reproductive cycle of the clams can be divided into five successive stages: the early active stage (Ea, from February to March), the late active stage (La, from January to March and October to December), the ripe stage (R, from January to May), the spawning stage (S, from June to December) and the degenerative and inactive stage (Ia, from January to February and November to December). The spawning periods were from June to December and the main spawning periods were from July to October. The shell length at 50% female group maturity (SL50) was estimated to be 63.6 mm, which can be converted as sexual maturity age of 2.2 year.

• Korean Journal of Ichthyology
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• v.22 no.4
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• pp.217-224
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• 2010

An investigation was carried out to obtain basic information needed to develop methods for artificial propagation and conservation of the mottled skate Raja pulchra, an important food resource in western Korea that has declined from overfishing. In this paper we provide evidence of multiple spawning and describe properties of the ovary, and morphology of the egg capsule and the fully-formed offspring. The vitellogenic follicles in the ovary was $179.8{\pm}57.1$ (54~247) and can be classified into five size groups, which the last group of ova are considered as the moving to the capsule gland where fertilization and encapsulation of ova take place. The morphology of the egg capsule of R. pulchra is unique among the species of the family Rajidae and showed multi-embryo characteristics, having two to six yolks in each capsule. The adaptive morphological changes of larvae developing inside the egg capsule are described based on specimens extracted from the capsule.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.52 no.1
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• pp.24-35
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• 2016

An acoustic and trawl pilot survey using a small vessel was conducted in Jinhae bay of the South Sea of South Korea on April 13~14, May 11~13 and June 8~10, 2015. During the survey, acoustic data was collected and bottom trawls were conducted at the same time. First, various noises were eliminated by using the Park method based on the Wang method (Wang et al., 2015; Park et al., 2015), the species compositions and catch rate from each bottom trawl were observed, and spatial distribution of fishery resources in the water column and their nautical area scattering coefficient (NASC) were investigated through acoustic data. During the entire survey period, 12 orders, 33 families and 41 species were caught. The most caught species in April, May and June were Okamejei kenojei, Zoarces gilli and Pholis nebulosa, respectively. Fish schools were observed near the line of net mouth height in April. Numerous weak scatters were presented on the echograms in May and June. Many fish schools appeared in between the water surface and 20 m deep in May. The NASC value from entire water columns was the lowest in April ($35.9m^2/n{\cdot}mile^2$) and highest in June ($1541.3m^2/n{\cdot}mile^2$).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.52 no.2
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• pp.149-161
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• 2016

Fishing characteristics of Korean tuna purse seine fishery in the Pacific Ocean were investigated using logbook data compiled from captain onboard and the statistical data from 1980 to 2014. Changes in fishing ground and correlation between marine environmental factors and fishing patterns were investigated using Oceanographic index. The proportion of unassociated set was higher than that of associated set. The catch proportion of yellowfin was higher in the unassociated set, while that of skipjack and bigeye was higher in the associated set. Due to vessels, fishing gears and Korean captains' high-level of skills in fishing technology optimized for the unassociated set and preference of large fishes, especially large yellowfin tuna, it showed unique fishing characteristics focusing on the unassociated set. As for fishing distributions of Korean tuna purse seine fishery and impacts of oceanographic conditions on the fishery, the main fishing ground was concentrated on the area of $5^{\circ}N{\sim}10^{\circ}S$, $140^{\circ}E{\sim}180^{\circ}$ through the decades. When stronger El-nino occurred, the range of fishing ground tended to expand and main fishing ground moved to the eastern part of western and central Pacific Ocean. During this season, yellowfin tuna had high CPUE and catch proportion of yellowfin tuna in the eastern part also increased. As for the proportion of fishing effort by set type, proportion of log associated set was high during El-nino season while that of FAD associated set was high during La-nina season.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.1
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• pp.107-111
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• 2020

In this study, we examined the maturation and spawning of yellowback seabream Dentex tumifrons using samples collected by monthly bottom trawling in Korean coastal waters from January to December 2018. We analyzed monthly changes in gonadosomatic index (GSI), maturity stage, histology, fecundity, and total length at group maturity. Spawning occurred in May and October. Fecundity varied with total length as F=1.3754TL^3.2664, with a range of 1,220 to 155,625 eggs per female. At group maturity, 50%, 75%, and 97.5% estimates of female total length were 18.4, 20.5, and 25.3 cm, respectively.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.4
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• pp.310-319
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• 2007

To investigate the catches of squid jigging fishery, a series of fishing experiments was conducted in the high seas of the Northwest Pacific($40^{\circ}-43^{\circ}N$, $150^{\circ}-155^{\circ}E$) during the period of 1 August to 22 October 2005 by commercial fishing vessel. The number of 142 test fishing was carried out in the Northwest Pacific during 83days. The total catch were 47,524kg as 4 squid species and CPUE was $8.9kg/line{\cdot}day$. CPUE showed high values in the frontal zone during the survey. Main squid species caught from the experimental fishing were the neon flying squid, Ommastrephes bartrami(96.8%) and the boreopacific gonate squid, Gonatopsis borealis(3.2%). Dorsal mantle length of the neon flying squid were increased by the time and increasing of the hook size. Loss rate of the neon flying squid in the water showed the highest values in 28.2% compare to the others. And the loss rate of the front roller and in the air were 1.1% and 1.0%, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.3
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• pp.362-367
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• 2015

We followed the development of Pacific herring Clupea pallasii larvae after natural hatching in Korean coastal waters off Dadaepo, where the water temperature was $9^{\circ}C$. Twenty days after hatching, the larvae had (i) reached a total length (TL) of 10.8-12.2 mm, (ii) developed 9-11 dorsal fin rays, and (iii) branched melanophores along the dorsal line of the gut in the anterior half of the body and along the posterior half of the dorsal and ventral line. Thirty days after hatching, the larvae had reached 12.2-13.5 mm TL, and the number of dorsal fin rays had increased to 13-14. Thirty-five days days after hatching, the larvae had reached 14.0-14.7 mm TL, and the posterior ends of their notochords had begun to flex upward. Forty-five days days after hatching, the larvae had (i) reached 15.6-15.9 mm TL, (ii) a complete set of dorsal fin rays (15-16), (iii) 12-13 anal fin rays, and (iv) branched melanophores along the dorsal part of the lateral surfaces of the head behind the caudal terminus. Preflexion, flexion and postflexion stage larvae had TL values of 13.5 mm, 14.0-15.3 mm, and 15.6-15.9 mm, respectively.