• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.4
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• pp.430-440
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• 2010

To investigate the catches of jack mackerel fishery, a series of fishing experiments was conducted in the high seas of the southeastern Pacific Ocean ($30^{\circ}S-38^{\circ}S,\;82^{\circ}W-95^{\circ}W$) during the period of 9 August to 18 December, 2003 by commercial fishing vessel and research vessel. The number of 205 tows fishing was carried out in the southeastern Pacific Ocean. The total catch was 1,988 ton and CPUE was 2.4 ton/hour. CPUE showed high values in the frontal zone during the survey. Main target species caught from the experimental fishing were the jack mackerel, Trachurus murphyi (98.1%) and chub mackerel, Scomber japonicus (1.9%) as bycatch. Body length of the jack mackerel was different between female and male. The high mean catch per unit effort of jack mackerel was showed when the fishing ground of jack mackerel fishery was over the $110^{\circ}W$ in the southeastern Pacific Ocean. But the fluctuation of the catch per unit effort in the western part of fishing ground was not matched with those year. Reliable physical and oceanographical information will be useful for the efficiency of fishing activity. According to the result of monthly movement of center of fishing ground, the fishing activity of jack mackerel fishery was performed northward in the southeastern Pacific Ocean as time passes.

• The Korean Journal of Applied Statistics
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• v.28 no.5
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• pp.847-858
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• 2015

Deep-sea fishery in the Antarctic Ocean has been actively progressed by the developed countries including Korea. In order to prevent the environmental destruction of the Antarctic Ocean, related countries have established the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) and have monitored any illegal unreported or unregulated fishing. Fishing of tooth fish, an expensive fish, in the Antarctic Ocean has increased recently and high catches per unit effort (CPUE) of fishing boats, which is suspicious for an illegal activity, have been frequently reported. The data of CPUEs in a fishing area of the Antarctic Ocean often show an extreme Distribution or a mixture of two extreme distributions. This paper proposes an algorithm to detect an outlier of CPUEs by using the mixture of two extreme distributions. The parameters of the mixture distribution are estimated by the EM algorithm. Log likelihood value and posterior probabilities are used to detect an outlier. Experiments show that the proposed algorithm to detect outlier of the data can be adopted instead of simple criteria such as a CPUE is greater than 1.

• Fisheries and Aquatic Sciences
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• v.9 no.2
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• pp.75-82
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• 2006

We evaluated the utility of applying isozyme analysis and two tagging methods, visible implant fluorescent elastomer (VIE) injection and uropod-cutting, to monitor the effects of releasing nursery-reared fleshy prawn (Fenneropenaeus chinensis) into natural habitat in Korea. One hundred thousand farmed prawns (70 mm long) were tagged by clipping off the outer left uropod and injecting them with VIE. This marked seed population was released at Muchangpo, Korea, on 11 and 19 July 2002. Two months later, total catch and catch per unit effort (CPUE) at three locations (Hongwon, Muchangpo, and Anmyundo) were determined. Total catch and CPUE increased nearly 18% over the previous year in Hongwon and Muchangpo. The mixing rate, estimated by uropod regeneration pattern, was 0.33% at Hongwon, 0.53% at Muchangpo, and 0.21% at Anmyundo. The recapture rate was about 3.5%. Isozyme analysis confirmed that the mixing rate was highest at Muchangpo. Moreover, fleshy prawns from Muchangpo were genetically most related to the seed population, indicating that the released prawns had largely remained near the released site. We also confirmed that isozyme genes are valuable as genetic markers for qualitative analyses of a released seed population.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.1
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• pp.61-66
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• 2022

Amphioctopus fangsiao is a crucial fishery stock located off Korea's western and southern coasts. In this study, we present data on the spawning period and estimated recreational catch of A. fangsiao in the coastal waters of Jeollanam-do, South Korea. The overall sex ratio was estimated to be 1:1.13 (female: male); in females and males, the gonadosomatic index ranged from 1.22 to 12.14 and 0.17 to 3.44, respectively. The breeding season lasted from December to May, with spawning peaks observed between March and May. Furthermore, the estimated total annual recreational catch of A. fangsiao was 185,085 kg, with November recording the highest recreational catch. A. fangsiao catch per unit effort (CPUE) ranged from 3 to 302.4 kg per vessel d^-1. Therefore, these findings underscore the need for additional monitoring, as any further assessment of A. fangsiao stock necessitates an understanding of recreational catch assessment and fishing efforts in Jeollanam- do's coastal waters.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.5
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• pp.625-637
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• 2022

The southern coast of the East Sea is an important area affected by large warm currents as it connects the coastal waters of Jeju Island, the South Sea, and Dokdo. From 2017 to 2021, the average catch per unit effort (CPUE; kg/day/ship) of set net fishery at six ports in the Gyeongbuk region off the southern coast of the East Sea was the highest in Gampo, Gyeongju, and the lowest in Hupo, Uljin. Although the seasonal variation in the CPUE differed by region and year, it was generally high in autumn. In the set net fishery in Pohang from 2019 to 2021, we identified 72 species, which decreased to 56 species in 2019, 46 in 2020, and 41 in 2021. The species diversity index slightly increased over the three-year periods. We found positive correlations between the total catch (kg) of subtropical species in autumn and the water temperature at 50 m. Among the most abundant species, we found substantially positive correlations between the CPUE of Scomber japonicus, Scomberomous spp. and Carangids. We also noted positive correlations between the CPUE of Todarodes pacificus, Seriola spp. and Carangids.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.4
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• pp.476-486
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• 2010

Fishing efficiency of a trawl vessel can be enhanced by increasing the swept area per unit time, which can be attained either by increasing the mouth size of the net, or by increasing the towing speed. To improve fishing and fuel efficiency of trawl vessels targeting fishes of greater mobility, in which the towing speed is more critical in determining fishing efficiency, we conducted a series of model tests to evaluate the performance of the newly-designed nozzle propeller before installing it in a trawl vessel to verify its towing speed and fuel efficiency in the sea. By conducting further model tests in the experimental basin, we redesigned the propeller of stern trawler to improve the resistance and propulsion performance. Through actual fishing operations, we evaluated the improvement in fuel and fishing efficiency by installing the new nozzle propeller. The trawling speed increased by 0.6kts at the same engine power (RPM), while the engine margin increased by more than 20%. The increased towing speed by installing the redesigned propeller is expected to enhance fishing performance through increasing the number of hauling- and casting operations per unit times, while shortening the towing duration. Analysis of the Catch-Per-Unit-Effort (CPUE) data indicated that the mean CPUE of trawl fishery increased from 3.04kg/m in year 2007 to 6.15kg/m in year 2008, confirming enhanced fishing efficiency by adopting the redesigned propeller.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.2
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• pp.105-116
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• 1998

This paper, examines the relationship between water temperatures and fishing conditions of common squid by the squid angling fishery from June to September in 1993-1995. The condition of the common squid fishing largely depended on the fluctuation of water temperature in the coastal area of Gampo. Monthly mean water temperatures during June m September in 1993 and 1994 were relatively higher than those in 1995 in Gampo area. But the values between July and August in 1995 were about 5$^{\circ}C$ lower than those in 1993 and 1995. Coefficients of variation (CV) of water temperature showed the lowest value during July ~ September in 1993, however, the highest value was observed in July and August in 1994. Catch per unit effort (CPUE ; kg/angling) showed a peak with 73.7kg in 1993 when the CV was low. On the other hand, the lowest CPUE of 39.6kg was observed in 1994 when the CV was high. It was concluded that the high stability of water temperatures and the weak strength of cold water have caused the good fishing conditions of common squid.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.22 no.4
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• pp.196-200
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• 1989

Fishery production of topshell in Cheju-do has been rapidly decreased in the last few years. To investigate the origin of this problem and estimate maximum sustainable yield (MSY) and catch per unit effort (CPUE) of topshell in Cheju-do, a survey has been done ysing the statistical data for 19 years (1968-1986) of topshell production in Cheju-do and data for 3 yea.5 (1984-1986) from an fishery village, Tonggui-ri, Pukcheju-gun, Cheju-do. Maximum sustainable yield of topshell in Cheju-do assumed to be 2,500-2,800 metric tons(M/T) per year. The annual fishery productions of topshell from 1982 to 1986 were 3,368, 3,649, 3,308, 3,136, and 1,400 M/T, respectively. These results show that topshell had been over-fished during 1982 to 1985. Because of the over-fishing, production sharply decreased down to 1,400 M/T in 1986. Total annual production of topshell in Tonggui-ri is a little less than one Percent of that of Cheju-do. To achieve this production, over the half of resistered diving women in this village have been worked. To estimate catch per unit effort of topshell in Cheju-do, it seems better to use the data which is the number of diving women who have been worked for certain period of time than the number of working days in the same period of time.

• Fisheries and Aquatic Sciences
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• v.24 no.4
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• pp.139-152
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• 2021

The main purpose of this study is to fit catch-per-unit-effort (CPUE) data about Korea chub mackerel (Scomber japonicus) stock with a state-space production (SSP) model, and to provide stock assessment results. We chose a surplus production model for the chub mackerel data, namely annual yield and CPUE. Then we employed a state-space layer for a production model to consider two sources of variability arising from unmodelled factors (process error) and noise in the data (observation error). We implemented the model via script software ADMB-RE because it reduces the computational cost of high-dimensional integration and provides Markov Chain Monte Carlo sampling, which is required for Bayesian approaches. To stabilize the numerical optimization, we considered prior distributions for model parameters. Applying the SSP model to data collected from commercial fisheries from 1999 to 2017, we estimated model parameters and management references, as well as uncertainties for the estimates. We also applied various production models and showed parameter estimates and goodness of fit statistics to compare the model performance. This study presents two significant findings. First, we concluded that the stock has been overexploited in terms of harvest rate from 1999 to 2017. Second, we suggest a SSP model for the smallest goodness of fit statistics among several production models, especially for fitting CPUE data with fluctuations.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.6
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• pp.934-941
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• 2020

The spatial and temporal catch variations of Argentine shortfin squid Illex argentinus in the Southwest Atlantic Ocean (SWA) were analyzed using Korean squid-jigging fishery data collected through electronic reporting system (ERS) from 2016 to 2020. The ERS linked with GPS has been implemented for collecting fishing data from all Korean fishing vessels operating in international waters since November 2015. The fishing period of the Korean squid-jigging fishery in the SWA runs from early summer to autumn (December to June) in the Southern Hemisphere. The fishing ground was extended from 42°S to 48°S along the Patagonian continental shelf and slope, and the main fishing ground was formed around the Falkland Islands. The yearly catch per unit effort (CPUE) of I. argentinus fluctuated between 1.69 and 7.53 tons/day. In this study, during the fishing season, a south and westward shift on the fishing ground was observed indicating the feeding migration of the south Patagonian stock. The shift in monthly fishing centroids differed according to fishing season. The gradual southward shifts of fishing centroids were observed in the catch years (2017 and 2018), whereas unapparent shifts in fishing centroids were observed in the low catch years (2016 and 2019).