• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.4
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• pp.310-316
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• 2022

Giant pacific octopus, Enteroctopus dofleini, is a large mollusk distributed in the East Sea of Korea. In this study, the catch status of giant pacific octopus by drift line fishery and the effect of sea temperature on fishing ground were investigated in Goseong-gun, Gangwon-do, which is the central coast of the East Sea. The average catch of giant pacific octopus in Gangwon-do was 1,570 tons over the past ten years, and it accounted for 21% in 2008 and 44% in 2021 compared to the total catch in the East Sea during the same period. Such data indicates that the catch in Gangwon-do has recently increased. In this study area, giant pacific octopus weighing 1.1-5.0 kg dominated accounting for 56% of the total individuals, and followed by those weighing 1 kg or less. However, the ratio of catch of giant pacific octopus over 5.1 kg tended to increase in 2021, which is thought to be related to the sea temperature that affected the fishing ground. The main depth of fishing ground was from 21 m to 50 m in this area and fishing grounds were widely distributed throughout the season except summer. Fishing ground was formed with the conditions of bottom sea temperature under 10℃ and was diminished by moving of giant pacific octopus to deeper depth with conditions of bottom sea temperature over 18℃.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.48 no.1
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• pp.72-81
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• 2012

Using artificial neural network (ANN) technique, auction prices for common mackerel were forecasted with the daily total sale and auction price data at the Busan Cooperative Fish Market before introducing Total Allowable Catch (TAC) system, when catch data had no limit in Korea. Virtual input data produced from actual data were used to improve the accuracy of prediction and the suitable neural network was induced for the prediction. We tested 35 networks to be retained 10, and found good performance network with regression ratio of 0.904 and determination coefficient of 0.695. There were significant variations between training and verification errors in this network. Ideally, it should require more training cases to avoid over-learning, which leads to improve performance and makes the results more reliable. And the precision of prediction was improved when environmental factors including physical and biological variables were added. This network for prediction of price and catch was considered to be applicable for other fishes.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.4
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• pp.251-256
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• 2001

Catch characteristics according to the tide and fishing time were analyzed through the fishing log data of trawls which work at Arafura Sea of Indonesia. This study aimed to provide basic data to make a fishing plan from the catch difference according to fishing time after analyzing the suitable fishing time of fish species. The results obtained are summarized as follows ; 1. Catches were the largest at the day of very weak tide as 22.8% of total catch and was the smallest at the day of a little strong tide as 16.9% of total catch. 2 Catches of croaker Argyrosomus sp. ＆ Johnius vogleri, silver hairtail Trichiurus lepturs and coachwhip ray Himantura sp. were the largest at the day of weak tide(20.8%), very weak tide(33.8%), a little strong tide(22.0%) and catch for croaker and silver hairtail were the smallest at the day of a little strong tide(18.7%-10.0%) and coachwhip ray was the smallest at the day of strong tide(16.8%). 3. Catches were the largest at the time of 08:00-12:00 as 19.7% of the total catch and were the smallest at the time of 20:00-24:00 as 14.1% of total catch. 4. Catches of croaker, silver hairtail and coachwhip ray were the largest at the time of 00:00- 04:00(21.0%), 08:00-12:00(35.0%) and 12:00-16:00 (21.2%) and were the smallest at the time of 12:00-16:00(12.7%), 20:00- 24:00(4.6%) and 20:00-24:00(13.4%).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.3
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• pp.414-423
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• 2015

Fishing trend and 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 2013. The historical catch of this fishery had sharply increased since mid-1980s, and it has shown fluctuations with about 2-3 hundred thousands, whereas the catch per number of vessel has steadily increased with fluctuations since commencing this fishery. As for the proportion of catch by set type, unassociated type had increased from the mid-1980s to the end of 1990s, and then has decreased up to 2010s. Associated type had decreased continually to the end of 1990s, however, it started to increase since the beginning of 2000s. As for the catch proportion of set type by main species, those of skipjack tuna and bigeye tuna showed higher in the associated type, whereas that of yellowfin tuna has the highest proportion in the unassociated type. Fishing distribution of Korean tuna purse seine fishery was concentrated on the area of $5^{\circ}N{\sim}10^{\circ}S$ and $140^{\circ}E{\sim}180^{\circ}$ through the decades. The monthly catch distribution by longitudinal zone of Korean tuna purse seine fishery expanded the most further to the eastward in September to October.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.32 no.2
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• pp.125-131
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• 1996

In order to investigate the relation between the environmental properties and the catch fluctuation of set net fishing grounds located in the coastal waters of Yosu, oceanographic observations on the fishing grounds were carried out by the training ship ofYosu Fisheries University from January, 1990 to September, 1992, and the data obtained were compared with the catch data from the joint market ofYosu fisheries cooperative society from 1984 to 1993. The resuItes obtained are summerized as follows : 1. The ranges of water temperature and salinity in the fishing ground was 7.0 to $27^{\circ}C.$and 26.6 to 33.2${\textperthousand}$, and water temperature increased from March to August and decreased from September to February of following year. 2. The salinity in the fishing grounds was relatively high without significant changes from November to June of the following year. From July, however, the salinity decreased to continue a low value till September and then increased. The salinity in the fishing ground was dominated mainly by the precipitation and its variation was large at the north entrance of set net fishing ground, influenced greatly by the land waters from the river of Somjin, but small in the offshore of the fishing grounds. 3. The fishes caught by the set nets were arranged in order of catch as follows; Spanish mackerel> Horse mackerel > Sardine > Anchovy > Hair tail. The catches of Anchovy and Sardine were high in April to May and those of Hair tail in June to July, but Spanish mackerel and Horse mackerel were caught for whole period of fishing. Spanish mackerel was caught most in September and least in April and their means were largest in August and smallest in June. 4. The ranges of optimum water temperature for fishing by the set nets was 13.5 to $25^{\circ}C.$, and in the ranges the catches increased with increasing temperature. The ranges of optimum salinity for fishing varied between 25.0 and 32.0${\textperthousand}$.

• 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).

• The Journal of Fisheries Business Administration
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• v.51 no.4
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• pp.1-18
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• 2020

The paper aims to explore existence and degree of remaining fisheries damages after the completion of undertaking the Four Major Rivers Project focusing on the case of Yeongsan river. The paper seeks to show the necessity of consideration of periods of fishery resources recovery in the estimation of ex-post fisheries damages of the project by inferring the analysis of the annual variation of environmental indicators in the river. Therefore, the paper suggests three years of remaining periods of fisheries damages of the project utilizing the variation trend of ex-ante and ex-post annual output data of inland fisheries in Jeonnam province and individual catch of fisheries. In the measurement of the annual degree of fisheries damages during periods of fishery resources recovery, the paper attempts to suggest the method of comparision of day catch data per vessel between ex-ante and ex-post periods of the project, which were investigated by the same institute. Here the paper tries to make correction of ex-post catch data for holding the same catching condition as ex-ante situation by adopting the concept of competitive intensity of catching which was derived from the decreasing rate of number of fishing households in the area of Yeongsan river.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.4
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• pp.489-497
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• 2015

To reveal the spatial and temporal variability in the distribution, growth, and maturation of skipjack tuna Katsuwonus pelamis in the western tropical Pacific, we compared two El $Ni{\tilde{n}}o$-Southern Oscillation (ENSO) signals and the sea surface temperature (SST) in the main fishing area with fishery and biological data. An index of skipjack tuna distribution was calculated using Korean purse seine fishery data from 1985 to 2003. Biological data for skipjack tuna were collected monthly from Korean catches during the 1994-2003 period. The catch was more closely related to the SST in the main fishing area than to the ENSO signals. However, cross-correlated function analysis showed delayed interactions between abiotic and biotic factors. The El $Ni{\tilde{n}}o$ events preceded the eastward movement of the fishing center by 2-3 months. El $Ni{\tilde{n}}o$ had a positive effect on the skipjack tuna catch, and the change in the Southern Oscillation Index (SOI) preceded the catch fluctuation by ca. 5-7 months. In addition, negative El $Ni{\tilde{n}}o$ effects on gonad maturation and the mean length of skipjack tuna were detected with time lags of 12 and 7 months, respectively. The length frequency indicated that the regime-specific growth pattern at each discrete period seemed to be related to the ENSO.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.1
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• pp.65-76
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• 2017

Since the late 1990s, walleye pollock Gadus chalcogrammus fisheries in Korean waters have been considered collapsed. Although many fisheries scientists suspect that the collapse might have been triggered by overexploitation of juvenile pollock or environmental changes, such conjectures have been neither tested nor investigated, partially because of limited data on the population. There has been no survey of the population, and the ages of fish in fishery catch have rarely been identified. Instead, fishery catch data from 1975-1997 included information about two life stages, 'juveniles and adults,' and data on catch-per-unit-effort (CPUE) during 1963-2007 and those on fish length and weight during 1965-2003 had been sporadically collected from commercial fisheries. To test hypotheses about the collapse of the pollock fisheries, we used a statistical linear model with juvenile CPUE as the response variable, and abiotic (e.g., water temperatures) and biotic factors [e.g., adult pollock, flatfishes (Pleuronectidae sp.), and sandfish (Arctoscopus japonicus) CPUEs] as the explanatory variables. The model results indicated that depletion of the pollock population was associated with both biotic (adult pollock and flatfishes abundance) and abiotic factors (mid-water temperatures in February and October). We further interpreted the results from ecological and biological perspectives, suggesting possible mechanisms.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.2
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• pp.116-123
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• 2018

Pacific bluefin tuna (Thunnus orientalis) has been mostly caught by the Korean offshore large purse seine fishery in Korean waters. The annual catch of Pacific bluefin tuna caught by the offshore large purse seine fishery in Korean waters showed less than 1,000 mt until the 1990s except for 1997. The catch sharply increased to 2,401 mt in 2000 and recorded the highest of 2,601 mt in 2003, but the catch has generally decreased with a fluctuation thereafter. The main fishing ground of Pacific bluefin tuna of this fishery is formed around Jeju Island. However, it expanded to the Yellow Sea, the coastal of Busan, and the East Sea, which depends on the migration patterns of Pacific bluefin tuna by season. The CPUE standardization of Pacific bluefin tuna was conducted using Generalized Linear Model (GLM) to assess the proxy of the abundance index. The data used for the GLM were catch (weight), effort (number of hauls), catch ratio of Pacific bluefin tuna, moon phase by year, quarter and area. The standardized CPUE from 2004 to 2011, except for 2003 and 2010, showed a steady trend, and then increased until 2014. The CPUE in 2015 decreased, and in 2016 was higher than that in 2015. The result of GLM suggests that the effect of the catch ratio of Pacific bluefin tuna is the largest factor affecting the nominal CPUE.