• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제29권4호
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• pp.260-271
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• 1993

Due to depletion of fish resources as time goes on, the trawl fishing industries which have caught the demersal fish is confronting with financial difficulties. For the purpose of breaking these difficulties, trawlers are expanding the fishing targets to the midwater from bottom stock. The trawlers become to be able to detect the fish schools not only vertical but also horizontal direction by equipping the sonar system on board. Even though the operator locates the fish school by sonar, it is not easy to make a desirable catch of the fish school which is detected, for the reason of the maneuverring characteristics of trawler. For the purpose of enhancing the efficiency of a fish catch, the auther performed a series of on board experiments to investigate the maneuverablilites of midwater trawaler. The obtained results are summerized as follows: 1. The higher the RPM of main engine, the smaller the magnitude of turning circle. And it is smaller in the right than in the left turning 2. Towing speed varies irregularly under turning novenment. When the RPM of main engine being 560, 680 the angular velocities are 11.3deg/min, 22.5deg/min respectively. 3. The difference of new course distance between calculated by maneuverring indices and measured by experimental ship is high when altering course being large and towing speed low. 4. The faster the towing speed is, the shorter the new course distance becomes. When towing speed is same in right and left turning movement, the now course distance is shorter in case of right turning movement than in left. 5. It is considered to be convenient for a navigator to utilize the curves for altering course in order to steer the ship rapidly and accurately.

• Journal of Internet Computing and Services
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• 제25권1호
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• pp.17-27
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• 2024

Overfishing, climate change, and competitive fishing have led to a continuous decline in fishery production. To address these issues, the Total Allowable Catch (TAC) system has been established, which sets annual catch quotas for individual fish species and allows fishing only within those limits. As part of the TAC system, land-based investigators measure the length and height of fish species at auction markets to calculate the weight and TAC depletion. However, the accuracy of the acquired data varies depending on the skill level of the land-based investigators, and the labor-intensive nature of the work makes it unsustainable. To address these issues, this paper proposes a fish species recognition and length measurement system that automatically measures the length, height, and weight of eight TAC-managed fish species using the camera of a smart pad that can measure the distance to the water surface. This system can help to automate the current labor-intensive work, minimize data loss, and facilitate the establishment of the TAC system.

• Fisheries and Aquatic Sciences
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• 제18권3호
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• pp.325-332
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• 2015

An active stimulating method for juvenile fishes to drive escaping from mesh of the codend was examined by shaking canvas in the bottom trawl followed by shrimp beam trawl. Field fishing trials by a bottom trawl were carried out between the Geomoondo and Jejudo in west of South sea, Korea by conver-net methods to examine the effect on the reduction of juvenile fish as a discard catch by generating a shaking movement of the codend using two pieces of asymmetrical semi-circular canvas. The mean period of the shaking motion with the round canvas was 10-15 s, and the range of amplitude as a vertical depth change was up to 0.4-0.6 m when towing speed 3.4-4.3 k't as estimated by peak event analysis. The escape rate of juvenile fish in conver-net by total juvenile bycatch (codend and cover-net) in 14 trials increased from 20% in a steady codend to 34% using a shaking codend in the bottom trawl, while the marketing catch or total bycatch was similar between steady and shaking cod ends. There was no difference in the body size of the fish and species composition between the steady and shaking cod ends. Above results demonstrate a new method for bycatch reduction actually up to 18% using an active stimulating device, although further experiments are needed to increase an effective shaking motion of the codend in amplitude and period for more bycatch reduction.

• Korean Journal of Ichthyology
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• 제10권2호
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• pp.155-163
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• 1998

To determine diel and seasonal variations in abundance and species composition of fishery resources, day and night samples were collected by a bag net from April through November 1997 off Kogunsan-gundo. A total of 75 species was collected. The total catch was consisted of 71% fish, 18% shrimps, 7% cephalopods and 4% crabs. Pholis fangi and Engraulis japonicus predominated, and accounted for 87% of the total number of fish collected. Most of them were larvae and juvniles. P. fangi and Ammodyres personatus occurred from April to June, and E. japonicus occurred from July to November, suggesting that they used the coastal areas as nursery ground at the different season to avoid competition. Dominant fish larvae and juveniles showed the significant diel difference in catch.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제40권3호
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• pp.182-188
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• 2004

It has been, in general, known that the catching efficiency of a trammel net is better than that of a gill net because of the variability of catch species and size. In this stidy, A fishing gear test was carried out to analyze the catching efficiency of the gill net and the trammel net on the coast of Geomun-do of southern Korean waters and fish school aggregation was also investigated using a underwater video camera. CPUE of the gill net was 49.2% higher than the trammel net but fish species was 34.5% lower where there was no difference on the significance level of 5% by ANOVA test. Main catch species caught by the gill net were red seabream(Pagrus major) and triggerfish(Aluterus monoceros), skate ray(Raja Kenojei) and red seabream for the trammel net, and the average body length of red seabream was shorter than the trammel net. It was thought that the reason of higher catch in the gill net than the trammel net was a fish school which can be caught easily by gill net and the size of population was suitable for the gill net.

• Korean Journal of Fisheries and Aquatic Sciences
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• 제2권1호
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• pp.25-32
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• 1969

The estimated annual catch of river fishes in the lower part of the Naktong River was derived from the questionnaire, as a part of the fundamental investigation which was carried out for the development of fisheries In that region during the period of May 1967, to June 1968. The data were submitted by fishermen, and the area covered for the present investigation is shown in Fig.1. The annual catch of the region was estimated to be about 500 tons, excluding the mussel Cerbicula elatior. Prussian carp Carassius carassius was the largest in amount followed by com-mon carp Cyprinus carpio, and then goby Synechogobius hasta, Japanese eel Anguilla japonica, mullet Mugil cephalus, ect. and in that order. Major species of the fishes of this region belong to the carp family Cyprinidae, its species counting 23 from the collection during the observation period, and the total number of species was 40, these belonging to 14 families. But occasional severe drought heavily increase the salt content of the region, and at that time the major catch of fish becomes marine fishes such as Harengula zunasi, Clupanodon Punctatus, etc.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제56권4호
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• pp.277-291
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• 2020

In order to understand characteristics on bycatch of Korean tuna purse seine fishery, especially operations associated with Fish Aggregating Device (FAD) in the Indian Ocean, we conducted analyses related to bycatch by school association type (unassociated school, FAD associated school and log associated school) using the data collected by scientific observers from 2016 to 2018. The FAD used by Korean tuna purse seine fishery in the Indian Ocean was a drifting FAD, which belongs to non-entangling FADs according to the category proposed by the International Seafood Sustainability Foundation (ISSF). The target species of Korean tuna purse seine fishery are skipjack, yellowfin and bigeye tunas, accounting for 99% of the total catch. The ratio of bycatch was 0.97% in total catch and the discard accounted for less than 1%, indicating that most catch was retained on board. In terms of bycatch ratio by school association type, it accounted for 0.12% for unassociated school, 1.09% for FAD associated school and 1.25% for log associated school. As for the catch proportion of shark species by school association type, it accounted for 0.01% for unassociated school, 0.11% for FAD associated school and 0.10% for log associated school, which showed that unassociated school type was the lowest to affect bycatch of non-target and shark species. Given the proportion of bycatch compositions, however, it is considered that FAD associated school of Korean tuna purse seine fishery has less caught bycatch species of non-target and shark, compared to other fleets operating in the Indian Ocean.

• Korean Journal of Fisheries and Aquatic Sciences
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• 제50권1호
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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.

• Korean Journal of Ichthyology
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• 제26권4호
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• pp.295-302
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• 2014

Mottled skates, Beringraja pulchra, mainly found in the Yellow Sea were caught by otter trawl at 30 stations from 2002 to 2013 to identify the distribution patterns and ecology of the fish in the eastern Yellow Sea. A total of 442 individuals of mottled skate were caught at the 112 hauls of the total 892 hauls. The fish was widely distributed in the entire survey area in spring and autumn, and mainly caught in the northern offshore in summer and in the southern part in winter. The under-yearlings of the mottled skate were mainly caught in the offshore in spring and autumn. The mottled skates were found at the temperature ranges of $3.8{\sim}14.5^{\circ}C$, and the salinity of 31.2~34.2. The catch data of the fish suggested that water temperature be a critical factor for the distribution with the optimal ranges of $5{\sim}14^{\circ}C$. Salinity and water depth were not critical as much as the water temperature for the distribution of the mottled skates in the Yellow Sea. Also, the annual fluctuations of the fish catch were reviewed using the catch data from korea fisheries cooperative and national statistics from 1991 to 2009.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제40권4호
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• pp.295-303
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• 2004

In order to estimate the effect of ceramic artificial reefs on the fisheries resources enhancement, we have studied the variation of catch and species, which were caught by trammel net on the three fishing grounds of ceramic artificial reef, natural reef, and control(non-reef)in the coast of Geomun-do, Korea from 2001 to 2003. Catch per unit effort (CPUE ; g/panel) of fishing ground with the ceramic artificial reef area was 1,621.9g, it was about 67.9% higher than the natural reef area 333.3% higher than the control area. The catch of fish with the ceramic artificial and the natural reef area was not significantly different based on statistical analysis of Tukey test, whereas the relationship between the ceramic artificial reef and the control area was significantly different (p<0.05). Monthly mean number of species caught by the artificial reef area, the natural reef area and the control area was no difference by ANOVA test. The catch of fish was highest in November and lowest in May, whish was associated with the natural reef and the control area. The dominant species were demersal fishes living around rock such as Pagrus majir, Thamnaconus modestus, Stephanolepis sirrhifer, Pleuronichthys curntus, and Ostracion cubicus in the artificial reef area, but demersal of migratory fishes in the natural reef and the control area.