• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.45 no.4
• /
• pp.201-210
• /
• 2009

Cast fishing gear needs some time for fishing progress, and catches and their composition by submerged time can change by several cause. Therefore, it is very importance to study fishing capacity of fishing gear by submerged time. This study is to investigate catches and their composition of shrimp trap, that is used in the coastal of the East Sea, and to find the fittest lifting time of trap. Experimental term are September 2006 and August 2007, the location is the coastal of Oho, Goseong, Gangwondo, Korea and one hundred trap is used at each casting and lifting of gear. For convenience of description, survey of 2006 and 2007 are dented as experimental code 1 and 2, and submerged time 21hr, 43hr and 66hr are dented as code A, B and C. The result of obtained from the above approach are summarized as follows: Many Northern shrimps(Pandalus eous), dominated 96.36%, are only catched in experimental code A, and in code B and C, some of coonstripe shrimp(Pandalus hypsinotus) and few morotoge shrimp(Pandalopsis japonica) are catched. CPUE of code 1A, 1B and 1C per trap were 21.67g, 29.51g and 28.48g, and those of code 2A, 2B and 2C per trap were 25.44g, 32.93g and 33.36g. Therefore, 24.66% of catch increased according as submerged time passes from 1 day to 2 days, and almost no change of catch was to be -1.1%. Carapace length of code 1A, 1B and 1C were 23.77mm, 25.00mm and 25.57mm, and those of code 2A, 2B and 2C per trap were 23.83mm, 24.95mm and 25.45mm. Thus, the more submerged time is, the less catch of small fish is and the more catch of large fish is. Consequently, fit lifting time of shrimp trap is after 2 days, and if considered trouble of fishing gear and condition of catch, the fittest lifting time is the third successive day of casting date.

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

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.48 no.4
• /
• pp.310-321
• /
• 2012

There are many studies of the biodegradable net for fishing to prevent marine pollution in Korea and the snow crab gill nets is developed effectively. Recently, the biodegradable gill net for fishes is being developed. This study is the experiment of the catch characteristics for the biodegradable flounder gill net. The 8 experiments were carried out using the nylon gill net and the biodegradable gill net in from August to October, 2011 in the southern East Sea. The results obtained from the above approaches are summarized as follows; A total of 16 species was caught with most dominant species of Cleisthenes pinetorum followed by Liparis tanakai, Glyptocephalus stelleri, Buccinum striatissimum and Dasycottus setiger. A total of catch of the nylon net was 342,885g and that of the biodegradable net was 236,857g. Thus catch of the nylon net was 1.45 times more than that of the biodegradable net. The length composition of Cleisthenes pinetorum, caught by the biodegradable net was very similar to that of nylon. As a result of analysis on the effect of submerged time, small fish escaped more easily than large fish as the submerged time is getting longer. And catches of the biodegradable net was less than the nylon net's as higher as wave height. Wave height was more influential factor for fishing capacity than submerged time based on the results of a comparison between catch difference of two kinds of gill nets and catch characteristics.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.38 no.3
• /
• pp.196-204
• /
• 2005

The horizontal and vertical distribution of yellowfin tuna, Thunnus albacares (Bonnaterre) and bigeye tuna, Tunnus obesus (Lowe) in relation to oceanic conditions such as thermal structure produced during El Nino/La Nina episodes were analyzed on the basis of data sets for the catches and efforts from the Korean tuna longline fishery and for the oceanographic observations from the NOAA during 1982-2002 in the tropical Pacific. The high density of fishing ground appeared in the western Pacific ($5^{\circ}N-5^{\circ}S,\;160^{\circ}E-180^{\circ}W$) for yellowfin tuna and in the eastern Pacific ($5^{\circ}N-15^{\circ}S,\;130^{\circ}W-100^{\circ}W$) for bigeye tuna. yellowfin and bigeye tunas were mainly distributed at the 110-250 m layer and 245-312 m layer, respectively, in the western Pacific. However, in the eastern Pacific, they were mostly caught at the 116-161 m and 205-276 m layer for yellowfin tuna and bigeye tuna, respectively. It can be suggested that bigeye tuna be distributed in the deepest layer among tunas and show a vertical size stratification. It was observed that during the El Nino events the main fishing ground of yellowfin tuna shifted from the western Pacific toward the eastern Pacific. In the eastern Pacific which showed a higher density of bigeye tuna, the vulnerability of bigeye tuna caught by deep longline increased during the El Nino events due to deepening of thermocline layer and a more intensively distribution of the fish schools in the lower layer of thermocline during the El Nino events.

• Journal of Korea Water Resources Association
• /
• v.30 no.6
• /
• pp.587-595
• /
• 1997

Experimental study on unsaturated flow in the soil is important to understand the characteristics of the water flow. Measurement of unsteady-state water movement using the traditional equipment (e.g. tensiometer) has a problem that requires relatively a long response time. In this study a quick measurement method of soil water flow using TDR is introduced. TDR consists of an electronic function generator which generates a squared wave, and an oscilloscope which catches the reflected wave. The wave is reflected where both the impedance of the transmission line and the propagation velocity are changed. The water content can be obtained from the travel time measured by means of TDR because the dielectric constant is affected by the change of soil water content. From the result of TDR calibration. TDR measurement error for the oven dried soil was found to be less than 3.5%. This supports that TDR is a viable technique to measure the unsteady-state water movement.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.42 no.4
• /
• pp.203-209
• /
• 2006

This paper described the experimental squid jigging fishery conducted by a commercial fishing vessel in the Northwest Atlantic Ocean from August to October 2005. Author carried out experimental jiggings of 65 times during 57 days by three type of jigs which were pick jig, soft jig and soft luminous jig. The total catch, effort/day and catches/line-day of northern shortfin squid (Illex illecebrosus) were 12,726kg, 35 auto jigging machine and 3.5kg, respectively. Higher CUPE was observed in September, August and October. Catch ratio of pick jig was higher by 57-86% than those of soft jig and soft luminous jig. Higher catch was recorded at the $42^{\circ}55'N,\;62^{\circ}10'W$ with surface temperature ranging $18-21^{\circ}C$. The range of the dorsal mantle length was from 13.5cm to 23.0cm with average 17.2cm for female and from 13.0cm to 20.0cm with average 17.0cm for male. Sex ratio showed 55.4% of female.

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

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.38 no.3
• /
• pp.241-248
• /
• 2002

The combined hydroacoustic and demersal trawl surveys to investigate the distribution characteristics of fish schools in the Yellow Sea and the East China Sea were carried out during the spring of 1997 by the training ship "Nagasaki Maru" of Nagasaki University. Fish samples were collected by bottom trawling from 9 trawl stations randomly selected in the survey area, and the species and length compositions of trawl catches are examined. Hydroacoustic data were collected by using a Furuno FQ-50 scientific echo sounder operating at 50KHz and the data stored in field were later processed in the laboratory. The results obtained can be summarized as follows ：1. In the 9 trawl surveys conducted in the Yellow Sea and the East China Sea, 78 species including 80 species of fishes, 4 species of Cephalopoda and 6 species of Crustacea, were identified. The most abundant species in these stations were swimming crab(Portunus trituberculatus), Japanese horse mackere(Trachurus japonicus), redlip croaker(Larimichthys polyactis) and the catch per one hour in each station ranged 7.7 to 182.5 kg/hour. 2. The mean volume backscattering strength for the entire water column and the bottom layer of the 0-10 m from bottom friction were -74.6 ㏈ and -68.2 ㏈, respectively. That is, the mean volume backscattering strength for the bottom layer was 6.4 ㏈ higher than that for the entire water column 3. In the surveys during the spring of 1997, the geographical distribution characteristics of fish schools suggests a trend of decreasing fish abundance toward the coast area of Korea and the highest demersal concentrations appeared in waters between the Cheju Island and the Tsushima Island 4. The distribution density of fish school in the East China Sea and Yellow Sea during the 1997 acoustic survey were estimated to be 6.65$\times$10$^{-5}$ kg/㎥ in the entire water column and 2.86$\times$l0$^{-4}$ kg/㎥ in the bottom layer, respectively.pectively.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.25 no.2
• /
• pp.44-53
• /
• 1989

In order to grasp the characteristics of a fishing ground at yeosu bay, the fluctuation in condition of the coast and that in catch by pound nets in the coast were investigated respectively. The results obtained are summarized as follows: 1. The water temperature in spring and summer was higher at the coast side than off shore, but in autumn and winter took the reverse. 2. The salinity was higher in spring and winter than in summer and autumn. A lower salinity zone was found at the Dolsan Do coast and higher ones were made off shore. 3. A eddy current was found at the Dolsan Do coast and a thermocline were made at the depth of 30 to 40 m in summer. But in autumn and winter the water became homogeneous. 4. The annual catch by the pound net was highest in 1984 and then decreased gradually. The monthly catch was highest in June and then decreased gradually. 5. The catches seemed to increase with the sea water temperature and salinity, and great catch was shown in 21$^{\circ}C$ to 27$^{\circ}C$ and 33.80% to 34.00%. 6. The component rate of fishes was 28.4% in spanish mackerel, 17.9% in anchovy, 19.5% in horse mackerel, 21.0% in sardine, 7.2% in hairtail, and 1% in common mackerel. 7. The fishes appeared continuously on way of fishing operation were spanish mackerel, hairtail, Yellow talil, crab, etc. An anchovy and sardine were caught mainly from March to July or August, horese mackerel and common mackerel from May to November. but puffer, swell fish, saury and filefish were caught mainly from April to October. 8. The sum of catch was largest in June, at which the wind direction was NE to SSW, the speed below 3.2m/sec, the atmospheric pressure below 1008mb, and precipitation beyond 154mm.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.19 no.5
• /
• pp.459-466
• /
• 2013

To understand the fishery characteristics by a beam trawl off the coast of the Chungnam province, covering $125^{\circ}$ 50'~$126^{\circ}$ 05'E, $36^{\circ}$ 15'~$36^{\circ}$ 25'N, a beam trawl was deployed 2~4 times a month from March 2008 to February 2009. The catch was consisted of 96 species of 63 families belonging to 19 orders. Among these, organisms were identified as 54 species of fish, 27 species of crustaceans, 9 species of gastropoda, bivalves, and 6 species of cephalopods. Trachysalambria curvirostris which is the target species of the beam trawl fishery occupied only 2.1% of the total catch, showing a low ratio of catches. Most of T. curvirostris was harvested from July to November while small amount of T. curvirostris was captured from May to December. In this study, we concluded that the bycatch ratio except T. curvirostris in T. curvirostris fishery was relatively high, thus the fishery of T. curvirostris might affect the fishery resource management of bycaught species off the coast of Chungnam province.