Chang-Heon Lee

Characteristics of lost fishing gear distribution on the sea bed around gillnet fishing ground for yellow croaker in the near sea of Jeju, Korea

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Hooking rate and bait loss rate of traditional hairtail hand line according to immersion time in the coastal waters of Jeju

This paper is to investigate the effect of the immersion time in the traditional hairtail hand line fordeveloping the fishing methods and the fishing gear in the coast of jeju. The operating of 32 times was madewith each different immersion time of hairtail hand line, and the relations between the catch and theimmersion time were examined. As the result, targeted species rate was over 98% of total catch. From about800 seconds after casting, the hooking rate was decreased and the bite loss rate was increased, it seems to bemade by the decreasing factors of predators including the cutting of branch lines etc. In addition, it wassupposed that the hooking rate and the bait loss rate had a deep connection with feeding time zone. The levelof the correlation coefficient of the bait loss rate according to the immersion time was 0.54 at p 0.01, in thecase of the hooking rate, 0.59 was chosen after about 800 seconds. The hooking rate and the bait loss rateaccording to the hook number were not irrelevant to the fish school layer. Additionally, it was assumed thatthe bait loss rate was related to the depth of water.Key words : Hairtail hand line, Hooking rate, Bait loss rate, Immersion time

A basic study on the improvement of the continuous type fishing system for largehead hairtail hand line in coastal area of Jeju island, Korea

This experimental study was carried out to obtain the base data for saving the man power in the fishingoperation of largehead hairtail hand line by using the continuous type hand line system with a rotary devicewhich could make a main line move automatically. In order to solve the twists and entangling on the mainline happened during operating test, the resistance board was suspended at the end of the main line at sea. Asthe result, there were no problems of tangling and so on due to up and down moving of a main line.According to the control of a fixed angle of guide roller, it was possible to prevent the main line to beseparated from a side roller and a guide roller. In addition, PVC tube between a guide roller and a side rollerenabled a main line to be moved smoothly without any entanglement.Key words : Continuous type hand line, Side roller, Guide roller, Guide tube, Resistance board

Catch fluctuation of the rectangular set net according to the tide age in the coastal waters of Jeju

The fundamental data on the catch fluctuation in the rectangular set net according to the tide age weredeveloped based on the catches recorded from the year 1986 to 2004 in the coastal waters of Hamdeok, Jeju.Total catch by the rectangular set net had a deep connection with the tide age. In particular, duringincreasing tide, total catch were reduced gradually from the neap tide to the high tide. As it turned out, theslope of total catch declined by degree and showed a correlation coefficient of determination of 0.76. On thecontrary, in the case of decreasing tide, there was little sign of rise in total catch. In particular, large catchseemed to occur at the next tide to the neap tide. In the relation between the catch and the tide age, the levelof the correlation coefficient chosen at p0.05 decreased in the order rabbitfish(0.84) and horsemackerel( 0.71), while the significance of other dominant species were not selected.Key words : Tide age, Neap tide, High tide, Catch fluctuation, Set net

Hearing Ability of Conger eel Conger myriaster caught in the Coast of jeju Island

In order to obtain the fundamental data about the behavior of conger by underwater audible sound, this experiment was carried out to investigate the hearing ability of Conger eel Conger myriaster which was in the coast of Jeju Island by heartbeat conditioning method using pure tones coupled with a delayed electric shock. The audible range of conger eel extended from 50Hz to 300Hz with a peak sensitivity at 80Hz including less sensitivity over 200Hz. The mean auditory thresholds of conger eel at the frequencies of 50Hz, 80Hz, 100Hz, 200Hz and 300Hz were 105dB, 92dB, 96dB, 128dB and 140dB, respectively. The positive response of conger eel was not evident after the sound projection of over 200Hz. At the results, the sensitive frequency range of conger eel is narrow in spite of swim bladder. Auditory masking was determined for Conger eel by using masking stimuli with the spectrum level range of about 60~70dB (0dB re ). According to white noise level, the auditory thresholds increased as compared with thresholds in a quiet background noise including critical ratio at 68dB of white noise from minimum 26dB to maximum 30dB at test frequencies of 80Hz and 100Hz. The noise spectrum level at the start of masking was distributed at the range of about 68dB within 80~100Hz.

The tendency and the effectiveness of policy in marine accident occurring in the sea around Jeju island

The objective of this paper is to aid in basic directions for the countermeasure against marine accidents by using the statistical data of Jeju Coast Guard from 1983 to 2012. Marine accidents of about 600~1,000 vessels was reported in all the waters around South Korea from 2000 to 2008. From 2009, these accidents increased rapidly and reached 1,600~2,000 vessels. Although marine accidents of longline fishing vessels did not show a big change prior to 1993, the number have increased steadily until 2007. This is considered a tendency that appears when longline vessels, using the Port of Sungsanpo as a base and operating in fishing grounds in the East China Sea, are converted to long-term fishing from short-term fishing for reasons such as cost reduction due to the sudden rise of oil prices and the performance improvement of the fishing vessels. The number of vessels in marine accidents decreased gradually from 1999 to 2002 and for nearly 7 years from 2002 to 2008, the annual average of marine accidents stayed at 97 vessels. This is seemed to be the result of a change in the policy of either the central or local government and largely associated with changes in the way of statistical processing. This tendency is resulted in lower number of the accidents due to careless navigation which can be viewed as a human error than the number of marine accidents due to poor maintenance as a cause of mechanical failure in the same period. The increase rate in the marine accidents of Jeju Island-based fishing vessels is greater than that of other area-based fishing vessels among the fishing vessels operating in coastal and near sea around Jeju Island each year.

Hearing Ability of Sharp Toothed Eel Muraenesox cinereus caught in the Southern Korean Waters

The auditory thresholds for 7 specimens of the sharp toothed eel Muraensox cinerus were measured at 5 frequencies by heartbeat conditioning method using pure tones coupled with a delayed electric shock. The audible range of the sharp toothed eel extended from 80Hz to 300Hz with the best sensitivity around 80Hz and 100Hz. In addition, the auditory thresholds over 200Hz increased rapidly. The mean auditory thresholds of the sharp toothed eel at the test frequencies of 80Hz, 100Hz, 200Hz and 300Hz were 87dB, 86dB, 105dB and 126dB, respectively. Auditory masking was determined for the sharp toothed eel by using masking stimuli with the spectrum level range of about 70~80dB (0dB re ). According to white noise level, the auditory thresholds increased as compared with thresholds in a quiet background noise. The noise spectrum level at the start of masking was distributed at the range of about 64dB within 80~100Hz. Critical ratio ranged from minimum 24dB to maximum 40dB at test frequencies of 80Hz~200Hz.

Stress response of black rock fish according to adapted time in measurement of auditory threshold

In order to obtain the fundamental data for the marine ranch, this paper was carried out to investigate cortisolvariation in blood according to adapted time in the measurement of auditory threshold. The groups wereadapted at the experimental tanks for 0.5, 1, 3 and 6 hours, respectively. At the results, cortisol concentrationhad a deep connection with adapted time. In particular, cortisol concentration in the experimental group of 1hour was significantly increased, whereas others showed no difference comparing with the control group.When classical conditioning method with the sound coupled with a delayed electric shock was given afterthe adapted time of 1 hour and 6 hours, the rate of the conditioning completion for 6 hours was higher thanthat of 1 hour. Therefore, this suggests that the sufficient adapted time was required for the accurate auditorythreshold. Key words : Stress, Auditory threshold, Adapted time

Hearing Ability of Redlip croaker Pseudosciaena polyactis cultured in the Coastal Sea of Jeju

The purpose of this paper is to improve the availability of underwater sound by the fundamental data on the hearing ability of Redlip croaker Pseudosciaena polyactis, which is cultured according to the cultivation technology, recently. The auditory thresholds of Redlip croaker were determined at 6 frequencies from 80Hz to 800Hz by heartbeat conditioning method using pure tones coupled with a delayed electric shock. The audible range of the Redlip croaker extended from 80Hz to 800Hz with the best sensitive frequency range including little difference in hearing ability from 80Hz to 500Hz. In addition, the auditory thresholds over 800Hz increased rapidly. The mean auditory thresholds of the Redlip croaker at the test frequencies from 80Hz to 800Hz were 90.7dB, 93.4dB, 92.9dB, 94.4dB, 95.5dB and 108dB, respectively. Auditory masking for the redlip croaker was measured using masking stimuli with the spectrum level range of about 66, 71, 75dB (0dB re 1PaHz ). According to white noise level, the auditory thresholds increased as compared with thresholds in a quiet background noise. The Auditory masking by the white noise spectrum level was stared over about 70dB within 80~500Hz. Critical ratio ranged from minimum 20.7dB to maximum 25.5dB at test frequencies of 80Hz~500Hz.

Fishing characteristics of small yellow croaker drift gill net by net height

Small yellow croaker is one of the important stocks in Korean waters. In this study, we conducted sea trials to estimate optimum height of a drift gill net for effective fishing of small yellow croaker. In the trial using existing net which has 9.2m in height, there was 22 species (1,180 fishes, 99.9kg) caught. The catch (in individuals) of small yellow croaker, especially larger fishes (over 22cm in FL), was higher as part of net height is higher, while the number of species bycaught and the catch of those species were higher as part of net height is lower. In the trial using extension net which has 18.4m in height, there was 27 species (2,030 fishes, 151.7kg). It showed same pattern with existing net in the section I to III, however, in the section IV which is over 13.8m of net height, the catch sharply decreased. The number of species bycaught and the catch of those species using extension net were also same as results using existing net. It showed that section III (9.2-13.8m) where is upper-middle part of the net has caught most of catch and large fishes having over 22cm in length. Through these results, it is judged that the setting depth of the net where is 4.6-13.8m above the sea bottom is the best to reduce bycatch and catch much more large size fishes, and the catch per net is proportional to filtering area of net. Therefore the Fisheries Resource Management Act (the clause 1, article 10) on the amount of usage for offshore drift gill net need to be considered not only length of a net but also net height.