• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.57 no.3
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• pp.185-193
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• 2021

This study was conducted to evaluate the performance of the octopus pot according to mesh sizes. Entering behavior of Octopus minor and bait (Macrophthalmus japonicus) escape rate on the mesh sizes of the pots were investigated for six times in indoor tank. The sea trials for evaluating the performance of Octopus minor pot to different mesh sizes (22, 20 and 18 mm) were conducted for six times from 2017 to 2018 in the coastal sea of Deukyang Bay, the Republic of Korea. Behavior patterns of contact pot to leaved pot were more frequent than contact pot to bait search. When the octopus contacted to the pot, there was no clear search behavior to distinguish the mesh sizes. Total catch of 46% was accounted for 18 mm pots, followed by 34% at 20 mm and 20% at 22 mm (P < 0.05). Catch per unit effort was calculated as 30 g/pot at 22 mm, 44 g/pot at 20 mm and 59 g/pot at 18 mm. As a result of evaluating 50% selection of mantle length and weight on the mesh sizes, mantle length (mm) and weight (g) were 84.6 and 147.8 in 22 mm, followed by 20 and 18 mm.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.4
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• pp.248-262
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• 2005

The purpose of this study was to identify the state of demersal fish resource catch by small trawlers, which live in the southern waters off Goheung. We investigated the results of catch of sample fishing vessels, and performed fishing experiments using the actual fishing operation vessels from early November in 2002 till end of October in 2003. The daily amount of catch per vessel of the 35 small trawlers selected as sample vessels was the highest in summer seasons(June and July) as 70kg and the lowest in winter seasons(January and February) as 45kg and Octopus minor occupied as 17 to 30kg nearly 30% of the total catch. Additionally the catch of Octopus minor per vessel, per dragging hour ranges 3 to 6kg, which is the highest in March and June and the low in January to February, April to May and September. In the fishing experiments using small trawler, during the study period, a total of 75 fish species were collected. The number of individuals by species consisted 58.2% in Shrimps, 17.8% in Fish, 2.3% in Cephalopod. Of these, Parapenaeopsis tenella was the highest in 29.2%, Squilla oratoria and Crangon hakodatel was 14.6% respectively and Octopus minor was 0.2% of the total number of individuals. As far as the appearance number of individuals by month was concerned, February was the highest and then May, April and June followed in order, and October showed the lowest. Additionally the monthly catch per dragging was the lowest in December to January as 20kg and the highest in July as 160kg. Specially, Octopus minor was caught throughout the year regardless of season and the catch was the highest at the period from March to June. When looking into the body mean length of dominant fishes caught, we could observe the followings; Trachurus japonicus 8.9cm, Cynoglossus robustus 10.8cm, Muraenesox cinereus 15.3cm, Setipinna taty 10.3cm, Amblchaeturichfhys hexanema 9.3 cm and Collichthys niveatus 8.9cm, most of which were in their immaturity when they were caught.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.42 no.1
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• pp.11-18
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• 2006

The behavior patterns of common octopus, Octopus minor to a cylindric trap were examined in the water tank using a video camera in order to know entering mechanism to the trap and to improve it. Fishing efficiency by 2 kinds of traps(A: 3 entrances, B: 2 entrances) was investigated in the coastal area of Deugryang Bay from May to July, 2005. Common octopus tends to approach by swimming more than walking towards trap. When they approached to the trap, they showed much more behaviors that sate at the around than upper part of it. Approaching behaviors of common octopus was more vigorous at nighttime than daytime on the trap, they showed the most vigorous action between 2 am and 4 am of the day. The rate of staying 30 seconds over around the trap was 41.5% in the nighttime. CPUE(g/trap) of common octopus caught by A type trap was 21.4% higher than the B type trap but there was no difference on the significance level of 5% by the ANOVA. Catch rate of common octopus and by-catch species caught by the A type trap were 97.2%, three and 98.7%, two for B type trap, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.6
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• pp.735-742
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• 2003

In order to develop a logical method for using selective fishing gear, the behaviour and habits of the aquatic animals must be investigated. However, until now, little national research has been carried out to investigate the behaviour and habits of the common octopus (Octopus minor). The purpose of this study henceforth, is to compile necessary behavioral data to develop fishing gear to catch the common octopus. Behaviour and habits of the common octopus were observed while breeding in a water tank from February to May, 2003. The feeding habits of common octopus are more vigorous at night than in the daytime. The common octopus feeds on 1-4 bait crabs per day and consume each crab in 40-50 min. The sensory organs of the common octopus are more influenced by the sense of touch and smell, than by vision. Using live bait is more effective and advantageous than using dead bait, as the common octopus responded more to live bait. The hiding habits of the common octopus were very intensive, as they hid around all the shelters that were provided in this study. They demonstrated territorial behavior and struggled to maintain their sphere of influence. In addition, out of the various colors for shelters and bait supplied, the common octopus preferred light colors.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.2
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• pp.113-120
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• 2022

The purpose of this study is to provide information about annual variations in catch size and changes in reproductive biology in the common octopus, Octopus vulgaris, a commercially important species in Jeju Island. Samples were collected from coastal waters of Jeju Island, Korea by coastal trap fishery from January to November 2021. Octopus vulgaris have been decreasing in this region since 1984. The mantle length (ML) ranged from 4.5 to 17.8 cm and body weight (BW) ranged form 88.5 to 2,657.5 g. A χ²-test revealed that the number of males was significantly greater than females (χ² = 32.712, df = 10, P<0.05). Mature females were found from January to July and male occurred January to August. The gonadosomatic index value was higher from July to August than other months. The relationship between mantle length and body weight was BW = 2.4527ML^2.3139 (female) and BW = 2.6785ML^2.3159 (male). At 50% group maturity, female and male average weight was estimated to be 554.7 g and 330.6 g, respectively.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.42 no.2
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• pp.78-85
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• 2006

A survey on the fishing gear for octopus drift-line fishing was done in Gangwon-do, Sacheon, Gyeongnam and Hokkaido, Japan, while a survey on the environments of fishing grounds used data from January to August from the Korea east coast farming forecast system of Donghae Fisheries Research and Development Institute. The present situation of fishing was examined with boats engaging in drift-line fishing from March to August in the coastal waters along Gangneung. The fishing tackle for octopus drift-line fishing was made manually, and the size, shape, and weight of the hook and number of shooting used vary according to the fishing time and region. Lead is used as the material for sinkers. As bait, pork fat with skin is mostly used in Gangwon-do. The temperature of the bottom water layer in the coastal fishing ground of Gangneung from April to June ranges from $3.2-12.4^{\circ}C$, which is the optimal temperature for octopuses. During July and August, the temperature ranges from $5.0-20.6^{\circ}C$. The maximum difference between day and night temperatures reached up to $9.2^{\circ}C$. Salinity is generally stable at $33.2-35.324.6%_{\circ}$, which does not affect the inhabitation of octopuses. The octopus catch reached its peak from May to July, while most octopuses weighed less than 1 kg (76.7%). The results show that it is effective to carry out octopus drift-line fishing up to a depth of 40 meters; and that the maximum number of octopuses per line is obtained with an operation time of six hours.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.57 no.4
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• pp.292-301
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• 2021

Interviews and boarding surveys were conducted in order to understand the actual usage of octopus pot in the coastal composite fishery in Jeollanam-do. According to the results of the interviews conduced by visiting the areas (Goheung, Yeosu and Wando), the number of octopus pots per nine-ton vessel were 30,000-80,000, and the number of daily usage pots were 7,000-10,000. The number of octopus pots per four-ton vessel was 40,000, and the number of daily usage pots were 4,000. As a result of the survey on two octopus pot fishing boats (9.77-ton and 4.99-ton) in Yeosu area, the daily catch weight of 9-ton class vessel was the minimum of 66.9 kg and the maximum of 159.6 kg. The daily catch weight of the four-ton class fishing vessel was from 31.3 kg to maximum 85.6 kg. The average number of octopus pot used per day in the nine-ton class vessel was 6,821 (the minimum of 6,031 and the maximum of 7,697) and 3,181 (the minimum of 2,282 and the maximum of 3,878) in the four-ton class vessel.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.55 no.3
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• pp.190-197
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• 2019

This study investigated the luring effect of the sardine bait, which is used to catch octopus with pot, as the preliminary study for the development of alternative bait for octopus pot. The soaking time for bait was divided into "5 days or less" and "11 days or longer" The number of times octopus entered the pot with bait and the empty pot was investigated under dark adaptation and light adaptation processes and the distribution of tank section was investigated under light adaptation process. The case of "11 days or longer" sardine soaking time showed higher rate of distribution in the section of pot with bait compared to the case of "5 days or less" In the case of "5 days or less" soaking time, the number of times the octopus entered the pot with bait was similar to that it entered the pot without it even during dark adaptation and light adaptation. However, in the case of "11 days or longer", the octopus entered the pot with bait more quickly than the pot without bait and more frequently during dark adaptation hours. There were cases where the octopus did not enter any pot. In the case of "5 days or less", with less decomposition of baits, the octopus entered the empty pot more during light adaptation process, and it appeared that the pot was used as a hideout.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.3
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• pp.199-204
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• 2022

The Pacific giant octopus (Enteroctopus dofleini) is one of the most important species in the East Sea fishery of Korea. The annual production of Pacific giant octopus in 2021 was 3,880 metric ton between Gangwon province and Gyeongsangbuk province. Most of the fishing gears for the octopus fishery were based on behavioral properties such as thigmotaxis and chemotaxis. Wooden octopus box is also one of the fishing gears, which is application of thigmotaxis for the octopus capture in fishing industry. In this study, the tank experiments were designed to examine the behaviour and the effect of surface roughness to the infiltration of the octopus quantitatively. Three different types of octopus boxes were used for the experiments with different surface roughness on the average of 701.6 ㎛, 141.7 ㎛ and 2.09 ㎛ for each gear. 22 trials were conducted from June to September 2021. The normality of the experiments was tested using Shapiro-Wilk normality test (p-value < 0.05). The significance of results was conducted by Kruskal-Wallis rank sum test (Chi-squarded = 21, Degree of freedom = 3, p-value < 0.05). The use of wooden octopus box with rough surface was found to enhance the catch efficiency and observe infiltration behaviour of the octopus frequently.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.1
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• pp.10-17
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• 2011

Biodegradable octopus pot was developed to reduce plastic pollution problem in the sea and fishing trouble between fishermen. It can be expect to recycle other wasted biodegrade fishing gear. Experimental fishing was carried out to understand the difference in fishing efficiency between Polyethylene (PE) octopus pots and biodegradable (Polybutylene Succinate and Polybutylene adipate-co-terephthalate) octopus pots which was tried to make in this study in the sea. There were caught by 237 numbers of fishing during the experimental period. Among the 237 numbers of fishing, 160 or 67.5% were PE pots which were more than the biodegradable pots. A comparison of the monthly catches between the PE pots and biodegradable pots shows that the catches were overall higher in the PE pots than in the other pots. The result is very similar with the comparison of total catches by each type of the pots. In terms of bycatch, the number of species, amount of catches and the number of fishing with bycatch were more significant in the biodegradable pots than in the PE pots.