• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.51 no.4
• /
• pp.493-503
• /
• 2015

Species composition and bycatch rate of the catches by dredge with bycatch reduction device to reduce bycatch were estimated around Yeongil Bay, Korea at June, 2015. Total catches were collected 31 species as Chordata 10 species, mollusca 8 species, arthropoda 6 species, echinodermata 5 species, sipunculida 1 species, annelida 1 species during the experiment at the Yeongil Bay. The dominant species were Scapharca broughtonii, Callithaca adamsi, and Atrina pectinata and they reached 79.9% of the total catch. The catch rate of Scapharca broughtonii and Callithaca adamsi was 69.6% and 10.4% respectively. The rate of bycatch was 20.1%, consisted with Echinodemata 13.0%, Chordata 3.6%. The catch of ordinary dredge was 27 species 1,307 number 85,052g and that of dredge with escapement device was 21 species 1,690 number 91,648g. In conclusion, the dredge gear with bycatch reduction device has higher catch rate of target species and lower bycatch rate to non-target species than ordinary one.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.44 no.4
• /
• pp.397-402
• /
• 2011

We surveyed the bycatch and discard of the shrimp-pot fishery in Hokkaido, Japan, three times during the major fishing period in September 2005. The surveyed catches were analyzed to separate bycatch, discard, and landings. To analyze bycatch and discard, we randomly selected 2 shrimp pots from each of 7 sets, for a total of 14 pots per survey. The total bycatch and discards from the rest of the shrimp pots were also analyzed in each survey. The total catch averaged 12 species. Coonstripe and pink shrimp catches averaged 74.7 kg/haul and 12.7 kg/haul, respectively. The weight of the bycatch averaged 33.4 kg/haul. The bycatch consisted mainly of snail fishes(5.1%), brittle stars(5.0%), and short-spined sea urchins(4.1%). Our analysis showed that the ratio of discard was 0.38, the rate of the discard was 27.4%, and the discard per unit effort was 33.4 kg/haul. The Hokkaido shrimp-pot fishermen discarded all of the bycatch except shrimps. Hence, the weight of the bycatch was equal to the weight of the discard. Our results comprise preliminary data that can be used to find ways to reduce bycatch and discard in the shrimp-pot fishery.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.50 no.4
• /
• pp.520-529
• /
• 2014

Experiment was set up to analyze bycatch and discards situation including snow crap Chionoecetes opilio of whelk trap. Four types of trap were used: drum type trap with PE net; drum type trap with PBS net; cylinder type trap with PE net; and cylinder type net with PBS net. Three funnels were attached in drum type trap and two funnels were used in cylinder type trap. A fleet of traps was consisted with one hundred traps. 25 traps of each type were set on a line in repeated sequence. Field experiments were conducted with 6 fishing operations in the Uljin waters, East Sea in July 2014. Catch of target whelks were 173,261 g and catch rate was 48.7% of total catch, while bycatch were 182,571 g, 51.3% of tatal catch. The catch rate of bycatch was 2.6% higher than that of target catch. Bycatch weight of snow crap was the highest as 142,987 g and formed about 40.2% of total catch, followed giant octopus, Enteroctopus dofleini, 31,762 g (8.9%). Bycatch rate of cylinder type trap was 2.3 times higher than that of drum type trap. Discard rate (discard/(discard+landing)) was 43.6%. Discard rate was the highest at cylinder type trap with PBS net as 63.1%, followed cylinder type trap with PE net as 47.9%, drum type trap with PE net as 33.4%, the lowest at drum type trap with PBS net as 22.1%.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.52 no.1
• /
• pp.72-77
• /
• 2016

We examined monthly changes in the rate of fishes by-caught by gape net with wings and their immature ratio in the coast of Yeosu and Jindo Island, Korea. A minus correlation between bycatch rate, the ratio of fishes except for anchovy, Engraulis japonicus, to all fishes collected by gape net with wings, and individuals of the collected anchovy was significantly observed, implying that as the anchovy catch decreased and the bycatch rate increased. Immature ratios by the dominant bycatch species during the study is the following; Leiognathus nuchalis was 72.7~99.0%, Sphyraena pinguis was 84.0%, Sardinella zunasi was 90.0%, others (Leptocephalus, Trichiurus lepturus, Ammodytes personatus, Sphyraena pinguis, Trachurus japonicas, Mugil cephalus and Erisphex pottii) were 100.0%. In order to decrease the high bycatch rates of immature fishes in spring and autumn, our study suggested increasing of codend mesh size and developing suitable bycatch reduction devices in a gape net with wings.

• Journal of Fisheries and Marine Sciences Education
• /
• v.24 no.2
• /
• pp.137-145
• /
• 2012

In order to survey the conditions of bycatch and discards for a gape net, a series of filed surveys was carried out total 10 surveys on two gape nets operated in the coastal area of Jindo during July to November 2008. The all catches in each survey were measured the body length, weight after sorted species. The analysis of catch data was conducted to separate 'first operation' and 'general operation'. In this study, the first operation defined as hauling the fishing gears that soaked over 10 hours because of setting on the previous day. The general operation means the haul of fishing gears conducted at intervals of one of or two hours after first operation. The bycatch in this study is defined as the other species except for anchovy, and bycatch rate refers to the proportion of bycatch to total catch. From the survey results, the average bycatch rates on first operations were 50% and 51% for Masa-ri and Supum-ri areas in Jindo, respectively. Also, the average bycatch rates on general operation were 2% and 3% for Masa-ri and Supum-ri areas in Jindo, respectively. The proportion of anchovy to total catch caught represented 75.5%. It needs the research on the selective fishing technology to reduce the bycatch on the gape net fishery.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.59 no.4
• /
• pp.290-300
• /
• 2023

This study aimed to identify the actual catch situation of offshore dredge gear which is newly regulated in the legislation. It's also conducted to identify the species composition, weight of the catch including the target species and incidental catches, and to provide the basic information necessary for the resource management of aquatic organisms caught by offshore dredge. During the investigation period (from September 2022 to May 2023), a total of 61 species appeared in the test operation sea of Boryeong, Chungcheongnam-do and Gunsan, Jeollabuk-do, with 31 species of fishes, 11 species of malacostraca, six species of gastropoda, five species of bivalvia, three species of cephalopoda, three species of asteroidea, one species each of asteroidea and holothuroidea appeared. According to the results of the test operation conducted in September and November 2022, the non-catch season of Atrina (Servatrina) pectinata, 1,203 shellfishes were caught out of 2,979 caught in number, showing a bycatch rate of 59.6%, and by weight, 157.9 kg of shellfish was caught out of the total catch of 448.4 kg, showing a bycatch rate of 64.8%. On the other hand, in February and May 2023, the catch season for Atrina (Servatrina) pectinata, 3,692 fishsells were caught out of the 4,232 catches in total, showing a bycatch rate of 12.8%, and by weight, 1,185.0 kg of shellfish was caught out of the total catch of 1,293.2 kg, showing an 8.3% bycatch rate.

• Fisheries and Aquatic Sciences
• /
• v.18 no.3
• /
• pp.325-332
• /
• 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.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.42 no.4
• /
• pp.210-216
• /
• 2006

The circle hook experiments were conducted to compare the catch rates of target and bycatch species between J hook and circle hooks in the tuna longline fishery of the eastern Pacific Ocean between $1^{\circ}48'S-7^{\circ}00'S\;and\;142^{\circ}00'-149^{\circ}13'W$ from July 15 to August 12, 2005. In the target species group no significant differences among 3 types hook, between size 4.0 traditional tuna hooks(J-4) and size 15 circle hooks(C15), and between C15 and size 18 circle hooks(C18) were revealed, but significant differences were found between J-4 and C18. In the bycatch species group significant differences were found among 3 types hook, between J 4 and C15, and between J-4 and C18, but no significant differences were revealed between C15 and C18. Large circle hook(C18) had the lowest catch rate for tunas and for other fishes, and the small circle hook(C15) had lowest rate for billfishes and sharks. The length distributions for bigeye tuna are very similar for the 3 hook types. There were very slight differences in length size between hook types in the bycatch species.

• Fisheries and Aquatic Sciences
• /
• v.25 no.12
• /
• pp.589-600
• /
• 2022

Longline fishery targeting tunas and tuna-like species is known to produce a significant amount of catch not only for the target species, but also for ecologically related species like sharks, marine turtles, sea birds and marine mammals. Recognizing this seriousness, tuna related regional fisheries management organizations (t-RFMOs) have established conservation and management measures (CMMs) to reduce bycatch and/or interaction with ecosystem vulnerable species including sea turtles and are obliged to implement bycatch mitigation measures and guidelines on safe release to their member countries. Along with development and strengthening of those measures, various case studies have been conducting to verify the effectiveness of bycatch mitigation for ecologically related species. This study examines the background and progress on developing CMMs of t-RFMOs and regulation programs of the United States related to sea turtles, which have recently become one of the main issues, and reviews case studies on sea turtle bycatch mitigation measures to find out the effectiveness of reducing bycatch rate and impacts to the fisheries. In order to respond the consultation process on certification determination with the United States, it was confirmed the current status of implementation on related measures conducted by Korean tuna longline fishery based on scientific observer data and survey for captains. Even though all Korean tuna longline fleets belong to the deep-set longline fishery (100-300m), which is not subject to the obligation of those mitigation measures, they are voluntarily implementing both measures, use of circle hook and whole finfish bait, regardless of which RFMO's Convention area they operate. And the national regulatory and management programs for sea turtle bycatch prevention adopted by Republic of Korea seems to be comparable in effectiveness to that of the United Stated. However, Korea needs to take preemptive measures in establishing sustainable fisheries, including the protection of the marine ecosystem and environment, as stronger requests are anticipated to be made by the international community on this matter.

• Animal cells and systems
• /
• v.14 no.4
• /
• pp.291-296
• /
• 2010

Population ecological characteristics of growth and mortality play an important role in understanding the population dynamics of marine mammals. The instantaneous coefficients of natural and bycatch mortality were estimated for minke whales (Balaenoptera acutorostrata) in Korean waters using a population assessment model composed of bycatch and abundance data. The survivorship curve of this population was fitted to the data, and then the curve was revised using age-specific relative bycatchability coefficients ($q_t$). Instantaneous coefficients of natural and bycatch mortality of minke whales were estimated as 0.024/year and 0.076/year, respectively, and from this the survival rate was estimated as 0.905. This estimated survival rate was comparable to other cetaceans in other regions. The $q_t$ for this population ranged from 0.020 to 0.193. The revised survival rates were higher when the $q_t$ was taken into account. The mortality coefficient, survival rate, $q_t$ and survivorship curves had not previously been determined for minke whale in this area. This estimate could serve as fundamental information to assess the status of this population and for conservation and rational management.