• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.6
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• pp.704-713
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• 2018

Globally, the survival of many marine mammals is threatened by entanglement in fishing gear and there is also a high bycatch in Korea. This study analyzed the bycatch data of most cetacean species for Korean waters from 2011 to 2017, including the narrow-ridged finless porpoise Neophocaena asiaeorientalis, common dolphin Delphinus delphis, common minke whale Balaenoptera acutorostrata, and Pacific white-sided dolphin Lagenorhynchus obliquidens. A total of 12,262 cetaceans were captured as bycatch. In the Yellow and South Seas, the main species affected was the narrow-ridged finless porpoise, with 82.9% caught in stow nets and 11.5% captured in trawls. In the East Sea, the common minke whale, common dolphin, and Pacific white-sided dolphin were reported. The main common minke whale bycatch (43.5%) was in set nets, while common dolphins (49.0%) and Pacific white-sided dolphins (91.4%) were mainly caught in gill nets. The narrow-ridged finless porpoise, common dolphin, and common minke whale were most commonly reported in March, April, and May, while the Pacific white-sided dolphin was most frequently captured as bycatch in January and December. Each of these factors (season and gear responsible for bycatch) depended on the characteristics of the cetacean species. To conserve cetaceans, it is necessary to reduce the bycatch.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.6
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• pp.892-900
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• 2013

In 2011, the system for conserving and managing cetacean resources in Korea changed. The status of the cetacean bycatch was analyzed using a distribution certificate that was issued by the coast guard. During 2011.2012, 12 species were bycatch in Korean waters: three species of baleen whale and nine species of dolphin. The finless porpoise (Neophocaena phocaenoides) was the dominant species, followed by the common dolphin (Delphinus delphis), harbor porpoise (Phocoena phocoena), and Pacific white-sided dolphin (Lagenorhynchus obliquidens). Among the baleen whales, the common minke whale (Balaenoptera bonaerensis) was first and Bryde's (Balaenoptera edeni) and humpback (Megaptera novaeangliae) whales appeared in the Korea Strait and East Sea, respectively. Among the dolphins, the finless porpoise ranked first in the Yellow Sea. The common dolphin, Pacific white-sided dolphin, and harbor porpoise were more frequent in the East Sea than in other waters. The cetacean bycatch was caused mainly by pots, set nets, gill nets, and stow nets. Among the three species of baleen whale, the common minke whale was caught by pots and set nets, and comprised over 68.9% of the total bycatch in 2011 and 56.2% in 2012. Comparing the bycatch caused by fishing gears by area in 2011 and 2012, 97.9% and 99.6%, respectively, of the finless porpoise bycatch in the Yellow Sea was by stow nets. In the Korea Strait, trawl bycatch comprised 67.3% in 2011 and 73.0% in 2012, followed by gill nets, set nets, and pots targeting finless porpoise and common minke whales. In the East Sea, gill nets were responsible for 46.7% in 2011 and 61.2% in 2012, followed by set nets and pots.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.59 no.4
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• pp.399-406
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• 2023

This study presents an analysis of bycatch data concerning Pacific white-sided dolphins (Lagenorhynchus obliquidens) along the Korean coast from 2016 to 2021. A total of 503 bycatches were examined, encompassing data on year, month, body length, sex, latitude (N), longitude (E), and fishing gear. Bycatch was the most frequent in waters with a longitude of less than 130°E, particularly in the southern coastal region at a latitude of 35.5°N, with a higher likelihood of bycatch in lower latitudes. Since 2017, a decreasing trend in bycatches has been observed. The sex distribution of bycaught dolphins showed a predominance of males (40%), followed by females (31%), with an unclassified category at 29%, though no statistically significant differences were found (p > 0.05). Seasonal analysis indicated that bycatch predominantly occurred during the winter months, with significant monthly variations (p < 0.01). Pacific white-sided dolphins were primarily ensnared in gill nets and, to a lesser extent, in stationary nets. Statistical analysis by gear type revealed a significant preference for gill nets (p < 0.001). Considering body length composition in relation to latitude, it is suggested that Pacific white-sided dolphins may utilize the southern waters of the East Sea as a potential nursery ground, though this was not confirmed at a significant level, emphasizing the need for further in-depth monitoring and ecological investigations. Given that there are approximately 27 different types of gill nets associated with the majority of bycatches, more detailed research is warranted to divide these gear types into finer subcategories for estimating bycatch relationships, ultimately leading to the development of effective conservation and management strategies.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.3
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• pp.207-212
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• 2005

Dual frequency acoustic pinger(AP) was manufactured to reduce study effect by long-term use of developed single frequency AP to prevent cetacean bycatch. Directivity characteristic of transducer was the omnidirectional pattern which showed less than ${\pm}3dB$ the change range of sensitivity on the beam pattern of right and left. Source power level(SPL) was 1384311pa with epoxy window before casing however after casing 1170B11Pa at sea. Dual frequency Af was tested to identify the avoidance behavior of bottlenose dolphin by its working. However the efficiency of dual frequency AP about the study effect was verified experiment repeatedly using single and dual frequency AP.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.6
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• pp.665-669
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• 2010

To confirm the distributon of finless porpoise, Neophocaena phocaenoides, in the South Sea of Korea, data on bycatch, stranding, and drifting of finless porpoises from 1999 to 2009 were used and a sighting survey was conducted from the R/V Tamgu No. 9 and 10 in June and November, 2009 and March, 2010. The total number of bycaught, stranded, and drifting finless porpoises was 607, with position being known for 186 of these. At the center of Yeosu, there were few position data on bycaught, stranded, and drifting finless porpoises, and data could not confirm the distribution of finless porpoises. Thus, there were limits on the usefulness of bycaught, stranded, and drifting data for confirming the distribution of finless porpoises. In the three sighting surveys, the sighting rate was highest at 0.231 ind./n.m. in the western South Sea in June, 2009. Sighting rate was less than 0.1 ind./n.m. in November, 2009 and March, 2010. This is likely to be due to seasonal migration in western South Sea. All sighting rates in the eastern South Sea were over 0.13 ind./n.m.. According to the results of the sighting survey, finless porpoises are distributed around the islands and inner bay along the path of the research vessel in the South Sea. There were numerous finless porpoises in the offshore areas of Mokpo, Yeosu, Tongyeong, Dadaepo, and Gaduk-do. This study will be utilized as part of a future abundance assessment of finless porpoise in the South Sea of Korea.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.6
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• pp.659-664
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• 2010

This study investigated the distribution of spotted seals, Phoca largha, inhabiting the coast of Baekryongdo. Monitoring of spotted seals in Baekryongdo was conducted between June 2006 and November 2008, using a 5-ton fishing vessel 1hour before low tide. The monthly maximum number of observed seals was 274 in September 2006, 139 in September 2007, and 213 in August 2008. Average observed monthly counts were largest in August and September. Relatively more spotted seals were observed when there were few cloudy days and plenty of sunshine. Bycatch, stranding, and observations of spotted seals have been reported along the coast of the Korean peninsula since 2000, and spotted seals were observed four times in the western coastal region, three times in the southeastern region, and 12 times on the east coast. This suggests that spotted seals inhabiting Baekryongdo migrate to the East Sea via the West and South seas as individuals or in groups.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.1
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• pp.78-84
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• 2011

We investigated the stomach contents of finless porpoises collected in the Yellow Sea. Prey organisms in the stomachs of 109 finless porpoises were identified as 11 species of fish, 8 species of shrimp and 4 species of cephalopod. Index of Relative Importance analysis revealed that the porpoises fed mainly on the Japanese sand shrimp (Crangon affinis). The energy density of the prey was estimated to be 5.46 kJ. The daily energy requirement was estimated to be 18,051 kJ/day for a porpoise with an average weight of 32.49 kg. The estimated annual consumption by finless porpoises in the Yellow Sea was 25,454 tons. The average commercial catch in the Yellow Sea by Korean fisheries was 135,913 tons from 2005 to 2009. Assuming that the abundance of finless porpoises is stable, porpoises ate approximately 18.7% of the commercial catch. The fishery catch may be influenced by the consumption by finless porpoises, while fishery bycatch is a cause of porpoise mortality in the Yellow Sea.

• Animal cells and systems
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• v.15 no.1
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• pp.79-84
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• 2011

The status of J stock minke whales (Balaenoptera acutorostrata) was assessed using potential biological removal (PBR) and mortality data. Using the estimated abundance of minke whales in this area (6260; CV = 0.212), the minimum population estimate of the stock was estimated as 5247. The PBR for J stock minke whales was calculated as 52.5 individuals using the minimum population estimate (5247), one-half of the maximum theoretical net productivity rate (0.02) and the recovery factor (0.5). The estimated mean annual level of anthropogenic mortality was 270.4 individuals. Thus, the status of this stock was considered as strategic. However, fortunately, the abundance of this population in the East Sea from 2000 to 2008 showed an increasing trend (rate of increase 0.0488; annual rate of increase 5.0%) although it is not statistically significant (P > 0.05). The primary sources of anthropogenic mortality were bycatch (set nets, pots and gill nets) and illegal catch. Because of the status of this population, it is urgently necessary to reduce the amount of bycatch and illegal catch of minke whales. Further study needs to use population health and viability analysis for investigating the long-term survival of this population more clearly.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.2
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• pp.231-239
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• 2021

There are six species of pinnipeds in Korean waters. Because of the lack of research on pinnipeds, it has been difficult to obtain ecological information on each species. All six species have been designated as endangered species, marine protected species, or national monuments by the government, depending on historical records. In this study, the current status of pinnipeds in Korea was investigated through reviewing the literature, and sighting and bycatch records, with the intention of providing new information for the review of the six species. Spotted seals and northern fur seals are well known inhabitants of Korea. The southern part of the East Sea is thought to be the margin of the distribution of Steller sea lions. Sightings of ribbon seals and ringed seals were not confirmed in Korean waters. Sea lions have not been seen since their last sighting on Dokdo in 1951 and are thought to have become extinct after that. It is necessary to delist undistributed or extinct species in Korea from the marine protected species list.