• 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.52 no.6
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• pp.740-744
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• 2019

Pacific white-sided dolphins Lagenorhynchus obliquidens inhabit cool temperate waters; in Korean waters, they concentrate near the coast of Gangwon and Gyeongbuk from late autumn to early spring. We collected 15 individuals from Yeongduk, Gyeongju, Ulsan, and Busan between December 2018 and February 2019 and analyzed their stomach contents. Fresh prey items were identified to the species level, and residual stomach contents that were unidentified due to digestion were filtered through a sieve to find fish otoliths and cephalopod beaks. The most important prey items of Pacific white-sided dolphins were cephalopods, composing 68.0% of the diet by occurrence. Fishes were the second largest dietary component, making up 32.0% of the diet by occurrence. Of the cephalopod species consumed, Watasenia scintilans was the principal prey item.

• Proceedings of the Acoustical Society of Korea Conference
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• 1996.06a
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• pp.51-54
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• 1996

동해 중부 연안(수심: 200 m)에서 해수 중 주위잡음을 측정하는 동안 태평양 흰줄무늬 돌고래(pacific white-sided dolphin, 학명: Lagenorhynchus obliquidens)의 발생음을 수신하였으며 그 음향 특성을 분석하였다. 그 결과 얻어진 결론을 요약하면 다음과 같다. 첫째, 돌고래 발생음의 파형은 임펄스의 형태로서 그것의 전체 길이는 0.25~60.50 ms였고, 처음에 음(-)의 방향으로 작은 진폭을 보였으며, 그 후 작은 진폭으로 빠르게 감쇠진동하고 있는 형태를 나타내었다. 둘째, 돌고래 발생음의 주파수 스펙트럼은 약 18~90kHz의 광범위한 성분을 포함하고 있었다. 셋째, 돌고래 발생음의 스펙트럼 레벨 피크는 주파수 범위 35~55 kHz에서 나타났으며, 이것은 돌고래의 발생음이 없는 경우 해수 중 주위잡음의 레벨에 비하여 약 30~40 dB 높게 나타났다.

• 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.

• Ocean and Polar Research
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• v.33 no.1
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• pp.35-43
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• 2011

Blubber plays different biological roles in cetaceans, including structural support, physiological demands (thermoregulation, streamlining, buoyancy, etc.), and energy storage. As such, biochemical composition, especially lipid, in the blubber may be vertically stratified in order to effectively assist with these functions. We analysed lipid content, class and fatty acid composition in the blubber of by-catch minke whale (Balaenoptera acutorostrata; n = 11), long-beaked common dolphin (Delphinus capensis; n = 3) and Pacific white-sided dolphin (Lagenorhynchus obiquidens; n = 2) from Korean waters. Lipid content for all three species ranged from 55 to 96% of wet weight, with a dominance of triacylglycerols. Vertical stratification of blubber lipid content was different between species. For minke whale and longbeaked common dolphin, it increased from inner (near the muscle) to outer (near the skin) layer, whereas it decreased for Pacific white-sided dolphin. Thirty-one fatty acids were found in all blubber samples and vertical stratification of fatty acid composition was similar among all three species. Among grouped fatty acids, monounsaturates were the most abundant, gradually increasing from inner to outer blubber layer, whereas polyunsaturates and saturates decreased. Such vertical stratification of lipid content and composition suggests that the modification and accumulation of lipid occur in the blubber itself in order to help cetaceans with their specific physiological needs.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.5
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• pp.486-492
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• 2012

In the late 1970s, the National Fisheries Research & Development Institute (NFRDI) started cetacean research to submit the Korean whale catch record to the International Whaling Commission. This continued until the moratorium on commercial whaling in 1986. The NFRDI resumed cetacean research with a pilot whale sighting survey in 1999. Subsequently, the NFRDI has conducted 53 cetacean sighting surveys within the Korean exclusive economic zone between 2000 and 2010. The surveys took a total of 760 days and cruising for 23,866 nautical miles. The finless porpoise Neophocaena asiaeorientalis was sighted most frequently (735 times), followed by the minke whale Balaenoptera acutorostrata (396 times), the long-beaked common dolphin Delphinus capensis (102 times), and the Pacific white-sided dolphin Lagenorhynchus obliquidens (27 times). Minke whales were distributed in the Yellow Sea and coastal area of the East Sea from spring to fall. Pacific white-sided dolphin sightings were restricted to the middle and upper coastal areas of the East Sea in summer. Common dolphins were sighted from east of the southern coast to the eastern coast of the Korean Peninsula from spring to fall. Finless porpoise occurred in all Korean coastal areas, except the middle and upper eastern coast.

• 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.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.6
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• pp.938-945
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• 2022

National Institute of Fisheries Science conducted a total of 39 sighting surveys for marine mammals over 624 sighting days that covered 20,771 nautical miles in Korean waters during 2011-2020. Marine mammals were detected when 83.9% of the marine environment was less than or equal to three on the Beaufort wind scale. Thirteen species of marine mammals were identified, including two species of pinniped, with a majority of cetacean species. Frequently found species were narrow-ridged finless porpoise, followed by common dolphin, minke whale, Dall's porpoise, and Pacific white-sided dolphin. Narrow-ridged finless porpoises and minke whales were located in and offshore around the Korean peninsula, common and Pacific white-sided dolphins were exclusively found in the East Sea for most seasons. The other marine mammals were spotted in some seas and for limited durations.