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The minke whale ( Balaenoptera acutorostrata ) is the most common baleen whale among several marine mammal species observed in Korea. Since a high concentrated condition of prey to whales can be obtained by physical structures, the foraging whale distribution can be an indicator of biological hotspot. Our main objective is verifying the coastal upwelling-southwestern East Sea as a productive biological hotspot based on the geographical distribution of minke whales. Among the cetacean research surveys of the National Institute of Fisheries Science since 1999, 9 years data for the minke whales available in the East Sea were used for this study. The regional primary productivity derived from Moderate-Resolution Imaging Spectroradiometer (MODIS) was used for a proxy of biological productivity. Minke whales observed during the sighting surveys were mostly concentrated in May and found mostly (approximately 70%) in the southwestern coastal areas ( −2 y −1 ) estimated in the southwestern coastal region of the East Sea belongs to the highly productive coastal upwelling regions in the world. A change in the main spatial distribution of minke whales was found in recent years, which indicate that the major habitats of mink whales have been shifted into the north of the common coastal upwelling regions. This is consistent with the recently reported unprecedented coastal upwelling in the mid-eastern coast of Korea. Based on high phytoplankton productivity and high distribution of minke whales, the southwestern coastal regions can be considered as one of biological hotspots in the East Sea. These regions are important for ecosystem dynamics and the population biology of top marine predators, especially migratory whales and needed to be carefully managed from a resource management perspective.

The west coast of Korea is the largest habitat for finless porpoises, with approximately 36,000 individuals reported in 2005 (Park et al., 2007). To date, there have been no subsequent finless porpoise population estimates. However, in recent bycatches, finless porpoises accounted for the highest proportion of all cetaceans and have been reported to be most frequently caught on the west coast of Korea (Kim et al., 2013). The present study, conducted in 2011, enumerated finless porpoises inhabiting the west coast of Korea using a line transect survey in offshore and inshore regions to assess variations in their abundance. In offshore regions we found the population density of finless porpoises to be 0.122 ind./km 2 , whereas it was 0.565 ind./km 2 in 2004. In inshore regions, the population density of finless porpoises was 0.151 ind./km 2 , whereas it was 0.638 ind./km 2 in 2005. Therefore, we estimate that the population densities of finless porpoises in both offshore and inshore regions of the west coast of Korea decreased by ap proximately 70% between 2004/2005 and 2011. It is imperative to mitigate the bycatch of finless porpoises and protective action is urgently needed in the near inshore regions.

The Indo-Pacific bottlenose dolphin Tursiops aduncus commonly inhabits the coastal waters of Jeju Island, Korea. An investigation was conducted using data from vessel sightings and point sightings from land. During 40 days of vessel sighting surveys between 2007 and 2010, a total of 18 dolphin groups were encountered. The overall sighting rate was 0.01 group/n.m. Most Indo-Pacific bottlenose dolphins were sighted within 500 m of the northern coast of Jeju Island during surveys. Also, dolphin groups were observed 47 times during 109 days of shore-based surveys conducted between 2011 and 2015. The results of a dolphin distribution survey conducted in 2011 were generally similar to the results of previous surveys. However, there were no dolphin sightings from 2012 in Hanllim-eup, in the north-western part of the island, where dolphins were sighted frequently until 2011, whereas dolphin observations increased in the southern part of the island. The mean group size was 35.4 (SD=18.08) individuals. The most frequently sighted group size was 36-40 individuals. To conserve resident dolphins off Jeju Island, long term sighting surveys and environmental assessment are required to monitor their distribution patterns.

Finless porpoise is the one of porpoises in Korean waters that frequently observed in the coastal area. This study reported parasite infection cases of stranded finless porpoise, Neophocaena asiaeorientalis which was stranded on the Saemangeum Dyke on the west coast of Korea 21 May, 2012. The finless porpoise was male, and estimated at 8 years old. Parasites were found in abdominal cavity, skull and lung. The parasites were identified as nematode, trematoda and lungworm. Nematoda in abdominal cavity was Crassicauda sp. Trematoda found in the skull was indentified Nasitrema sp. Lungworm in lung seemed one of genus Pseudaliids. Anisakis spp. has not been found.

Vessel-based sighting surveys for cetaceans have been conducted in Korean waters since 2000. The supporting data estimate the abundance of finless porpoises along the west coast of Korea; however, they are insufficient because of the coverage and frequency of the surveys. A preliminary aerial survey was conducted in 2011, and the results were assessed with respect to a sighting survey operated by a research vessel in order to compare effectiveness and potentiality. A total of 110.00 nautical miles of effective efforts were made with three sightings under Beaufort scale 4 in the aerial survey, while the vessel-operated survey covered 403.38 nautical miles over 7 days without any sightings under Beaufort scale 4. The standard deviation of the altitude in this survey was 22.7 m, which was significantly higher than that of the referenced study of 4.3 m.

The Fraser’s dolphin, Lagenodelphis hosei has a pantropical distribution. Only several stranding or catch data were available from Japan and Taiwan in the north-west Pacific region. An adult female L. hosei stranded in Jeju-do, Korea. The specimen was identified by external features and skull measurements. It showed the same external appearance ratio and range in the number of teeth with L. hosei former described. The cranial measurements also well corresponded to condylobasal length proportions given in the previous descriptions of the holotype. This is the first record of the species in Korean waters. We report the information on external and osteological characters of the specimen.

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.

To investigate the distribution and migrations of sea turtles occurring in Korean waters, an adult female green sea turtle Chelonia mydas was tagged with a satellite transmitter and released at Busan in October 2009. The confirmation was made for the first time that the released green sea turtle migrated back to Korea after visiting Jeju Island and Japan for approximately 9 months. The green sea turtle spent the winter in Jeju and Japan because of low water temperatures in the East Sea and South Sea during winter months, which were not suitable for turtle survival. Compared with an immature green sea turtle that was released at Jeju Island, the adult green showed a markedly different migration pattern, suggesting that juvenile and adult greens move differently because of their peculiar life cycle and their stage of maturity, in addition to responses to temperature changes. Additional satellite tracking with increased representation of species, sexes and sizes of turtles, and regions is required to gather information on the distribution and movements of sea turtles in Korean waters.

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.

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.

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.

Bottlenose dolphins (Tursiops sp.) commonly inhabit Korean waters, including the coastal waters of Jeju Island. However, their taxonomic position was unclear because of the validity of this genus. The genus Tursiops has recently been determined to comprise two species: the common bottlenose dolphin (Tursiops truncatus) and the Indo-Pacific bottlenose dolphin (Tursiops aduncus). To confirm the taxonomic position of bottlenose dolphins frequenting the coastal waters of Jeju Island, the external morphology and osteology of specimens from Jeju Island were examined. Photographs of free-swimming individuals were also used for determining external morphological characters. The cranial and meristic measurements fell within the ranges of T. aduncus. Osteological ratios were also consistent with those of T. aduncus. The presence of a prominent ventral spot was observed among some individuals. As a result, the dolphins mainly distributed in the coastal waters of Jeju Island were identified as Indo-Pacific b...

First record of a stranded Melon-headed whale (Peponocephala electra) on the south-east coast of Korea was described. Full body and skull measurements were taken from the specimen. It was identified as P. electra by unique pointed flipper tips. Skull measurements of the specimen corresponded to condylobasal length proportions given in the previous descriptions of the holotype.

Recently, bottlenose dolphins have frequently appeared in coastal waters of the Jeju Islands. To determine whether these individuals belong to one or more pods, the Cetacean Research Institute (CRI) established visual and photo-identification surveys in the Jeju Islands from November 2007 to July 2009. During visual surveys, pods composed of 10 to 80 individuals were sighted mainly in the northeastern and northwestern of Jeju Islands. Eighty-nine individuals were identified and cataloged by photo-identification using natural nicks and notches on their dorsal fins. Thirty-six individuals were identified three times or more, and nine individuals were identified five times during seven surveys. One individual appeared in November 2007, August 2008, October 2008, April 2009, and July 2009. The results of our study confirm that these dolphins represent a coastal resident stock. Futhermore, we will establish dolphin abundance, management, and usage studies using continuous visual and photo-identification surveys.

This paper reports the strandings of sea turtles on Korean shores monitored for the first time in 2008. A total of 19 sea turtles, consisting of 12 greens and 7 loggerheads, were recorded as stranded from the east coast to the south including Jeju Island. Reported strandings reached a peak in July and dominant area was Jeju Island. The curved carapace length of loggerhead sea turtles ranged 65-84.2cm and that of green sea turtles ranged 39.2-90cm, indicating most of them were immature to sub-adult. Out of 19 turtles, 11 were found dead with unknown reasons. Possible causes of death may include drawning by fishing gear, swallowing of marine debris, boat collision, and diseases. An immature green sea turtle tagged with a satellite transmitter spent winter near Jeju Island where it was released, suggesting that the Island provide immature greens a feeding ground. Considering thousands of sea turtles crawl on Japanese shores for nesting every year, the number of sea turtles reported in Korean waters was relatively small. Therefore, it is suggested that an appropriate monitoring system be necessary to protect and conserve endangered sea turtle species in Korean waters.

whale in the survey in 2000 was estimated as 0.026 individuals/km 2 (CV=0.409; 95% CI 0.011-0.065) and was higher than the survey in 2002 estimated as 0.018 individuals/km 2 (CV=0.329; 95% CI: 0.009-0.034). The estimated density of minke whale in the survey in 2003 was estimated as 0.033 individuals/km 2 (95% CI: 0.008-0.139) with the highest CV 0.760. The highest density was estimated in the survey in 2005 with 0.053 individuals/km 2 (95% CI: 0.020-0.141). The Lowest CV (0.306) was estimated in the survey in 2006 with 0.025 individuals/km 2 (95% CI: 0.014-0.046). A total of 500 bootstrap samples were generated within each stratum. Density, CV and 95% CI of each surveys were increased than analytic results except the survey in 2003. There were no increasing or decreasing annual trends in the density of minke whales observed during the study period. A long-term monitor and survey is needed to assess project minke whale abundance in the East Sea.

Data on levels and accumulation profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/ Fs) and dioxin-like polychlorinated biphenyls (PCBs) in cetaceans are scarce. This paper presents data on the concentrations and accumulation features of PCDD/Fs and dioxin-like PCBs in muscle of minke whales (Balaenoptera acutorostrata) and long-beaked common dolphins (Delphinus capensis) collected from Korean coastal waters. The residue levels in cetaceans were in the order of mono-ortho PCBs> non-ortho PCBs>PCDFs>PCDDs. Total toxic equivalent (TEQ) concentrations in muscle of minke whales and common dolphins from Korea were lower than those reported for cetaceans and seals from other countries. The accumulation profiles of PCDD/Fs and dioxin-like PCBs were different between the cetacean species. Concentrations of PCDD/Fs and dioxin-like PCBs in common dolphins were significantly higher than those measured in minke whales, due to differences in the habitat and diet. The relative contribution of individual chemical groups to total TEQs was different between the cetacean species, suggesting different exposures and metabolic activity.

The feasibility of photo-identification techniques for the bottlenose dolphins from Jeju Island, Korea, and the potential for dolphin watching were simultaneously evaluated in this study. During the sighting survey, a pod of bottlenose dolphins composed of approximately 30 individuals was observed in the southwestern coastal area of Jeju Island. Among 35 suitable photographs, five bottlenose dolphin individuals were identified and cataloged using unique nicks and notches on their dorsal fins. This shows that the Jeju Island dolphins can be individually identified by the nicks and notches on their dorsal fins using photo-identification techniques. Furthermore, the Jeju Island population appears to be suitable for long-term population biology studies using this technique. The potential for dolphin watching around the island would be higher if more information on the seasonal distribution, movement, and residency of this population were obtained.

Monthly fish samples were collected using bottom gill nets and analyzed to study species composition and seasonal variation of fish assemblages in the coastal waters off Gadeok-do, Korea in 1998. During the study period, a total of 49 fish species representing 30 families were collected. The fish assemblages predominantly consisted of Limanda yokohamae, which accounted for of the number of individuals and in the biomass. The fish species, which had over 100 individuals, included Cynoglossus abbreviatus, Ditrema temmincki, Hexagrammos otakii, and Stephanolepis cirrhifer. These four species accounted for of the number of individuals and of the biomass. More fish species were collected in May and June than in any other months. The number of individuals and the amount of biomass peaked in April and May and reached a low in August. While the predominance of L. yokohamae caused the lowest species diversity by number of individuals in April, the predominance of Platycephalus indicus caused the lowest species diversity by biomass in July. Although gill nets show a strong selectivity for the target species or for size, gill nets can be used as an alternative fishing gear to collect fish in waters with rough bottoms, like rocky reefs, where other kinds of fishing gear such as trawls can not be used.

The monthly collected fish samples by crab pots were analyzed in order to study the species composition and seasonal variation of fish assemblage in the coastal water off Gadeok-do, Korea in 1998, During the study period, 49 species of fishes representing 26 families were collected, The dominant species were Conger myriaster, Sebastes inermis, Hexagrammos otakii, H. agrammus, Stephanolepis cirrhifer and Acanthogobius flavimanus. These 6 dominant species accounted for and in the number of individuals and biomass, respectively. The secondary importance species were Thamnaconus modestus, Takifugu niphobles, Rudarius ercodes, Dictyosoma burgeri, Sebastes longispinis and Epinephelus septemfasciatus. The highest number of species was collected in November, and the number of individuals and biomass were highest in March. But the lowest numbers of species and individuals were collected in July and the lowest biomass in September, Although the species diversity indices varied little monthly, the lowest value was recorded in August because of small number of species and predominance of 5. cirrhifer and T. modestus

The monthly collected fish samples by three sides tyke nets were analyzed in order to study species composition and seasonal variation of fish assemblage in the coastal water off Gadeok-do, Korea through a year of 1998, During the study period, a total of 136 fish species of 69 families were collected. Trachums japonicus, Konosims punctatus and Mugil cephaus were three dominant species in the fish assemblage and they accounted for and in the number of individuals and biomass, respectively. Fish species of secondary importance in abundance were Leiognathus nuchalis, Takifugu niphobles, Somber japonious, Trichiurus lepturus, Chelon affinis, Apogon lineatus, Nibea aibiflora and Acanthopagrus schlegeli. The highest number of species was collected in July and the lowest in february. Abundance was high in spring, and low in winter. Species diversity indices showed that the fish assemblage was less diverse in spring than any other seasons.

Data on the occurrence and accumulation profiles of butyltins (BTs), including tributyltin (TBT), in marine mammals are scarce. This is the first study to investigate residue levels and accumulation patterns of BTs in cetaceans from Korean coastal waters. The total concentrations of BTs (sum of mono- to tri-butyltins) in minke whales (Balaenoptera acutorostrata) and long-beaked common dolphins (Delphinus capensis) ranged from 15.7 to 297 ng/g wet weight (mean: 100 ng/g wet weight) and from 59.0 to 412 ng/g wet weight (mean: 228 ng/g wet weight), respectively. Dibutyltin (DBT) accounted for 63% of the total BTs in all cetacean samples. Significant species-specific differences in BT concentrations, possibly due to the differences in their habitat and diet, were found between the two cetacean species. The concentrations of DBT and TBT in most cetacean samples exceeded the threshold value for cytotoxic effects in cetaceans, implying potentially adverse health risks from exposure to BTs.

This is the first study to report the concentrations and accumulation profiles of PFCs in marine mammals from Korea. The concentrations and profiles of 10 PFCs in the liver of minke whales and common dolphins from Korean coastal waters were recorded in this study. The mean concentrations of PFOS and PFUnDA were 3-20 times higher than that found for other PFCs analyzed. The concentrations of PFOS in cetaceans from Korea were relatively lower than those reported in other countries. Inter-species differences in the concentrations of PFOS, PFOSA and PFNA were found between two cetacean species, while no difference was observed in the concentrations of PFDA, PFUnDA and PFDoDA between the species. The dominant PFC compounds found in cetaceans were PFUnDA and PFOS, accounting for 70-80% of the PFCs. The accumulation profiles and correlation analysis indicated that two cetacean species have different exposure routes and metabolic capacity for PFCs.