Hawsun Sohn

Age and reproduction of the finless porpoises, Neophocaena asiaeorientalis, in the Yellow Sea, Korea

A total of 116 finless porpoises, Neophocaena asiaeorientalis, were collected in the Yellow Sea off Korea. About 111 specimens were incidentally caught by stow nets on anchors from March to June 2010, and five were stranded in February 2011. Age was determined by counting dentinal growth layer groups (GLGs) in thin-sectioned teeth, and sexual maturity rating (SMR) was classified by investigating ovaries and testis macroscopically and microscopically. Immature females were ranged 1–4 years old and 92.6–141.2 cm in total body length (TBL), pubertal ones were all 5 years old and 125.4–136.0 cm, and mature ones ranged 5–19 years old and 131.6–155.2 cm. Age at attainment of sexual maturity of females was 4–5 years old. Parturition season estimated based on TBL of eight fetuses was from April to August with a peak in April to May. The first age at parturition was 5 years old. Among 62 males, immature males were 1–4 years old and 87.9–154.6 cm, pubertal ones were 3–5 years old and 121.5–134.5 cm, and mature ones were 4–19 years old and 125.3–229.0 cm. Males reached sexual maturity at 4–5 years old. Testicular mass and the diameters of seminiferous tubules were dramatically increased with SMR and regressed in testis of the individuals stranded in February. It suggested that male finless porpoises have aspermatogenic period between October and February. It is presumed that the breeding season would be May–September with a peak in May–June.

Distribution of Whales and Dolphins in Korean Waters Based on a Sighting Survey from 2000 to 2010

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.

Pilot research on species composition of Korean purse seine catch at cannery

Apreliminary study on species composition of aKorean purse seine catch landed at cannery was conducted inApril2011. In the cannery, alltuna catch are sliding through asorting grid panelthatfilters and drops fish in thebuckets by size class (above 9kg, 3.4－9kg, 1.8－3.4kg, 1.4－1.8kg and below 1.4kg). In cannery processing,species sorting was made for skipjack tuna and yellowfin tuna only from catches greater than 3.4kg duringfiltering butnotfor bigeye tuna because of difficulties in species identification between bigeye tuna and yellowfintuna under frozen state. As no species identification was carried outfor catch groups less than 3.4kg in the canneryprocess, this study focused on sorting outskipjack tuna and yellowfin tuna from these groups and then identifyingbigeye tuna from all size groups of yellowfin tuna. Using the mixture rate of species obtained from the samplestaken, species composition of the landed catch was estimated. As results, cannery research showed 95% forskipjack tuna, 3% for yellowfin tuna and 2% for bigeye tuna in species composition, while vessel logbook datarepresented 96%, 3% and 1% for skipjack tuna, yellowfin tuna and bigeye tuna, respectively. The proportion ofbigeye tuna identified in the cannery was slightly higher than shown in logbook data by 1%.Keywords: Purse seine catch, Species composition, Mixture rate, Skipjack tuna, Yellowfin tuna, Bigeye tuna

Determination of the haplotype and complete mitochondrial genome of the leatherback turtle Dermochelys coriacea (Testudines: Dermochelyidae) found in the vicinity of Korea

Although several strandings of the leatherback turtle (Dermochelys coriacea Vandelli, 1761) have been reported in Korea, its haplotype or mitogenome have yet to be investigated. Herein, we report the first complete mitogenome of D. coriacea. The 16,501-bp sequenced mitogenome is similar to those of other marine turtles, and the particular genetic features reported in birds and turtles were also found in ND3 and ATP8. The comparison of the control region verified that D. coriacea stranded in Korea belonged to the haplotype JD1 (identical to haplotypes I and Dc9.1). Multigene phylogeny revealed that D. coriacea was well separated from other Cheloniidae species, and the overall tree topology was congruent with the recent phylogenetic analysis of marine turtles. These results provide information fundamental for genetic and conservation studies on leatherbacks, especially the critically endangered West Pacific Ocean subpopulation.

A New Abundance Estimate for the Finless Porpoise Neophocaena asiaeorientalis on the West Coast of Korea: An Indication of Population Decline

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.

Occurrence of Indo-Pacific Bottlenose Dolphins Tursiops aduncus off Jeju Island, Korea during the Early 2000s

【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.】

Population structure of minke whales (balaenoptera acutorostrata) in the Korean waters based upon mitochondrial DNA polymorphism

Abstract The Minke whale, Balaenoptera acutorostrata, is the smallest baleen whale in the suborder Mysticeti. Because this species inhabits coastal areas, it became a main target species of coastal small‐type whaling in the North Atlantic and the Northwest Pacific Oceans, and the species’ population size dramatically decreased because of over‐exploitation. As a result, the International Whaling Commission declared a global moratorium on whaling and launched the development of a management procedure for protecting the whales. Morphological studies, whaling history analysis, and genetic studies conducted mainly by Japanese scientists showed the existence of one unique “E” stock that inhabits the waters around the Korean peninsula and mixes with the “O” stock in the southern part of the Sea of Okhotsk. We used the mitochondrial DNA control region polymorphism of 348 Minke whales bycaught or stranded in Korean waters from 30 October 1998 to 25 June 2005 to assess the whale population structure by year. The frequency of the 10 major haplotypes from the 40 identified haplotypes was not significantly different among groups, suggesting that a sub‐population was not present. A comparison of the genetic distances calculated with Tamura‐Neis method showed that the distances between groups were lower than those within groups, which suggests that there was no genetic difference in the Minke whale populations. The Fst comparison between groups and the phylogenetic tree constructed using the unweighted pair group method with arithmetic mean (UPGMA) and Neighbor Joining (NJ) method also detected no obvious sub‐stock structure.

Characterization of the complete mitochondrial genome and phylogenetic analysis of the common dolphin Delphinus delphis (Cetacea: Delphinidae)

Abstract We report the complete mitogenome of the common dolphin, Delphinus delphis. Overall structure of the 16,387 bp mitogenome was very similar to those of other delphinid species, including the ancient D. delphis individuals. Multigene phylogeny revealed that D. delphis was most closely related to Stenella coeruleoalba, and clustered well with other species within the subfamily Delphininae.

Status of the Cetacean Bycatch near Korean Waters

어구에 의한 고래류의 혼획은 혼획된 개체의 생존을 위협하 는 요인으로 작용하며(Northridge, 1991; Read and Rosenberg, 2002) 이는 전세계적으로 문제가 되고 있는 현상으로 많은 고 래류의 개체군에도 악영향을 끼치고 있는 것으로 알려지고 있 다(Norman, 2000; Read et al., 2006). 우리나라에도 예외는 아 니어서 매년 어구에 의해 많은 양의 고래류가 혼획되며 정부에 서는 좌초 및 표류되는 개체까지 포함해 관련 고시에 의해 현황 을 파악하고 있다. 우리나라 연안에 분포하는 고래류에 관한 연구는 1978년 우 리나라가 국제포경위원회(IWC, International Whaling Commission)에 가입하면서 시작되었다(Gong, 1981, 1982, 1987, 1988; Gong and Hwang, 1983, 1984). IWC의 밍크고래 자원 평가를 위한 조사 목적으로 고래연구소에서 1999년 목시조사 를 실시(Kim et al., 2000)한 이후 매년 목시조사를 통해 연근 해에 분포하는 고래류의 조사를 통한 자원량 추정 연구를 하고 있다. 또한, 혼획, 좌초 및 표류되는 고래류 현황을 파악하기 위 해 고래연구소 자체적으로 전국 연안의 자료를 수집하였으며, 2011년 1월 『고래자원의 보존과 관리에 관한 고시』가 제정된 이후에는 혼획되는 개체뿐만 아니라 좌초 및 표류되어 폐기되 는 개체까지 모두 체계적으로 관리하기 시작하였다. 고시 제정 초기에는 연안에서 혼획, 좌초되는 상괭이를 포함한 소형 고래 류의 신고가 다소 누락되기도 하였으나, 해를 거듭하며 안정적 인 고시 이행으로 연안에서 누락되던 자료까지 체계적으로 수 집되고 있다. 최근에는 어구에 혼획된 개체를 민관 합동으로 구

Feasibility of Aerial Surveys of Finless Porpoise Neophocaena asiaeorientalis off the West Coast of Korea

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.