Suam Kim

Climatic regime shifts and their impacts on marine ecosystem and fisheries resources in Korean waters

Abstract There were climatic regime shifts over the North Pacific in 1976 and 1988 which affected the dynamics of the marine ecosystem and fisheries resources in Korean waters. Precipitation in Korean waters showed a decadal scale climatic jump, especially of Ullungdo Island, reflecting the regime shift that occurred in the North Pacific. The variation was also detected in East Asian atmospheric systems. The Aleutian Low and North Pacific High Pressure Systems showed substantial changes in 1976 and around 1987–89. 1976 was an unusually warm year for Korea; mean sea surface temperature (SST) was higher than ‘normal’ and was accompanied by a northward shift in the thermal front. Post 1976, the volume transport of the Kuroshio Current increased and higher seawater and air temperatures persisted until 1988. Other shifts occurred after 1976 such as an increase in mixed layer depth (MLD) and biological changes in the ecosystem of Korean waters including decreases in spring primary production and an increase in autumn primary production. Primary production increased again after 1988, and was followed by a significant increase in zooplankton biomass after 1991. The 1976 regime shift was manifested by a decreased biomass and production of saury, but an increase in biomass and production of sardine and filefish in Korean waters. After 1988, recruitment, biomass, and production of sardine collapsed while those of mackerel substantially increased. Based on these observations, hypotheses on the relationship between the climate-driven oceanic changes and changes in fisheries resources were developed and are discussed.

Changes in ecosystem components induced by climate variability off the eastern coast of the Korean Peninsula during 1960–1990

To understand the variations of ecosystem components in response to changing environment, especially relating to a shift in the climate regime during mid 1970s, we analyzed the physical and biological time-series data collected from the eastern part of the Korean Peninsula during 1960-1990. The Northeast Pacific Pressure Index (NEPPI) in winter seasons showed a negative correlation (r=-0.384, p<0.05) with SOI in summer. The standardized chronologies of tree ring-width showed high correlations with precipitation of Ulleung Island and Kangrung city (r=0.408, p<0.05; r=0.410, p<0.05) and seawater temperatures (r=0.407, p<0.05). Sharp increases in tree growth appeared in 1969, 1973, 1979, 1983, and 1987. Among these years, all except 1979 seem to have a close connection with the El Nino which had persisted more than five seasons. Air temperatures in spring at Ulleung Island and Kangrung area appeared comparatively higher during the intense Aleutian low period after 1976. The Mixed Layer Depth (MLD) was shallower (18.2 m) and less variable during 1961-1975 compared to that (26.1 m) of 1976-1990. The shallower MLD in spring during the earlier period resulted in the higher chl a concentration than in the later years. Consequently, estimated zooplankton biomass in spring tended to decrease from the 1960s to the late 1980s in accordance with the phytoplankton decreases. In the East Sea, composition changes in fish species as well as fish catches were observed. Catches of pollock, sardine, and saury had good correlations with annual NEPPI.

Climate variability and its effects on major fisheries in Korea

Understanding in climate effects on marine ecosystem is essential to utilize, predict, and conserve marine living resources in the 21s t century. In this review paper, we summariz ed t h e past history and current status of Korean fisheries as well as the changes in climate and oceanographic phenomena since the 1960s. Ocean ecosystems in Korean waters can be divided into three, based on the marine commercial fish catches; the demersal ecosystem in the Yellow Sea and the East China Sea, the pelagic ecosystem in the Tsushima Warm Current from the East China Sea to the East/Japan Sea, and the demersal ecosystem in the northern part of the East/Japan Sea. Through the interdisciplinary retrospective analysis using available fisheries, oceanographic, and meteorological information in three important fish communities, the trend patterns in major commercial catches and the relationship between climate/ environmental variability and responses of fish populations were identified. Much evidence revealed that marine ecosystems, including the fish community in Korean waters, has been seriously affected by oceanographic changes, and each species has responded differently. In general, species diversity is lessening, and mean trophic level of each ecosystem has decreased during the last 3~4 decades. Future changes in fisheries due to global warming are also considered for major fisheries and aquaculture in Korean waters.

Characterization of two vitellogenin cDNAs from a Pandalus shrimp (Pandalopsis japonica): Expression in hepatopancreas is down-regulated by endosulfan exposure

Endosulfan is a neurotoxic organochlorine insecticide of the cyclodiene family of pesticides that inhibits molting and reproduction in aquatic crustaceans. In order to determine the molecular mechanism of endosulfan as an endocrine disrupting chemical (EDC), differential display RT-PCR (DDRT-PCR) was used to isolate genes in the shrimp, Pandalopsis japonica, affected by endosulfan exposure. PCR screening of cDNA from the hepatopancreas from control and endosulfan-exposed animals, using 120 sets of random primers, yielded partial cDNAs encoding two vitellogenin-like proteins (Pj-Vg1 and -Vg2). Complete sequences were obtained using a combination of RT-PCR and RACE-PCR. Pj-Vg1 (7883bp) encoded a protein composed of 2533 amino acid residues (283.27 kDa estimated mass), whereas Pj-Vg2 (7792 bp) encoded a protein composed of 2537 amino acids residues (284.87 kDa estimated mass). Alignment of the Pj-Vgs with those of other vitellogenins identified a conserved subtilisin cleavage site (RQKR) and the lipoprotein N-terminal (vitellin), DUF1081, and von Willebrand factor type D domains, indicating both genes encoded functional proteins. Phylogenetic analysis showed that Pj-Vg1 and -Vg2 were most similar to Pandalus hypsinotus Vg. Both Pj-Vg1 and -Vg2 were expressed primarily in the hepatopancreas, although the Pj-Vg2 transcript was also detected in the ovary. The effects of the 3-day endosulfan exposure (2.5 microg/L and 25 microg/L) on Vg expression in the hepatopancreas were determined by quantitative RT-PCR. Expression of both transcripts was significantly inhibited at 25 microg/L suggesting that Pj-Vgs can be used as indicator for endosulfan exposure.

Size-class Estimation of the Number of Walleye Pollock Theragra chalcogramma Caught in the Southwestern East Sea during the 1970s-1990s

Walleye pollock Theragra chalcogramma fisheries in Korean waters have changed dramatically during the last three decades: the highest catches occurred in 1981, followed by continuous decreases through the 1990s, ending with a complete collapse of the population in the 2000s. The major spawning ground of walleye pollock is located in North Korean waters, and some juveniles (called nogari in Korean,

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.

Seasonal Characteristics of Todarodes pacificus Paralarval Distribution in the Northern East China Sea

살오징어(Todarodes pacificus)는 살오징어목(Order Teuthoidea), 살오징어과(Family Ommastrephidae)에 속하는 두족류 (Cephalopod)이다. 우리나라 동, 서, 남해 및 동중국해, 일본 남 부 태평양 측 근해에 주로 분포하며, 우리나라와 일본의 주요수 산자원이다. 과거 주로 채낚기에 의해 어획되었으나, 1990년대 이후 대형트롤에 의한 어획비율이 증가하는 추세이다. 우리나 라에서는 1970-80년대 중반까지 연간 10만 톤 미만의 어획량 을 기록하였으나, 1980년대 후반 이후 어획량이 급격하게 증 가하기 시작하여 최근까지 20만 톤 내외의 어획량을 기록하고 있다. 한편 일본의 경우 1970-80년대에 20만 톤 내외의 어획량 을 기록하였으나, 1990년대 이후 증가하기 시작하여, 현재까지 20-30만 톤의 어획량을 유지하고 있다(FAO, 2010). 1980년대 중반까지 우리나라의 어획량은 일본 어획량의 절반에 못 미쳤 으나, 2000년대 이후 일본과 대등한 수준을 나타내고 있다. 우 리나라의 어획비율 증가는 우리나라로 내유해오는 자원량의 증 가와 더불어 어로기술향상에 기인한 것으로 알려져 있다. 특히, 1980년대 후반부터 시작된 북서태평양에서의 온난한 기후체 제(climate regime)는 난류성 어종인 살오징어의 자원량 증가 에 크게 기여한 것으로 인식된다(Sakurai et al., 2000). 또한 자 원량 추정에 가장 일반적인 지표로서 이용되는 단위노력당 어 획량(CPUE)은 1980년대 후반 이후 우리나라와 일본에서 동시 에 급격히 증가하였다(Choi et al., 2008). 살오징어의 수명은 1년 내외로, 산란 후 사망하는 것으로 알 려져 있다. 표층에서 200 m 수심에 주로 분포하고 서식가능

Ecological relationship between environmental factors and Pacific cod (Gadus macrocephalus) catch in the southern East/Japan Sea

The habitat characteristics of Pacific cod (Gadus macrocephalus) and the ecological relationship between Pacific cod catch and environmental parameters in the southern East/Japan Sea were investigated. Pacific cod is sexually matured at age of 4–5. The highest catch of Pacific cod off the eastern Korean Peninsula occurred in seawater temperature range of 0–4°C and salinity range of 33.8–34.2 practical salinity unit at 100 m. The Cross-Correlation Function analysis showed that there was a significant negative correlation between Pacific cod catch and February seawater temperature at 75 m nearby spawning area with a time lag of 5 years in Korean waters (r = –0.360, p < 0.05). The annual catch of Pacific cod also had a significant correlation (p < 0.05) with zooplankton biomass in coastal nursery areas with a time lag, i.e., the highest ones, r = 0.432 and r = 0.452, for total zooplankton biomass in June of 5 years ago, and for euphausiids abundance in February of 4 years ago from the period when Pacific cod was caught, respectively. Furthermore, total catches of Pacific cod in the southern East/Japan Sea (i.e., sum of Korean and Japanese catches) were negatively correlated with winter Arctic Oscillation Index, and the highest negative correlation (r = –0.364, p < 0.05) was shown with a time lag of 4 years. Considering sexual maturation at ages 4–5, such statistical analyses imply that biotic and abiotic environmental factors during the early life stages of Pacific cod have a significant influence on recruitment after 4–5 years of spawning.

Introduction: from the birth to the table of walleye pollock Theragra chalcogramma

Fisheries provide food, feedstuff, and materials which are reliant on ecosystem services provided by marine and freshwater systems. Fish spawn and mature in aquatic systems, from which they are harvested by fishers, distributed and processed in households, restaurants, or processing plants, and either eaten by consumers, used in aquaculture, horticulture or agriculture, or used in manufacturing. The movement of fish from sea to plate follows distinct sequential stages. We call this the “fisheries system”. While each stage of the fisheries system has been the focus of specific research activities, these activities have generally proceeded from the perspective of individual disciplines, e.g., oceanography, chemistry, biology, ecology, resource dynamics, economics, business management, food science, processing, nutrition studies, etc. As a result, their objectives, data, models, discussions, etc., do not present an effectively integrated perspective of the fisheries system as a whole. This Special Feature brings together research from across disciplines to provide a broad perspective of the walleye pollock Theragra chalcogramma fisheries system. While this falls short of being a fully integrated model, it highlights key interfaces among disciplines and illustrates fundamental research questions for each stage. By highlighting these questions and interfaces, we hope to foster an intellectual environment that will lead to true “integrated research” that can best be pursued by multi-disciplinary teams rather than by individual scientists who limit their research activities to the narrow scope of their specific disciplines.

Genetic stock identification of immature chum salmon (Oncorhynchus keta) in the western Bering Sea, 2004

Genetic stock identification studies have been widely applied to Pacific salmon species to estimate stock composition of complex mixed-stock fisheries. In a September-October 2004 survey, 739 chum salmon (Oncorhynchus keta) specimens were collected from 23 stations in the western Bering Sea. We determined the genetic stock composition of immature chum salmon based on the previous mitochondria DNA baseline. Each regional estimate was computed based on the conditional maximum likelihood method using 1,000 bootstrap resampling and then pooled to the major regional groups: Korea - Japan - Primorie (KJP) / Russia (RU) / Northwest Alaska (NWA) / Alaska Peninsula - Southcentral Alaska - Southeast Alaska - British Columbia - Washington (ONA). The stock composition of immature chum salmon in the western Bering Sea was a mix of 0.424 KJP, 0.421 RU, 0.116 NWA, and 0.039 ONA stocks. During the study period, the contribution of Asian chum salmon stocks gradually changed from RU to KJP stock. In addition, North American populations from NWA and ONA were small but present near the vicinity of the Russian coast and the Commander Islands, suggesting that the study areas in the western Bering Sea were an important migration route for Pacific chum salmon originating both from Asia and North America during the months of September and October. These results make it possible to better understand the chum salmon stock composition of the mixed-stock fisheries in the western Bering Sea and the stock-specific distribution pattern of chum salmon on the high-seas.