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Hwang S.W.,Marine Ecosystem Research Division | Choi K.H.,Ballast Water Center South Sea Institute | Hwang H.,South Korean National Fisheries Research and Development Institute | Kim C.K.,Marine Ecosystem Research Division | Lee T.W.,Chungnam National University
Journal of Coastal Research | Year: 2015

The habitat use and migration of Javelin goby Synechogobius hasta that were collected from the estuaries of the Geum River and the Mangyeong River of Korea were examined on the basis of the environmental signature of otolith strontium and calcium concentrations determined by laser ablation-inductively coupled plasma mass spectrometry. The otolith Sr:Ca ratios suggested that S. hasta spawned in brackish water, and inhabited a broad range of salinities, including seawater, brackish water, and freshwater, during their lifetime. The migration histories of S. hasta were highly variable within habitats, indicating flexible movement patterns that permit use of the full range of salinity throughout their lifetime. © Coastal Education and Research Foundation, Inc. 2015.

Hwang S.W.,Marine Ecosystem Research Division | Lee T.W.,Chungnam National University | Hwang S.D.,Fisheries Resources Agency | Lee E.K.,Marine Ecosystem Research Division | Yoo J.M.,Marine Ecosystem Research Division
Journal of Coastal Research | Year: 2015

We measured Sr:Ca ratios in otoliths to examine the habitat use patterns of 50 Chelon haematocheilus collected from two estuaries of the Geum River and the Mangyeong River on the midwest coast of South Korea. The average ratio was 5 × 10-3 ± 0.6 × 10-3 (mean ± SD) in the core of the otolith and ranged from 3 × 10-3 to 7 × 10-3 in the opaque zone surrounding the core. We applied the criteria used to analyze otoliths in the closely related species Mugil cephalus in a previous study and concluded from the otolith Sr:Ca ratios that C. haematocheilus spawns and grows in brackish water during the early part of its life cycle. Most fish showed otolith Sr:Ca ratios ranging from 3 × 10-3 to 7 × 10-3, indicating that they primarily live in brackish water. Some fish had ratios outside that range, indicating that they had potentially spent time in the upper, less-saline or lower, more-saline parts of the estuaries. Of C. haematocheilus in the Mangyeong River estuary, 34.8% had inhabited freshwater, but of those in the Geum River estuary, where a dike causes the water to be more saline, only 22.2% had inhabited freshwater. The findings of our study offer useful new information on the habitat choice of C. haematocheilus, allowing more sustainable use of the species. © Coastal Education and Research Foundation, Inc. 2015.

Oh S.-Y.,Marine Ecosystem Research Division | Kim M.-S.,Marine Ecosystem Research Division | Kwon J.Y.,Sun Moon University | Maran B.A.V.,Marine Ecosystem Research Division
Ocean Science Journal | Year: 2013

The feed intake, growth and body composition of juvenile blackhead seabream Acanthopagrus schlegelii schlegelii (Sparidae) (5.6 g fish-1) were investigated for 16 weeks in sea cages under seven repetitive feeding cycles: every day feeding (control), 6-day feeding and 1-day fasting (F6.1), 5-day feeding and 1-day fasting (F5.1), 4-day feeding and 1-day fasting (F4.1), 3-day feeding and 1-day fasting (F3.1), 2-day feeding and 1-day fasting (F2.1), and 1-day feeding and 1-day fasting (F1.1). The survival of the fish during the experimental period was not different among the feeding cycles. The greatest weight gain of fish was observed in the control, but not significantly different from that of the F6.1 and F5.1 groups (p > 0.05). Total feed intake and daily feed intake decreased with the increase of fasting frequency, however, actual feed intake, feed efficiency and protein efficiency ratio increased with the increase of the fasting frequency. Proximate composition of the whole body of fish was not affected by different feeding cycles. These results suggest that juvenile blackhead seabreams subjected to repetitive feeding cycles of 6- or 5-days feeding and 1 day fasting for 16 weeks could achieve compensatory growth, and that such mild feeding deprivation could save significant amounts of feed without causing any profit reduction that might result from a decrease in fish size or quality. © 2013 Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht.

Koo B.J.,Marine Ecosystem Research Division | Koh C.-H.,Seoul National University
Ocean Science Journal | Year: 2013

Macrofaunal burrows increase the surface area of the sediment-water interface, which has a great impact on the metabolism of aerobic microbes and the oscillation of reduced metabolites within the sediment. Given the importance of macrofauna in surficial sediments, the aim of this study is to examine the effects of burrow architectures on dissolved oxygen diffusion rates in comparison with unburrowed sediment, and thereby to evaluate the theoretical assumption used for modeling solute distribution in the burrow system using field samples. Employing microsensors, horizontal oxygen profiles were measured on a micrometer scale around burrows of seven invertebrates in tidal flats of the west coast of Korea. Oxygen diffusion distance through the burrow walls of seven invertebrates showed spatio-temporal variation with a range of 0.6 to 2.9 mm. Two groups of burrows were identified based on their oxygen diffusive properties relative to unburrowed sediments: 1) oxygen penetration similar to that of ambient sediments and 2) clearly enhanced oxygen penetration. Differences in the diffusive properties of the burrow wall were related to the burrow depth and diameter, existence of mucus lining on the wall, sediment grain size, and tidal phases. Also inhabitant activity was an important factor affecting oxygen penetration, which is discussed in the paper. These results further demonstrate that simplified assumptions (i.e. burrow structures are viewed as direct biogeochemical extensions of the sediment-water interface) may not be exact representation of the nature. © 2013 Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht.

PubMed | Marine Ecosystem Research Division and Annamalai University
Type: Journal Article | Journal: Journal of parasitic diseases : official organ of the Indian Society for Parasitology | Year: 2014

In the present study, 68 fishes were infested out of 544 specimens examined from six different species of Carangid fishes which were collected from Parangipettai coastal waters. Eight species of parasitic copepods were found on gill filaments, body surface and nasal capsule regions. The maximum prevalence was recorded in Carangoides malabaricus (22.5%) and minimum was noticed in (2.4%) Selaroides leptolepis. The intensity of infection ranged from 1 to 1.2. Thus, considerable variation in the respiratory area was observed owing to the attachment of parasites in the infected fishes. Caligus sp. and C. epidemicus parasites were attached to body surface and only one Sphyriid sp. parasites were found in nasal capsule region. It is very difficult to estimate the actual harm to fish caused by the presence of parasites; if this is uneasy in cultured fish, it is almost impossible in feral fish populations. It should also be emphasized that the presence of a parasite does not necessarily imply manifestation of a disease. In aquaculture, some parasites are able to reproduce rapidly and heavily infect a large proportion of fish which may lead to diseases with significant economic consequences.

Kim Y.-O.,South Sea Research Institute | Shin K.,South Sea Research Institute | Jang P.-G.,South Sea Research Institute | Choi H.-W.,Oceanogaphic Data and Information Center | And 4 more authors.
Ocean Science Journal | Year: 2012

This study examined seasonal and annual occurrences of warm oceanic tintinnid species in southern Korea coastal waters. The indicative species of tintinnids was monitored using three approaches: monitoring from cruises traveling from the warm pool in the western North Pacific to the Korea Strait; biweekly or monthly monitoring in the Korea Strait; and daily monitoring in the nearshore water. Annual pulses of warm oceanic indicator species were regularly observed in the Korea Strait. In September 2008 recorded a maximum species number of warm water indicators, a representative species for warm oceanic waters, Climacocylis scalaroides was simultaneously detected in the nearshore water as well as the Korea Strait. The result indicates that the greater warm water extension into Korean coastal areas was in September 2008. Sharp declines in species diversity were observed in the transitional area between neritic and Kuroshio zone in East China Sea (ECS). Epiplocyloides reticulata, reported previously as a Kuroshio indicator, was considered an ECS indicator species, as it was undetected in the western North Pacific central zone but was found abundantly in the ECS. Tintinnid species can be used as biological indicators to detect the inflow of warm oceanic waters into Korean coastal waters. © 2012 Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht.

Yoon J.-E.,Marine Ecosystem Research Division | Yoon J.-E.,Daejeon University | Park J.,Korea Polar Research Institute | Yoo S.,Marine Ecosystem Research Division
Ocean Science Journal | Year: 2012

This study compares five primary productivity algorithms for Korean waters. Five algorithms are in the form of vertical generalized production models: One algorithm is for gross primary production and four are for net primary production. The five algorithms were evaluated using 117 in situ primary production datasets observed by 20 cruises from 1994 to 2011 in Korean waters (East Sea, Yellow Sea, East China Sea, and Yeosu Bay). The results show that the regionally-tuned variants give better results than the original formulation. We recommend, among the tested algorithms, YSVGPM (Yellow Sea Vertically Generalized Productivity Model) for gross primary productivity algorithm and Kameda-Ishizaka algorithm for net primary productivity algorithm for estimating primary production in Korean waters. © 2012 Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht.

Hwang S.-W.,Marine Ecosystem Research Division | Kang H.-K.,Marine Ecosystem Research Division | Son Y.-B.,Korea Ocean Satellite Center | Jang M.-C.,Ballast Water Center South Sea Institute | Choi K.-H.,Ballast Water Center South Sea Institute
Journal of Coastal Research | Year: 2013

The damming of major rivers can have broad impacts on ecological processes in adjacent marine ecosystems. Thirty years of sampling data from the northern East China Sea show that the recent impounding of water by the Three Gorges Dam on the Changjiang River (Yangtze River) might have had dramatic impacts on the mesozooplankton community. The reduction in freshwater discharge and subsequent increases in phytoplankton biomass have resulted in a substantial increase in total mesozooplankton wet weight but sharp declines in the abundance of all of the crustacean components. The increase in mesozooplankton biomass is probably associated with an increase in small, gelatinous zooplankton. Together with an increase in sea surface temperature in the region, the reduced freshwater and sediment discharge might have led to the proliferation of gelatinous mesozooplankton in this historically overfished region, generating significantly increased grazing pressure on planktonic crustaceans. © Coastal Education & Research Foundation 2013.

Koo B.J.,Marine Ecosystem Research Division | Kim M.,Marine Ecosystem Research Division
Ocean and Polar Research | Year: 2013

In order to investigate the topography and exposure duration of the Siheung tidal flat, tidal ranges and DEM constructed by remote sensing techniques were analyzed. A cross-sectional diagram of the intertidal area reveals that it is relatively flat in the upper zone and then abruptly plunges into the bottom of the main channel where elevations increase in an upstream direction. The waterline during the Highest Low Water (HLW) is drawn back to the bottom of the channel at the middle part of the tidal flat and is formed along the slant of the channel during the Lowest High Water (LHW). The intertidal zone is located between -410 cm and 510 cm in terms of elevation and its total area is 0.65 km2. An area between the Highest High Water (HHW) and Lowest High Water (LHW), occupying about 80% of the total area, occupies 0.52 km2 of total area and accounts for 56% of the exposure duration. The boundary of wetland protection area in the Siheung tidal flat did not exactly coincide with the intertidal regime and differs by more than 15%. This study, which precisely analyzed the tidal flat area, tidal environment, and topography, would be useful in making a conservation plan and in learning how to use a wetland protection area in a sustainable manner.

Yu O.H.,Marine Ecosystem Research Division | Lee H.-G.,Marine Ecosystem Research Division | Lee J.-H.,Marine Ecosystem Research Division
Ocean Science Journal | Year: 2012

We compared environmental effects on the macrobenthic community of the Han River Estuary in summer, when freshwater input from the Han River increased, and in spring, when freshwater input decreased. Field samples were taken from the upper region of the Shingok reservoir to the southern area of Ganghwado at 18 sampling sites after rainy (August 2006) and dry (March 2007) seasons. Macrobenthic fauna were collected using a Van Veen Grab (0. 025 m2 and 0.1 m2) and environmental factors were measured simultaneously. Dominant species of macrobenthic fauna and the macrobenthic community were divided into two areas, the area of the Han River with no salinity (< 0.1 psu) and the southern part of Ganghwado with salinity (> 20 psu). The dominant species Byblis japonicus appeared at Junruri in the dry season. The distributions of two polychaetes, Hediste japonica and Nephtys caeca, were divided into the lower and upper areas of the Singok submerged weir. BIO-ENV (the matching of biotic to environmental patterns) analysis revealed that salinity was the most important factor affecting macrobenthic communities in the Han River Estuary, with other factors such as sediment grain size, bottom dissolved oxygen, and total organic carbon of sediment being secondary. © 2012 Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht.

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