• Fisheries and Aquatic Sciences
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• v.27 no.3
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• pp.195-205
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• 2024

Amphipoda is a benthic fauna occupying aquatic environments that can be used as a live feed for mud crabs. The abundance of amphipods in the water is thought to impact the preying capacity of crablets, which in turn will affect their growth performance. This study aims to determine the preying capacity of the crablet stage of Scylla tranquebarica exposed at different densities (20, 30, and 40 amphipods / 0.5 L) of amphipod, Grandidierella megnae. The preying capacity was estimated by counting the number of amphipods ingested by an individual crablet during the 60-day rearing period. The main parameters measured were daily consumption rate (DCR), Cumulative molting (CM), Feed conversion ratio (FCR), and the specific growth rate of weight (SGR-W). The results showed that the DCR and FCR were not affected by amphipod densities but the higher the amphipod density the higher the SGR-W and CM. Based on this study, 30 amphipods / 0.5 L is recommended as the optimal density to optimize the DCR and improve the growth performance of crablets. It is also proposed that surplus live feed will potentially reduce the cannibalism rate of crablets during weaning. However, more research needs to be carried out to elucidate the benefits of crablet-feeding amphipods in communal systems.

• Journal of Ecology and Environment
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• v.37 no.4
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• pp.341-350
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• 2014

In this study, aquatic and aerial algae were collected in various environments in Hongcheon-river of Gangwan-do between December 2011 and June 2012, with the aim of adding newly described genera and species to the Korean flora. As a result, five genera and eight species were recorded for the first time in Korea. These newly recorded genera and species were Cylindrocapsa geminella, Leptosira mediciana, Pseudendoclonium basiliense var. brandii, Stichococcus minor, S. deasonii, Eustigmatos polyphem, Nephrodiella lunaris, and Xanthonema exile. The eight taxa identified in this study mostly corresponded to their reported morphological characteristics. However, some differences from previous published descriptions were found; N. lunaria, reported to be an aquatic species in a previous study, was found to be an aerial algae inhabiting on rocks and mosses. Cylindrocapsa geminella was found to transform into attached or planktonic algae depending on the environmental condition, and the cell wall was found to be changed. Likewise, E. polyphem was seen to change cell-shape or chloroplast color according to the environment.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.2
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• pp.195-206
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• 2017

Joint time-frequency images of the broadband echo signals of six fish species were obtained using the smoothed pseudo-Wigner-Ville distribution in controlled environments. Affine transformation and principal component analysis were used to obtain eigenimages that provided species-specific acoustic features for each of the six fish species. The echo images of an unknown fish species, acquired in real time and in a fully automated fashion, were identified by finding the smallest Euclidean or Mahalanobis distance between each combination of weight matrices of the test image of the fish species to be identified and of the eigenimage classes of each of six fish species in the training set. The experimental results showed that the Mahalanobis classifier performed better than the Euclidean classifier in identifying both single- and mixed-species groups of all species assessed.

• Fisheries and Aquatic Sciences
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• v.16 no.1
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• pp.41-44
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• 2013

We developed a poly(butylene succinate) (PBS) indicator plate and isolated a marine bacterial colony capable of biodegrading PBS based on the appearance of a clear zone. Growth of the PBS-2 isolate was observed over 4 days of culture at $37^{\circ}C$ in PBS-tryptone basal liquid medium, but not in PBS-deprived control medium. The PBS-2 isolate was named Paenibacillus sp. PBS-2 based on 16S rDNA gene sequencing. The PBS-biodegrading marine bacterium isolated in this study will contribute to the effective management of PBS waste problems in marine environments.

• Fisheries and Aquatic Sciences
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• v.16 no.1
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• pp.49-52
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• 2013

A single specimen of Epinephelus lanceolatus, belonging to Epinephelinae of the family Serranidae, was newly collected from Jeju Island, South Korea, in December 2009. Epinephelus lanceolatus is characterized by anterior lateral-line scales with branched tubules, cycloid scales, irregular white spots, and fins with numerous small black spots. We propose a Korean name, "Dae-wang-ba-ri' for this species.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.05a
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• pp.185-186
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• 2001

Recently, industrial activities have increased atmospheric concentration of sulfur and nitrogen oxides, resulting in acidification in the environments. In addition, acidification accelerates the mobilization of metals that are toxic to fish and increases their concentrations in the aquatic environment. Increased metals may interfere with reproductive physiology in fish. Al and Cd are such metals that impaired the preduction of Vitellogenin (VTG), a egg yolk precursor proteins. (omitted)

• Mycobiology
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• v.47 no.3
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• pp.273-279
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• 2019

A new species, Pythium subutonaiense, isolated from aquatic environments (lake) in China is being described based on morphological characters and molecular evidence. The isolates grew at temperatures between $5^{\circ}C$ and $38^{\circ}C$, and the optimum temperature was $30^{\circ}C$, with a radial growth rate of 17.6 mm at $25^{\circ}C$ per day. It is homothallic and characterized by globose to sub-globose shaped and mostly terminal or sometimes catenulate hyphal swellings, filamentous non-inflated sporangia, and smooth oogonia with hypogynous and monoclinous antheridia that contained one plerotic oospore. In phylogenetic analysis, inferred based on the internal transcribed spacer region of the ribosomal RNA gene and mitochondrial cytochrome c oxidase subunit 1 gene, the new species formed a distinct lineage in Pythium clade B. Differences between the new species and phylogenetically related and morphologically similar species are discussed.

• Korean Journal of Ecology and Environment
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• v.39 no.1 s.115
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• pp.62-72
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• 2006

Biological health in aquatic environments has been assessed by several approaches using various bio-taxa. Especially, fish has been identified as one of the best ecological indicators for an integrative health assessments in aquatic environments. In this preliminary study, the necropsy-based approach using the Health Assessment Index (Adams et al., 1993; HAI, Blazer, 2000), was employed for the assessments of aquatic environments influenced by effluent water from wastewater disposal plants (WDP) near a urban stream (i.e., Cap-Stream). For the impact analysis from the effluents, we developed 10 metric necropsy-based model including $M_l\;skin,\;M_2\;fin,\;M_3\;thymus,\;M_4\;spleen,\;M_5\;hindgut,\;M_6\;kidney,\;M_7\;liver.\;M_8\;eyes,\;M_9\;gill,\;and\;M_{10}$ pseudobranch. We set up duplicate controls (natural upstream water plus 5 fishes in each control tank) and duplicate treatments (effluent water from the WDP plus 5 fishes in each treatment tank) in the laboratory. Preliminary results showed that HAI values in the controls were zero, indicating an excellent condition by the criteria of HAI, while the HAI values in the treatments ranged between 40 and 150, indicating a poor condition. Also, various health conditions, based on the index of biological integrity (IBI), species richness, tolerance guilds, and trophic guilds supported the HAI approach. The HAI approach, not applied in Korea, not may be used as an surrogate fer ecological health assessment in lotic ecosystems.

• Journal of Environmental Health Sciences
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• v.34 no.5
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• pp.382-386
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• 2008

This study was designed to establish the time frame of viability and infectivity of Cryptosporidium, when the Cryptosporidium is discharged to the aquatic environment. Changes in viability and infectivity of Cryptosporidium in relation to temperature and pH were investigated during winter (Dec 05-Feb 06) using semipermeable cellulose tubes containing infective Cryptosporidium. Infectivity was maintained at 50% after 30 days and almost completely lost after 50 days. It was also established that viability was maintained at about 8% after 90 days.

• Korean Journal of Environmental Biology
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• v.20 no.3
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• pp.189-196
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• 2002

The direct detection of intestinal pathogens and viruses often requires costly, tedious, and time-consuming procedures. These requirements developed a test to show that the water was contaminated with sewage-borne pathogens by assessing the hygienic quality of water based on indicator microorganisms whose presence indicates that pathogenic microorganisms may also be present. Various groups of microorganisms have been suggested and used as indicator microorganisms. Proposed and commonly used microbial indicators are total coliforms, fecal coliforms, fecal streptococci, Clostridium perfringens, heterotrophic plate count, bacteriophage, and so on. Unfortunately, most, if not all, of these indicators are not ideal because of the sensitivity and resistance to environment stresses and disinfection. However, the development of gene probes and PCR technology may give hope for the discovery of rapid and simple methods toy detecting small number of fecal pathogens in various environments.