• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.1
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• pp.44-50
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• 2015

The basic and main nutritive ingredients of two temperature (Anguilla japonica and A. rostrata) and two tropical (A. bicolor pacifica and A. marmorata) fresh water eel species that are farmed domestically were evaluated. With exception of A. rostrata, eels cultured at the same farm were used for analysis. The contents of crude protein were in the order A. marmorata (17.7%)>A. rostrata (17.5%)>A. bicolor pacifica (17.4%)>A. japonica (15.8%) and the contents of crude lipids were A. japonica (21.5%)>A. rostrata (15.4%)>A. bicolor pacifica (10.5%)>A. marmorata (8.9%). These values differed significantly even among the three species of eel farmed under identical culture conditions. In comparison, all four species of eel showed similar pattern in overall amino acid composition, although slight differences in the compositions of some amino acids were observed. The fatty acid compositions of muscle tissues were notably different among four species of eel, especially between the tropical and temperature eels. In a taste-test of the meat of the four eel species, which considered taste, flavor and texture, the overall preference was in the order A. japonica, A. marmorata, A. bicolor pacifica and A. rostrata.

• Journal of Korea Water Resources Association
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• v.46 no.7
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• pp.783-794
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• 2013

Saline groundwater, in addition to fresh groundwater, is actively developed for inland aqua culture in Jeju Island where groundwater is practically the only source of freshwater. In this work we analyzed impacts of saline and fresh groundwater development on groundwater systems in Sungsan subwatershed in Jeju. A sharp-interface model was used to simulate fresh and saline groundwater flows. Withdrawal of freshwater imparted adverse impacts by lowering groundwater level and inducing saltwater encroachment. Withdrawal of saline water imparted mixed results: on one hand it lowered groundwater level, on the other hand it reduced saltwater encroachments. However, freshwater development lowered groundwater level much more than salinewater development did. Modified Ghyben-Herzberg ratio was developed for a transition zone with finite width. Comparison against observed data resulted in fair agreement.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.2
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• pp.315-322
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• 2016

This study determined the optimum microalgae species and concentration for growth of small rotifer Proales similis, in community cultures by feeding it several different foods. Four single trials (Tetraselmis suecica, TET; Isochrysis galbana, ISO; Nannochloropsis oculata, NAN; freshwater Chlorella vulgaris, CHL) were conducted at 5 psu and $25^{\circ}C$. The maximum density and specific growth rate (SRG) were highest for rotifer fed CHL reaching 1,075 individuals (inds.)/mL and 0.83 respectively. By contrast, other foods of ISO, NAN and TET resulted in poor growth rates and maximum density. In the freshwater C. vulgaris experiments examining a range of 0.05 to $8.8mg/10^4rotifers$, the growth of rotifer tended to decrease with the amount of supplement. The maximum density and SGR of females was highest at 910 inds./mL and 0.55 respectively, at $0.05mg/10^4rotifers$. These results suggest that the best microalgae species for the culture of P. similis is freshwater C. vulgaris and the optimum concentration is $0.05mg/10^4rotifers$.

• Korean Journal of Environmental Biology
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• v.42 no.2
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• pp.143-157
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• 2024

As part of the research program "Freshwater Prokaryotic Organisms Research and Discovery," freshwater samples were collected from the Nakdonggang River. After plating the samples on several culture media and incubating aerobically, approximately 900 bacterial strains were isolated and identified using 16S rRNA gene sequences. Among the bacterial isolates showing higher than 98.7% 16S rRNA gene sequence similarity with those of already confirmed bacterial species previously unreported in Korea, 29 strains were selected. These strains were phylogenetically diverse and belonged to 3 phyla, 6 classes, 13 orders, and 21 genera. At the genus level, these previously unreported species were found to be affiliated with Novosphingobium, Sphingomonas, Polymorphobacter, Croceibacterium, Devosia, Endobacterium, Agaricicola, Bradyrhizobium, Paracoccus, and Pseudotabrizicola of the class Alphaproteobacteria; Undibacterium, Azonexus, and Dechloromonas of the class Betaproteobacteria; Acinetobacter and Budvicia of the class Gammaproteobacteria; Streptomyces, Nocardioides, Mycobacterium, and Cellulomonas of the phylum Actinomycetota; Flavobacterium and Pedobacter of the phylum Bacteroidota. These species were further characterized by examining their Gram reaction, colony and cell morphologies, biochemical properties, and phylogenetic positions. Detailed descriptions of these 29 previously unreported species are provided.

• Journal of Microbiology and Biotechnology
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• v.20 no.10
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• pp.1386-1392
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• 2010

A bacterial strain designated GR5$^T$, previously isolated from a freshwater culture pond in Taiwan while screening for bacteria for antimicrobial compounds, was characterized using a polyphasic taxonomic approach. Strain GR5$^T$ was found to be Gram-negative, aerobic, greenish-yellow colored, rod-shaped, and motile by means of a single polar flagellum. Growth occurred at $10-40^{\circ}C$ (optimum, $35^{\circ}C$), pH 7.0-8.0 (optimum pH 8.0), and with 0-2.0% NaCl (optimum, 0.5-1.0%). The major fatty acids were $C_{16:1}{\omega}7c$(36.3%), $C_{16:0}$(16.6%), $C_{12:0}$ 3-OH (12.5%), and $C_{18:1}{\omega}7c$(9.1%). The major respiratory quinone was Q-8, and the DNA G+C content of the genomic DNA was 51.9 mol%. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain GR5$^T$ belongs to the genus Rheinheimera, where its most closely related neighbors are Rheinheimera texasensis A62-14B$^T$ and Rheinheimera tangshanensis JA3-B52$^T$ with sequence similarities of 98.1% and 97.5%, respectively, and the sequence similarities to any other recognized species within Gammaproteobacteria are less than 96.5%. The mean level of DNA-DNA relatedness between strain GR5$^T$ and R. texasensis A62-14B$^T$, the strain most closely related to the isolate, was $26.5{\pm}7.6%$. Therefore, based on the phylogenetic and phenotypic data, strain GR5$^T$ should be classified as a novel species, for which the name Rheinheimera aquatica sp. nov. is proposed. The type strain is GR5$^T$ (=BCRC 80081$^T$=LMG 25379$^T$).

• Fisheries and Aquatic Sciences
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• v.17 no.1
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• pp.1-11
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• 2014

The Kenyan aquaculture sector is broadly categorized into freshwater aquaculture and mariculture. Whereas freshwater aquaculture has recorded significant progress over the last decade, the mariculture sector has yet to be fully exploited. The Kenyan aquaculture industry has seen slow growth for decades until recently, when the government-funded Economic Stimulus Program increased fish farming nationwide. Thus far, the program has facilitated the alleviation of poverty, spurred regional development, and led to increased commercial thinking among Kenyan fish farmers. Indeed, national aquaculture production grew from 1,000 MT/y in 2000 (equivalent to 1% of national fish production) to 12,000 MT/y, representing 7% of the national harvest, in 2010. The production is projected to hit 20,000 MT/y, representing 10% of total production and valued at USD 22.5 million over the next 5 years. The dominant aquaculture systems in Kenya include earthen and lined ponds, dams, and tanks distributed across the country. The most commonly farmed fish species are Nile tilapia Oreochromis niloticus, which accounts for about 75% of production, followed by African catfish Clarias gariepinus, which contributes about 21% of aquaculture production. Other species include common carp Cyprinus carpio, rainbow trout Oncorhynchus mykiss, koi carp Cyprinus carpio carpio, and goldfish Carassius auratus. Recently, Kenyan researchers have begun culturing native fish species such as Labeo victorianus and Labeo cylindricus at the National Aquaculture Research Development and Training Centre in Sagana. Apart from limited knowledge of modern aquaculture technology, the Kenyan aquaculture sector still suffers from an inadequate supply of certified quality seed fish and feed, incomprehensive aquaculture policy, and low funding for research. Glaring opportunities in the Kenyan aquaculture industry include the production of live fish food, e.g., Artemia, daphnia and rotifers, marine fish and shellfish larviculture; seaweed farming; cage culture; integrated fish farming; culture of indigenous fish species; and investment in the fish feed industry.

• Journal of Aquaculture
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• v.13 no.2
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• pp.147-152
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• 2000

To reduce the production cost of the rotifer, different combinations of Chlorella and Baker's yeast were used to mass culture of Brachionus calyciflorus. Rotifer density tended to decrease abruptly at 100% Chlorella-feeding, when unionized ammonia level ranged from 14.1 to 29.6 ppm and DO level from 0.2 to 0.3 ppm. Hence DO level > 0.3 ppm and unionized ammonia level < 14 ppm should be maintained. Production cost of the rotifer was the highest, when a combination of 100 % Chlorella was chosen as food source, but it was about 1.8 times less, when a combination of 70 % Chlorella and 30% yeast was used as food source. However, the highest rotifer density remained almost at the same level, when either of the combination was chosen as food source. A combination of 70 % Chlorella and 30 % yeast is recommended for maximum production of the rotifer at the lowest feed cost.

• ALGAE
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• v.28 no.1
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• pp.93-99
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• 2013

A freshwater cyanobacterium, Phormidium autumnale KNUA026, was isolated from puddles of icy water in Gyeongsan City, South Korea and its potential as a biofuel feedstock was investigated. Maximal growth was obtained when the culture was incubated at $25^{\circ}C$ and around pH 9.0. The total lipid content of the isolate was approximately 14.0% of dry weight and it was found that strain KNUA026 was able to autotrophically synthesize heptadecane ($C_{17}H_{36}$) which can be directly used as fuel without requiring a transesterification step. As this benthic cyanobacterium was capable of forming thick mats, it could be easily harvested by gravitational settling and this property may reduce the cost of production in commercial applications. Hence, P. autumnale KNUA026 appears to be a promising resource for use in the production of microalgae-based biofuels.

• Journal of Aquaculture
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• v.22 no.1
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• pp.122-125
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• 2009

Salinity tolerance on survival rate of 2, 4 and 6-week-old larvae and juvenile of black porgy Acanthopagrus schlegeli was investigated at 0, 7.5, 15, 22.5 and 30 psu for 21 days. In the 2 and 4-week-old larvae and juvenile (TL: 1.23 and 1.72 cm) were all died within 12 and 26 hours after to the 0 psu transfer, respectively. However, survival rate of other experimental group (7.5, 15, 22.5 and 30 psu) was significantly difference in the range between 27.3% and 95% (P<0.05). However survival rate of 6-weeks-old juvenile (TL: 2.83 cm) were over 99.0% during experimental periods and they appeared in good health. There was no significant difference in survival those reared to the salinities of all experimental groups (P>0.05). The present study suggests that the freshwater and saline groundwater of low salinity could be used to grow early juveniles of black porgy and it may be possible to culture in freshwater.

• Korean Journal of Environmental Biology
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• v.39 no.1
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• pp.32-38
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• 2021

Cyanobium is a genus of picoprokaryotic cyanophytes, which includes species worldwide. The present study investigated the morphology, ultrastructure, and molecular phylogeny of the unrecorded genus Cyanobium Rippka & Cohen-Bazire 1983 and species Cyanobium gracile Rippka & Cohen-Bazire 1983. A C. gracile culture from a freshwater sample collected from the Adongji pond was established by single-cell isolation. Morphological data were analyzed using light and transmission electron microscopy. C. gracile lives as solitary cells without gelatinous envelopes and is ovate, oval, or shortly rod-shaped. Thylakoids are laid along the cell walls, with three thylakoid membranes parallel to each other. Nucleoplasm was observed in the center of the cell. Molecular phylogeny performed with data from 16S small subunit ribosomal DNA gene (SSU rDNA) sequences showed that the three strains of C. gracile, including the type strain (PCC6307) and a newly recorded strain (Adong101619), formed a distinct clade with a high supporting value (maximum-likelihood=100, pp=1.00). Based on morphology and molecular data, we report the newly recorded C. gracile in Korea.