• Journal of Ecology and Environment
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• v.39 no.1
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• pp.99-110
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• 2016

The objective of this study was to analyze chemical water quality, ecological characteristics of fish compositions, and ecosystem health before- (B_wc; 2008-2009) and after-the weir construction (A_wc; 2011-2012) at Juksan Weir and Seungchon Weir of Yeongsan River watershed. Suspended solids (SS) and chlorophyll-a (Chl-a) in Juksan Weir increased, whereas nutrients such as total nitrogen (TN) and total phosphorus (TP) decreased in the epilimnetic water. In Juksan and Seungchon weirs, fish species distribution analysis in the periods of B_wc and A_wc showed that sensitive species were rare and tolerant species were dominant in the community. In the analysis of trophic guild, relative abundance of carnivore species are increased to 22% and 12%, respectively, after the constructions of Seungchon Weir and Juksan Weir. Mann-Whitney U-tests of nonparametric statistical analysis indicated that omnivore and carnivore species had significant differences (p < 0.05) between the B_wc and A_wc. The massive population growth of an exotic species, Micropterus salmoides, was evident in Seungchon Weir to influence on the structures of fish communities. The model values of mean Index of Biological Integrity (IBI), based on fish assemblages, were < 15, which indicates "poor" condition in the river health, and the significant difference of IBI values was not found between the B_wc and A_wc.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.56 no.4
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• pp.407-418
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• 2020

Mass mortality of mariculture fish due to high summer temperatures is a major issue in the mariculture industry in many coastal waters of Korea, yet measures to mitigate the impact are generally limited. We injected a micro-bubble of liquefied oxygen into the bottom of rockfish cages (about 6-8 m deep) in order to maximize the dispersal of micro-bubbled seawater and reduce fish mortality. The injection of low-temperature oxygen in micro-bubbles lowered the water temperature at the injection area by as much as 1℃ and increased dissolved oxygen concentration by 0.5 ppm. In early August, following a week with persistent high water temperature (above 28.5℃), there was an increase in fish mortality despite the micro-bubble system, which resulted in approximately 7% death of the total introduced fish population. However, this mortality appeared to be much lower than mortality reported in a neighboring mariculture facility (approximately 50% mortality). We also estimated the volume that can be recirculated with pumped seawater using a micro-bubble system. We suggest that this approach of injecting liquefied oxygen through a micro-bubble system may reduce fish mortality during high temperature periods.

• The Journal of Information Systems
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• v.32 no.4
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• pp.137-147
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• 2023

Purpose The domestic aquaculture industry in South Korea utilizes both formulated feeds and live feeds for the cultivation of fish. While nutrient-rich live feeds, particularly using fry, have been preferred since the past, formulated feeds are gaining attention due to issues related to overfishing and environmental concerns. Formulated feeds are advantageous for storage and supply but require a sustained feeding regimen due to the comparatively slower growth rate compared to live feeds. As the aging population in rural areas leads to a shortage of labor, automated feeding systems are increasingly being adopted in aquaculture facilities. To enhance the efficiency of such systems, it is crucial to quantitatively analyze the behavioral changes in fish based on the presence or absence of feed. Design/methodology/approach In the study, RGB cameras and infrared cameras were used to analyze fish activity according to feeding, and an outline extraction algorithm was applied to analyze the differences resulting from this. Findings Unlike RGB cameras, infrared cameras are more suitable for analyzing underwater fish activity as they convert objects' thermal energy into images. It was observed that Canny, Sobel, and Prewitt filters showed the most distinct identification of fish activity.

• Journal of Aquaculture
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• v.21 no.1
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• pp.47-53
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• 2008

The purpose of this study was to suggest that selecting method of rotifer with high activity of digestive enzymes for the enrichment effect of rotifer and the increasing of digestive enzymes of fish larvae. the populations assayed the activities of the digestive enzymes were randomly selected out of several population communities cultured with freshwater condensed Chlorella. The relationship with the population density and the growth rate of selected populations was shown to RD=5865 SGR-350.08(P<0.001). The relationships with fecundity of the growth rate and the population density were shown to F=-36.147 SGR+61.652(P<0.05) and F=-0.0085 RD+66.38(P<0.001), respectively. The relationships of the growth rate and the individual activities of digestive enzymes in rotifer were assayed to Amyl=-1.6482 SGR+3.2498(P<0.05), TAP=-0.8115 SGR+1.1361(P<0.001) and TGL+0.0055 SGR+0.0079(P=0.239), respectively. But in TG-lipase was not related significantly with the growth rate. Also the relationships of the fecundity and the individual activities of digestive enzymes in rotifer were shown to Amyl=0.0296 F+1.0981(P<0.001), TAP=0.0252 F+0.0975(P<0.001) and TGL=-6E-06 F+0.0113(P=0.915), respectively. But in TG-lipase was not related significantly with the fecundity. And the relationships with the specific activity of TG-lipase of the fecundity, the growth rate and the population density were TGL=-0.024 F+0.2332(P=0.132), TGL=0.1267 SGR+0.005(P<0.01) and TGL=0.0002 F-0.0594(P<0.001), respectively. In this case, specific activity of TG-lipase was shown the significant relationship with the population density and the growth rate, but it was not related significantly with fecundity. Therefore, Because a population shown the high activity of digestive enzymes for increasing a lipid enrichment effect of a rotifers and receiving the many exogenous digestive enzymes to fish larvae was the population of high fecundity than the population of high rotifer density, to select the population of a high fecundity was suggested to benefit than a high growth rate for fish larvae.

• Fisheries and Aquatic Sciences
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• v.11 no.2
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• pp.82-87
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• 2008

Marine fisheries are important natural resources and must be maintained, especially fish species that are important sources of food. Despite the increase in stocking programs to maintain fisheries with artificially raised fish, the genetic impact stocking has on the wild fry population has not been addressed. Genetic variation in rock bream, Oplegnathus fasciatus, within and between wild-caught parents and the $F_1$ generation produced by them in 1 day was assayed using nine highly variable micro satellite markers. The nine micro satellite loci used in this study displayed diverse polymorphisms, and in total, 98 different alleles were observed over all loci. Differences in genetic variability of the $F_1$ offspring compared to their wild-caught parents (brood stock) were observed in terms of allele frequency, gene diversity, and heterozygosity. Although the $F_1$ generation of rock bream was missing 16% of the micro satellite alleles, no significant reduction was found in mean heterozygosity of the $F_1$ population compared to the brood stock. Eight of nine loci showed significant Hardy-Weinberg equilibrium (HWE) deviations in the $F_1$ population, while the brood stock deviated from HWE at three micro satellite loci (KOF85, KOF360 and KOF374). These deviations showed mostly a deficit of heterozygotes. Our results provide evidence for genetic differences in the $F_1$ hatchery offspring compared to their wild-caught parents and reinforce the need for a series of consecutive egg collections to avoid the loss of genetic variability. This also further underscores the importance of monitoring genetic variability of hatchery populations for the conservation of natural rock bream resources.

• Korean Journal of Environmental Biology
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• v.30 no.4
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• pp.319-327
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• 2012

This paper was the result of investigation on fish fauna of natural estuary at Seomjin River, Korea. The total number of fish species collected in this study was 68 species belonging to 26 families. Dominant species in number was Acheilognathus majusculus (relative abundance: 37.4%), subdominant was Tribolodon hakonensis (10.5%). There were seven migrating fishes including Anguilla japonica and T. hakonensis. There were twenty Korean endemic species including Acheilognathus koreensis and Acheilognathus somjinensis. Thirty five species belonging to eight families were collected in upper part of river that dominant species was A. majusculus (38.2%). Thirty seven species were collected in lower part of river that dominant species was A. majusculus (48.5%). Thirty four species were collected in near estuary that dominant species was T. hakonensis (42.6%). In the comparison result of condition factor for several main species populations of Seomjin River were better than Nagdong River populations having estuary barrage. It was considered that almost fish populations of mid-to lower Seomjin River without estuary bank have stable life with natural environment.

• Korean Journal of Ichthyology
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• v.33 no.2
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• pp.84-94
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• 2021

This study was conducted to elucidate the impact of invasive species, Micropterus salmoides and Lepomis macrochirus in Geumgyeji, Samgaji and Naejangji reservoirs of National Parks, Korea in 2020. In the Geumgyeji, 1,221 individuals of 11 species in 7 families were collected including M. salmoides (relative abundance, 96.3%) and L. macrochirus (0.3%), M. salmoides fed mainly on Rhinogobius brunneus (IRI, 37.2%), Odonata (25.6%), Megaloptera (11.6%), and M. salmoides (7.0%). In the results of Samgaji showed that 854 individuals of 10 species in 5 families were collected including M. salmoides (60.8%), and M. salmoides fed mainly on Decapoda (shrimp, 33.6%), Odonata (34.4%), R. brunneus (21.2%), and Zacco platypus (6.1%). In the Naejangji showed that 1,075 individuals of 13 species belonging to 7 families were collected including L. macrochirus (38.1%) and M. salmoides (9.5%), and L. macrochirus fed mainly on Branchiopoda (77.5%), Diptera (9.8%), Decapoda (4.0%) and M. salmoides fed mainly on R. brunneus (73.3%), Decapoda (21.2%). M. salmoides of Geumgyeji and Samgaji were apparently introduced more than a 10 years ago. The fish population declined rapidly since the introduction of M. salmoides. L. macrochirus of Naejangji was introduced more than 20 years ago, which increased its relative abundance to 40%. M. salmoides was introduced five to six years ago, and the fish species and population declined rapidly since the introduction of M. salmoides. Finally, we discussed the inhabitat status and management of M. salmoides and L. macrochirus in the National Park.

• Korean Journal of Environment and Ecology
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• v.37 no.3
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• pp.198-208
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• 2023

This study collected samples of Korean dark sleepers (Odontobutis interrupta) in the Keumdang Stream from March to November 2021 to investigate their feeding habits. The sizes were classified by age (1 year and 2 years old, and 3 years or older). The food organisms of O. interrupta included Isopoda, Amphipoda, and Decapoda of the Malacostraca, Ephemeroptera, Odonata, Hemiptera, Plecoptera, Coleoptera, Diptera, and Trichoptera belonging to the aquatic insect of Arthropoda (accounting for 86.6% of the population), Tubificida, Haplotaxida, and Rhynchobdellida belonging to the Clitellata of Annelida (accounting for 7.3%), Systellommatophora and Mesogastropoda belonging to the Gastropodo of Mollusca (accounting for 2.8%), fish (accounting for 3.3%), and fish eggs. Korean dark sleepers fed mostly on aquatic insects, fish, crustaceans, and annelids. Aquatic insects were the most important food source, with 70.1% of the population, 31.7% in biomass, and 72.6% in the index of relative importance. Korean dark sleepers were carnivorous in diet and belonged to the stalker in food intake characteristics and forms. A food migration was observed since less Diptera was found, and more fish, Decapoda, Trichoptera, and Odonata were found in the biomass of the feed consumed by larger species. Diptera (65.3%), Haplotaxida (14.5%), Ephemeroptera (7.0%), Diptera (58.6%), Ephemeroptera (24.5%), fish (4.8%) Diptera (30.1%), Ephemeroptera (20.4%), Isopoda (13.3%) were mainly fed in the autumn.

• Korean Journal of Environment and Ecology
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• v.31 no.5
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• pp.461-471
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• 2017

Population genetic studies of 10 groups of Iksookimia pacifica were conducted to investigate the genetic diversity and population genetic structure across its known range in South Korea. Population DNA sequences of one mitochondrial gene (mtCOI) and three nuclear genes (IRBP, EGR2B, RAG1) were examined in samples collected from ten streams that flow into the East Sea. Both mitochondrial and nuclear sequences exhibited significant differentiation among populations except a few cases. The Bayesian analysis of the multi-locus genotypes inferred from the DNA sequences of nuclear genes clustered the individual fish largely into two geographical groups: a northern group (from Baebong stream to Cheonjin stream) and a southern group (Yangyangnamdae stream to Gangneungnamdae stream). Given that the streams flowing into the East Sea are geographically isolated water systems, such separation of genotypes can be interpreted by the geographical separation of common ancestors into north and south that had colonized South Korea. Since the initial geographical separation of the ancestral population by north and south, the ancestral groups seem to have experienced further differentiation into the current genetic clusters through the physical isolation of streams by the East Sea in each region. It is notable that many individuals in the Jasan stream formed a genetic cluster with those of Yangyangnamdae and Gangneungnamdae streams which are distant from each other. In addition, mitochondrial gene showed low genetic differentiation between some neighboring populations and very low level of genetic diversity in several populations. The present population genetic study will provide valuable information for the conservation and management of the Korean endemic fish species, I. paicifica.

• Korean Journal of Ichthyology
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• v.21 no.2
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• pp.76-80
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• 2009

Genetic diversity and genetic structure within the Geum River and Mankyung River populations of the Korean endangered Black shinner (Pseudopungtungia nigra) were assessed by amplified fragment length polymorphism (AFLP). AFLP analysis using five primer combinations generated 447 AFLP bands with 64.1% polymorphism (Geum River 74.6% and Mankyung River 53.6%). The heterozygosities within the two populations were calculated to be 0.170 and 0.104, respectively. Their average genetic diversities are 0.240 and 0.147, respectively. The pairwise Fst value (0.150) indicated distinct genetic differentiation between the two populations. A UPGMA dendrogram based on genetic distance among the individuals revealed a division corresponding to geographical regions, with low genetic variation within the Mankyung River population, and low genetic distance (0.026) between the two populations. Consequently, the two populations may have the same genetic origin The Geum River population will be more suitable than the Mankyung River population for conservation plans to increase the population sizes. Genetic and habitat management will be necessary for the Mankyung River population.