• Korean Journal of Ecology and Environment
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• v.43 no.2
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• pp.212-220
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• 2010

Effects of sediment and toxic cyanobacterium Microcystis aeruginosa on feeding behaviors of an omnivorous fish, gold fish (Carassius auratus) were examined in laboratory and in situ mesocosm. Laboratory feeding experiments were performed in small aquaria (7 L) with cyanobacterial blooms (mainly M. aeruginosa) under the condition of sediments and no-sediments, and toxic (NIES-298) and non-toxic M. aeruginosa (NIES-101). In situ feeding experiments were conducted at the shore of eutrophic lake (Lake Ilgam, Seoul) in the mid-July, 2005. Results showed that fish introduction decreased the concentration of Chlorophyll-a (Chl-a) at higher rate in no sediment-containing aquaria. In contrast, there was a drastic increase of Chl-a in the sedimentcontaining aquaria. Fish effectively removed the M. aeruginosa cells without algal toxin (microcystin). Fish also selectively removed the large size Chl-a (>$50{\mu}m$), although all kinds of nutrients were increased after fish introduction, especially ammonia. Our results indicate that the strategic introduction of domestic omnivores Carassius auratus, to control cyanobacterial bloom in eutrophic lake will negatively play in the water quality improvement via a sediment disturbance and a density-dependent digestion.

• Korean Journal of Environment and Ecology
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• v.30 no.5
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• pp.888-895
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• 2016

The population ecology (Ecological characteristics) of Squalidus chankaensis tsuchigae were investigated at Geum River from March to November, 2013. This species inhabited midstream of the river where was mostly covered with cobble and sand. The depth of the habitat was 30~60 cm and velocity of stream was 2.27~4.88 cm/sec. The sex ratio of female to male was 1 : 0.86. They were sexually mature when they were over two years of age. The spawning period was from June to July with water temperatures from $25^{\circ}C$ to $25^{\circ}C$. Sexually matured individuals appeared over the two year of age. Frequency analysis of total length indicated that the group with 55~70 mm in total length was one year old, the 71~90 mm was two years old, and the group over 91 mm was three years old. The average number of eggs in the ovaries was estimated as 2,219 per matured female. The number of matured eggs size in ovaries was 0.64~0.98 (mean: 0.85) mm. Calulation length-weight relation of S. chankaensis tsuchigae show the value of contant a as 0.0002 and b as 2.81, and condition factor (K) was 1.06 on average. The stomach contents were Cyanophyta, Chlorophyta, Bacillariophyta, Crustaceae, Copepoda, Nematota, Actithocephala, and Ephemeroptera, Hemiptera, Diptera, and Trichoptera that belong to Aquatic insect, and dormant bud of Pectinatella that belongs to Phylactolaemata. The diet of S. chankaensis tsuchigae was omnivorous, mainly vegetable feed on attached algae (filament form), and mainly animality feeded on benthic invertebrates such as Chironomidae larvae.

• Korean Journal of Environment and Ecology
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• v.34 no.6
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• pp.551-557
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• 2020

This study surveyed the ecological characteristics of Ladislabia taczanowskii at Songcheon Stream from March to November 2019. The species inhabited upstream, where the riverbed structure was mostly covered with boulders and cobbles. The water depth was 31-148 cm, and the stream velocity was fast at 0.94±0.23 (0.51-1.39) m/sec. The gender ratio of females to males was 1 : 0.89. The age according to the total length frequency distribution indicated that the group with 38-70 mm below in total length was one year old, the group with 70-100 mm was two years old, the group with 100-120 mm was three years old, and the group over 120-128 mm was over four years old. The total length of sexually mature fishes was 70 mm for females and 75 mm or more for males. The spawning season was from May to August, and the water temperature was 15.5-20.1℃ during the period. The prosperous spawning season was from June to July, and the water temperature was 15.8-17.2℃ during the period. The spawning ground was where the riffle began in the pool, and its bottom was formed of sand and gravel. The width was about 150 cm, and the water depth was 20 to 50 cm. The average number of eggs in the ovaries was 821 (401-1,314) per matured female, and the matured eggs were yellowish and spherical with a mean diameter of 1.62±0.02 (1.43-2.01) mm. The live foods of L. taczanowskii Cyanophyta, Chlorophyta, Bacillariophyta, Ephemeroptera, and Diptera. The feeding habit of L. taczanowskii is omnivorous, but more than 90% of the stomach content was attached algae.

• Korean Journal of Environment and Ecology
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• v.35 no.3
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• pp.277-284
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• 2021

This study surveyed the ecological characteristics of Squalidus gracilis majimae at Nakdong River tributary Sinan Stream from January to December 2020. The species inhabited the riverbed that was mostly covered with gravel and sand. The water depth was 27-158 cm, and the average was rather deep at 54 cm. The stream velocity was slow at 0.41±0.19 (0.24-0.86) m/sec. The gender ratio of females to males was 1:0.73. According to the total length-frequency distribution, the age indicated that the group with less than 50 mm in total length was one year old, the group with 70-69 mm was two years old, and the group over 70 mm was three years old. The total length of sexually mature fishes was 50 mm for females and 60 mm for males. The spawning season was from June to July, and the water temperature was 20.9-23.4℃ during the period. The prosperous spawning season was July. The average number of eggs in the ovaries was 1,009 (595-1,630) per matured female, and the matured eggs were yellowish and spherical with a mean diameter of 0.78±0.08 (0.57-0.83) mm. The live foods were S. gracilis majimae Protozoa, attached algae, zooplankton, and aquatic insects. The feeding habits of S. gracilis majimae are omnivorous, but more than 80% of the stomach content was aquatic insects, Chironomidae spp. The larger the size of this species, the greater the amount and frequency of eating aquatic insects, which are animal feeds. The population that ate aquatic insects did not eat vegetable food.

• Journal of Marine Life Science
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• v.6 no.2
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• pp.106-116
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• 2021

To secure basic data by monitoring the growth of salmon (Oncorhynchus keta) released to the Taehwa River. After discharge, the characteristics of the young salmon distribution and migration rate habitat were investigated for two years. A total of 4 points [Sunbawi bridge (St.1), Guyeong bridge (St.2), Samho bridge (St.3), and Myeongchon bridge (St.4)] were investigated. The survey of 2017 indicating an increase of 10 mm in average length and 0.8 g in average weight, and the survey of 2018 indicating an increase of 10 mm in average length and 0.5 g in average weight. Among 39 species, 10 insectivorous and 12 omnivorous, are believed to compete with young salmon for food. 6, 5, 6 and 8 predatory fish species has emerged at each site, respectively. According to this study, it is believed that St.1 and St.2 points are more proper as discharge location of young salmon because these two points have less varied in depth, flow rate, salt concentration etc. In addition, it is thought that the night or dawn time in early January is the best discharge time of young salmon fish because predatory fish such as Korean piscivorous chub and bass etc. does not eat food actively at that time.

• Korean Journal of Environment and Ecology
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• v.35 no.6
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• pp.601-608
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• 2021

This study surveyed the ecological characteristics of Squalidus multimacultus at Taehwa River tributary Cheokgwa Stream from January to December 2020. The species inhabited the riverbed that was mostly covered with sand. The water depth was 25-164 cm, and the average was rather deep at 68 cm. The stream velocity was slow at 0.21±0.26 (0.16-0.43) m/sec. The gender ratio of females to males was 1:0.99. The age according to the total length-frequency distribution indicated that the group with less than 50 mm (29.4 - 49 mm) in total length was one year old, the group with 50 - 69 mm was two years old, the group with 70 - 89 mm was three years old, and the group over 90 mm was four years old. The total length of sexually mature fishes was 40 mm for both males and females. The spawning season was from July to August, and the water temperatures was 23.8 - 25.4℃ during the period. The prosperous spawning season was August. The average number of eggs in the ovaries was 1,395 (648 - 2,201) per matured female, and the matured eggs were yellowish and spherical with a mean diameter of 0.67±0.24 (0.62 - 0.83) mm. The live foods were of S. multimacultus attached algae, zooplankton, aquatic insects, and Mollusca. The feeding habits of S. multimacultus were omnivorous, but more than 95% of the stomach content was plant-attached algae. The larger the size of this species, the greater the amount and frequency of eating aquatic insects, which were animal feeds. The population that ate aquatic insects did not eat vegetable food.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.652-663
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• 2019

The purpose of this study was to conduct ecological health assessments by using the fish communities in the Manchurian trout habitat. Sampling was conducted twice in July and September 2018. In the survey, 1,119 individuals belonging to 16 species and seven families were collected. The dominant species by number was Rhynchocypris kumgangensis and the subdominant species was Zacco koreanus. Korean endemic species represented 73.33% at Geybang Stream and 76.92% at Naerin Stream. Community analysis revealed that the structure of the fish community was unstable by the dominance index 0.63 (±0.09)-0.97 (±0.01), the diversity index 1.63 (±0.23)-0.33 (±0.09), the evenness index 0.79 (±0.06)-0.24 (±0.07) and the richness index 0.67 (±0.14)-1.80(±0.16). According to the analysis of the tolerance guilds, the total individual number of sensitive species was higher than the intermediate and tolerant species. The insectivore species accounted for 65.09-98.56% of the total trophic guilds, which was the highest observed. The value of the QHEI (Qualitative habitat evaluation index) in the Brachymystax lenok tsinlingensis habitat was 119.5 (±0.5)-153.5 (±0.5), indicating an optimal-suboptimal condition. The FAI (Fish assessment index) stream health value was A to B in the study sites. Correlation analysis with FAI and various factors was conducted and a high correlation in QHEI, Brachymystax lenok tsinlingensis individuals, species, individuals, diversity, richness, sensitive species, carnivorous species, insectivorous species, and omnivorous species was found. The similarity analysis was divided into three groups from A to C, based on 56.9%.

• Korean Journal of Environment and Ecology
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• v.33 no.2
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• pp.187-201
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• 2019

This study examined the physicochemical water quality and evaluated the ecological health in 14 sites of Geum River (upstream, mid-stream, and downstream) using the fish community distribution and guilds and eight multi-variable matrices of FAI (Fish Assessment Index) during June 2008-May 2009. The analysis of the water quality variables showed no significant variation in the upstream and mid-stream but a sharp variation due to the accumulation of organic matter from the point where the treated water of Gap and Miho streams flew. The analysis of physicochemical water properties showed that BOD, COD, TN, TP, Cond, and Chl-a tended to increase while DO decreased to cause eutrophication and algae development from the downstream where Miho and Gap stream merged. The analysis of fish community showed that the species richness index and species diversity index increased in the mid-stream area but decreased in the downstream area, indicating the stable ecosystem in the upper stream and the relatively unstable ecosystem in the downstream. The analysis of the species distribution showed that the dominant species were Zacco platypus that accounted for 20.9% of all fish species and Zacco koreanus that accounted for 13.1%. The analysis of the fish tolerance and feeding guild characteristics showed that the sensitive species, the insectivore species, and the aquatic species were dominant in the mid-stream point. On the other hand, contaminants from the sewage water treatment plant of Miho stream had a profound effect in the downstream to show the dominance of tolerant species, omnivorous species, and lentic species. Therefore, it is necessary to improve water quality by reducing the load of urban pollutants and to pay attention to the conservation and restoration of aquatic ecosystems.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.1
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• pp.128-138
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• 2019

Effects of feeding type and food resource availability on community structure of mollusks inhabiting hard-bottom subtidal areas were investigated. By following guidance from several references, mollusks observed in this study were divided into 5 groups according to feeding type - 1) grazing, 2) filter feeding, 3) deposit feeding, 4) omnivorous and 5) predation. The results showed that both grazing and filter feeders were the most numerous, explaining grazing type in the East Sea accounting for 47.9%, 32.6% in the South Sea and 29.6% for filter feeding, and filter feeding as a dominant feeding type in Yellow Sea accounting for 42.3%. Results of this study showed distinctive difference in community structure depending on mechanism of feeding type and geographical areas where sampling took place. With the results, attempts were made to understand whether community structure could be affected by feeding type or feeding availability and found out that community structure depended heavily on food resource availability. In the East Sea where marine algal density was high, the algal community in the forms of thick-leathery and sheet often occurred in water column with high transparency which provides proper environment for growth. In the South Sea where grazing and filter feeding types were predominated similarly, the algal density was high, but had the relative highest phytoplankton density. Whereas in the Yellow Sea showing the lowest algal biomass compared to the one in the East and the South Sea, and phytoplankton density was similar to those. It might be a adequate environment for filter feeders than grazers. This study concluded that community structure of mollusks showing high abundance was present where food resource availability with types and quantity was high.