• 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.

• Animal Systematics, Evolution and Diversity
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• v.7 no.2
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• pp.189-194
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• 1991

A new speices of cyprinid fish, Acheilognathus somjinensis is described based on the specimens collected in the Somjin River, Sinpyong-myon, Imsil -gun , Chollabuk-do province of Korea. In general morphology it is similar to A. koreensis. however, the new speices differs from the latter in having longer ovipositor of female in spawing season and showing pear-shaped eggs. In hybridization experiments, it was found that A.somjinensis is repoductively isolated from A.koreensis.

• Korean Journal of Environment and Ecology
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• v.34 no.3
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• pp.216-223
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• 2020

This study investigated the ecological characteristics of Coreoperca herzi at Jaho stream from September 2018 to August 2019. This species inhabited riffle and midstream of the stream, where the riverbed structure was mostly covered with cobble and pebble. The depth of the habitat was 32-157 cm, and the velocity of stream fast at 0.64±0.28 (0.32-1.28) m/sec. The gender ratio of females to males was 1:0.95. The age according to the frequency analysis of total length indicated that the group with 42-80 mm in total length was one year old, the group with 80-130 mm was two years old, the group with130-200 mm was three years old, and the group over 200 mm was four years old. The total length of sexually mature fishes was 65 mm for females and 70 mm for males. The sexually mature individuals grown in nature had a smaller total length than those reared in a laboratory. The spawning season was from May to late July, and the water temperature was 18.4-26.4℃ during the period. The prosperous spawning season was from May to June, and the water temperature was 18.4-21.8℃ during the period. The average number of eggs in the ovaries was 462 (151-919) per mature female, and the matured eggs were yellowish and spherical with a mean diameter of 2.31±0.33 (1.93-3.10) mm. Calculation length-weight relation of Korean aucha perch showed the constant a as 0.00002 and b as 3.01, condition factor (K) as 1.76 (1.01-2.63) on average, and the slope was a positive value of 0.0005.

• Korean Journal of Environment and Ecology
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• v.33 no.3
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• pp.256-265
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• 2019

We investigated the ecological characteristics of Phoxinus phoxinus in the spring water in Eocheon stream from January to December 2016. The water temperature was $9.7{\sim}14.3^{\circ}C$ and remained below $15^{\circ}C$ throughout the year. The fishes cohabiting with minnow were Rhynchocypris kumgangensis (70.14%), Cottus koreanus (13.63%), Rhynchocypris oxycephalus (3.16%), Oncorhynchus mykiss (0.97%), Zacco koreanus (0.49%), and Iksookimia koreensis (0.24%). The sex ratio of female to male was 1:0.86. The frequency analysis of total length indicated that the fishes with the total length of 30 - 50 mm were one year old, those of 50 - 65 mm were two years old, those of 65 - 75 mm were three years old, and those of 75 mm or more were four years old. The sexually mature fishes were 50 mm or longer for female and 60 mm or longer for male. The spawning season was from April to July, and the water temperature was $12.3-14.3^{\circ}C$ during the period. The prosperous spawning season was from June to July, and the water temperature was $13.8-4.3^{\circ}C$ during the period. The average number of eggs in the ovaries was 508 per matured female, and the matured eggs were yellowish and spherical with a mean diameter of $1.58{\pm}0.13mm$. The length-weight correlation of P. phoxinus was $BW=0.000007TL^{3.09}$ with the constant a as 0.000007 and the parameter b as 3.09. The condition factor (K) was 0.99 (0.76 - 1.32) in average.

• 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.

• 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 Fisheries and Aquatic Sciences
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• v.37 no.2
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• pp.105-115
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• 2004

Growth pattern of the soft clam (Mya arenaria oonogei) was estimated based on samples collected from the Yeongsan River estuary on the southwest coast of Korea between August 1996 and September 1997. Mean density of the clam during study period was $55\;ind./m^2$ and varied monthly from 281 to $8\;ind./m^2.$ The clams from the study area ranged in age from one year to seven years, with shell lengths between 40.4 mm and 104.1 mm and biomass between 8.4 and 152.3 g in total wet weight. The spawing season was estimated to occur between September and October based upon a reduced fatness index, an indication of spawning, during these months. Burial depths increased with growth of the clams and most were found buried between 10 and 20 cm in the sediments. Significant relationships were found between shell length and shell height (SH), total wet weight, (TWt), meat wet weight (MWt), meat dry weight (DWt), ash free dry weight (AFDW) and burial depth. The von Bertalanffy growth equations of the clams were $L_t(mm)=138.98(1-e^{-0.1325(t+0.8853)})\;and\;W_t\;(gTWt)=325.93\;(1-e^{0.1325(t+0.8853)})^{2.6982}.$ These equations suggest that in their first year the clams should reach 31 mm in length with a biomass of 5.7 g in total wet weight.

• Korean Journal of Environment and Ecology
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• v.33 no.6
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• pp.677-685
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• 2019

We investigated the ecological characteristics of kumgang fat minnow (Rhynchocypris kumgangensis) in the Eocheon stream from October 2017 to September 2018. The water temperature was 10.2- 14.3℃ and remained below 15℃ during the year. The fishes in cohabitation with kumgang fat minnow were Cottus koreanus (16.62%), Phoxinus phoxinus (10.74%), Rhynchocypris oxycephalus (1.55%), Oncorhynchus mykiss (0.56%), Zacco koreanus (0.28%), and Iksookimia koreensis (0.14%%). The ratio of females to males was 1:0.91 and did not vary widely. The frequency analysis of total length indicated that the fishes with less than 40 mm in total length were one year old, those with 40 - 69 mm were two years old, those with 70 - 84 mm were three years old, and those with 85 mm or more were four years old for individuals collected in May through June. The sexually mature fishes were over two years old. The spawning season was from late May to late August, and the water temperature was 12.5~14.5℃ during the period. The prosperous spawning season was from June to July, and the water temperature was 13.6 - 14.5℃ during the spawning period. The average number of eggs in the ovaries was 1,006 (664 - 1,666) per matured female, and the matured eggs were yellowish and spherical with a mean diameter of 1.34±0.17 mm. The length-weight correlation of R. kumgangensis was BW = 0.00003TL^2.77 with the constant a as 0.00003, b as 2.77, the average condition factor (K) as 1.04(0.65~1.48), and the slope as -0.0012. The kumgang fat minnows inhabiting in the spring water had a longer spawning period, a fewer number of eggs in ovaries, and the lower condition factor (K) than those inhabiting other areas.

• Korean Journal of Environment and Ecology
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• v.37 no.1
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• pp.86-93
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• 2023

This study investigated the ecological characteristics of Odontobutis interrupta at the Geumdang Stream from January to December 2021. The riverbed structure of the species habitat was rich in sand and mud. The water was deep, ranging from 21 to 124 cm, with an average of 48 cm. The stream velocity was slow at 0.24 (0.08-0.36) m/sec. The ratio of females to males was 1:0.98, and the total length of collected individuals ranged from 23 mm to 162 mm. The age according to the total length-frequency distribution as of May indicated that the group with a total length of 23-59 mm was one year old, the group with 60-99 mm was two years old, the group with 100-139 mm was three years old, and the group with 140-162 mm was four years old. As a secondary gender characteristic, the females genital papilla had a cylindrical shape, a hollow inside of the tip, and a longer diameter than males. The males had a cone shape with a pointed end. Sexually mature males had the nuptial color, with a black abdomen and whole body. Some females with a length ranging from 60 to 69 mm and all females 70 mm longer were sexually mature. Some males with a length ranging from 70 to 79 mm and all males 80 mm longer were sexually mature. The spawning season was from May to July, and the water temperature was between 19.6℃ to 29℃ during that period. The prosperous spawning season was June (26℃). The average number of eggs in the ovaries was 2,473 (883-4,955) per matured female, and the matured eggs were yellowish and spherical with a mean diameter of 1.42 (1.20-0.54) mm. The correlation between total length and weight was BW=0.0000006TL^3.21 with the constant a as 0.0000006 and parameter b as 3.21. The condition factor (K) was 1.67 (1.18-2.43) on average, and the slope was 0.116.

• Journal of Aquaculture
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• v.4 no.2
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• pp.85-95
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• 1991

Spawning inducement of flounder, Paralichthys olivaceus, was attemped by the control of water temperature and photoperiod from June 1, 1989 through January 5, 1990 (189 days) Water temperature was gradually decreased from $21.7^{\circ}C$ to $10.6^{\circ}C$ which was the minim biological temperature for spawning of flounder. Water temperature was increased asain to $15^{\circ}C$ gradually, and then maintained at this level through the end of spawning. Photoperiod was also changed gradually from 10L/14D in June 1, 1989 to 14L/10D in July 25, 1989. Spawning of the fish occurred from October 4, 1989 through January 5, 1990 (93 days). The average number of eggs spawned during the spawning season per female were 2.67 billion. The first spawning occurred on the 60th day after the time of minimun water temperature $10.6^{\circ}C$. The water temperature and photoperiod at the first spawning were $13^{\circ}C$ and 14L/10D respectively It took 71 days to spawn since the photoperiod had changed from 10L/14D to 14L/10D. Spawning period can be devided into three terms. The first term was continued for 30 days from the beginning of the spawning. The second term for 41 days was the major spawning period followed by the third term, the final period of the spawning, for 22 days. The percentage of average fertilization rate of the eggs in the first, second and third spawning terms were $37.4{\%},\;54.1\%\;and\;19.6\%$, respectively. Feeding rate was increased in the maturing period but, decreased in the spawing period. During the final spawning period, the abrubt decreasing of the feeding occurred again.