• Korean Journal of Ecology and Environment
• /
• v.37 no.1 s.106
• /
• pp.130-136
• /
• 2004

In the present study, prey preference of juvenile fishes was examined using an experimental approach. Zooplankton composition, as a prey of the fish, was evaluated by taking into account the species as well as body size of juveniles in the aquarium. The predation of juvenile fishes is known to be an important factor in changes of zooplankton communities. In some previous studies at the regulated Nakdong River, the collapse of large cladcoerans and an increase in the rotifer population by selective predation during spring and summer were observed. This study focused on the predation of juvenile fishes such as Hyporhamphus sajori, Rhinogobius brunneus, and Opsariichtys uncirostris amurensis on zooplankton community structure in mesocosm scale experiments. These fishes selected the cladoceran Moina micrura with highest individual preference value (Manly/Chesson index)among zooplankton prey in the experimental aquarium. When the size-selective prey preferences of the juvenile fish were compared, both small (body size <2 cm) and large (body size >2cm) juveniles of O. uncirostris positively selected M. micrura. In the outdoor experimental tanks, juvenile fishes consumed the cladoceran M. micrura, resulting in an high abundance of the rotifer, Polyarthra spp. The results suggest that juvenile fish predation may play an important role in regulating the zooplankton community structure by reducing the cladoceran density and increase of rotifers in the Nakdong River during spring and summer.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.32 no.4
• /
• pp.466-469
• /
• 1999

Cladocera are important food organism for seed production of finfishes. freshwater cladocera such as Daphnia and Moina are well known food organisms for the larval rearing of freshwater fishes and are easy for mass culture. However, mass culture technique for marine cladocera are not yet developed, The only mass produced food organisms available these days for the larval production of marine finfishes are rotifer and Artemia. An estuarine cladoceran, Diaphanosoma celebensis, has a high possibility of being used as a food organism for the larval rearing of marine finfishes because this species is much easier to mass culture than marine ones. Therefore many studies are needed for this species. In this study, the effects of the volumes of culture container, 40, 1,500 and 15,000 ml, on the stable production of this species were tested and results are as follow: The maximum densities of this species in each of the culture volumes were reached after 14 days in 40 ml, 12 days in 1,500 ml, and 21 days in 15,000 ml with values of 3.4 $\pm$ 0.4, 14.2 $\pm$ 2.1 and 2.5 $\pm$ 1.6 per ml, respectively. The relative population growth index (RPGI) was stable in the culture volume of 1,500 ml. Moreover, possible harvesting number(individual/ml/day) was much higher in the 1,500 ml container than the other culture volumes. Therefore, optimum culture volume among the tested volumes for mass production of this species was 1,500 ml.

• Animal cells and systems
• /
• v.1 no.3
• /
• pp.435-445
• /
• 1997

Specimens of Bosmina longirostris collected from various freshwater habitats of 84 localities in South Korea from October 1981 to August 1997 were examined, and seasonal changes of the cladoceran populations in Late Kwangjuho from October 1995 to August 1977 were analysed. In this paper, B. longirostris in Korea was redescribed and figured, with a discussion of morphological characteristics. Some ecological features of the species were noted.

• Animal Systematics, Evolution and Diversity
• /
• v.11 no.2
• /
• pp.265-274
• /
• 1995

A freshwater chydorid cladoceran, Alona quadrangularis (O.F. $M\ddot{u}ller$, 1785), collected from a streatmlet on Paektam Valley in Mt. Sorak is described.

• Fisheries and Aquatic Sciences
• /
• v.3 no.2
• /
• pp.126-134
• /
• 2000

We investigated the distribution of the marine cladoceran resting eggs in the intertidal sediments of Gomso Bay, Korea and compared the data with those in the subtidal sediments. The abundance of the eggs in the top 6cm of the sediments was higher than that in the other depths. The abundances of the eggs in seaward intertidal sediments below mean sea level (MSL) were higher than those in the sediments over MSL, but were not significantly different from those in the subtidal sediments. The distribution of the resting eggs of cladocerans in the intertidal sediments was affected by the grain-size and moisture content of sediments. The results of the present study suggest that the intertidal sediments as well as the subtidal sediments are a potential egg bank which plays important roles in population dynamics of zooplankton in coastal waters, in particular, recruitment of eggs into plankton.

• Korean Journal of Ecology and Environment
• /
• v.34 no.4 s.96
• /
• pp.310-318
• /
• 2001

In the large regulated Nakdong River, the Predation effect of juvenile fish on the zooplankton community was evaluated by gut and stomach analyses of fish in 1999. Juvenile fish of five species showed high density from May to early June when river discharge was low and water body became stagnant. During this period, large rotifers, Asplanchna spp. and Brachionus spp. declined and the decrease of cladoceran (Moina micrura and Bosminopsis deitersi) density was also obeserved. At this time, small rotifers including Polyarthra spp. reached maximum density. Gut analysis of fish demonstrated that small-sized juvenile fish (< 15 mm in total length)preferred large rotifers as well as cladocerans, while large sized fish (> 15 mm)selected only cladocerans. On the other hand, juvenile Micropterus salmoides of which size was larger than other juvenile fish consumed not only zooplankton but also other small juvenile fish. Based on these results, the decline of large rotifers and cladocerans during early summer in the river seems to be result of predation by juvenile fish. However, the period when juvenile fish maintained their high density was as short as one month and the decreased density of cladocera rapidly recovered as soon as juvenile fish became scarce. Such a short period of juvenile fish devel-opment in the river can be attributed to the consumption of juvenile fish by the young-of-the-year cohorts as well as adults of M. salmoides. The high trophic state of the river might permit the rapid recovery of the cladoceran community. The predation impact of juvenile fish in the Nakdong River seems to be affected by the existence of piscivore as well as high trophic status.

• Korean Journal of Ecology and Environment
• /
• v.56 no.2
• /
• pp.161-171
• /
• 2023

The medium-large cladoceran species Simocephalus spp. predominantly occur in habitats with developed aquatic vegetation. Accordingly, due to Simocephalus' high contribution to zooplankton community biomass in the lake's littoral zone and wetland habitats, estimating their biomass is important to understand the matter cycling based on biological interactions within the aquatic food web. In this study, we reviewed the length-weight regression equations used previously to estimate Simocephalus biomass, directly measured S. serrulatus' body specification (length, width and area) and their biomass(dry weight) using instruments such as a microscopic digital camera and a microscale, and performed regression analysis between each other. When S. serrulatus biomass was estimated using the equation (Kawabata and Urabe, 1998) presented in 『Biomonitoring Survey and Assessment Manual』, Korea, errors between estimates and measures were relatively large compared to the S. serrulatus species-specific biomass estimate equation developed by Lemke and Benke (2003). In addition, both equations showed not only increasing trends in error (estimate-measure) with increasing S. serrulatus' body length, but also in error variance among similar-sized individuals. The results of regression analysis with dry weight by body specifications indicated that the most appropriate equation for estimating the biomass of S. serrulatus was derived from the width-dry weight exponential regression equation (R²=0.9555). The review and development study of such species-specific biomass estimation equations for zooplankton can be used as a tool to understand their role and function in aquatic ecosystem food webs.

• Korean Journal of Environmental Biology
• /
• v.33 no.2
• /
• pp.223-229
• /
• 2015

Pre-monsoon dynamics of zooplankton community were investigated in the downstream of the Gagok stream flowing into the East Sea of Korea. Monthly sampling was carried out to collect zooplankters at five sites in the stream during the period between April and July 2014. Dissolved oxygen contents exceeded $7.0mg\;L^{-1}$ all the time. Water temperature was in a range of 15.7 to $24.9^{\circ}C$ and pH 7.4 to 8.8, respectively. A total of 75 taxa consisted of 36 species of rotifers, 16 species of cladocerans, 16 species of copepods, four kinds of aquatic insects, two kinds of decapods and one nematod was occurred. One species of marine copepod and one cladoceran, and one species of brackish rotifer and one copepod distributed at the station located in the stream mouth. Zooplankton abundance showed to vary from 42 to 4202 individuals $m^{-3}$ due to the explosion of aquatic insects and Alona sp. at site 2 located in the downstream in April. Heavy rainfall during the monsoon period seems to decrease the zooplankton abundance caused by diffusion and drifting to the sea. Species diversity indices were generally high between 1.2~2.3 and were recorded to be high at the downstream throughout the study period. With the zooplankton dynamics, the influence of the input of sea waters into the stream seemed to be confined to some hundred meters of the stream mouth facing the East Sea.

• Korean Journal of Ecology and Environment
• /
• v.33 no.2 s.90
• /
• pp.152-161
• /
• 2000

Simocephalus mixtus Sars was redescribed and illustrated from Korea. It had been frequently confused with S. vetulus (O.F. M$\"{u}$ller) and S. vetuloides Sars in the Far East. Redescription was based on the materials collected from various freshwater habitats at 97 localities in South Korea during the period from May 1981 to June 1999. Previous records of Simocephalus species from Korea were examined. S. mixtus is well distinguishable from other related species by having short and wide dorso-posterior carapace angle prominence, distally protruding dorsal margin of carapace, deep depression of the ventral head margin near the rostrum, elongate ocellus, and postabdominal claw lacking the basal pecten of denticles.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.26 no.1
• /
• pp.41-46
• /
• 2013

The cladoceran Daphniamagna has been used as an aquatic test species in aquatic toxicology. To evaluate the aquatic toxicity of leachate from concrete, the immobilization of D. magna was observed after treatment of various concentrations of leachate specimens. Reliabilities of the culture condition and the experimental protocol for acute toxicity test were successfully achieved from the standard toxicity test. The leachates were prepared from the mixture of Ordinary Portland Cement (OPC) and pozzolanic admixtures, Pulverised fuel ash (PFA), Ground granulated blast furnace slag (GGBS) and GGBS containing loess. Acute toxicity test showed 100% immobilization of D. magna for OPC or PFA. The leachates from OPC or PFA had high pH 10 to 12. However, GGBS and GGBS containing loess showed less toxicity according to the concentrations. Especially, immobilization was not observed at the concentrations below 12.5% of GGBS containing loess. Also the range of pH for these specimens was 8 to 9. This suggested that the use of loess as the admixture in concrete may be useful to reduce eco-toxicity of leachates from concrete. This our study provided the harmfulness of the alkali leaching from concrete in aquatic environment and the usefulness of D. magna to evaluate the toxicity of leachates from concrete.