• Korean Journal of Environment and Ecology
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• v.24 no.6
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• pp.744-750
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• 2010

This study examined the different polyphenism of larval salamander Hynobius ieechii according to two habitats, pond and stream. We collected salamander's eggs from three regions including Mountain Inwang, Surak and Gwangju. Eggs were treated by four different conditions according to predation level and habitat: high risk - which had a predation risk three times a day; low risk - which had no predation risk, pond and stream habitat. Predation risk was conducted by using chemical cue from Chinese minnows. The chemical cue treatment started from the day of collection and ended one week after the hatching. After the treatment phase, we measured the head width at the level of the eyes(HWE) and the largest head width(LHW) and snout-vent length of the each larva. We calculated the ratio of the head size by dividing HWE by LHW and made a comparison with each of the average ratio of head size according to the predation risk. The results showed that there was a significant difference in the ratio of the head size and snout-vent length according to the predation risk and habitat. From these results we found that predation risk and habitat condition can cause the different polyphenism to the larval salamander and these morphological changes could be affect their mortality.

• Journal of Aquaculture
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• v.20 no.4
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• pp.270-277
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• 2007

White spot syndrome virus (WSSV) which is the most serious threat to cultured shrimp around the world has given enormous economic damages to shrimp culture industry every year since it was found from the shrimp ponds in the west coast of the South Korea in 1993. WSSV has strong infectivity as well as virulence and it can be rapidly transmitted among shrimps in ponds by cannibalism of infected ones. Polyculture of shrimps with carnivorous fish has been applied in commercial shrimp farms to suppress or delay the viral outbreak because the fish may selectively eat the moribund shrimps infected by virus. To determine the selective predatory effect of a carnivorous fish, river puffer Takifugu obscurus on white shrimp Litopenaeus vannamei, polyculture trials in laboratory scale of WSSV-infected and non-infected shrimps with river puffer were conducted in concrete round tanks of $28.26\;m^2$ in surface area as followings: 1) juvenile shrimps (B. W. 0.62 g) with 5 months old puffer (B. W. 11.60 g) cultured for 8 days, and 2) sub-adult shrimps (B. W. 6.84 g) with 16 months old puffer (B. W. 85.82 g) cultured for 5 days in order to know the effects according to size difference of cultured animals. In polyculture of juvenile shrimp with 5 months old puffer, survival rates of infected and non-infected shrimps were 46.0% and 89.1% respectively and in that of sub-adult shrimp with 16 months old puffer those were4% and 48% respectively. The results showed that puffer tends to selectively prey on virus infected shrimps among infected and non-infected ones in a limited space with although there is difference in predatory rate with age and density of animals. Regardless of different densities and ages of animals as well as health condition of shrimps, however, there were low differences in daily biomass of shrimp consumed per kg body weight of puffer. This finding suggests that puffer preys on healthy shrimps when moribund shrimps were not sufficient. Therefore, farmers should consider the total biomass of puffer as well as density and stocking time when they stock puffer into shrimp ponds for polyculture.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.3 no.1
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• pp.52-64
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• 1970

Fingerlings hatched from the eggs of the puffer, Fugu rubripes, which were spawned on May 21, 1969, and were cultivated. The results of their growth during 150 days, until October 25th, are summarized as follows: 1. The eggs began to hatch after 163 hours, at a water temperature of 15.9 to $17.4^{\circ}C$, and the hatching rate was $61.56\%$. 2. They reached the post-larval stage 6 to 7 days after hatching, and at this time a high mortality occurred. The mortality rate was 57.26 to $68.0\%$. 3. Sixteen days after hatching some of the larger fingerlings (6.7mm in total length) began attacking some of the smaller ones (4.6mm in to total length). 4. Twenty five to twenty eight days after hatching, the fish changed their food, and at this time a second high mortality occured. The total mortality rate amounted to 90.7 to $90.9\%$ of the total hatch. 5. After the fingerling stage. cannibalism occurs. The fish usually attack the caudal part of other fingerlings. It occurs regardless of body length and when the food supply is short. 6. The food coeffiicient at the age of 46 days (when body length is 53 to 68 mm) was 5.5 for short-necked clams, 8.5 for earth-worms, and 8.7 for fishes. 7. A third hish mortality occurred 53 to 63 days after hatching, the total mortality amounting to 95.76 to $97.34\%$, and the main cause of the mortality was found to be rickets resulting from nutritional deficiency 8. The growth rates were as follows: 2.68mm just after hatching, 3.84mm at the age of 10 days; 7.96mm after 25 days; 20.96mm or 130mg after 40 days; 73.68mm or 9.06g after 80 days: and 123mm or 31.8g after 150 days. 9. The water temperature during the above period was 15.7 to $28.4^{\circ}C$ with an average of $22.10^{\circ}C$ and the salinity was 25.53 to $34.50\%$ with an average of $32.07\%$, 10. The young of this species could endure well a wide range and sudden rise in salinity, and could survive easily when the salinity suddenly fell to $5\%$, but a considerable mortality occured when it fell to $3\%$. 11. When the fish were tranferred directly to fresh water from normal sea water they died out in 9 hours and 40minutes. However, when transferred from water of $5\%$ salinity at which they were reared for 54 days, they survived for 60 hours and 40 mimutes longer than in the former case.

• Journal of Aquaculture
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• v.5 no.1
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• pp.29-67
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• 1992

Life cycle and seed production of the freshwater prawn, Macrobrachium nipponense, were studied and the results are as follows : 1. Larval development : Embryos hatched out as zoea larvae of 2.06 mm in mean body length. The larvae passed through 9 zoea stages in $15{\~}20$ days and then metamorphosed into postlarvae measuring 5.68 mm in mean body length. Each zoea stage can be identified based on the shapes of the first and second antennae, exo- and endopodites of the first and second pereiopods, telson and maxillae. 2. Environmental requirements of zoea larvae : Zoea larvae grew healthy when fed with Artemia nauplii. Metamorphosing rate was $65{\~}72{\%}$ at $26{\~}28\%$ and $7.85{\~}8.28\%_{\circ}Cl.$. The relationship between the zoeal period (Y in days) and water temperature (X in $^{\circ}C$) is expressed as Y=46.0900-0.9673X. Zoeas showed best survival in a water temperature range of $26{\~}32^{\circ}C$ (optimum temperature $28^{\circ}C$), at which the metamorphosing rate into postlarvae was $54{\~}72\%$ The zoeas survived more successfully in chlorinity range of $4.12{\~}14.08{\%_{\circ}}Cl.$, (optimum chlorinity $7.6{\~}11.6\;{\%_{\circ}}Cl.$.), at which the metamorphosing rate was $42{\~}76{\%}$. The whole zoeal stages tended to be longer in proportion as the chlorinity deviated from the optimum range and particularly toward high chlorinity. Zoeas at all stages could not tolerate in the freshwater. 3. Environmental requirements of postlarvae and juveniles : Postlarvae showed normal growth at water temperatures between $24{\~}32^{\circ}C$ (optimun temperature $26{\~}28^{\circ}$. The survival rate up to the juvenile stage was $41{\~}63{\%}$. Water temperatures below $24^{\circ}C$ and above $32^{\circ}$ resulted in lower growth, and postlarvae scarcely grew at below $17^{\circ}C$. Cannibalism tended to occur more frequently under optimum range of temperatures. The range of chlorinity for normal growth of postlarvae and juveniles was from 0.00 (freshwater) to $11.24{\%_{\circ}}Cl.$, at which the survival rate was $32{\~}35\%$. The postlarvae grew more successfully in low chlorinities, and the best growth was found at $0.00\~2.21{\%_{\circ}}Cl.$. The postlarvae and juveniles showed better growth in freshwater but did not survive in normal sea water. 4. Feeding effect of diet on zoea Ilarvae : Zoea larvae were successfully survived and metamorposed into postlarvae when fed commercial artificial plankton, rotifers, and Artemia nauplii in the aquaria. However, the zoea larvae that were fed Artemia nauplii and reared in Chlorella mixed green water showed better results. The rate of metamorphosis was $68\~{\%}75$. The larvae fed cow live powder, egg powder, and Chlorella alone did not survive. 5. Diets of postlarvae, juveniles and adults : Artemia nauplii and/or copepods were good food for postlarvae. Juveniles and adults were successfully fed fish or shellfish flesh, annelids, corn grain, pelleted feed along with viscera of domestic animals or fruits. 6. Growth of postlarvae, juveniles and adults : Under favorable conditions, postlarvae molted every five or six days and attained to the juvenile stage within two months and they reached 1.78 cm in body length and 0.17 g in body weight. The juveniles grew to 3.52 cm in body length and 1.07 g in body weight in about four months. Their sexes became determinable based on the appearance of male's rudimental processes (a secondary sex character) on the endopodites of second pereiopods of males. The males commonly reached sexual maturity in seven months after attaining the postlarvae stage and they grew to 5.65 cm in body length and 3.41 g in body weight. Whereas the females attained sexual maturity within six to seven months, when they measured 4.93 cm in body length and 2.43 g in body weight. Nine or ten months after hatching, the males grew $6.62{\~}7.14$ cm in body length and $6.68{\~}8.36$ g in body weight, while females became $5.58{\~}6.08$ cm and $4.04{\~}5.54$ g. 7. Stocking density : The maximum stocking density in aquaria for successful survival and growth was $60{\~}100$ individuals/$\ell$ for zoeas in 30-days rearing (survival rate to postlarvae, $73{\~}80{\%}$) ; $100{\~}300$ individuals/$m^2$ for postlarvae of 0.57 cm in body length (survival rate for 120 days, $78{\~}85{\%}$) ; $40{\~}60$ individuals/$m^2$ for juveniles of 2.72 cm in body length (survival rate for 120 days, $63{\~}90{\%}$) : $20{\~}40$ individuals/$m^2$ for young prawns of 5.2 cm in body length (survival rate for 120 days, $62\~90{\%}$) ; and $10\~30$ individuals/$m^2$ for adults of 6.1 cm in body length (survival rate for 60 days, $73\~100{\%}$). The stocking density of juveniles, youngs and adults could be increased up to twice by providing shelters.