• Journal of Aquaculture
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• v.6 no.4
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• pp.255-271
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• 1993

For the development of seedling production techniques of the freshwater crab Eriocheir japonicus, the effects of salinity and temperature on the growth of larvae of the crab were studied. Embryos hatched out as zoea larvae were measured 0.421 mm in average carapace length. Five zoea stages needed 16-26 days for metamorphosis from zoea to megalopa at $22^{\circ}C$ and $24.5\%o$. The average carapace length of the 5th zoea was 1.16 mm and that of the megalopa larvae was 1.89 mm. Each zoea stage could be identified based on both the number of plumosed seatae on the exopodite of maxilliped, and the number of spines on the posteroinner margin of tel son and also based on the rudimentary pleopods appearence. Zoea larvae fed rotifers and Artemia nauplii were healthy and metamorphosing rate from zoea to megalopa was $80\~90\%\;at\;22\~26^{\circ}C\;and\;17.5\~31.5\%o$. The relationship between larval period (Y in days) and water temperature $(X\;in\;^{\circ}C)$ is expressed as Log Y = 3.8604-1.91735 LogX. Water temperature and salinity ranges for better survival and metamorphosis of the larvae were $ 22^{\circ}C\~26^{\circ}C\;(optimum\;at\; 26^{\circ}C)\;and\;17.5\%o\~31.5\%o\;(optimum\;at\;24.5\%)$, respectively. The duration of larval stages tend to longer as salinity levels deviated from optimum particulaly at lower end. All zoea larvae did not survive in freshwater.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.4
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• pp.265-281
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• 1992

The materials of this study consist of both specimens and survey records of the mollusks and crustaceans which were obtained from 30 collection sites in the Naktong Estuary during Aug.-Nov., 1991. The mollusks and crustaceans collected and identified in this study are 31 and 50 species, respectively. Of these two species of mollusks and six species of crustaceans were newly recored in this area. Including the previous records, the occurrence and distribution of 63 molluscan species and 138 crustacean species were compared in eight zones, before and after the construction of the Naktong Estuary Barrage. During this investigation, only a few species of mollusks occurred in the northern freshwaters off the Barrage. The habitats for the intertidal species were greatly destructed along the eastern part of the UIsuk Is. and the riverside of Tadaep'o where the bank was recently constructed. The commercial bivalves including Corbicula fluminea and Ruditapes Philkippinarum were greatly decreased in number in all the eatuarine waters. A freshwater crab, Eriocheir japonicus, seems to be extinguished in the Naktong River and its neighbouring streams.

• Parasites, Hosts and Diseases
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• v.47 no.4
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• pp.425-426
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• 2009

The present study investigated the infection status of Paragonimus westermani metacercariae in freshwater crabs (n = 363) and crayfish (n = 31) from October 2007 to October 2008 using the crush method. All of the freshwater crabs, Eriocheir japonicus, were negative for P. westermani metacercariae while 10 (32.3%) of the 31 examined crayfish were positive. The 10 positive crayfish were caught in Haenam, Jeollanam-do, and there were 8-59 (mean 28.4) metacrcariae per infected crayfish. These results suggest that P. westermani metacerariae are still transmitted by crayfish enzootically in southern Korea, and that freshwater crabs may transmit metacercariae only on rare occasions.