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Vol. 43 No. 2, 2004
Sea Lice, Lepeophtheirus salmonis and Caligus orientalis (Copepoda: Caligidae), of Wild and Farmed Fish in Sea and Brackish Waters of Japan and Adjacent Regions: A Review
Kazuya Nagasawa*
Nikko Branch, National Research Institute of Aquaculture, Fisheries Research Agency, Chugushi, Nikko, Tochigi 321-1661, Japan
Kazuya Nagasawa (2004) This paper reviews various aspects of the biology and effects of 2 caligid copepods, Lepeophtheirus salmonis and Caligus orientalis, on wild and farmed fish in sea and brackish waters of Japan and adjacent regions. Lepeophtheirus salmonis is a common parasite of wild adult chum (Oncorhynchus keta) and pink (O. gorbuscha) salmon migrating in northern Japanese waters. Masu salmon (O. masou)
have the lowest level of infection. Juvenile chum salmon are sometimes
infected. This parasite is also found on salmonids in Korean and
Russian waters. The species occurs on coho salmon (O. kisutch) and rainbow trout (O. mykiss)
farmed in coastal waters of northern Japan, but its infection is not a
serious problem, because only young fish are reared and harvested in
less than a year of culture and thus no fish are cultured during
summer. This situation is very different from that in Scotland,
Ireland, Norway, and Canada where L. salmonis causes serious damage to farms of Atlantic salmon (Salmo salar). Caligus orientalis
is a parasite of coastal marine and brackish-water fish in Japan and
neighboring countries (Taiwan, China, Korea, and Russia). This parasite
has a wide host range and has been reported from over 20 fish species
from different orders and families. It infects farmed and
experimentally reared fish, such as rainbow trout in Japan, grey mullet
(Mugil cephalus) and black porgy (Acanthopagrus schlegeli) in Taiwan, and Mozambique tilapia (Oreochromis mossambicus)
in China. Heavy infection results in appetite reduction and death of
fish. The parasite is one of the most important pathogens at
brackish-water fish farms in Far East Asia.
Key words: Parasitic copepods, Sea lice, Lepeophtheirus salmonis, Caligus orientalis, Pathogenicity.
*Correspondence: E-mail: ornatus@fra.affrc.go.jp
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