Why Infestation by Lepeophtheirus Salmonis (Copepoda:Caligidae) is Not a Problem in the Coho Salmon Farming Industry in Japan (original) (raw)

2001, Journal of Crustacean Biology

salmon, but farming of rainbow trout [Oncorhynchus mykiss (Walbaum, 1792) = Salmo gairdneri Richardson, 1836] has also been carried out on a much smaller scale, about The salmon louse Lepeophtheirus salmonis (Krøyer, 1838) is known to cause a serious problem in the farming of Atlantic salmon Salmo salar L., 1758, in northwest Europe and North America (Boxshall and Defaye, 1993; Pike and Wadsworth, 1999). So serious is the problem that an annual loss of 20% of the production was attributed to the infestations by this species of parasite (MacKinnon, 1997). Farming of coho salmon Oncorhynchus kisutch (Walbaum, 1792) in sea water has been in practice in Japan for more than two decades (Mahnken, 1991) and salmon louse has also been reported from both wild (Nagasawa, 1985; Nagasawa et al., 1987, 1994) and cultured salmonids (Nagasawa and Sakamoto, 1993; Urawa et al., 1998); yet, curiously, infestation by L. salmonis is not a serious problem in salmon farms in Japan. This paper reports the results of our study in an attempt to elucidate this distinct phenomenon. In Japan the culture of salmonids in sea water is largely operated along the Pacific coast of northern Honshu in Iwate and Miyagi Prefectures (Mahnken, 1991), with an annual production of over 20,000 metric tons in the early 1990s (Nagasawa and Sakamoto, 1993). The species being cultured are largely coho