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Experimental evidence on prevention of infection by the ectoparasitic protozoans Ichthyobodo salmonis and Trichodina truttae in juvenile chum salmon using ultraviolet disinfection of rearing water
Author(s) -
Mizuno Shinya,
Urawa Shigehiko,
Miyamoto Mahito,
Hatakeyama Makoto,
Koide Nobuhisa,
Ueda Hiroshi
Publication year - 2019
Publication title -
journal of fish diseases
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 85
eISSN - 1365-2761
pISSN - 0140-7775
DOI - 10.1111/jfd.12920
Subject(s) - biology , juvenile , trichodina , hatchery , oncorhynchus , fishery , zoology , parasite hosting , aquatic animal , veterinary medicine , ecology , fish <actinopterygii> , gill , medicine , world wide web , computer science
In northern Japan, juvenile chum salmon Oncorhynchus keta (Walbaum) are released from hatcheries to enhance the fishery resource. Infections with ectoparasitic protozoans, particularly the flagellate Ichthyobodo salmonis and the ciliate Trichodina truttae , occasionally cause severe mortality among hatchery‐reared juveniles. This study examined the susceptibility of the two parasites to wide‐ranging UV irradiation (experiment 1) and then investigated whether UV disinfection of the rearing water using a commercial device was useful for preventing infections among juveniles in a small‐scale rearing system over a 28‐day period (experiment 2). In experiment 1, parasite mortality reached 100% with UV irradiation doses of ≥9.60 × 10 5 μW s/cm 2 for I. salmonis and ≥8.40 × 10 5 μW s/cm 2 for T. truttae . In experiment 2, disinfection of the rearing water at a UV irradiation dose of 2.2 × 10 6 μW s/cm 2 succeeded in complete prevention of both parasites in the juvenile salmon. These results elucidate the minimum dose of UV irradiation for inactivation of I. salmonis and T. truttae , and demonstrate the usefulness of water disinfection using a commercial UV irradiation device to prevent infections by these parasites in hatchery‐reared juvenile chum salmon.