Effects of temperature and salinity on the course of infection with the haemoflagellate Cryptobia salmositica in juvenile Pacific salmon, Oncorhynchus spp. |
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| Authors: | SUSAN M BOWER L MARGOLIS |
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| Institution: | Department of Fisheries and Oceans, Fisheries Research Branch, Pacific Biological Station, Nanaimo, British Columbia, Canada |
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| Abstract: | Abstract. At 9°C juvenile sockeye salmon, Oncorhynchus nerka , inoculated intraperitoneally with 105 Cryptobia (= Trypanoplasma ) salmositica began to succumb about day 15, with mortalities exceeding 90% by day 28. Fish inoculated at 8°C and acclimatized to 13°C began to die at about the same time but total mortalities were only about 75%. At 5°C the infection progressed more slowly, with the first mortalities occurring about day 25, but the disease seemed equally as lethal as at 9°C. All fish inoculated at 8°C and acclimatized to 20°C within 11 days survived the infection. Changes in salinity from fresh to sea water (30%o salinity) at 9°C or 13°C had almost no effect on the course of infection either when presmolts were slowly acclimatized to sea water over a period of 6-8 days or when smolts were transferred to sea water quickly (within 1-2 days). However, there were differences in susceptibility to disease among three species of salmon of smoking age. The order of decreasing sensitivity was chinook salmon, Oncorhynchus tshawytscha , with 100% mortality, sockeye salmon with 56 to 74% mortality and coho salmon, Oncorhynchus kisutch , with no mortality. |
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