Arctic | Fishes and Fish Habitats
Update on Saprolegnia parasitica infections on subsistence fish near Nuiqsut, Alaska Presenter: Todd Sformo , Todd.Sformo@north-slope.org The emergence of the freshwater mold Saprolegnia parasitica was initially observed by local fishers in Nuiqsut on Aanaakłiq (broad whitefish, Coregonus nasus ) in 2013. Working with local fishers, the City of Nuiqsut, the Kuukpikmiut Subsistence Oversight Panel, and Kuukpik Corporation, we identified the disease saprolegniosis caused by this mold in 2017, which is a new infection in the Colville River area. Historically, only one fish in the North Slope Borough from the Inaru River had been verified with this infection in 1980. In recent years (2020), three additional species—Qaaktaq (Arctic cisco, Coregonus autumnalis ), Iqalusaaq (least cisco, Coregonus sardinella ), and Pikuktuuq (humpback whitefish, Coregonus pidschian )—have been confirmed by nucleotide sequence analysis to have contracted saprolegniosis. In addition to identifying and monitoring for mold, the Nuiqsut community requested an experimental study on the growth rate of this pathogen under the scenario of variable water temperature and salinity. The growth rate of an isolate cultured from Nuiqsut was compared to an isolate cultured from a commercial salmon aquaculture facility in British Columbia, Canada, where water temperature was routinely maintained within ~1°C of 15°C. The growth rates from low (4°C) to high (24°C) temperatures were not statistically different between the two isolates, while increasing salinity decreased growth rate of the two isolates proportionately, and high temperature and low salt concentration were associated with the highest growth rate, 4.4 mm-h−1 (2021). While growth rate was confirmed to increase with temperature experimentally, we noted that no fish had been observed with the infection during the summer fishery when water temperature in the Colville River has been recorded as high as 18°C; however, in late July 2020, we received a photograph from a local fisher of the first Aanaakłiq with putative saprolegniosis. In 2022, two studies were successfully funded to continue to address this issue. The first will expand the testing for the presence of Saprolegnia parasitica in North Slope Borough watersheds and conduct a histopathology study of infected fish, exploring tissue changes and putative biological consequences at varying infection severity. The second study will evaluate levels of polycyclic aromatic hydrocarbons in fish with mold in comparison to healthy fish with no infection.
Alaska Marine Science Symposium 2023 218
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