Effects of Dissolved Gas Supersaturation on Fish Residing in the Snake and Columbia Rivers, 1996 Annual Report. Page: 4 of 68
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V
Gas Bubble Disease in Captive Fish
Resident nonsalmonid fish used for the net-pen studies were taken from the river and often
had signs of GBD at introduction to the pens. After 4 days of holding, GBD signs among the
captive fish usually persisted and generally showed an increase in prevalence.
Downstream from Bonneville Dam, fish held in the 0- to 4-m pen showed external GBD
signs in 7 of the 13 holding periods; prevalence of external GBD signs ranged from 0 to 58.4%.
Prevalence of external GBD signs increased during every 4-day holding period between 17 May
and 24 June. When prevalence of external GBD signs increased, mortality ranged from 0 to 4%.
Upstream from Priest Rapids Dam, fish held in the 0- to 4-m pen showed increases of
external GBD signs in 15 of the 16 holding periods; prevalence of external GBD signs ranged
from 0 to 70 0% When prevalence of external GBD signs increased, mortality ranged from 0 to
33%
Downstream from Ice Harbor Dam, fish held in the 0- to 4-m pen showed increases of
external GBD signs in 9 of the 13 holding periods; prevalence of external signs ranged from 0 to
86 0% When prevalence of external signs of GBD increased, mortality ranged from 4 to 33%.
Model of Gas Bubble Disease Impacts
In general, we observed high prevalence of GBD signs in fish collected within the sample
areas when average daily TDGS exceeded 120%. When TDGS dropped below 120%, we
observed low prevalence of GBD signs in sampled fish and low mortalities in captive fish.
Our goal was to provide fishery managers with a definition of TDGS impacts to resident
fish throughout affected areas in the Columbia and Snake Rivers. We used sampling and previous
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Schrank, Boyd P. Effects of Dissolved Gas Supersaturation on Fish Residing in the Snake and Columbia Rivers, 1996 Annual Report., report, March 1, 1998; United States. (https://digital.library.unt.edu/ark:/67531/metadc619938/m1/4/: accessed April 2, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.