BPA Fish and Wildlife FY 1997 Proposal

Section 1. Administrative
Section 2. Narrative
Section 3. Budget

see CBFWA and BPA funding recommendations

Section 1. Administrative

Title of project
Relationship of Gas Supersaturation in Infectious Diseases of Fish

BPA project number   5522500

Business name of agency, institution or organization requesting funding
Oregon State University

Sponsor type   

Proposal contact person or principal investigator

BPA technical contact   ,

Biological opinion ID   

NWPPC Program number   8.5

Short description
In 1994, a NMFS appointed Panel of Experts in Gas Bubble Disease and Supersaturation requested research to determine if gas suspersaturation could increase the susceptibility of salmon to infectious disease agents, and if so, at exposure to what gas supersaturation levels. The proposed research addresses this research need. Its research objectives are: 1. Determine whether exposure to gas supersaturated conditions make fish more susceptible to infection by selected pathogens of salmon, and if so, what threshold levels of superasaturation and exposure time. 2. Determine whether the stress from gas supersaturation diminish the survival of already infected fish, and if so, at what threshold levels of supersaturation and exposure time. Fish will be exposed to different levels of dissolved gasses for different periods of time and then tested for their sensitivity to lethal infection with Renibacterium salmoninarum, Flexibacter columnaris, Ceratomyxa shasta, and IHNV. In the first set of experiments, each test group will be exposed to two different challenge levels of one pathogen to assessthe relative susceptibility of the fish to the disease agent. All assays will be done in duplicate. A second series of experiments will be carried out with greater variation in gas level expsoure time and more pathogen challenge levels if these initial studies inducate that gas superasturation has a serious effect on increasing disease susceptibility.

Project start year   1996    End year   2001

Start of operation and/or maintenance   0

Project development phase   IMPLEMENTATION

Section 2. Narrative

Related projects
BPA Project 92-024 Enhanced

Project history

Biological results achieved

Annual reports and technical papers

Management implications

Specific measureable objectives
The specific measurable objective for the propose project is the determination of whether exposure to gas supersaturation makes fish more susceptible to different pathogens. Since gas supersaturation is a very real and documented problem in rivers that contain dams, the possibility that gas supersaturation predisposes fish to other pathogens in the system is potentially serious and needs addressing.

Testable hypothesis
1. Does exposure to gas supersaturated conditions make fish more susceptible to infection by selected pathogens of salmon, and if so, at what threshold levels of supersaturation and exposure time? This will be tested as a null hypothesis and rejected only if the resulting differences are statistically significant at P=0.90.

2. Does the stress from gas supersaturation diminish the survival of already infected fish, and if so, at what threshold levels of supersaturation and exposure time? Again, this will be tested as a null hypothesis and rejected only if the resulting differences are statistically significant at P=0.90.

Underlying assumptions or critical constraints
Since the experiments will be conducted in the laboratory so that the effects of different parameters such as gas supersaturation level and pathogen challenge dose can be controlled, the underlying assumption is that these experiments will accurately reflect what takes place in the river. This is a critical assumption but it is the only appropriate way to ask these questions.

Methods
Please see attached proposal.

Brief schedule of activities
Please see attached proposal.

Biological need
The relationship between chronic gas bubble disease and susceptibility to infectious diseases is an important determination that must be made if rational decisions regarding water quality guidelines are to be made.

Critical uncertainties
The relationship between chronic gas bubble disease and susceptibility to infectious disease is difficult to discern in the river for several reasons. First, chronic infectious diseases may allow continued migration into the ocean before mortality occurs. Second, smolts debilitated by an infectious agent are more susceptible to predation and therefore the true cause of death is often ascribed to the predator. Further, many smolts already carry pathogens when first collected and this prevalence would confuse the cause-effect relationship. As a result of these problems, there is little data on the influence of gas supersaturation on disease susceptibility or recovery. Because of the difficulties in evaluating the interaction between exposure to gas supersaturated conditions and disease agents in the wild, we are proposing a laboratory-based investigation where variable gas levels can be maintained and fish can be challenged to disease agents under controlled conditions. While laboratory experiments cannot duplicate exactly a smolt’s exposure to supersaturation in a river, the proposed experiments can determine whether a significant proportion of the fish population may experience sublethal effects of supersaturation and what conditions lead to those effects.

Summary of expected outcome
The study will assess the effects of gas supersaturation on the susceptibility of fish to lethal infection by several different pathogens and on the survival of previously infected animals (carrier fish) in gas supersaturated waters. Thus, animals exposed to different levels of dissolved gasses for different periods of time will be tested for their sensitivity to lethal infection with Renibacterium salmoninarum, Flexibacter columnaris, Ceratomyxa shasta, and IHNV. In the first set of experiments, each test group will be exposed to two different challenge levels of one pathogen to assess the relative susceptibility of the fish to the disease agent. All assays will be done in duplicate. A second series of experiments will be carried out with greater variation in gas level exposure time and more pathogen challenge levels if these initial studies indicate that gas supersaturation has a serious effect on increasing disease susceptibility. The data will be analyzed by analysis of variance and the central tendencies for each study will be examined by comparing means, median, and modal values. Confidence limits will be derived for the means.

Dependencies/opportunities for cooperation

Risks

Monitoring activity
The first hypothesis will be tested in a series of experiments in which naive fish are exposed to a repetitive but sublethal levels of dissolved gasses before challenge with a pathogen. In these tests, fish will be exposed to several levels of dissolved gasses similar to the exposure levels experienced by feral smolts in their downstream migration. Exposure levels will approximate those levels that would normally permit survival but might debilitate the fish sufficiently to increase their susceptibility to lethal pathogens. Thus, the exposure to dissolved gases will be sublethal, well defined, and continue diurnally for a period of 21 days (the estimated mean travel time from Lower Granite Dam to Jones Beach). Each experiment will include a range of gas levels, beginning with the highest likely to be encountered (135% TGP, 268mm Hg). In the first set of experiments, fish will be exposed daily for 21 days to uncompensated gas levels of 135 % (268 mm Hg), 120% (150 mm Hg), 110% (76 mm Hg) and 100% (0 mm Hg) TGP for 70% and 30% of the estimated time to first mortality. After 21 days, the uncompensated DP will be reduced to 0 and the fish will be challenged at two concentrations of a selected pathogen. Then, both control and experimental fish will be challenged with the pathogen. To enable comparison of data between the different gas exposure levels, it is important to carry out a comparison of disease susceptibility for a single pathogen at all of the exposure levels in one assay. If an effect is realized at any of the indicated exposure levels (gas supersaturation level versus exposure time) further testing will proceed along two lines: one will proceed to test lower incremental levels of supersaturation, i.e., TGP 130% , 125%, 120%, etc., and the other will test a wider range of diurnal exposure periods, i.e. 60%, 50%, 40% , etc. of lethal exposure. Testing will proceed adaptively, until no significant effect is discernible.

The second hypothesis will be tested with fish that are challenged with different serial doses of a particular pathogen, held for one to two weeks, and then infected fish will be exposed to different gas supersaturation levels over a range of diurnal exposure periods for 21 days.

The results of the laboratory experiments will be communicated by oral and written presentations to the relevant agencies and public forums. The consideration of the data generated in the study for inclusion in guidelines for water quality in the Columbia River basin will be an important benchmark to measure the projects outcome.

Section 3. Budget

* For most projects, Authorized is the amount recommended by CBFWA and the Council. Planned is amount currently allocated. Contracted is the amount obligated to date of printout.

Funding recommendations

CBFWA funding review group   Bonneville Dam - Priest Rapids Dam

Recommendation    Tier 3 - do not fund