Modeling Renibacterium Salmoninarum Dynamics among Chinook Salmon (Oncorhynchus tshawytscha) and Lake Whitefish (Coregonus clupeaformis) Populations in the Great Lakes
Grant: # 0665
Grant Amount: $42,898.30
Board Decision Year: 2005
Michigan State University - Michigan Sea Grant Extension (East Lansing)
Michigan Sea Grant Extension
Tsao, Jean ([email protected]) 517-353-1737
GLFT - Ecosystem Health and Sustainable Fish Populations-C - Ecological and biological fisheries research to inform management
Project Details
Background
In this project, funded by the Great Lakes Fishery Trust, we developed a model to investigate
bacterial kidney disease (BKD) dynamics in free-swimming (i.e., non-captive) fish populations
in Lake Michigan. Renibacterium salmoninarum (Rs) is the causative agent for BKD and infects
multiple fish species in Lake Michigan. Knowledge of Rs/BKD dynamics in Lake Michigan is
currently very limited, despite evidence of the importance of this disease for salmonid dynamics.
We believe that better information is needed on the dynamics and distribution of this pathogen in
Lake Michigan. Because of the large cost of empirical studies, we proposed an epidemiological
modeling study to first organize current knowledge about Rs/BKD in free-swimming
populations. Furthermore, our goal was to expose critical uncertainties about the Rs system in
free-swimming fish populations in Lake Michigan, identify opportunities for efficient and
insightful data collection, and pose testable hypotheses for future investigations.
Objectives
• To develop a multiple-host epidemiological model for Rs in free-swimming fish
populations in Lake Michigan based on knowledge of fish health experts and fisheries
biologists.
• To expose fish health researchers and fisheries biologists to epidemiological models as a
tool for investigating pathogen dynamics among free-swimming fish populations.
Outcomes
To develop this host-pathogen system model, we sought out expert knowledge and advice
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regarding the Rs/BKD system by conducting two workshops where both fish health experts and
fisheries biologists participated. The first workshop allowed us to organize the current
knowledge on Rs/BKD epidemiology. Most of the knowledge on Rs/BKD comes from disease
and treatment in hatcheries, but little is known for free-swimming populations. Workshop
participants gave key recommendations that informed model structure. After developing,
running, and analyzing model simulations, we presented the model and results at a second
workshop. The work was well received and a number of refinements were suggested.
To our knowledge, this study is the first to apply a host-pathogen modeling framework to a
managed, freshwater ecosystem. In particular, model simulations suggest two main areas of
uncertainty affecting Rs/BKD dynamics in free-swimming fish populations in Lake Michigan: 1)
the role played by hatchery practices in Lake Michigan Rs dynamics; and 2) the interaction
between disease dynamics and Chinook salmon density particularly insofar as the latter is
affected by both stocking and wild recruitment dynamics.
Recommendations
1. To employ a method for discriminating hatchery from wild fish in order compare the
prevalence in the two stocks, thereby enabling quantification of the influence of hatchery
practices on pathogen dynamics in free-swimming populations.
2. To determine and measure the stock-recruitment relationship of wild spawning Chinook
salmon and the influence of stocked salmon on this relationship.
3. To quantify the magnitude of vertical transmission in wild fish to understand their
contribution to pathogen maintenance in nature as well through propagation in the hatcheries.
4. To investigate the relationship between nutritional stress and the advancement of disease in
infected individuals, in particular from exposed to infectious states.
5. In order to calibrate models for fish health management, better data are needed to quantify
epidemiological parameters such as transmission rates. Specifically, sampling protocols and
estimation procedures are needed that reflect populations; one approach may be to integrate
fish health surveys into stock assessment.
6. Using museum specimens, determine whether Rs was present in whitefish and other host
populations prior to salmonine introductions to obtain a more informed understanding of
ecological dynamics of Rs in Lake Michigan.
7. Investigate the role of other fish species in Rs maintenance either by direct transmission or by
contributing to an environmental reservoir.
Documents
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Final Report
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