Assessing disease impacts of hatcheries on downstream salmonids in the Willamette River Basin, Oregon Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/w9505365b

Descriptions

Attribute NameValues
Creator
Abstract or Summary
  • Hatcheries are often perceived as a source of pathogen amplification, potentially increasing disease risk to free-ranging populations; at the same time, free-ranging fishes may introduce pathogens into hatcheries through untreated water sources. Many pathogens exist naturally within the environment (with the exception of introduced pathogens) and the presence of a pathogen does not guarantee infection or disease (Naish, Taylor III, Levin, Quinn, Winton, Huppert & Hilborn 2007). Infections can be acute, chronic, or asymptomatic, fish may die, recover, or become carriers (Naish et al. 2007), and pathogens may be shed from any of these stages (Scottish Executive 2002). Most salmon and trout hatcheries along the Willamette River Basin, Oregon, USA, utilize an untreated river water supply for their rearing ponds and release this water, untreated, back into the river. This creates a potential for waterborne pathogens present in free-ranging hosts to be transmitted through the water supply to hatchery populations. Moreover, any hatchery epizootic can amplify pathogens and release these into the water, which could have a direct impact on free-ranging populations exposed to those pathogens in hatchery effluent. The goal of this thesis was to assess transmission of the pathogens Flavobacterium columnare, F. psychrophilum, Aeromonas salmonicida, Renibacterium salmonicida, and Infectious Hematopoietic Necrosis Virus (IHNV), at selected hatcheries in the Willamette River Basin. To accomplish this, I considered historical data and hatchery-specific and pathogen-specific factors involved in transmission and disease. Additionally, I conducted sentinel fishes exposures (Oncorhynchus mykiss and O. tshawytscha) at hatcheries during both epizootics and non-epizootic periods. Naïve sentinel fish were placed in hatchery influents and effluents to determine transmission direction and pathogen prevalence associated with hatcheries. I found that sentinel fishes developed infections downstream of hatcheries that were undergoing specific bacterial epizootics, or had low levels of pathogen prevalence within the hatchery, but not at any other time. Infections and mortality were due to the same pathogens responsible for hatchery epizootics, indicating the hatchery as a potential source. This may be a limited effect dependent on distance, dilution, and pathogen. The presence of large numbers of returning, congregating adult fishes may also contribute pathogens to the river in hatchery areas. Sentinel fishes held in hatchery influents did not, at any point, become infected with target pathogens, even during hatchery epizootics. Although I was unable to identify the pathogen entry point leading to hatchery epizootics, I determined that pathogen transmission appeared to be dependent on the pathogen, species, and location where sentinel fish were held. This thesis identifies routes and risks of pathogen transmission at selected Oregon hatcheries, with applications to inform state-wide fish health management.
Resource Type
Date Copyright
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Committee Member
Academic Affiliation
Non-Academic Affiliation
Subject
Rights Statement
Peer Reviewed
Language
Replaces
Additional Information
  • description.provenance : Submitted by Michelle Jakaitis (jakaitim@onid.orst.edu) on 2014-11-22T04:03:39Z No. of bitstreams: 1 JakaitisMichelle2014.pdf: 1928086 bytes, checksum: 13774381b6e59170133f84d6fe34b411 (MD5)
  • description.provenance : Made available in DSpace on 2014-12-01T16:57:28Z (GMT). No. of bitstreams: 1 JakaitisMichelle2014.pdf: 1928086 bytes, checksum: 13774381b6e59170133f84d6fe34b411 (MD5) Previous issue date: 2014-11-04
  • description.provenance : Approved for entry into archive by Julie Kurtz(julie.kurtz@oregonstate.edu) on 2014-11-25T17:34:38Z (GMT) No. of bitstreams: 1 JakaitisMichelle2014.pdf: 1928086 bytes, checksum: 13774381b6e59170133f84d6fe34b411 (MD5)
  • description.provenance : Approved for entry into archive by Laura Wilson(laura.wilson@oregonstate.edu) on 2014-12-01T16:57:28Z (GMT) No. of bitstreams: 1 JakaitisMichelle2014.pdf: 1928086 bytes, checksum: 13774381b6e59170133f84d6fe34b411 (MD5)

Relationships

Parents:

This work has no parents.

Last modified

Downloadable Content

Download PDF

Items