Mortality of Coho Salmon (Oncorhynchus kisutch) Associated with Burdens of Multiple Parasite Species Public Deposited

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  • Multiple analytical techniques were used to evaluate the impact of multiple parasite species on the mortality of threatened juvenile coho salmon (Oncorhynchus kisutch) from the West Fork Smith River, Oregon, USA. We also proposed a novel parsimonious mathematical representation of macroparasite distribution, congestion rate, which i) is easier to use than traditional models, and ii) is based on Malthusian parameters rather than probability theory. Heavy infections of Myxobolus insidiosus (Myxozoa) and metacercariae of Nanophyetus salmincola and Apophallus sp. occurred in parr (subyearlings) from the lower mainstem of this river collected in 2007 and 2008. Smolts (yearlings) collected in 2006 - 2009 always harbored fewer Apophallus sp. with host mortality recognized as a function of intensity for this parasite. Mean intensity of Apophallus sp. in lower mainstem parr was 753 per fish in 2007 and 856 per fish in 2008, while parr from the tributaries had a mean of only 37 or 13 parasites per fish, respectively. Mean intensity of this parasite in smolts ranged between 47 - 251 parasites per fish. Over-dispersion (variance to mean ratios) of Apophallus sp. was always lower in smolts compared with all parr combined or lower mainstem parr. Retrospective analysis based on smolt data using both the traditional negative binomial truncation technique and our proposed congestion rate model showed identical results. The estimated threshold level for mortality involving Apophallus sp. was at 400 - 500 parasites per fish using both analytical methods. Unique to this study, we documented the actual existence of these heavy infections prior to the predicted mortality. Most of the lower mainstem parr (approximately 75%) had infections above this level. Heavy infections of Apophallus sp. metacercariae may be an important contributing factor to the high over-wintering mortality previously reported for these fish that grow and develop in this section of the river. Analyses using the same methods for M. insidiosus and N. salmincola generally pointed to minimal parasite-associated mortality.
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  • Ferguson, J., Koketsu, W., Ninomiya, I., Rossignol, P. A., Jacobson, K. C., & Kent, M. L. (2011). Mortality of Coho Salmon (Oncorhynchus kisutch) Associated with Burdens of Multiple Parasite Species. International Journal for Parasitology.
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  • description.provenance : Submitted by Sue Kunda (sue.kunda@oregonstate.edu) on 2011-08-05T18:33:46Z No. of bitstreams: 1 KentMichael.Microbiology.MortalityofCohoSalmon.pdf: 2609576 bytes, checksum: 46761926ff9c71dbbea09416f45b5973 (MD5)
  • description.provenance : Made available in DSpace on 2011-08-05T18:34:14Z (GMT). No. of bitstreams: 1 KentMichael.Microbiology.MortalityofCohoSalmon.pdf: 2609576 bytes, checksum: 46761926ff9c71dbbea09416f45b5973 (MD5) Previous issue date: 2011
  • description.provenance : Approved for entry into archive by Sue Kunda(sue.kunda@oregonstate.edu) on 2011-08-05T18:34:14Z (GMT) No. of bitstreams: 1 KentMichael.Microbiology.MortalityofCohoSalmon.pdf: 2609576 bytes, checksum: 46761926ff9c71dbbea09416f45b5973 (MD5)

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