Ef Effects of the Parasite Ich chthyophonus (s (spp.) ) on Pa - - PowerPoint PPT Presentation

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ef effects of the parasite ich chthyophonus s spp on pa
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Ef Effects of the Parasite Ich chthyophonus (s (spp.) ) on Pa - - PowerPoint PPT Presentation

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Ef Effects of the Parasite Ich chthyophonus (s (spp.) ) on Pa Pacific Halibut ( Hip Hippog oglos lossus st stenolepis ) ) Gr Growth an and Condit itio ion Sioned Sitkiewicz 1 , Bradley P. Harris 1 , Nathan Wolf 1 , Paul K. Hershberger 2

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Ef Effects of the Parasite Ich chthyophonus (s (spp.) ) on Pa Pacific Halibut (Hip Hippog

  • glos

lossus st stenolepis) ) Gr Growth an and Condit itio ion

Sioned Sitkiewicz1, Bradley P. Harris1, Nathan Wolf1, Paul K. Hershberger2

1Fisheries, Aquatic Science and Technology Lab, Alaska Pacific University 2United States Geological Survey Marrowstone

November 2017

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  • Mesomycetozoea
  • Schizonts & hyphae
  • First described in 1893
  • Reported in 145 fish species
  • Globally distributed
  • Linked to mass mortalities & epizootics

[Rahimian and Thulin 1996; Kocan et al. 2004; Hershberger et al. 2002]

Ichthyophonus (spp.)

www.bioone.org

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  • “Ichthyophoniasis”
  • Infection routes debated
  • Physical & physiological effects
  • General prevalence increase with host

age and size

[Hershberger et al. 2002; Kramer-Schadt et al. 2010]

Host signs

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SLIDE 4

Ichthyophonus in Alaska (AK), United States

ALASKA

[Olson 1986; Gregg et al. 2014; Kocal et al. 2004; Kocan et al. 2009; Marty et al. 2004; F.A.S.T. Lab Unpublished Data]

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  • Pacific halibut (Hippoglossus stenolepis)

Study subject/host species

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Research objectives

  • 1. Explore Ichthyophonus trends in AK P. halibut from 2011-2017
  • 2. Assess physiological effects of parasite using condition analyses
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SLIDE 7

Methods – study site

www.alaska.net

“Post-mortem, pre-dumpster”

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Methods

Bioelectrical Impedance Analysis

Resistance (R) PHASE ANGLE

= poorer condition

IMPEDANCE (Z)

Z R

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Methods

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  • Parasite detection via tissue explant culture
  • Tissue examined after 7 and 14 days

Methods

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Results

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Results

  • General linear models (binomial)

Culture (+/- Ich) ~ Year + Sex + Length + Age + Length*Sex + Gape

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 2011 2012 2013 2016 2017

Prevalence Year

Ichthyophonus Prevalence in P. Halibut from Homer, AK from 2011-2017

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Results – he

hear art we weigh ght

5 10 15 20 25 30 5 10 15 20 25 30 35 Heart Weight (g) Whole Weight (kg)

Heart vs. Whole Weights in Infected and Non-infected P. Halibut

Infected Non-infected

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SLIDE 14

Results – phas

phase angl angle

  • GLM indicated culture was not a

significant predictor of phase angle

  • No relationship between Fulton’s K

and infection status either

10 12 14 16 18 20 22 24 26 28 30 1 Phase angle (degrees) Infection status

Phase Angles of Infected vs. Non-infected P. Halibut

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SLIDE 15

Conclusions

  • Ichthyophonus prevalence ranged from 19-59%
  • Highest levels in most recent years
  • Ichthyophonus may cause subclinical infections in P. halibut

Next steps:

  • BIA-based body composition model
  • Additional condition analyses
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SLIDE 16
  • Dr. Nathan Wolf, APU
  • Dr. Paul Hershberger, USGS
  • Dr. Bradley Harris, APU
  • Sheyna Wisdom, FWS
  • USGS Marrowstone Lab
  • Washington Disease & Diagnostics Lab (WADDL)
  • Western Fisheries Research Center (WFRC)
  • APU student & staff research support

Acknowledgements

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SLIDE 17

Questions?