TRENDS IN PARASITIC COPEPOD INFECTION AMONG JUVENILE SALMONIDS IN WVP RESERVOIRS Principal...

TRENDS IN PARASITIC COPEPODINFECTION

AMONG JUVENILE SALMONIDSIN WVP RESERVOIRS

Principal Investigators:

Fred R. Monzyk Jeremy D. Romer

Ryan EmigThomas A. Friesen

Oregon Department of Fish and WildlifeCorvallis Research Lab

Corvallis, Oregon

Background

Adult ♀28-32 dto hatch

Infectous free-swimming stage

(live for ~2 d)

Re-attaches to tissue(4 -14 d)

Can produce 2 broods

Eggs Copepodid Chalimus stages (1-4)

Life Cycle

• Salmincola californiensis only infect Oncorhynchus spp.• Endemic to PNW freshwater habitats• Can cause physical damage to gill structure/mortality• Incidence of infection tends to increase with fish size

Objectives

Compare infection levels between stream-rearing and reservoir-rearing Chinook

Compare susceptibility to parasitic copepods among Oncorhynchus species in reservoirs

Evaluate changes in infection through time Prevalence and Intensity on gills

Methods

All fish collected were examined macroscopically for ♀ copepods on gills and fins

• Counted copepods on subsample of fish

Screw traps, gill nets, electrofishing, seining• Detroit, Foster, Cougar, Lookout Point, and Fall Creek (USACE)

Results

Month

May Jun Jul Aug Sep Oct Nov Dec

Pre

va

len

ce

(%) 0

20

40

60

80

100Cougar ReservoirDetroit ReservoirLookout Pt. Reservoir M.F. Willamette N. Santiam S.F. McKenzie

Infection Prevalence much greater in reservoirs compared to streams

Subyearling Chinook

Attached to gillsReservoirs: 80%

Streams: 19%

2012-2013

ResultsChinook are more vulnerable to infection

• Factors could be habitat, behavioral (feeding, schooling), or evolutionary (immunity)

Month

Jun Jul Aug Sep Oct Nov Dec

Pre

vale

nc

e (%

) 0

20

40

60

80

100Chinook, age 0 Kokanee, age 0Rainbow trout, age 1

Detroit2012-2013 96%

28%

1%

Results2012

0 5 10 15 20

Pro

po

rtion

of C

hin

oo

k

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Cougar Detroit LOPFall Cr

2013

Number of copepods on gills

0 5 10 15 20

0.00

0.05

0.10

0.15

0.20

0.25

0.30

16-24% of Fall Creek Chinook >20 copepods• 85% mortality during saltwater transition (Pawaputanon 1980)

Subyearling Chinook in Nov-Dec

+

+

Fall (Nov-Dec)

Mean intensity

0 2 4 6 8 10 12 14 16

Preva

lence

(%) 70

75

80

85

90

95

100

Cougar 2012 Cougar 2013 Cougar 2014 Detroit 2012 Detroit 2013 Detroit 2014 Fall Creek 2012 Fall Creek 2013 Fall Creek 2014 Lookout Pt 2012 Lookout Pt 2013 Lookout Pt 2014

Results

Lower infection levels in Lookout PointHigher infection levels in Fall Creek Reservoir

Infected adults

Fall Creek• Steelhead and Chinook adults (Mar-Sep)• Released near or in

reservoir

Lookout Point• Chinook release >30km

above reservoir

Late arriving adults released @ Gold Creek

What can be done?

Infected adults

Don’t release infected adults near reservoiro Not feasible in many WVPs

Treat adults prior to transportingo Ivermectin gavage (Johnson and Heindel 2001)-IDFG

• Individual fish handled at least twice

o H2O2 (Hydrogen peroxide)• Design Fall Creek AFF with holding pool

and bioswale/settling pond

o Possible added benefit of < PSM• Resolve necrosis of gill tissue

Acknowledgments

Doug GarlettsChad HelmsGreg TaylorTodd PierceNat EricksonTerri BerlingRich Piaskowski

Jeff ZillerKelly Reis

The ‘Reservoir Dogs’Khoury HickmanChris AbbesAndrew NordickGreg GilhamMeghan Horne-BrineJohn ElliottKevin StertzRyan FlahertyJD Hansen

Questions?

2014

Number of copepods on gills

0 5 10 15 20

Prop

ortion of Chino

ok

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Cougar14 Detroit14 LOP14 Fall Cr14