trends in parasitic copepod infection among juvenile salmonids in wvp reservoirs principal...
TRANSCRIPT
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