riparian management and fish productivity
DESCRIPTION
Riparian Management and Fish Productivity. Peggy Wilzbach and Ken Cummins USGS CA Cooperative Fish Research Unit Humboldt State University. Habitat isn’t enough. Fish need food!. Many streams with pristine habitat support low production of salmonid fishes - PowerPoint PPT PresentationTRANSCRIPT
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Riparian Management and Fish Productivity
Peggy Wilzbach and Ken CumminsUSGS CA Cooperative Fish Research UnitHumboldt State University
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Habitat isn’t enough. Fish need food!
• Many streams with pristine habitat support low production of salmonid fishes
• Some of the most productive streams have suboptimal habitat (but abundant food)
The greatest salmonid production is realized in hatchery channels!
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Options for increasing salmonid production? • Direct addition of food organisms
(not realistic over long-term)• Nutrient or organic matter
enrichment• Increasing autotrophic production
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Case study: Effects of riparian canopy opening and salmon carcass addition on the abundance and growth of resident salmonids
Wilzbach, M.A. et al. 2005. Can. J. Fish. Aquat. Sci. 62: 1-10.
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buffer
Experimental Design
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Tectah
Tarup
Pac
ific
Oce
an
Pac
ific
Oce
an SF Rowdy
Little Mill
Peacock
Savoy
0 5 10 15
kilometers
N
Lower Smith River Lower Klamath River
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Savoy Creek: closed canopy
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Tarup Ck– Open Section
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Time of day (h)1 2 3 4 5 6 7 8 9 10 1112 13 1415 16 17 18 19 20 21 22 23 24
µmol
•s-1
•m-2
0
50
100
150
200
250
300
350
Closed Open
Incident Radiation: Savoy Ck, July 6, 2003
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Stream temperature did not differ between cut and uncut reaches in these coastal streams
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Total Salmonid Biomass
Treatment effects:riparian date
(but not carcasses)
June 2002
-4
-2
0
2
4
6
8October 2002
UncutCut
June 2003
Carcass treatment
None Added
Cha
nge
in b
iom
ass
afte
r man
ipul
atio
n(g
l m
- 2)
-4
-2
0
2
4
6
8October 2003
None Added
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Specific Growth Rates
Significant treatment effects: riparian, date, riparian* carcass
None Added
Spec
ific
grow
th ra
te (%
l da
y-1 )
0.0
0.1
0.2
0.3
0.4
0.5
Uncut Riparian Cut Riparian
overwinter 2002
Carcass treatment
None Added
oversummer 2002 overwinter 2003
None Added
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Conclusions:• Increased light was more effective than carcass addition
in enhancing salmonid productivity of study sites
• Carcass enhancement may fail to increase salmonid production in settings where light is limiting or other factors prevent its successful use
• Selective trimming of riparian alder should be evaluated as a management tool for enhancing salmonid production
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Can the food-generating capacity of a stream be readily assessed? Across broad spatial scales, highly
productive streams are associated with:
• moderate temperatures, groundwater inputs
• relatively low vegetative canopy coverage
• hard waters, relatively high concentrations of inorganic nutrients
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• Within regions, need to directly measure prey availability
• Macroinvertebrate drift more accurately reflects prey availability than does the benthos
• The ratio of behavioral to accidental drifters may provide a good index of prey availability during low flow conditions
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Behavioral drifter: predictably available on a diel basis
Accidental drifter: without predictable pattern of drift entry; “windfall” diet items
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-0.1 0.0 0.1 0.2 0.3 0.40
10
20
30
40
50
60Pe
rcen
t of d
rift m
ass
from
beh
avio
ral d
rifte
rs
(ASI
N S
QR
T)
Specific growth rate of salmonids (% · day-1)
R2 = 0.42
Summer
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-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.60
10
20
30
40
50
60
70
Perc
ent o
f Ter
rest
rial I
nver
tebr
ates
in D
rift
(ASI
N S
QR
T)
Specific growth rate of salmonids (%· day-1)
R2 = 0.62
In our study, % of terrestrial inverts was negatively related to fish growth
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to establish the amount, spatial pattern of light gain, and riparian composition needed to optimize local food supplies - without sacrificing beneficial functions of riparian vegetation or cumulating temperature loadings downstream.
Research needs:
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