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Species of Concern: Hatchery Strays and Natural Production
Coastal Cutthroat Tule Fall Chinook
Winter Steelhead Coho Salmon
Grist Mill SiteRiver Mile 2.5
Fishway constructed in 1958Adult trap operated since 1999
Smolt Trap operated since 1998
Smolt Monitoring Goals•Unbiased estimates of coho, steelhead, & cutthroat smolt yield (CV < 10%). Estimates of juvenile Chinook outmigrants if funding is available
•Contribution of coho from a remote site incubator program is based on otolith marks.
•CWT natural origin coho to estimate marine survival and fishery contributions
Cedar Creek Coho and Steelhead Smolt Estimates
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
19981999
20002001
20022003
20042005
20062007
2009
Year
Esti
mat
e
Coho Smolts
STD Smolts
Cedar Creek Adult Monitoring Goals & Methods
• Estimate the abundance, age, & origin for Tule Fall Chinook, coho, and winter steelhead populations
• BioSample all adult salmonids trapped at the fishway (River Mile 2.5)
• Tag all fish captured in the fishway for mark-recapture abundance estimates
• Monitor Petersen assumptions needed for an unbiased estimate
• Recover adult salmonids through a variety of methods
Recapture Events• Recapture event is a combination of carcass
recoveries (salmon), along with hoop trap & resistance board weir recoveries (4 miles upstream of the fishway)
• Recover steelhead kelts in the screw trap & through seining above the resistance board weir
• Estimate trap efficiency for steelhead– Trapped fish are tagged and released below the fishway– Enumerate number of steelhead that successfully re-
ascend the fishway– Estimate the proportion fish using the ladder
2001-03 Hoop Trap
Pre High Water Event Post High Water Event
• limited success at recapturing coho and steelhead due to trap avoidance and large debris loads
2009 Cedar Creek Adult Estimates
0
500
1000
1500
2000
2500
3000
3500
Coho Steelhead
Species
Ab
un
da
nc
e
Mark-recapture statistics & summary for unmarked adult coho salmon and winter
steelhead2009 2009
Category Coho SteelheadMarks 1244 26
Recaptures 321 3Captures 508 24U95%CI 2973 1840L95%CI 1463 80
N 2218 200CV 17% >100%
Maximum Likelihood Estimates• trap efficiency
• % fish using ladder•binomial distribution•skewed or long tailed•imprecise estimates
Maximum Likelihood Estimates• Abundance
•binomial approximation tohypergeometric distribution•skewed or long tailed•very imprecise estimates
Cedar Cr. Adult Steelhead Trap Effeciencies
0
0.05
0.1
0.15
0.2
0.25
0% 20% 40% 60% 80%
Trap Efficiency
Lik
elih
oo
d
2002
2003
2004
2005
2006
2007
2008
2009
Cedar Cr. Adult Steelhead Population Estimates
0
0.05
0.1
0.15
0.2
0.25
0 200 400 600 800
Abundance
Lik
elih
oo
d2002
2003
2004
2005
2006
2007
2008
2009
Rivot, E., and E. Prevost. 2002. Hierarchical Bayesian analysis of capture-mark-recapture data. Can. J. Fish. Aquat.
Sci. 53:2157-2165. • Application of Rivot et al. 2002 to Cedar
Creek adult steelhead estimate• Posterior probability = prior X likelihood• Non-informative priors & hyperpriors
(hierarchical models) – priors have little influence on posterior probabilities
• Common distributions for trap efficiency & population estimate are the beta and normal probability distributions, respectively
• Other distributions could be used
Hierarchical Modeling• all annual trap efficiencies come from a common distribution of trap efficiencies and their ordering does not affect the model (exchangeable)• borrow strength from other trap efficiencies because they are similar
Hierarchical Modeling• shrink estimates toward the mean, which yields improved precision• can be used for both trap efficiency & population abundance• compromise between individual and fully pooled estimates
Cedar Cr. Adult Steelhead Trap Effeciencies
0
0.05
0.1
0.15
0.2
0.25
0% 20% 40% 60% 80%
Trap Efficiency
Lik
elih
oo
d
2002
2003
2004
2005
2006
2007
2008
2009
Hierarchical
Cedar Cr. Adult Steelhead Population Estimates
0
0.05
0.1
0.15
0.2
0.25
0 200 400 600 800
Abundance
Lik
elih
oo
d2002
2003
2004
2005
2006
2007
2008
2009
Hierarchical
Cedar Creek Adult Steelhead Estimates (median) with 95%CI by Year and Method
0
500
1000
1500
2000
Method_Year
Po
pu
lati
on
Es
tim
ate
CV for Adult Steelhead Estimates by Year and Method
0%
25%
50%
75%
100%
Year_Method
Co
effic
ien
t of V
aria
tion
Summary• Annual steelhead smolt estimates are an
order of magnitude lower than coho. Mean steelhead smolts are 2,900 compared to 38,000 for coho salmon.
• Our adult steelhead estimates are also an order of magnitude lower than coho. For example, in 2009 the steelhead abundance was 200 fish compared to 2,200 for coho.
• Cedar Cr. Steelhead program should be designed to provide more precise abundance estimates.
• Hierarchical approach is a good approach when dealing with sparse data and common distributions.
Cedar Creek Adult Steelhead Recommendations
• Mark all wild steelhead captured at the fishway trap.
• Release all marked steelhead below the fishway trap to estimate ladder use.
• The recapture events should be designed to obtain at least 10 recaptures through the resistance board weir, seining and the screw trap catch of kelts.
• If recaptures are sparse, recaptures can be supplemented through snorkeling.