U.S. Department of the Interior

U.S. Geological Survey

GCMRC Monitoring and 

Research Updates

Scott VanderKooi

Southwest Biological Science Center

Grand Canyon Monitoring and Research Center
Kanab Ambersnail Genetics Report
Status of Length Structured 

Mark-Recapture Model (LSMR)

Progress October, 2012

Dr. Steve Martell
Accomplishments

• ASMR

– Updated ASMR model with most recent data.

• LSMR

– Estimated changes in growth and size transition 

matrixes from tag-recapture data.

– Abundance estimates with fixed asymptotic sizeselectivity (Run1)

– Abundance estimates with size based selectivity 

coefficients (Run4)
HBC Age-4+ (ASMR) and >200 mm (LSMR)

5000

10000

15000

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Year

Abundance

Model

RUN1

RUN4

ASMR

(S. Martell, preliminary data, subject to revision)
Humpback Chub Recruitment

0

2000

4000

6000

8000

10000

1990 1995 2000 2005 2010

Year

Recruitment

Model

RUN1

RUN4

ASMR

(S. Martell, preliminary data, subject to revision)
LSMR Preliminary Findings

• Growth increment data suggest increases in 

growth rates since ~ 2001.

• Trends in abundance between LSMR and ASMR 

are similar for fish > 150 mm.

• Estimated natural mortality rates are much higher 

in LSMR (0.21-0.27) Vs. ASMR (0.08-0.13)

• Greater uncertainty in abundance estimates (as 

expected) using a length-based model.

• Greater recruitment variability in length-based 

model.

(S. Martell, preliminary data, subject to revision)
Fish Sampling Fall 2012

 RTELSS Sampling in Glen Canyon

 HBC Aggregation Sampling

 Natal Origins/Juvenile Chub Monitoring

 Lees Ferry Electrofishing

 Diamond Down Mainstem Electrofishing

 HBC Monitoring in the Little Colorado River

 Natal Origins RBT Marking Trip
Natal Origins/Juvenile Chub Monitoring
Natal Origins – Rainbow Trout Data

April, 2012 July, 2012 September, 2012

Reach Catch pCap N/km Catch pCap N/km Catch pCap N/km

I (Lees Ferry) 4,421 0.08 6,952 4,405 0.04* 14,213* 5891 - -

II (~ 20 Mile) 3,945 0.07 6,852 3,961 0.1 3,860 7,810 - -

III (~ 40 mile) 2,689 0.13 2,313 2,730 0.14 2,375 3,938 - -

IVa (Upstream 

LCR) 376 0.21 352 428 0.19 479 437 - -

IVb (Downstream 

LCR) 55 0.17 90 99 0.21 98 79 - -

Total 11,486 11,623 18,155

(Preliminary Data from Korman et al. 2012, Unpublished)

(*Estimates of pCap and density 

affected by equipment issues)
Mainstem Juvenile Chub Monitoring

(Preliminary Data from Korman et al. 2012, Unpublished)
Whirling Disease & Implications

(Figure from Elwell et al., 2009)
Biology and Key Facts

 Only infects salmonids and Tubifex tubifex

 Rainbow trout highly susceptible; brown 

trout carry parasite, usually asymptomatic

 Young, small fish most susceptible; 

resistance increases with age and growth

 One infected fish can carry millions of 

myxospores
Environmental Factors

 Triactinomyxon production highest at 10-15 °C

 Silt and clay best habitat for T. tubifex and 

triactinomyxon production

 T. tubifex abundance associated with high 

levels of organic material 

 Scouring flows displace T. tubifex and habitat

(Images from Elwell et al., 2009)
Management Actions and Risk of 

Spreading Whirling Disease

 Live removal and relocation of trout – high 

risk of spreading disease

 Colorado River trout population infected

 Millions of myxospores per infected fish

 No treatment once infected
Management Actions and Risk of 

Spreading Whirling Disease

 High-Flow Experiments – low risk of 

spreading disease

 Downstream spread already occurring – fish 

movement and drift of triactinomyxons

 Flushing flows disrupt parasite’s life cycle – 

displace T. tubifex, scour out fine sediments and 

organics preferred by worms

 Lower infection prevalence and severity at higher 

flows 

 Mostly larger, older trout downstream – more 

resistant to disease
Questions?