Aquatic food base resea

monitoring—what do w

and what don’t we kn

Theodore Kennedy

Aquatic Ecologist

Grand Canyon Monitoring and Resea
Outline

• What do we know?

– Why conduct research/monitoring of a

base?

– What is the aquatic food base?– Downstream and seasonal patterns of 

base components

– Effects of fluctuations, MLFF, BHBF

volume shifts on food base componen

• What don’t we know?

– Problems/Limitations of past approach– PEP & SA recommendations
What do we know

•

Why should we study the aqua

base?

•

What is the aquatic food base?

•

Downstream and seasonal patte

important food base componen

•

Effects of fluctuations, MLFF, 

monthly volume shifts on food components
Why should we study the 

foodbase?

“...food is almost always the critic

that ultimately limits [animal] pdensity in a given habitat.” (Kr
Why should we study the 

food base?

•

Recent trends for fish in the Co

River may be due in part to chafood availability and/or quality

–

Decline in condition of humpbac

(Meretsky

and others 2000)

–

Decline in condition of LF rainb

(McKinney and others 2001) 
Why should we study the 

food base?

•

Understanding spatial and temp

variability, and what controls/lavailability, of food is critical tdetermining what controls nativnative fish density in the Color
What is the Aquatic Foo

Angradi

1994, McKinney and others 2001,

Shannon and others 1994, 

Valdez and Ryel 1995, StHaden and others 1999, Y

Algae

Gammarus

Rainbow Trout

Simuliids

Rainbow Trout

Chironomids

New Zealandmudsnail

X

Leaf litter

Hu

Chirono

mids

Lees Ferry Colorado River at LCR 

Ga
Downstream and Sea

Patterns—Bentho

What’s missing?

Allochthonous material/Particulate Organic Matter

Simuliids
Downstream and Sea

Patterns—Bentho
Downstream and Sea

Patterns—Drift

Composition of drift shifts from algae to terrestrial 
Downstream and Sea

Patterns—Drift

Downstream increase in Fine POM (food for b
Downstream and Sea

Patterns—Drift

•

Unclear whether/what seasonal 

exist in invertebrate drift

–

Some found drift density of inve

spring (McKinney and others 1999)

–

Others found invert drift density 

in summer and lowest in winter a

(Leibfrie

d and Blinn 1987, Blinn

and others 1994, S

hann
Effects of Fluctuations on F

Components
Effects of Fluctuations o

Base Components—Alg

Invertebrates

•

Even short periods of exposure 

reductions in algae and invertemass/density

•

Recovery of snails following e

occurs quickly (~1week), but aother invertebrates take considlonger to recover (>4months)
Effects of Fluctuations o

Base Components—D

•

Particulate Organic Matter (PO

–

Mass flux of POM increases w/ d

concentration unrelated to discha

Kubly 1994, Benenati and others 2001)

–

Ramping rate has no effect on dr

(Shannon and others 1996)
Effects of Fluctuations o

Base Components—D

Density of Gammarus in drift increases during 

limb of hydrograph

Low Ascend Peak De

Stage

Gammarus density (#/m3)
Effects of MLFF on Foo

Components

By increasing minimum discharge and restrict

fluctuations, MLFF most likely increased of algae and invertebrates

B
1996 BHBF Effects on 

Base Component

BHBF had short term and minor impact on algae and invBut, trout stomachs actually contained more food after fl
• Quantify organic matter and inve

drift at LCR confluence (Yard an

• Quantify algae production in Gle

using methods employed by Marothers (1999) during ’96 (Kenneothers)

• Results will be presented at Oct. 

Science Symposium

2004 BHBF Effects on 

Base Components—Ap
Effects of Shifts in Mo

Volumes on Food Base Com

• Large increase in monthly volume

–

Short-term reduction in algae productivi

•

Nearshore

algae and inverts suddenly under 

water = less light

–

Long-term increase in algae standing ma

•

More surface area available for algae and in

• Large decrease in monthly volume

–

Abrupt decrease in algae and invertebrat

– If new high water is less than old low w

10k cfs, new high = 8k cfs), large quantibehind 
What do we know—Con

•

Algae drives food web in LF. Down

•

Gammarus and midges dominant fo

LF, Simuliids

dominant food item f

and trout downstream

•

Algae and invertebrate mass decrea

downstream

•

Abundance of allochthonous detritu

simuliids

increases downstream
What do we know—Con

•

MLFF probably led to greater food 

•

1996 BHBF had short-term negativ

food base standing mass, but trout factually increased

• Large shifts in monthly volume pro

abrupt decreases in food quantity, odecreases in algae production, and/significant quantities of food behind
What don’t we kno

•

Problems/Limitations of past a

•

PEP & SA recommendations
Recent Research & Moni

Problems/Limitatio

•

Very little statistical power to detec

•

Algal standing crop is a poor proxy 

production

–

interpretation of data complicated by a

differences in invertebrate consumptio

•

Algae probably not a good indicato

availability across the entire CRE cdownstream increase in POM
Recent Research & Moni

Problems/Limitatio

•

We don’t know what the food base is at s

downstream from LF!

–

What is the relative contribution of allochthonous 

RBT production at downstream sites?

–

How does it vary over space and time?

–

Is it from tributary floods or mainstem riparian veg

–

Is algae locally derived or imported from LF?

•

Answers will determine the kinds of man

actions we could employ to increase food 

– If algae is the most important carbon source at dow

sediment augmentation would reduce already limit

– If allochthonous material is important at downstrea

cfs, or greater, flows could be used to capture this 
PEP & SA Recommend

“The food base program needs to be criticbecause the current level of understandinlinkages between lower trophic

levels and 

availability of native fishes is not adequafood base data in relation to the managemPEP 2001

Bottom line—we don’t know what the food ba

downstream sites.
PEP & SA Recommend

“Since there are scientific as well as statistical unassociated with any approach for studying the relto trends in abundance of fish populations the besa fully integrated one, utilizing data on the abundavailable to fish in the CRE, the apparent food hastomach content analysis, and indicators from the including isotopes, growth and condition, and bodPEP 2001

Bottom line—don’t just measure trends in lower trophic

out what foods are available, what fish are actuallwhether food availability/quality is affecting fish etc.
PEP & SA Recommend

“3.c. It is recommended that GCMRC draft an RFFY 2005 on aquatic food base science activity. Tshould identify a specific research effort for immedetermines most efficient and useful approaches fmonitoring/trends of the aquatic food base. This involve stable isotope analysis of food web [linkatrophic

base (detritus, algae) to invertebrates, to f

would help identify the energetic base in this systat higher trophic

levels”—SA Review of Food Ba

Bottom line—Determine what the aquatic food base is, 

what the most appropriate monitoring metrics are
Conclusions

• Previous research 

– Documented downstream and seasonal pattern

foodbase components

– Documented impacts of fluctuations and BHB

basis for speculations on MLFF and monthly 

– Resolved trophic linkages at LF

• Future directions

– Integrated research that will clarify trophic lin

downstream locations

– Will provide the basis for developing new mo

that accurately characterize availability of fooand non-native fish in the CRE
What is the Aquatic Foo

Algae

Gammarus

Rainbow Trout

Simuliids

Rainbow Trout

Chironomids

New Zealandmudsnail

X

Leaf litter

Hu

Chirono

mids

Lees Ferry Colorado River at LCR 

Ga
PEP & SA Recommend

“3.f. These new proposed [research direcweb analysis using multiple stable isotopare significantly complex, especially whewith the vagaries of the research environmstrongly believe that input from a mid-calevel ecosystem ecologist needs to be avaGCMRC staff, either through the RFP prpossibly as a staff position.”—SA Review Program 2004.

Bottom line—Conducting this research via a c

process will allow us to get high quality rsubstantial input from experts in the field