Predation and Gut Evacuation Rates

as Measured by Acoustic Tags in the

Tracy Fish Collection Facility Primary Channel

Andrew Schultz, PhD (Reclamation) and Kevin Kumagai (HTI)

Overview

• Sacramento-San Joaquin Delta - several salmonid

species are listed as threatened or endangered

• Acoustic telemetry - powerful tool to study movement

and survival of juvenile salmonids

• Predation may lower salmonid survival and confounds

ability to adequately assess acoustic data

• Evacuation rate or time taken by an acoustic tag to pass

through the digestive tract of a predatory fish is largely

unknown

Objective

• Proof of concept experiment to determine the rate free

swimming predatory fish digestively pass acoustic tags

that were implanted in Chinook salmon

Methods

• Tags (0.5 g) removed from recaptured fish used in the Tracy Loss

Study (Karp et al, In prep)

Methods

• Tags reprogrammed for this proof of concept experiment

(Kumagai, In prep)

Methods

• Deployed acoustically-tagged dead chinook salmon via a binder clip

and a fishing pole (n=14) (Schultz et al, In prep)

Methods

• Acoustically-tagged striped bass in primary channel as part of the

Tracy Loss Study (n = 7) (Karp et al, In prep)

Methods• Verified predation time via 2-dimensional tracks and detection signal

DEPLOYED

Tagged salmon

separate from

striped bass

(6/21/13 10:20)

CONSUMED

Simultaneous tag

tracks in striped bass

and salmon

(6/21/13 10:20-10:25)

Methods• Verified tag evacuation time via 2-dimensional tracks and detection signal

IN GUT

Simultaneous tag

tracks in striped bass

and salmon continues

for almost 2 days

(6/23/13 9:10-9:15)

EVACUATED

Moving as two

separate tags after

(6/23/13 9:15:39)

Verified tag evacuation times via detection signal patterns:

single hydrophone (Kumagai, In Prep)

IN GUT EVACUATED

Methods

Verified tag defecation times via detection signal patterns:

multiple hydrophones (Kumagai, In prep)

IN GUT EVACUATED

Methods

Results

• Mean tag evacuation time was 1.8 days

(n = 14, SD = 0.49, range = 1.2 to 2.7)

• Mean FL of tagged salmon was 146.6 mm

(n = 14, SD = 7.6, range = 131 to 165)

Salmon Length vs Days to Tag Evacuation

130

140

150

160

170

1 2 3

Fo

rk L

en

gth

(m

m)

Days to Tag Evacuation

Tagged striped bass (2897.18) was 2.53 kg and 588 mm FL

when released on 5/2/2013

2 days (average) to evacuate

tag within 157 mm FL salmon

Tagged striped bass (2729.18) was 1.59 kg and 505 mm FL

when released on 5/3/2013

1.4 days to evacuate tag

within 145 mm FL salmon

Same defecation time but consumed 32 minutes apart

2.7 days (average) to evacuate

tag within 142 mm salmon

Mean tag evacuation time was 1.8 days.

Mean tagged salmon was 147 mm FL.

Summary / Discussion

• Mean tag evacuation time was 1.8 days (n = 14, SD = 0.49, range

= 1.2 to 2.7) across a naturally variable water temperature ranging

from 23 to 26oC during the study.

• Evacuation times for this study appear much shorter than times for

predation tags (1.1 g) in relatively sedentary laboratory fish held in

16oC water (Schultz et al, in prep)

• High confidence in ability to confirm predation and measure the

rate at which free swimming predatory fish digestively pass

acoustic tags that were implanted in Chinook salmon

• As a result of this proof of concept experiment, the Bureau of

Reclamation is collecting similar data in the primary channel at

different temperature and food availability levels

References

• Ehrenberg, J. E. and T.W. Steig. 2009. A study of the relationship

between tag-signal characteristics and achievable performances in

acoustic fish-tag studies. ICES Journal of Marine Science, 66:

1278–1283.

• Karp, C., A.A. Schultz, B. Wu, and J. Israel. In prep. Evaluation of

Chinook Salmon and Central Valley Steelhead Facility Losses at the

Tracy Fish Collection Facility. Bureau Of Reclamation.

• Kumagai, K.K. In prep. Acoustic tag detections and tracking of fish

predation and acoustic tag defecation at the Tracy Fish Collection

Facility in 2013. Report to Bureau of Reclamation, Byron, Calif., by

Hydroacoustic Technology, Inc., Seattle, Wash.

• Schultz, A.A., V.B. Afentoulis, K.W. Clark, and B.B. Bridges. In prep.

Evacuation Rates of Acoustic Tags in Striped Bass. Bureau of

Reclamation.

Acknowledgments

• Reclamation

Brent Bridges, Cathy Karp, Scott Porter, Rene

Reyes, Mike Trask, Brandon Wu

• CA–DWR

Virginia Afentoulis and Kevin Clark

• HTI

Sam Johnston and Colleen Sullivan

Questions

Removal of fish from the nets (BOR, unpublished data)

Striped bass, 6/21/13 10:05-10:10

Tagged striped bass (red spheres) in primary channel. Data courtesy of

BOR.

Striped bass, 6/21/13 10:10-10:15

Tagged striped bass (red spheres) in primary channel. Data courtesy of

BOR.

Predation, 6/21/13 10:15-10:20

Tagged striped bass (red spheres) consumes dead chinook (blue

spheres) approximately 6/21/13 10:20. Data courtesy of BOR.

Simultaneous tags, 6/21/13 10:20-10:25

Two tags are simultaneous for almost two days. Data courtesy of BOR.

Simultaneous tags continues for almost two

days, 6/23/13 9:10-9:15

Simultaneous tags together for almost two days. Data courtesy of BOR.

Tag defecation, 9:15-9:20

Chinook tag (blue spheres) defecated approximately 6/23/13 9:15:39.

Data courtesy of BOR.

Separate tags, 9:20-9:25

Striped bass continues moving around primary channel while chinook

tag stationary. Data courtesy of BOR.

Separate tags, 9:25-9:30

Striped bass moving around primary channel while chinook tag

stationary. Data courtesy of BOR.

Separate tags, 9:30-9:35

Striped bass continues moving around primary channel while chinook

tag stationary. Data courtesy of BOR.

Separate tags, 9:35-9:40

Striped bass continues moving around primary channel while chinook

tag stationary. Data courtesy of BOR.

Separate tags, 9:40-9:45

Striped bass continues moving around primary channel while chinook

tag stationary. Data courtesy of BOR.

Predation and simultaneous tags summary

Downstream

Upstream

Barrier

Time Slider

Steelhead 2D positions(green)

Striped bass 2D positions(red)

Sun and moon gadget

Tagged striped bass (red spheres) consumed tagged dead chinook (blue

spheres) and the two tags swim simultaneouly for almost two days. Data

courtesy of BOR.

Defecation Summary

Data courtesy of BOR.

Single hydrophone: tag defecation

Time duration 1 hour

Multiple hydrophones: tag defecation

Time duration 1 hour