Andrew Schultz, Virginia Afentoulis California Department of Water Resources Prototype HTI acoustic predation tags designed to indicate an acoustic tagged fish had been eaten by a predator were tested by DWR and Reclamation staff at the Tracy Fish Collection Facility’s Tracy Aquaculture Facility. Six adult striped bass (> 400 mm FL) were each sequentially fed ten Chinook salmon with implanted predation tags. Initial feeding time to predation tag activation time, was recorded for 54 of the 60 predation tags (6 tags failed to activate). Average time for a tag to activate was 57:30:59 (range: 22:18:00 to 140:01:00). Control predation tags (tags turned on but not in predation indication mode) were surgically implanted in to two groups of ten control Chinook salmon. The control Chinook salmon were held for at least 30 days post‐surgery to check for effects of the predation tag on fish health and recovery from surgery. There were 3 mortalities within 2 weeks after the surgical implantation. There were no false positives in the control fish, meaning that the tags did not activate in the target species. Predation tags are a promising new technology for determining the fate of acoustically‐tagged salmonids. Once field tested, these tags could be used in many applications to understand the magnitude of predator impacts on salmonids near manmade structures.

1. Efficacy of a New Acoustic Tag
Designed to Indicate Occurrence of
a Predation Event
Andrew Schultz PhD, Reclamation
Virginia Afentoulis, CA DWR

2. Acoustic Telemetry Technology
• Advancements have generally followed those
of the electronics field
• Reduction in tag size, improving detection
range and tag life, continues to be primary
objective of innovation
• Widespread and proven tool to study
salmonid behavior and survival

3. What’s the problem?
• Predation on acoustic-tagged fishes may be
high
• Are data from the tagged-fish or inside a
predator?
• Common methods used to determine fates of
acoustic-tagged fish are problematic and
unproven
• High priority, often costly projects, are
providing potentially inaccurate data for use
toward management, conservation and
regulatory actions/decisions

4. Led Vogel (2011) to conclude:
“Until this critically important issue is
resolved, it is recommended that
acoustic telemetry studies on juvenile
salmon to estimate fish survival over
long Delta reaches be postponed until
the problem can be reliably resolved.”

5. Solutions…Predation Tag?
• Need a tag that can identify an acoustic-
tagged fish has been eaten by a predator
• In 2013 HTI developed a prototype
Predation Tag
• Based on digestion
• Similar in size, shape and weight (1.3 g) to
normal acoustic tags used for juvenile
salmonids

7. Objectives
• Evaluate the efficacy of HTI’s Predation Tag
• Quantify time required for Predation Tag to
indicate a predation event has occurred
• Compare results within and between test
subjects

8. Methods
• Experiments conducted at the Tracy Fish Collection
Facility’s Tracy Aquaculture Facility
• 6 adult striped bass (512 – 688 mm FL) used as
subjects
• Held in 711 L tanks on the same indoor recirculating
system at 16C
• Trained to eat on demand via a tether system
• Each striped bass was sequentially fed 10 live
juvenile Chinook salmon surgically implanted with
the new Predation Tag
• Control group – 20 juvenile salmon surgically
implanted with new Predation Tag and held for 30
days

9. Methods
• Hydrophones placed in each tank
• Predation Tags continually monitored for a
change in signal using an HTI Acoustic Tag
Receiver
• Data processed using HTI Mark Tags software
• Mixed-model univariate method of analysis to
test for between and within subject effects

10. Results
• 54 of 60 tags ‘triggered’ as intended
• Overall mean trigger time was 59.3 hr
(SD = 28.1; range = 22.3 to 140)
• No difference in trigger time within (P = 0.89)
or between (P = 0.93) subjects
• No significant trend in trigger time with
respect to subject size was observed within
the size range tested
• Control group had no false positives

11. Results
Trigger Time by Subject (ordered by size)

12. Discussion / Management Implications
• Efficacy of Predation Tag
• Impact of Predation Tag
• Improvement of Predation Tag
• Further expenditure of resources and effort
toward development of this and similar
technologies
• Acoustic tag technology featuring a method to
determine if tag was consumed, will likely
become the new standard

13. Recommendations
• Shorten length of time and improve precision
at which tag ‘triggers’
• Tag life, size and range should come in line
with current non-predation tags
• Further efficacy testing warranted as tag
modified
• Test efficacy in field setting
• Test relationship of trigger time and
evacuation rate across variables such as
temperature, food, predator size and species

14. Acknowledgements
• Curtis Yip and Nikki Johnson (CA-DWR)
• Kevin Clark (CA-DWR) and Brent Bridges (Reclamation)
• Tracy Technical Advisory Team: Carl Dealy, Donald Portz,
Zachary Sutphin and Connie Svoboda
• Reclamation Staff: Scott Porter, Mike Trask, Rene Reyes,
Brandon Wu, Terry Bartlett, Domingo Sanchez,
Thomas Walden and Joel Imai
• CA-DWR Staff: Oliver Patton, Laura Rudolph, Elaine Jeu,
Benjamin Martin, Kendall Pegan, Jamie Suria, Don Santos
and Bryce Kozak
• HTI Staff: Kevin Kumagai, Sam Johnston, Patrick Nealson,
Barbara Rowdon, Scott Hemmings and Caroline Mercado

15. Acknowledgements
• Curtis Yip and Nikki Johnson (CA-DWR)
• Kevin Clark (CA-DWR) and Brent Bridges (Reclamation)
• Tracy Technical Advisory Team: Carl Dealy, Donald Portz,
Zachary Sutphin and Connie Svoboda
• Reclamation Staff: Scott Porter, Mike Trask, Rene Reyes,
Brandon Wu, Terry Bartlett, Domingo Sanchez,
Thomas Walden and Joel Imai
• CA-DWR Staff: Oliver Patton, Laura Rudolph, Elaine Jeu,
Benjamin Martin, Kendall Pegan, Jamie Suria, Don Santos
and Bryce Kozak
• HTI Staff: Kevin Kumagai, Sam Johnston, Patrick Nealson,
Barbara Rowdon, Scott Hemmings and Caroline Mercado