Efficacy of a New Acoustic Tag Designed to Indicate Occurrence of a Predation Event

Andrew Schultz PhD, Reclamation Virginia Afentoulis, CA DWR

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

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

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.”

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

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

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

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

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

Results Trigger Time by Subject (ordered by size)

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

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

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

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