Report of the

National Marine Fisheries Service

Workshop on Advancing

Electronic Tag Technologies and

Their Use in Stock Assessments

August 23–25, 2005

Pete Sheridan, John W. Ferguson, and Sandra L. Downing, editors

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

NOAA Technical Memorandum NMFS-F/SPO-82

Report of the

National Marine Fisheries Service

Workshop on Advancing Electronic 

Tag Technology and Their Use in Stock 

Assessments

August 23–25, 2005

Pete Sheridan, John W. Ferguson, and Sandra L. Downing, editors

NOAA Technical Memorandum NMFS-F/SPO-82

June 2007

U.S. Department of Commerce

Carlos M. Gutierrez, Secretary

National Oceanic and Atmospheric Administration

Vice Admiral Conrad C. Lautenbacher, Jr., USN (Ret.)

Under Secretary for Oceans and Atmosphere
ii

Suggested citation:

Sheridan, P., J. W. Ferguson, and S. L. Downing (editors). 2007. Report of the National 

Marine Fisheries Service Workshop on Advancing Electronic Tag Technology and 

Their Use in Stock Assessments. U.S. Dept. Commerce, NOAA Tech. Memo. NMFS- F/SPO-82, 82 p.

A copy of this report may be obtained from:

Northwest Fisheries Science Center

2725 Montlake Boulevard East

Seattle, Washington 98112

Or online at:

http://spo.nmfs.noaa.gov/tm/
iii

Contents Introduction

Workshop Recommendations

Acoustic Tags

1 Using Acoustic Tags for Life History Studies of the Red King Crab 

Near Kodiak, Alaska

Peter A. Cummiskey and Eric Munk

2 Acoustic Tagging of Green Sturgeon

Steve Lindley and Mary Moser

3 Using Acoustic Telemetry to Document English Sole Movements: 

Application to Management of Contaminated Sediments

Mary Moser, Mark S. Myers, Steve L. Katz, Sandra M. O’Neill, Stephen 

R. Quinnell, and James E. West

4 Developing Shallow-Water Acoustic Telemetry Methods for 

Juvenile Snapper Habitat Studies in the Florida Keys National Marine 

Sanctuary

Samantha Whitcraft, Lisa Pytka, Bill Richards, John Lamkin, Trika 

Gerard, Tom Carlson, Geoffrey A. McMichael, Jessica Vucelick, and 

Greg Williams

5 Tag Effects Considerations in Electronic Tagging Studies

R. Lynn McComas, Brad Ryan, and Geoffrey A. McMichael

6 Unmanned Underwater Vehicles for Fish and Marine Mammal 

Shadowing and Data Acquisition: A Concept

Earl F. Prentice and R. Lynn McComas

7 Movements of Yellowfin and Bigeye Tuna in a Network of Fish 

Aggregating Devices as Determined by Acoustic Telemetry

Kim Holland, David Itano, and Laurent Dagorn

Pop-up Tags

8 Status of the Argos Joint Tariff Agreement

Stephen Auer

9 Acoustic, Archival, and Pop-up Satellite Tags and Large Pelagic 

Fishes: A 30-Year Perspective

Richard Brill and Michael Musyl

10 Evaluation of Pop-up Archival Transmitters to Determine Cause 

of Failure for Satellite Transmitters Deployed on Pacific Leatherback 

Turtles

Scott R. Benson and Peter H. Dutton

11 Pop-up Archival Transmitting Tags and Their Application to 

Loggerhead Sea Turtle Survival Studies

Sheryan Epperly, Christopher Sasso, Eric Prince, Carlos Rivero, Alan 

Bolten, Jeanette Wyneken, Joseph Flanagan, and Craig Harms

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12 Combined Use of PAT and SPOT Tags to Study Three-Dimensional 

Habitat Use Patterns of Shortfin Mako Sharks

Suzanne Kohin and David Holts

13 Shark Research in the Gulf of Alaska with Satellite, Sonic, and 

Archival Tags

Dean L. Courtney and Lee Hulbert

14 PSAT Performance and Metadata Analysis Project

Michael Musyl, Geoff Arnold, Michael Domeier, Molly 

Lutcavage, Lianne McNaughton, Yonat Swimmer, Steve Wilson, 

and Richard W. Brill

Radio Tags

15 Utilizing Radiotelemetry to Investigate Passage Behavior and 

Survival of Juvenile Salmonids in the Columbia River Basin

Gordon A. Axel, Eric E. Hockersmith, Byron L. Iverson, Samuel 

L. Rambo, Darren A. Ogden, and Douglas B. Dey

16 Automated Telemetry Data Retrieval and Organization

Brian J. Burke, Bruce F. Jonasson, Eric E. Hockersmith, Kinsey E. 

Frick, Gordon A. Axel, Byron L. Iverson, Samuel L. Rambo, Mark 

A. Kaminski, and Ron L. Helgeson 

17 Failure Modes of Dorsal Fin-Mounted Small Cetacean Telemetry 

Tags

Aleta A. Hohn, M. Bradley Hanson, Forrest Townsend, Frank 

Deckert, and Tiu Similä

18 Foraging Studies of Hawaiian Monk Seals Using Satellite-Linked 

Depth Recorders

Charles L. Littnan and Brent S. Stewart

19 Combination of Satellite Telemetry and Molecular Genetic Analysis 

in the Study of Beluga Whales in the Western Nearctic

Greg O’Corry-Crowe, Robert Suydam, Jack Orr, Lloyd Lowry, 

Kathy Frost, Dennis Litovka, and Rod Hobbs

Archival Tags

20 Documenting Elephant Seal Movement with a Geographic 

Location, Time-Depth Recording Archival Tag

Robert L. DeLong, Sharon Melin, Brent S. Stewart, and Roger D. 

Hill

21 Archival Tagging of Salmonids on the Central California Coast

Sean A. Hayes, Ellen V. Freund, Chad V. Hanson, Morgan H. 

Bond, and R. Bruce MacFarlane

22 Archival Tagging of Atka Mackerel, Pacific Cod, and Flatfish in the 

Aleutians, Gulf of Alaska, and Eastern Bering Sea

Dan Nichol

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23 Application of Electronic Data Storage Tags in Studies of Black Sea 

Bass and Yellowtail Flounder in the Northwest Atlantic

Joshua Moser, Gary Shepherd, Steve Cadrin, Azure Westwood, 

and Stacy Kubis

Linkages between Tagging and Environmental Data

24 Hypoxia-Based Habitat Compression of Tropical Pelagic Fishes

Eric D. Prince and C. Phillip Goodyear

25 Kuroshio Extension Current Bifurcation Region: A Pelagic Hotspot 

for Juvenile Loggerhead Sea Turtles

Jeffrey J. Polovina, George Balazs, Evan Howell, Itaru Uchida, 

Denise Parker, and Peter H. Dutton

26 Merging Satellite Telemetry with Oceanographic and Archival Tag 

Data to Assess Foraging Ecology of Alaskan Pinnipeds

Jeremy T. Sterling, Rolf Ream, Brian S. Fadely, and Tom Gelatt

27 Spatial Patterns of Juvenile Stellar Sea Lions at Sea with Respect to 

Corresponding Patterns of Environmental Features

Michelle E. Lander, Jeremy T. Sterling, and Brian S. Fadely

28 Critters in Context: A Method for Integrating Tag Data with Other 

Environmental Information

David G. Foley and Lynn deWitt

29 Seasonal Movements and Habitat Use of Dall’s and Harbor 

Porpoises in the Inland and Coastal Waters of Washington State as 

Determined by Radiotelemetry

M. Bradley Hanson

30 Assessing Habitat Use and Movement Patterns of Coastal Sharks 

with an Automated Acoustic Telemetry System

John K. Carlson, Michelle Heupel, and Colin Simpfendorfer

Stock Assessment and Ecosystem Applications

31 Potential Role of Electronic Tags in Stock Assessments

Richard D. Methot

32 How Can Pinniped Telemetry Data Fit into Fisheries Management? 

Examples from Stellar Sea Lions and Northern Fur Seals in Alaska

Brian S. Fadely, Lowell Fritz, Jeremy T. Sterling, Rolf Ream, and 

Shane Capron

33 Using Information from Electronic Tags for Stock Assessment of 

Northeast Fishery Resources

Steven Cadrin, Gary Shepherd, Tim Sheehan, Stacy Kubis,

Joshua Moser, and Azure Westwood

34 Using Location Data from Telemetry Tagged Marine Mammals to 

Improve Stock Assessments

M. Bradley Hanson

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35 Using Archival Tagging to Better Understand Stock Structure and 

to Develop Habitat-Based Models for North Pacific Albacore

Suzanne Kohin and John Childers

36 Virtual Population Analyses of Atlantic Bluefin Tuna that Include 

Information from Electronic Pop-up Tags

Clay E. Porch

37 Using Electronic Tags in Marine Mammal Stock Assessment 

Reports

Robyn P. Angliss and Ray Outlaw 

Breakout Session Summaries

Acoustic Tags

Pop-up Satellite Tags

Radio Tags

Archival Tags

Recent NMFS Publications and Reports Derived from Electronic 

Tagging

Workshop Attendees

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On 23–25 August 2005, the National Marine Fisheries Service (NMFS or NOAA 

Fisheries Service) Advanced Sampling Technology Working Group (ASTWG) 

sponsored a workshop at the Northwest Fisheries Science Center (NWFSC) in Seattle. 

The intent of the workshop was to advance the use of electronic tagging technologies 

and the scientific data gathered through these technologies, and to improve fisheries 

stock assessments and the implementation of ecosystem-based management strategies. 

The overall goal was to develop a list of recommendations for improving tagging 

technologies that would be submitted to the ASTWG for future funding. The specific 

goals were to 1) identify present and future research needed to improve electronic 

tagging technologies, 2) discuss specific data management requirements for each 

technology, and 3) develop ways to improve how tagging and environmental data are 

incorporated into stock assessments.

Approximately 80 scientists from the NOAA Fisheries Service attended the workshop. 

Vendors were specifically excluded from the workshop so that scientists could openly 

share their experiences using the various technologies. The workshop was organized 

into two days of researchers giving presentations of their experiences applying the 

various technologies. The presentations were grouped into the following sessions:

 • acoustic tags,

 • pop-up tags (including pop-up satellite tags),

 • radio tags,

 • archival tags,

• linkages between tagging and environmental data, and

 • stock assessment and ecosystem applications.

A third day was devoted to smaller breakout sessions that were organized by type of 

tagging technology (acoustic, pop-up, radio, and archival) and animals (pinnipeds, 

cetaceans, turtles, pelagic fish, bottom fish, and invertebrates).

Electronic tagging is a key methodology NOAA Fisheries Service scientists use 

to gather information on stock productivity and recruitment, fish behavior and 

feeding ecology, habitat selection, and individual and population-level responses 

to environmental and climate variability. This information is needed for accurate 

and responsible fisheries management. The workshop highlighted the cutting-edge 

nature of these technologies. In many cases, scientists are just at the beginning stages 

of developing electronic tagging techniques to sample animals in their habitats in 

real time; to address specific questions about patterns of vertical, diel, and feeding 

movements; and to identify intra- and interspecific behavioral differences. Obtaining 

more detailed information on habitat selection at smaller time scales and linking this 

information to concurrently measured environmental parameters will greatly enhance 

knowledge of what species require to maintain their viability and productivity 

through time and in varying environmental conditions.

The workshop produced the following recommendations for the ASTWG to consider:

 • improve tag power management,

 • decrease tag size,

 • increase the use of sensors on tags,

 • improve the accuracy of geolocation data,

 • enhance data transmission capabilities between tags and receivers,

 • reduce biofouling on tags,

 • establish database sharing mechanisms and protocols,

 • increase tag and software reliability,

 • reduce tag costs through bulk purchases,

 • cosponsor an international tagging symposium with invited vendors,

 • improve collaboration and communication, and

 • develop a budget initiative within the agency to address the workshop 

 recommendations.

Workshop participants expressed an overwhelming appreciation for the information 

and lessons learned, and supported conducting similar workshops in the future. 

Introduction
2

These workshops could be held every 2 or 3 years, since electronic tagging 

technologies are developing and changing rapidly. Future workshops could also 

address specific topics such as the integration of environmental data into stock 

assessments, and the sharing of animal location and environmental databases.
3

Each tag type presents a unique set of requirements needed to improve the utility 

of the data developed from the technology. However, many recommendations 

were similar across tag types and the data that specific technology produced. We 

present these summary recommendations for ASTWG to consider as the next steps 

needed to enhance the effectiveness of how data on the environmental parameters 

of tagged individuals are gathered, so these important environmental variables 

can be incorporated into NOAA Fisheries Service stock assessments and resource 

management decisions.

Improve Tag Power Management

A universal theme across tag types was the need for improved power management 

and thus tag longevity, cost effectiveness, and data volume and quality. NOAA 

researchers should work with tag vendors to develop new methods of saving energy 

through use of active and passive energy management, using batteries developed for 

cold-water temperatures, developing batteries that are recharged by water flow or 

solar cells, and verifying tag performance prior to attachment without using battery 

life.

Decrease Tag Size

The need for smaller tags is highly dependent on the application and question being 

asked. As researchers ask more detailed questions about the biology and ecology of all 

life stages, there is a need for smaller tags that are placed inside an animal and more 

streamlined external tags.

Increase Use of Sensors on Tags

Understanding the environmental parameters animals select could be greatly 

enhanced by incorporating sensors into electronic tags and storing or transmitting 

the data. These data could include salinity, pressure (depth), compass/magnetic 

anomalies (general geolocation), light level (chlorophyll), ice thickness, and 

conductivity. Sensors could also be used to monitor the behavior and physiology of 

the tagged animal, including pitch, roll, dive, inactivity, and whether the individual 

has been preyed on.

Improve Geolocation

A common need is for increased precision of geolocation data. Developing costeffective, global positioning system (GPS)–based tags or acoustic listening tags and 

their support systems is a high priority.

Improve Data Transmission

Enhanced data transmission capabilities are needed to increase transmission rates 

so more data can be transmitted during brief surfacing periods or during haul 

outs, to allow two-way communication between tags and receivers (radio tags and 

arrays, pop-up tags and satellites), to limit transmissions to periods when receivers 

are within view or range, to develop communicating history acoustic transponding 

(CHAT) technology that would allow researchers to locate and track animals using 

transponding tags and retrieve data without recapturing the animal, and to develop 

enhanced wireless communication capabilities.

Reduce Biofouling

For externally attached tags, biofouling is a considerable problem. Tags made of 

antibiofouling materials are needed to reduce impacts to tag life and data accuracy.

Share Databases

Shared databases could create efficiencies for research. The workshop attendees 

recommended establishing a common site where environmental, habitat selection, 

and location data could be stored for use by stock assessment analysts. Creating 

this database would include developing software for merging different data sets and 

standardizing reporting criteria so that data can be merged. They also recommended 

that a data manager be hired to manage the site.

Workshop 

Recommendations
4

Increase Tag and Software Reliability, and Initiate Bulk Purchases with Vendors

In general, the relationship between NMFS and its vendors needs improvement. 

The reliability of tags and software needs to be enhanced to reduce the probability 

of tag failure and ensure data are not lost. Vendors typically replace defective tags, 

but this is a minimal cost of the study compared to lost opportunity, ship time, and 

personnel costs. Vendors need to warranty their products such that true costs are 

covered, not just tag costs, and an increased interaction with vendors is needed for 

them to understand and meet specific study requirements. Bulk purchasing across 

NMFS centers and line offices could result in reduced tag and equipment costs. This 

purchasing could be coordinated through the centralized database coordinator located 

in headquarters or one of the centers, as discussed above.

Improve Collaboration and Communication

Electronic tagging technology and data use changes rapidly. NMFS researchers 

agree that regularly scheduled internal workshops (every 2–3 years) are necessary 

for improved collaboration and information exchanges. An international tagging 

symposium that includes vendors and manufacturers is also needed, since the last 

such session was held in 1988 with U.S. Fish and Wildlife Service and American 

Fisheries Society sponsorship.

Develop a Budget Initiative

NMFS researchers recognize the value that data gathered from electronic tagging 

studies brings to the development of stock assessments and to agency resource 

management decisions. This value is reflected in the type of data collected, as well 

as the fact that data are collected in a cost-effective manner. Therefore, workshop 

participants strongly propose developing a budget initiative within the agency to 

address the recommendations produced from the workshop to advance and expand 

the effectiveness and utility of electronic tagging, and how this important sampling 

tool is used within NOAA Fisheries Service. To implement the initiative, it is 

recommended that in fiscal year 2007 the ASTWG provide funds to convene a team of 

scientists represented by each science center that will meet and develop the documents 

necessary for an electronic tagging budget initiative.
5

The red king crab (Paralithodes camtschaticus) has supported large 

commercial fisheries in North American and Asian waters. The fishery 

in Alaska peaked in 1980 and then declined abruptly, resulting in 

closures in most of the Gulf of Alaska. The sudden decline of red king 

crab generated considerable interest in habitat requirements and life 

history, particularly during the juvenile stages. After a brief larval 

period, crab settle to the bottom and spend the first year as individuals. 

In their second year crab start to aggregate, forming pods of hundreds 

to thousands of crab (Figure 1). Podding behavior continues 

throughout the juvenile stage and intermittently into adulthood.

The study area, Womens Bay, is a shallow semienclosed 18 km2

 estuary 

near Kodiak, Alaska. Womens Bay is considered a nursery area for 

red king crab and has supported populations throughout this period 

of decreased abundance. Before 1990, biologists at the NMFS lab 

in Kodiak used scuba observations to document the behavior and 

movements of pods of smaller juveniles nearshore, before they moved 

into deeper water where visual location proved impractical.

In 1990, we started to use acoustic tags, which allowed us to expand 

dive observations throughout Womens Bay, as well as track general 

movements of crab pods over time. When divers located a pod, several 

crab were collected, tagged on the surface, and returned. Sonotronics 

(Tucson, Arizona) CT-04-1 tags are used for smaller crab or CT-82-3 for 

larger. The tags were fixed to the crab carapace using marine epoxy 

(Sea Goin Poxy Quick, Permalite Plastics, Costa Mesa, California). 

Multiple tags are deployed to minimize chances that the pod is lost due 

to molting or mortality.

All tagged crab are located weekly with a Sonotronics USR-4HL surface 

receiver and DH-2 hydrophone from a small boat. GPS locations, date, 

time, depth, and tag numbers are recorded. Scuba observations are 

made at least weekly using a Datasonics (Cataumet, Massachusetts) 

DPL-275-H dive receiver. Crab numbers, activity, associations, bottom 

type, and depth are recorded. Crab are often collected, measured on 

the surface, and then released, providing information on pod dynamics.

A database using Microsoft Access was developed to track the 

data generated. All tables include, and are interrelated by, tag and 

deployment numbers. The four main tables are 1) sonic tags, which 

records tag release and recovery dates, crab size, sex, and the nature 

of tag loss; 2) location, which records tag locations, date, time, depth, 

and collocation with other tags; 3) dive summary, which records crab 

observations, numbers, activity, associations, bottom type, and depth; 

and 4) measurements, which records crab size, sex, and the shell and 

reproductive conditions.

Since 1990 we have tagged 190 crabs from 42 to 167 mm in carapace 

length and tracked them for an average of 157 days (Figure 2). The 

epoxy attachment has been highly reliable, with only a few tags 

that may have detached from the crab. The Sonotronics CT-04-1 tag 

detection range is limited, perhaps 100 m, but its size has allowed us to 

successfully track crab too small for a larger tag. The CT-82-3 tag, with 

a battery life of 48 months, is reliable and the signal strength does not 

diminish over time. We have used the same Sonotronics USR 4HL for 

12 years and had only a few shorts in the hydrophone wire that can be 

easily changed with minimal expense. The average detection range of 

this receiver and tag combination is about 400 m with a high degree of 

tag detection in often demanding conditions. We recover our lost tags 

Figure 1. A pod of aggregating 

juvenile red king crab. Pods 

range in size from hundreds 

to thousands of crabs. Divers 

located this pod in Womens Bay.

1

Using Acoustic Tags

for Life History Studies

of the Red King Crab

near Kodiak, Alaska

Peter A. Cummiskey and Eric Munk

Alaska Fisheries Science Center

Kodiak, Alaska

peter.a.cummiskey@noaa.gov
6

and have reused them up to six times. The tags may also 

be inexpensively fit with new batteries. We have been 

satisfied with both the equipment and service provided 

by Sonotronics.

We used our Datasonics dive receiver (Figure 3) after we 

located the tag from the surface. We have made 557 dive 

observations with this receiver. Tag detection range is 

40 to 50 m, but as the battery ages, this range gradually 

diminishes. Variable conditions and other aspects 

of a demanding dive environment often mask this 

range reduction, until it fails to detect tags all together. 

Equipment failures have occurred at critical times, for 

example, during molting seasons, when we tag newly 

molted crabs before old tags are shed in the molt. We 

have found the cost and, particularly, the turnaround 

time involved in repairing our receiver to be detrimental 

to our ongoing project.

We are working on two new subprojects using acoustictag equipment. First, we plan to combine acoustic 

tags with three Lotek LTD-1100 archival tags (Lotek, 

Newmarket, Ontario) to test an economical way to 

obtain continuous depth and temperature data on 

individual crab. Second, we hope to use PIT (passive 

integrated transponder) tags in podded crab to get 

better growth data. Dive observations have shown 100% 

molting of 3- and 4-year-old crab in the winter, while 

20% to 30% of the same crab also molt the following 

summer. This makes molting intervals and growth more 

difficult to assess as the crab age. We are starting live 

tank experiments using PIT tags on smaller crab to test 

mortality rates. If successful with small crab, we hope 

to PIT tag hundreds of podded crab and track them 

with acoustic tags to improve crab growth and molting 

information. It is not uncommon to double tag animals 

in order to track different kinds of information—in 

this case long-term data (PIT tags) and short-term data 

(acoustic tags).

Figure 2. An acoustic tag glued with marine epoxy onto the back of a 

king crab. The crab are returned to the crab pod.

Figure 3. A diver holding a Datasonics DPL-275-H 

dive receiver. Scuba observations are made at least 

weekly to monitor crab movements.

Overall, although we use basic equipment, it has proven 

to be reliable in a demanding environment. The size 

and protected nature of our study area is conducive to 

using basic equipment and makes our project feasible. 

Using direct scuba observations provides important 

data on crab life history, for example, when crab molt 

or how they die. Merely using surface tracking would 

otherwise miss this information. We dive on crab 

year-round, producing 3,122 tag locations, 557 dive 

observations, and 245 collections since 1990. Recently, 

we successfully followed a pod of a several thousand 

crab for over 4 years; we used 33 tags, and produced 900 

tag locations, 107 dives, and 66 collections. This resulted 

in a continuous record of growth of a single crab cohort, 

potentially allowing for better predictions of crab 

recruitment for management.
7

Green sturgeon (Acipenser medirostris) are of rising importance to NOAA 

Fisheries Service, with one distinct population segment (DPS) proposed 

as a threatened species under the Endangered Species Act (ESA) and 

the other DPS a species of concern. The lack of basic knowledge on 

population size, structure, and distribution severely hampers managing 

green sturgeon. Given their rarity, electronic tagging offers the most 

practical way to gain some of this information.

In 2002, we recognized that a number of studies of freshwater habitat 

use by green sturgeon could be leveraged to provide information on 

stock structure and movement among freshwater and coastal habitats. 

This was possible because many researchers on the west coast use 

Vemco (Shad Bay, Nova Scotia) acoustic tags and receivers with default 

frequencies and code maps. We supplied the existing projects with 

additional tags and receivers, initiated new tagging projects in estuarine 

areas where green sturgeon aggregate, and developed collaborations 

with people studying salmonids and rockfish from Monterey Bay 

to southeast Alaska (see Figure 1). Green sturgeon are an excellent 

subject for long-term acoustic tagging because they can carry a large 

tag that has extended battery life and their migrations are extensive but 

typically restricted to shallow depths on the shelf. With a shoestring 

budget and the goodwill of many people and agencies, we have been 

2

Acoustic Tagging

of Green Sturgeon

Steve Lindley

Southwest Fisheries Science Center

Santa Cruz, California

steve.lindley@noaa.gov

Mary Moser

Northwest Fisheries Science Center

Seattle, Washington

Figure 1. Map of the west coast 

of North America showing Vemco 

receiver locations for various 

agencies and sites where green 

sturgeon were tagged.
8

remarkably successful in describing movement among 

systems, patterns of migration along the coast, and the 

source of mixed stocks (Figure 2).

While we have learned much about green sturgeon 

from our work thus far, much more could be learned 

using this technology as the basis for more ambitious 

studies. Because acoustically tagged green sturgeon are 

readily “resighted,” mark-recapture studies are feasible 

with modest tagging efforts, compared to traditional 

approaches that require physical recapture of the fish. 

For example, the Cormack-Jolly-Seber capture-recapture 

model could be used to estimate survival rates from 

the temporal pattern of tag detections. Stage-based 

models of the tagged animals could be developed that 

could estimate movement rates among habitat types as a 

function of animal size or spawning history. Ultimately, 

a nonacoustic sighting component would be added to 

allow estimation of the tagging rate. With this kind of 

information, the complete dynamics of the population 

could be estimated with a multistage open population 

model.

The basic approach of using acoustic tagging and 

mark-recapture designs could be expanded to other 

species (such as salmon, sharks, other large coastal 

pelagics, and the more migratory groundfish) as part 

of the developing Pacific Coast Ocean Observing 

System (PaCOOS). A major goal of PaCOOS is to 

provide the information required for fishery resource 

management. The backbone of the system would be 

a series of hydrophone arrays along the continental 

shelf, extending and embracing the Pacific Ocean 

Shelf Tracking (POST) Project (formerly known as 

the Pacific Ocean Salmon Tracking Project). Such a 

system, combined with appropriate tagging, could 

allow accurate description of the temporal and spatial 

dynamics of populations at a resolution not achievable 

with other available technologies.

Figure 2. Researchers tagging a green sturgeon with a Vemco acoustic 

tag.

In addition to substantial funding, the long-term 

nature of such studies will require coordination of 

tag codes, receiver settings, and data sharing. Ideally, 

this coordination would happen through a neutral 

party. The Pacific States Marine Fisheries Commission 

(PSMFC) coded-wire tag and PIT tag systems might 

provide a useful model for managing acoustic tagging 

on a coast-wide scale. Similarly, managing a coast-wide 

receiver array is a major endeavor for which NOAA 

Fisheries Service is well suited, with its long experience 

with numerous and widespread coastal and open-ocean 

data buoys.
9

Assessments of estuarine and marine fish exposure to contaminated 

sites have traditionally relied on indirect evidence, such as the capture 

of sentinel species in these areas or the presence of high contaminant 

levels in various fish tissues. Along the Pacific Coast of North America, 

English sole (Parophrys vetulus) are used as a sentinel species because 

they are broadly distributed in benthic habitats where they would 

contact contaminated sediment. English sole are also an effective 

sentinel species because they seem to show high fidelity to feeding 

areas, migrating only in winter for spawning. Strong correlations 

between sediment polycyclic aromatic hydrocarbons (PAHs) and the 

prevalence of neoplastic and preneoplastic liver diseases in English 

sole collected from contaminated areas also suggest high site fidelity. 

However, the amount of time adult English sole spend in contaminated 

areas and the spatial extent of their summer feeding movements have 

never been assessed directly.

We tested the use of acoustic telemetry to document the time individual 

English sole spent in contaminated areas and whether they showed 

interannual fidelity to these sites. This work was conducted in Eagle 

Harbor, a small, PAH-contaminated embayment of Puget Sound

(Figure 1). This site was selected because it has been the subject of an 

ongoing study of sediment contamination and its effects on fish health. 

In 1994, a contaminated subtidal area of Eagle Harbor was covered with 

a cap of clean sediment (Figure 1). Subsequent testing for toxicopathic 

lesions and several direct measures of PAH exposure in English 

sole trawled from this embayment were used to determine whether 

remediation was successful. Now estimates of English sole home range 

are needed to more precisely link the degree of contaminant exposure 

with fish health. Acoustic telemetry in this small study area seemed to 

be a logical tool for documentation of English sole movements in and 

around contaminated sites.

3

Using Acoustic Telemetry 

to Document English Sole 

Movements: Application 

to Management of 

Contaminated Sediments

Mary L. Moser, Mark S. Myers, and

Steve L. Katz

Northwest Fisheries Science Center

Seattle, Washington

mary.moser@noaa.gov

Sandra M. O’Neill, Stephen R. Quinnell, 

and James E. West

Washington Department of Fish and Wildlife

Olympia, Washington

Figure 1. Aerial view of Eagle 

Harbor in Puget Sound with 

fixed receiver locations (red), 

mobile listening posts (yellow), 

trawl lines (white), and location 

of the sediment cap (light blue) 

denoted.

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10

Initial laboratory experiments in 2003 verified that 

acoustic transmitters could be surgically implanted into 

adult English sole without tag expulsion or negative 

effects on survival or feeding within the first month of 

tagging. In the summers of 2003 and 2004, we trawled 

adult English sole from Eagle Harbor and surgically 

implanted uniquely coded acoustic transmitters in 39 of 

the largest (>27 cm) fish. The transmitters (Vemco V8 

series, Shad Bay, Nova Scotia) were 9 × 30 mm cylinders 

weighing 5 g. We tested both high (147 decibels, or dB) 

and low (139 dB) power transmitters set at a variety of 

pulse intervals (20–60 s, 40–120 s, and 180–360 s).

After their release near the capture site, the sole were 

detected during periodic scans of set listening posts with 

a portable receiver (Vemco VR60) or by a continuously 

scanning array of underwater receivers (Vemco VR2) 

(Figure 1). We also tested use of a three-dimensional 

positioning system (Vemco VRAP, Vemco’s radio 

acoustic position system) to document small-scale (on 

the order of meters) sole movements. The positioning 

system was deployed in Eagle Harbor near the known 

locations of two English sole and two stationary 

transmitting beacons were also deployed nearby. 

Position information for the four targets was taken 

over a 24-hour period, with the hope of observing diel 

patterns of fish movement.

Surgical implantation of the transmitters seemed to work 

well, particularly in the second year when fish were 

allowed to recover from surgery in a submerged cage for 

several days prior to release. The fixed receiver arrays 

detected all but one of the English sole that exited Eagle 

Harbor and provided valuable information on the diel 

and seasonal patterns of fish movement. The low-power 

transmitters set at a 20–60 s pulse interval proved most 

useful. The low power reduced transmission collisions 

(which result in the inability to identify fish codes) and 

improved spatial resolution, while the shorter burst 

interval reduced the time needed to scan listening posts. 

In addition, these transmitters had an extended battery 

life, which allowed us to document the return of English 

sole to Eagle Harbor in the second and third summers of 

the project.

Our study was limited by the inability to develop 

accurate, high resolution (<100 m) maps of English sole 

home range from mobile tracking. The time-intensive 

process of scanning listening posts would have been 

easier with a receiver that automatically triangulates fish 

position (expensive). We needed daily or even hourly 

calibration of transmission range, due to the effects of 

passing algal blooms and ferry traffic in this acoustically 

challenging study area (time consuming). An automated 

system to conduct and incorporate these calibrations 

would result in more accurate home range delineation. 

Tag miniaturization would also allow study of a greater 

size range of English sole.

Downloading receiver arrays, which in some cases 

required dive operations, would have been eased by the 

addition of wireless communication with the receivers. 

Cell phone links would allow downloading from the 

laboratory and reduce the need for expensive boat and 

dive operations. The usefulness of data obtained from 

the fixed receiver arrays was constrained by the large 

(over one second per day) and unpredictable amount of 

drift in receiver time stamps. This is a common problem 

among logging receivers and should be remedied.

Finally, we were disappointed with the results from 

the VRAP system. In addition to the high cost of this 

equipment and the expertise needed to set it up, we 

found that its application was very restricted. The 

system was most accurate (+1.5 m) when stationary 

targets were inside the relatively small envelope 

of system reception (a triangle of 450 m on a side). 

Precision of stationary target location outside of this 

envelope was unsatisfactory (+60 m). Thus, the system 

was strongly dependant on the position of the fish, 

which move relative to the hydrophone array. Dynamic 

position referencing, via onboard GPS or referencing 

stationary pingers perhaps, would greatly improve 

the performance of systems like VRAP. Although this 

technology shows great promise, we did not pursue its

use further due to results of this trial. 
11

The background of this pilot project includes using high resolution 

inductively coupled plasma mass spectrometry (ICPMS) to establish 

an otolith “chemical signature” unique to Florida Bay that identifies 

juvenile snapper nursery areas of Florida Bay (Figure 1). This ongoing 

study provides an excellent spatial habitat context for our microacoustic 

tagging work in that the results separate subpopulations of juvenile 

snapper between broad nursery areas. Understanding foraging 

movements, home ranges, and habitat use patterns of these juvenile fish 

both within multihabitat protected areas, such as the Western Sambo 

Ecological Reserve (WSER) within the Florida Keys National Marine 

Sanctuary (FKNMS) and in single habitat-protected areas of Florida 

Bay, is essential to understanding the effectiveness of marine protected 

area (MPA) design and what habitat types, associated with healthy 

coral reefs and coral reef-dependent fish populations such as seagrass 

and mangroves (Rhizophora mangle), may need further ecosystem-wide 

protection in the future.

This pilot study supports the goal of increasing our understanding of the 

full life history habitat protection requirements for two recreationally and 

commercially important reef-associated snapper species, gray snapper 

(Lutjanus griseus) and yellowtail snapper (Ocyurus chrysurus), focusing on 

90–150-mm total length (TL) juveniles. The general approach is to begin 

a microacoustic tagging study that will use cutting-edge, customized 

microacoustic tagging technology to identify specific movement patterns 

of young-of-the-year gray snapper between home and foraging ranges 

associated with specific habitat areas both in the WSER and in selected 

similar habitat areas in Florida Bay. The end goal of the study is to 

establish acoustic arrays in these areas in order to collect data on the 

short- and long-term habitat-associated movements of young-of-the-year 

snappers via surgically implanted microacoustic tags.

Our study uses customized, coded microacoustic tags (5.5 × 19 mm, 

0.65 g dry weight, 0.39 g wet weight, 417 kilohertz [kHz]; see figure on 

page 15 for examples) and standard acoustic telemetry methodologies 

developed for juvenile salmonid survivorship studies. We will use 

similar microacoustic tagging technology to investigate questions 

of general movement and specific habitat use patterns of juvenile 

snappers in FKNMS reserve areas. We apply these methodologies 

to examine physical, environmental, and biological factors with the 

4

Developing ShallowWater Acoustic Telemetry 

Methods for Juvenile 

Snapper Habitat 

Studies in the Florida 

Keys National Marine 

Sanctuary

Samantha Whitcraft and Lisa Pytka

Southeast Fisheries Science Center

Cooperative Institute for Marine and 

Atmospheric Science

Miami, Florida

samantha.whitcraft@noaa.gov

Bill Richards, John Lamkin,

and Trika Gerard

Southeast Fisheries Science Center

Miami, Florida

Tom Carlson

Pacific Northwest National Lab/Battelle 

Portland, Oregon

Geoffrey A. McMichael

and Jessica Vucelick

Pacific Northwest National Lab/Battelle 

Richland, Washington

Greg Williams

Pacific Northwest National Lab/Battelle 

Sequim, Washington

Figure 1. Map of different 

habitats in Florida Bay and WSER

used by gray snapper and 

yellowtail snapper during 

different life stages. It also 

identifies the locations of 

juveniles with microacoustic tags.
12

goal of optimizing telemetry instrumentation and field 

techniques for this application.

In February 2005, initial field testing of the tag and node 

configuration in obstruction-rich shallow water was 

conducted on the lower Yakima River. Stationary beacon 

tags were placed along the riverbank in submerged 

branch litter to simulate an obstruction-rich, shallowwater mangrove environment. We tested acoustic 

reception (417 kHz) between the beacon tag deployed at 

approximately 1.5-, 0.9-, and less than 0.3-m depths and 

two sedentary nodes deployed at 1.8 and 2.7 m. We also 

tested three different ranges between tags and nodes, 

approximately 10, 40, and 90 m. Initial results indicated 

that the total number of acoustic signal “hits” from the 

beacon tags to the nodes decreased with increasing 

obstructions between the acoustic receiver and sender. 

However, we found that with an intermediate amount 

of branch litter we were able to detect and decode 

approximately 50 “hits” within an hour. Furthermore, 

the average time between receptions of the acoustic 

signal was circa 5 minutes given the greatest amount 

of obstruction and approximately 2 minutes given 

intermediate obstruction. Thus, given our initial field 

observations of movement patterns of some juvenile 

snapper species in mangrove and seagrass habitats, 

these results, if applicable to salt water, may prove 

adequate to detect the presence and movement of these 

fish in association with specific habitat types.

In May 2005, samples of mangrove prop roots were 

acoustically tested with a 25-mm-wide transducer to 

measure attenuation levels. Attenuation was fairly 

significant in all cases and is most likely due to small 

air bubbles present on the roots, which were exposed 

to air and not treated with a surfactant prior to 

submergence for testing. In nature, roots submerged 

for long periods are not likely to have a coating of 

microbubbles. However, the lab tests showed that 

attenuation through dense root aggregations decreases 

with frequency. As transmit frequency decreases, sound 

wavelength increases and the ratio of the dimensions of 

root structure to wavelength also decreases, reducing 

disruption of the transmitted signal. During the summer 

of 2006 we conducted in situ testing of three different 

frequencies: 107, approximately 260, and 417 kHz. 

Results from range testing of 417 kHz microacoustic tags 

in 2-m deep salt water (33 practical salinity units or psu) 

found a maximum range of 142 m. Similar ranges were 

recorded in obstruction-rich, nearshore habitat such as 

eelgrass (Zostera marina).

In order to determine optimal microacoustic tag 

implantation protocols for juvenile snappers and size 

effects with regards to survivorship, research is now in 

progress to conduct surgical trials of these microacoustic 

tags in 90–150-mm TL gray snapper (Figure 2). For 

tagging survivorship trials, 40 fish will be treated 

with each of the following treatments: intraperitoneal 

implantation, surgery with no tag implantation, and 

control. Prior trials found 100% survivorship of juvenile 

(6–23 g) sockeye salmon (Oncorhynchus nerka) across 

all three treatments. Additionally, in February 2005, 

40 juvenile rainbow trout (O. mykiss, 100–128-mm full 

length [FL]) were surgically tagged, as part of a training 

exercise for NOAA staff, and 100% survived in captivity 

for 111 days postsurgery while retaining their tags. Our 

initial juvenile snapper microacoustic surgical tagging 

and survivorship trials were completed in September 

2005.

Additional tag bioeffects studies are planned as we 

anticipate further reduction in the size of acoustic 

transmitters, enabling tagging of smaller juveniles and 

further reduction of any impacts of tag size on juveniles 

within the size range currently being tested. All juvenile 

snappers from tagging survivorship trials will be aged 

via otolith ageing techniques; specifically using silvernitrate additive for staining, extensive polishing, and 

microscopy or visual reading techniques to reveal daily 

growth rings. We anticipate ageing these fish to the 

number of days since birth within their first year by 

counting these rings.

After the workshop, we will continue this study by 

conducting range-testing trials in three juvenile snapper 

habitat types in Florida Bay and WSER. We will test 

multiple acoustic frequencies within each habitat type 

in order to minimize sound signal attenuation. We will 

also manipulate code length, source level, and other 

aspects of the transmitted signal to find a combination 

of frequency and coding that maximizes decode ranges 

while minimizing signal attenuation and multipath 

for the very shallow water and high vegetative density 

habitats of juvenile snappers.

Figure 2. Researcher surgically implanting the 

acoustic tag into a juvenile snapper.
13

Advances in the development of electronic tagging technology have 

resulted in a proliferation of applications for providing data directed at 

specific fisheries management goals. The preponderance of electronic 

tagging techniques involves implanting or attaching a device to the 

subject. Both cases involve invasive procedures, and since even 

the use of anesthetic can alter body chemistry, use of these devices 

can be both behaviorally and physiologically disruptive, resulting 

in uncharacteristic performance of tagged individuals relative to 

the untagged population. Tag effects studies can be conducted to 

characterize the extent of divergence from a control condition. For 

the most part these have been laboratory studies involving immediate 

influence on growth and survival over the life of the electronic 

instrument. This abstract suggests that tag effects considerations 

should be revisited periodically in the laboratory and in the field.

The term “laboratory studies” is used here to describe work to appraise 

the effects of tagging where otherwise free-ranging animals are 

held captive. This process can fall into several categories, including 

intermediate-term studies for animals held in raceways, net pens, 

or tanks for extended periods, as well as retention groups held for 

short-term assessment. Longer-term efforts are generally designed 

to evaluate some aspect of physiological or behavioral response of a 

tagged group relative to a reference (control) group of similar animals, 

while retention groups are often used to make relatively shorter 

duration inferences about a simultaneously tagged and released cohort.

Assuming that captive animal response is similar to what the subject 

will experience in a natural condition, there are good reasons to 

implement lab or retention studies. Relative comparisons of growth, 

survival, pathology, anatomical effects, behavior, and predation 

are strengths of this approach. For example, observations of tag 

rejection (shedding or expulsion) and wound healing development 

(encapsulation, adhesion progression, altered or eroded organs, and 

so on) are most easily and economically accomplished using captive 

animals, as are initial comparisons among tag devices, coating or 

potting types, or form factors (Figures 1 and 2). Lab studies can also be 

important where a surrogate species may be used to refine a device or 

procedure for a protected target species.

It seems obvious that feasibility studies must be undertaken with 

captive animals to assess immediate effects of a new tag on the target 

organism before full-blown field studies are attempted. However, 

it is also advisable to revisit key aspects of the original evaluation 

during the field study using retention groups. Holding a portion of 

the released group in as near ambient conditions as possible can afford 

insight into perturbations resulting from changes in conditions over the 

tagging season.

There are two outstanding limitations to using the laboratory approach. 

The most obvious is that the captive cohort is shielded from synergistic 

physical and biological influences that it would normally be subjected 

to in a natural system. The second weakness is that prolonged captivity 

may be at least as traumatic as the tagging procedure, particularly in 

the longer term.

Both of these limitations can be at least partially overcome by 

developing procedures for evaluating postrelease tag effects. Given 

the increasing importance of electronic tagging, it would be advisable 

to begin to build tag effects objectives into the study design. One 

5

Tag Effects Considerations 

in Electronic Tagging 

Studies

R. Lynn McComas, Brad Ryan, and 

Geoffrey A. McMichael

Northwest Fisheries Science Center

Seattle, Washington

lynn.mccomas@noaa.gov

Figure 1. Tests were conducted 

to determine how salmonids 

responded to being tagged with 

microacoustic tags. As depicted, 

common salmonid responses 

exhibited during the tag-retention

study include adhesion 

development, device encapsulation, and wound healing.

Adhesion development

Device encapsulation

Wound healing
14

way this can be done is to compare developmental 

and established tagging methods to create a tag effects 

index. For example, this technique has recently been 

applied during survival studies of acoustically tagged 

steelhead (Oncorhynchus mykiss) in the Columbia 

River. Groups of fish tagged with acoustic and passive 

integrated transponder (PIT) tags were released 

simultaneously with groups of steelhead with PIT 

tags only. Comparison of the percentages of PIT tag 

recoveries from bird droppings will be used as an 

index to tag effects for acoustically tagged individuals. 

A similar method could be designed to specifically 

compare tag effects among electronic tags with different 

characteristics (shape, size, coating type, and so on) 

under field conditions.

Finally, a discussion of electronic tagging effects must 

include an examination of ethical considerations for the 

tagged subject. The debate should inform deliberation 

relating proper tagging protocols, relevance of the 

research to the target species, and the long-term fate 

of the tagged subject. One area of this debate involves 

surgical procedures. Researchers are increasingly using 

surgical techniques to implant transmitters, in part due 

to evidence that adverse effects of surgical implants 

decrease over time. Surgical procedures require training 

and practice for proficiency, and surgical and handling 

techniques should also be reviewed periodically to 

include new developments. The ultimate ethical 

purpose of a tagging effort should be to reduce tagrelated effects to the point where tagged individuals 

survive to reproduce at the same rate as untagged 

animals.

Figure 2. During the tag-retention study, some of 

the fish rejected the prototype tags.
15

Extensive resource monitoring and near real-time data acquisition are 

required to accomplish the NMFS mission. Resource monitoring and 

information gathering will only be achieved through the development 

and deployment of new technology and approaches. Customized 

underwater vehicles (UVs) such as semiautonomous and autonomous 

underwater vehicles (SAUVs and AUVs) in concert with new tags and 

sensors can play an important role in achieving the goals outlined. The

information gleaned from use of this new technology will be required to 

conserve and manage our marine resources on an ecosystem level.

Monitoring and information-gathering challenges can be partially 

addressed using present technology by reconfiguring existing datagathering systems and tools, and by developing new tools and products 

using existing technology (Figure 1). One of the new tools required is a 

miniature transponding pressure sensitive tag. Miniature pinger-type 

acoustic tags (without pressure-sensing capability) exist but miniature 

sub-22-mm tags having pressure sensors that can be automatically 

calibrated do not. This class of acoustic tag is considered essential to 

obtain accurate target position information.

Using existing techniques and equipment, mobile tracking of aquatic 

targets is not reliable from an active tracking, three-dimensional 

positioning, or at times from a safety standpoint. For instance, using 

fixed interrogation points (“picket fence” target intercept approach) 

to track animals only provides information for one point in time. In 

addition, the receiver may not be in the correct location for target 

detection and thus no information is collected. Furthermore, limited 

spatial, temporal, hydrographical, or environmental data, if any, are 

obtained using this approach.

Causal relationships between the physical environment and animal 

behavior remain a mystery for many fish and marine mammal species 

and for various life stages of these animals. Using UVs in concert with 

a new class of acoustic tag would provide new and critical information 

needed to address many questions and concerns of fisheries managers. 

The proposed concept is not limited to any one area of fisheries or 

marine mammal and has national and international application. What 

is being proposed is a suite of tools and approaches that can be used 

to gather data on free-roaming targets of interest (e.g., fish and marine 

mammals) in situ (Figure 2).

6

Unmanned Underwater 

Vehicles for Fish and 

Marine Mammal 

Shadowing and Data 

Acquisition: A Concept

Earl F. Prentice and R. Lynn McComas

Northwest Fisheries Science Center

Seattle, Washington

earl.prentice@noaa.gov

Figure 1. Sample microacoustic 

tags used to tag juvenile 

salmonids shown to scale against 

a penny and a millimeter rule.
16

Technology objectives include 1) identifying or 

developing technology to shadow (track) acoustically 

tagged and nontagged fish and marine mammals using 

unmanned, underwater-type vehicles (e.g., SAUVs and 

AUVs), while gathering environmental and hydrological 

data; and 2) developing a suite of transponding acoustic 

tags suitable for use with juvenile and adult fish and 

marine mammals that are capable of being accurately 

and precisely tracked by AUVs and similar vehicles. 

An abbreviated list of technology challenges includes 

1) target acquisition, tracking, and positioning; 2) UV 

positioning and object avoidance; 3) mission duration; 

4) power for propulsion and its management for the 

instrument suite; 5) tag miniaturization (weight and 

size), read range, and duration; and 6) tag battery size, 

shape, and power density.

Fisheries science is experiencing rapidly expanding 

capabilities through developments in computational, 

robotic, communications, and sensor industries. This 

expansion is further driven by the biological sciences’ 

need to understand the interactive dynamics between 

organisms and the environments in which they live, 

in order to manage, restore, and maintain our natural 

resources. To satisfy this informational need, an 

extensive, remote, continual, and interactive sensor 

presence within particular areas of interest is required. 

The following concepts are presented as a means of 

obtaining some of the required information about 

the interaction between aquatic animals and their 

environment.

The basic concept is to shadow targets of interest (e.g., 

fish and marine mammals) using underwater vehicles 

(e.g., SAUVs and AUVs) while continuously collecting 

environmental, hydrographical, and other information 

of interest in the immediate vicinity of the tracking 

vehicle. Besides obtaining information on the movement 

of individual fish, in the future it may also be possible 

to passively identify stocks of fish using DNA sensors 

Figure 2. In future technology, an unmanned 

underwater vehicle tracks an acoustically tagged 

fish and relays that information back to a ship. 

The vehicle would also collect environmental and 

hydrological data.

aboard the UV. NASA scientists have developed an 

ultrasensitive electronic DNA detector that uses a forest 

of carbon nanotubes and probe DNA molecules to sense 

meager amounts of specific DNA. The basic detector 

could be used in practical land-based applications 

within 2 years and in the aquatic environment a short 

time later.

Once the above objectives are achieved, the resulting 

tools could be used to collect information on the 

seasonal movements of fish and mammals, their 

responses to environmental and hydrographic factors, 

their responses to trophic interactions (i.e., predator-prey 

relationships), and their responses to and use of microand monohabitats. In addition, the system could be 

used to document habitat use during various life history 

stages to augment existing life history information 

and demographics, and to help define the functional 

relationships governing animal spatial and temporal 

distribution and movement. Finally, the system could 

be used to collect information on fish and marine 

mammals so that ecosystem-based considerations can 

be incorporated into management decisions and to 

provide near real-time information on the environment 

they inhabit so that adaptive management strategies can 

be applied. In other words, in contrast to traditional 

Eularian sampling strategies, Lagrangian methods 

could be used to monitor specific species. The concepts 

and ideas presented do not cover all scenarios for the 

use of such vehicles but do provide a vision for the 

development of a program to address goals and needs 

outlined in NOAA Fisheries Strategic Plan for FY 2003–

FY 2008 and Beyond (online at http://www.ppi.noaa.gov/

pdfs/Strategic_Plans/2003_NOAA_Strategic_Plan.pdf) and, 

in part, to serve the fishery communities’ information 

needs on a global scale.
17

Understanding the impact of fish aggregating devices (FADs) on the 

behavior and distribution of tuna is important in evaluating FADinduced changes in fishing and refining population assessments. We 

placed Vemco VR2 (Shad Bay, Nova Scotia) acoustic data loggers on 

all 13 FADs surrounding the island of Oahu, Hawaii. Yellowfin and 

bigeye tuna (Thunnus albacares and T. obesus) captured at the FADs were 

equipped with coded sonic transmitters and released. The results show 

that although some fish moved among several FADs, the predominant 

trend was for individual tuna to associate tightly with one FAD and not 

visit others in the network (Figure 1).

When other FADs were visited, they were the FADs closest to the FAD 

where the fish were released. Data were also collected on duration 

of residence, times of arrival and departure of fish from the FAD, 

and school cohesion. This latter component would be advanced by 

development of archiving sonic tags that could communicate among 

themselves and report to a FAD or be interrogated on recapture. 

Development of tags with longer transmission distances would also 

be useful in this regard. It would be useful as well if real-time FAD 

association data or midocean FAD or buoy data could be acquired by 

cell phone or satellite telemetry of the acoustic detection events; this 

technological improvement is currently under development and beta 

testing.

7

Movements of Yellowfin 

and Bigeye Tuna in 

a Network of Fish 

Aggregating Devices as 

Determined by Acoustic 

Telemetry

Kim Holland, David Itano, and Laurent 

Dagorn

Hawaii Institute of Marine Biology

Kaneohe, Hawaii

kholland@hawaii.edu

Figure 1. Locations of the 13 FADs surrounding the island of Oahu, Hawaii. Vemco VR2 

acoustic data loggers were placed on all 13 FADs to monitor movement of tuna tagged 

with sonic tags. Most individuals stayed near the FAD where they were tagged and 

released.
18

The U.S. biological community’s use of the Argos Satellite Data 

Collection System and Joint Tariff Agreement (JTA) has exploded in 

recent years so that it is now the largest sector of users. The JTA has 

made several beneficial adjustments to the tariff structure over the 

previous 5 years to reduce JTA costs for biologists, and the JTA has 

attempted to garner more input from its biologists to better serve 

them, for example, regarding system requirements or tariff structure. 

The objective of the JTA is to provide a fair, cost-effective, and simple 

tariff for its users; this has achieved mixed results. The tariff has been 

negotiated and modified many times during its history due to changes 

in the Argos system, the processing service provider’s (CLS, or Collecte, 

Localisation, Satellites, a subsidiary of the French space agency, CNES, 

or Centre National d’Etudes Spatiales) operational costs, and the 

composition and needs of users.

In 2004 the JTA closely examined the service provider’s cost basis for 

the total Argos system with an aim toward achieving a cost basis that 

corresponds to real and required JTA services and the ability of users 

to cover these costs. The JTA tariff cost basis is and should remain 

preferential in comparison with the growing non-JTA (commercial) user 

community. At the 2004 JTA annual meeting, the 25 member-country 

Representatives of Countries (ROCs) considered a new global tariff 

proposed by CLS. The 25-year history of the JTA was reviewed, with 

emphasis on negotiation of the new tariff structure in 2005. The ROCs 

negotiated and approved a user cost structure that they believed was 

fairer for the global body of JTA users. The resultant tariff was expected 

to reduce the average cost for most users, and CLS promised that it 

would provide a “soft landing” to any users negatively impacted. A 

reduction in the average user cost is possible because the total Argos 

usership has dramatically increased in recent years. At the 2005 annual 

JTA meeting, the ROCs planned to review the initial year’s experience 

with this new tariff and to consider fine-tuning adjustments to better 

achieve the above aims.

8

Status of the Argos Joint 

Tariff Agreement

Stephen Auer

NOAA Research, Office of Global Programs 

Washington, DC

stephen.auer@noaa.gov
19

Acoustic telemetry has been used with large pelagic fishes (i.e., tuna 

and billfish) for over 30 years (Figure 1). The early studies revealed 

species-specific vertical movement patterns and widely divergent 

tolerances of the changes in temperature and oxygen conditions 

occurring with depth. For example, bigeye tuna (Thunnus obesus) 

show much greater vertical mobility than yellowfin tuna (T. albacares) 

and swordfish much greater vertical mobility than the istiophorid 

billfish (blue, black, and striped marlin, Makaira nigricans, M. indica, 

and Tetrapturus audax). Bigeye tuna and swordfish make diurnal 

vertical movements that mirror the movements of the organisms of 

the deep sound scattering layer (e.g., from the surface layer to >500 

m where water temperatures may be <5°C), effectively exploiting this 

community as a prey resource both day and night. In contrast, the 

vertical movements of yellowfin tuna and marlins appear constrained 

to depths where water temperatures are no more than 8°C colder than 

surface layer temperature. Acoustic telemetry has also shown that 

tuna have very highly developed navigational abilities in that they can 

repeatedly return to the same location at the same time over several 

days. Subsequent acoustic telemetry projects have demonstrated the 

importance of specific environmental features (e.g., prey density and 

water clarity) to tuna horizontal movements and aggregations.

Implanted archival tags have confirmed the species-specific vertical 

movement patterns of tuna, and pop-up satellite archival tags (PSATs) 

have done the same for billfish (marlins and swordfish) (Figure 2). 

PSATs have also been shown to be particularly effective at assessing 

postrelease mortality in a variety of species ranging from sharks to 

billfish to sea turtles. PSATs have clear advantages in these sorts of 

studies in that the data returned and fail-safe mechanisms programmed 

into the tags allow a mortality event to be clearly differentiated from 

tag failure (i.e., with PSATs you can tell “dead” from “shed”). Both 

implanted archival tags and PSATs rely on light-based geolocations, 

and recently developed data analysis techniques (e.g., Kalman filter and 

use of sea surface temperature, or SST, data) have improved geolocation 

accuracy. Archival tag technology is clearly suitable for answering 

ocean basin-scale movement questions. However, light-based 

geolocation data still are not, and may never be, of sufficient precision 

to allow interactions of pelagic fishes with mesoscale oceanographic 

features to be defined. Because of generally low return rates, implanted 

archival tags are not usable with rare event species (e.g., swordfish, 

certain species of sharks, and so on) because a sufficient number of tags 

cannot be deployed. PSATs are preferable in this situation, but issues 

with long-term attachment, low reporting rates, and the high costs of 

deployment for the amount of data returned remain to be solved.

Because tuna and billfish are so highly mobile, robust population 

assessments depend on a good understanding of short- and longterm horizontal and vertical movement patterns. In other words, it 

is necessary to be able to differentiate changes in abundance from 

changes in “availability” or “gear vulnerability” due to variations in 

environmental conditions and fish response to them. Deterministic 

habitat-based standardization (HBS) models have been used to 

predict fish distributions, where effective effort is modeled as the 

joint probability of the effectiveness of the gear (e.g., depth of longline 

hooks) and the depth distribution of the target species. To be a 

significant improvement, HBS models need accurate habitat envelopes 

(i.e., accurate assessment of the impact of temperature and oxygen 

levels on depth distributions). Without these, HBS models may not 

offer any improvement to population assessments based on nominal 

9

Acoustic, Archival, and 

Pop-up Satellite Tags and 

Large Pelagic Fishes: 

A 30-Year Perspective

Richard Brill

Northeast Fisheries Science Center

Virginia Institute of Marine Science 

Gloucester Point, Virginia

richard.brill@noaa.gov

Michael Musyl

Pacific Islands Fisheries Science Center

Joint Institute for Marine and Atmospheric 

Research

Honolulu, Hawaii

Figure 1. A yellowfin tuna tagged 

with a PSAT near its dorsal fin.
20

catch and effort data. Measuring and ultimately 

predicting the effects of oceanographic conditions on 

the behaviors of pelagic fishes requires the types of 

direct observations provided by acoustic telemetry and 

electronic data recording tags.

Figure 2. Diagram of the movement patterns near Hawaii of blue marlin tagged with 

PSATs. The black dots (end points) indicate where the PSATs were recovered. Various 

colored lines represent individual marlin movements.
21

Pacific leatherback turtles (Dermochelys coriacea) are in decline, and 

better knowledge of migration routes, stock structure, foraging habits, 

and renesting intervals is essential for their successful recovery. 

Satellite-linked transmitters (platform transmitter terminals, PTTs) have 

been useful tools for determination of leatherback stock identification, 

migratory routes, internesting behavior, habitat use, diving behavior, 

and locations of potential fisheries interactions.

Since 2000, 69 satellite transmitters have been deployed on leatherback 

turtles in California, Papua New Guinea, and Papua, Indonesia. 

Expected transmitter life was 18–24 months; however, only 8 

transmitters (16%) had durations greater than 12 months and 16 of 

the 69 (23%) failed within 2 months. It is unknown whether shorter 

deployments represented transmitter failure, attachment failure, 

or turtle mortality. To determine the cause of satellite transmitter 

failure, we evaluated records of pop-up archival transmitting (PAT) 

tags deployed on leatherback turtles simultaneously with satellite 

transmitters. The PAT tags were programmed to release after a 

specified number of days or under conditions indicating a prolonged, 

uninterrupted time at depth, which could suggest turtle mortality.

Satellite-linked transmitters were attached to the carapace of 

leatherback turtles, using a harness made of polypropylene webbing 

and polyvinyl tubing (Figure 1), at foraging grounds off central 

California and at nesting beaches in New Guinea and Costa Rica. PAT 

tags (n = 61) were attached to the satellite tag harness or directly to 

the turtle by drilling a small hole through the pygal process of the 

carapace (Figure 2). These two techniques permitted PAT attachment 

that was either dependent or independent of the harness apparatus. 

PAT tags were programmed to release and transmit data if 1) specified 

deployment period was complete, or 2) depth of tag remained constant 

for a prolonged period (48–96 hours). Combined, these techniques 

allowed specific inferences about the potential fate of the satellite 

transmitters and turtles.

Data from PAT tags were insufficient to resolve the nature of satellite 

transmitter “failure events” in most cases. Twenty-nine (49%) of 

deployed PAT tags failed to report, 25 (41%) reported as scheduled, 

and seven (11%) reported early. No PAT tags deployed for greater 

than 6 months ever reported. Among the PAT tags that reported as 

programmed, one attached to the PTT harness apparatus released 

75 days after the last PTT transmission, indicating PTT failure at 111 

days. Among the PAT tags that reported early, five were cases of 

either harness or PTT failure where satellite transmitters ceased after 

0–47 days and associated PAT tags, attached to the harness apparatus, 

reported at approximately the same time. Among the PAT tags that 

were attached independently of the harness apparatus (i.e., pygal 

attachment), two reported early suggesting mortality as the cause of the 

short deployment records. Although PAT tags were programmed to 

transmit data around the time of premature release at a higher priority, 

resolution was too coarse to resolve the sequence of events causing 

mortality.

Leatherback turtles perform migrations that span entire ocean 

basins, often requiring more than a year to complete. Many PAT tags 

failed to report after the programmed date, particularly with longer 

deployments (Figure 3). Causes of PAT tag failures are unknown, but 

could be attributable to malfunction of the tag (i.e., release failure, 

programming error, or transmission failure) or to external factors that 

10

Evaluation of Pop-up 

Archival Transmitters to 

Determine Cause of 

Failure for Satellite 

Transmitters Deployed on 

Pacific Leatherback 

Turtles

Scott R. Benson and Peter H. Dutton

Southwest Fisheries Science Center

Moss Landing, California

scott.benson@noaa.gov

Figure 1. Satellite-linked 

transmitter (PTT) attached to 

shoulder harness of leatherback 

turtle in Papua New Guinea.
22

could impact the tag (i.e., biofouling or pressure). PAT 

tags were originally designed for use with large fastmoving fish species (i.e., tuna); therefore, biofouling and 

failure due to the effects of pressure may be more likely 

for tags attached to relatively slow-moving and deepdiving species such as leatherback turtles.

Fishery interaction has been considered one of the 

primary causes of decline for the leatherback turtle, 

particularly in the Pacific Ocean; however, records from 

telemetry deployments failed to clearly demonstrate 

the link. Satellite transmitters have demonstrated great 

variability in duration of transmissions, and shorter 

durations could be attributable to attachment failure or 

transmitter malfunction in addition to mortality. PAT 

tags could play a significant role in resolving these 

multiple causes of transmitter failure if PAT tags were 

able to reliably provide greater detail around the time 

of premature release. Presently, time-at-depth data are 

saved as binned data to permit storage and efficient 

transmission of the large volume of recorded data; 

however, binned data do not provide the resolution 

necessary to determine the cause of a premature release, 

and dive profile data may be necessary for determining 

cause of premature PAT tag release.

Unless PAT tags are able to reliably report after 

deployments greater than 6 months, it will be difficult 

to resolve the causes of satellite transmitter failure. 

Improvements to PAT tag design that would help 

resolve the nature of apparent PTT failures include

1) greater reliability of PAT tag reporting and 2) greater 

temporal resolution of binned depth data and more 

sophisticated algorithms identifying a turtle mortality 

event.

Figure 3. Performance of PAT tags attached to leatherback turtles from 

2001 to 2005. Causes of PAT tag failures are unknown.

Figure 2. PAT tag attached at pygal process of leatherback turtle in 

Papua New Guinea.
23

Pop-up archival transmitting (PAT) tags are used in survival 

studies. They are designed to provide information on the fate of the 

animal—more so than conventional satellite tags. We developed a 

new attachment methodology for cheloniid sea turtles. In May 2003, 

disabled PAT tags were attached to three approximately 50-cm straight 

carapace length (SCL) loggerhead turtles (Caretta caretta) of the 2000 

year-class held in captivity at the NOAA Fisheries Service Galveston 

Laboratory. The attachments were monitored daily, photographed 

weekly, and removed a year later. The posterior carapace of each 

animal was scanned radiographically using computer-assisted 

tomography (CT) and the radiographs were evaluated for the longterm impact of the attachment on the underlying bone. There was no 

evidence of significant reaction to the attachment.

We also conducted a feasibility study of using PAT tags for a full 

survival study of sea turtles. After deciding that the post-hooking 

mortality of sea turtles likely would not be expressed in a short time, 

we selected the Wildlife Computers (Redmond, Washington) PAT tags 

because of their ability to collect data every minute, summarize the data 

from a long period of deployment into histograms of durations defined 

by the user, and transmit them after pop up. We deployed 39 tags on 

wild loggerhead turtles in the North Atlantic. Most had interacted with 

the pelagic longline fishery, but some were control turtles dipnetted 

from the surface. We monitored the fate of these turtles for up to 

a year and assessed our ability to use this technology in sea turtle 

studies. Over 40% of the tags remained attached until the pop-up date, 

indicating those animals had survived. About 30% of the tags never 

transmitted data, and the remainder popped up prematurely. A few 

premature releases were categorized as mortalities, but the fate of most 

of the premature releases could not be determined.

Last, we combined sea turtle data with data from PAT-tagged pelagic 

fish and grouper and evaluated tag performance over three generations 

of Wildlife Computers tags. Early performance of PAT 2 tags was 

relatively poor. Over 30% of the tags deployed did not transmit, and a 

small percentage of histograms transmitted by the remaining tags were 

received uncorrupted. Improvement was observed with subsequent 

versions of the tag, with only about 15% of the PAT 4 tags not 

transmitting, and a greater proportion of the histograms were received 

uncorrupted (Figure 1).

Figure 1. Wildlife Computers 

PAT tag performance on pelagic 

fish, grouper, and sea turtles. In 

total, 213 tags were deployed: 

96 PAT 2s, 78 PAT 3s, and 39 PAT 

4s. The expected number of 

time-at-depth histograms for 

each tag is based on the number 

of days at large and the number 

of histograms produced daily. 

The actual number received is 

expressed as a proportion of the 

total expected. Note that it is 

possible to receive more than one 

copy of a particular histogram 

and, for short deployments, the 

actual number received may 

exceed the total expected.

11

Pop-up Archival 

Transmitting Tags and 

Their Application to 

Loggerhead Sea Turtle 

Survival Studies

Sheryan Epperly, Christopher Sasso,

Eric Prince, and Carlos Rivero

Southeast Fisheries Science Center

Miami, Florida

sheryan.epperly@noaa.gov

Alan Bolten

University of Florida

Gainesville, Florida

Jeanette Wyneken

Florida Atlantic University

Boca Raton, Florida

Joseph Flanagan

Houston Zoo

Houston, Texas

Craig Harms

North Carolina State University

Morehead City, North Carolina

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24

We tagged shortfin mako sharks (Isurus oxyrinchus) with both popup archival transmitting (PAT) tags and satellite-linked transmitting 

tags (Smart Position or Temperature Transmitting tags, or SPOT tags, 

Wildlife Computers, Redmond, Washington) in order to study their 

horizontal and vertical movements. PAT tags transmitted depth and 

temperature profiles, and depth and temperature frequency histograms 

collected during 4-hour periods providing information on vertical 

habitat preferences. Without including ancillary information such as 

sea surface temperature (SST), geolocation estimates from PAT tags are 

unsatisfactory for fine-scale movement information. Therefore, SPOT 

tags, mounted on the first dorsal fin of the sharks, transmitted when the 

fin broke the surface of the water. High-quality locations (classes 1, 2, 

and 3) were obtained from Argos satellites for each shark nearly every 

day and frequently several times each day.

Figure 1 demonstrates the track of a shortfin mako shark carrying 

both tags for a period of 45 days. Double tagging has enabled us to 

obtain accurate horizontal movement information to characterize 

the essential habitats of these highly migratory sharks. In addition, 

the accurate locations obtained from the Argos-linked tags are being 

used to improve light-based geolocation algorithms currently in 

development by several research groups. The data were combined 

by fitting a curvilinear model to the derived locations in order to 

estimate each shark’s position during each 4-hour period. Tracks 

were plotted in three dimensions using ArcView GIS software (ESRI, 

Redlands, California) with maximum depths and water temperature 

profiles shown in the vertical dimension. When archiving data into 

4-hour bins, PAT tag battery failure occurred before all binned data 

could be transmitted when deployments exceeded approximately a 

month. Hence, this technique of examining three-dimensional habitat 

preferences was most effective when deployments were relatively short, 

such that the majority of the binned water column profile data were 

available.

12

Combined Use of PAT and 

SPOT Tags to Study ThreeDimensional Habitat Use 

Patterns of Shortfin Mako 

Sharks

Suzanne Kohin and David Holts

Southwest Fisheries Science Center

La Jolla, California

suzanne.kohin@noaa.gov

Figure 1. Movements of a 

shortfin mako shark double 

tagged with a radio-transmitting, 

satellite-linked position tag and a 

pop-up archival tag off the coast 

of southern California and Baja 

California, Mexico.
25

Figure 3. The anchoring hardware used to attach the PAT and SPOT 

tags to the sharks.

We have had great success using satellite-linked tags on 

sharks, in part due to a specially designed tagging cradle 

used to immobilize the sharks during tag attachment. 

PAT tags are anchored with nylon anchors near the base 

of the first dorsal fin and loosely secured with a cable 

tie around the stalk of the tag (see Figures 2 and 3). PAT 

tags attached in this manner have remained on sharks 

up to 9 months. SPOT tags are secured with three nylon 

bolts through the dorsal fin and, in most cases, have 

provided locations for well over a year.

Figure 2. Researchers onboard a research vessel tagging a shark with 

PAT and SPOT tags.
26

The Auke Bay Laboratory has used satellite, sonic, and archival 

electronic tags to study the ecological role and life history of the Pacific 

sleeper shark (Somniousus pacificus), salmon shark (Lamna ditropi), and 

spiny dogfish (Squalus acanthias) in Alaskan waters. Electronic tags 

can be programmed to continuously record temperature and depth. 

Satellite tags transmit to polar orbiting satellites when the tagged 

animal is at the surface or after the tag has detached from the animal at 

a preprogrammed time. Sonic tags transmit to hydrophones deployed 

remotely in an array or manually from a vessel that follows tagged 

animals. Archival tags retain data onboard and must be physically 

recovered to retrieve data.

Satellite tags were attached externally to the dorsal region of 36 Pacific 

sleeper sharks and 16 salmon sharks in the Gulf of Alaska and Prince 

William Sound during 2002 and 2003 (Figure 1). Movement or depth 

data have been recovered from 24 satellite-tagged Pacific sleeper 

sharks. Behavior was analyzed from depth data recorded by the tags. 

Systematic vertical oscillations were most common (60%), followed 

by diel vertical migrations (25%), and irregular vertical movements 

(15%). Median vertical movement from 4,781 hours of recorded data 

from one shark was 6 km/day. Movement data have been recovered 

from 13 satellite-tagged salmon sharks. Up to 121 geographic locations 

have been recovered from a single animal. During summer, depth 

distribution was bimodal, with the surface (0–2 m) and the thermocline 

preferred. Most female salmon sharks tagged during the study left 

Prince William Sound and migrated south and east as Pacific salmon 

spawning migrations declined in autumn.

Sonic tags were surgically implanted in the abdominal cavity of 24 

Pacific sleeper sharks in Chatham Strait in 2004. Thirteen sonic-tagged 

Pacific sleeper sharks were acoustically relocated with hydrophones 

deployed from a vessel in a search area of 588 km2

 within a month 

after release. Acoustically relocated sharks were tracked at depths 

greater than 500 m, made horizontal movements of 6 km/day, and 

made vertical migrations off the bottom. Sonic-tagged sharks were not 

acoustically recovered with an array of hydrophones deployed within 

the same region 8 months after release.

Archival tags were attached externally to the dorsal fins of 88 Pacific 

sleeper sharks in Chatham Strait from 2003 to 2005 and surgically 

implanted in the abdominal cavity of 99 spiny dogfish in Yakutat Bay 

from 2004 to 2005 (Figure 2). Pacific sleeper sharks and spiny dogfish 

are occasionally encountered as bycatch in Alaskan commercial 

fisheries. The Auke Bay Laboratory offers a $200 reward for the return 

of electronic archival tags. Reward posters have been distributed to the 

Alaska commercial fishing industry and to the local communities where 

tags were released. To date, no archival tags have been recovered.

Recovery rates for satellite tags (62%), sonic tags (54%), and archival 

tags (0%) have been low. Possible causes for low recovery rates 

include shorter than expected battery life of sonic and archival tags, 

failed external attachments of archival and satellite tags, premature 

termination of satellite data transmission, limited acoustic tracking 

technology for sonic tags, and low interception rates of archivally 

tagged sharks in Alaskan commercial fisheries (Figure 3). In spite of 

low recovery rates, electronic tags have proved to be a valuable tool 

for gathering information on the geographic distribution and vertical 

habitat of sharks in Alaskan waters.

13

Shark Research in the Gulf 

of Alaska with Satellite,

Sonic, and Archival Tags

Dean L. Courtney

Alaska Fisheries Science Center

Juneau, Alaska

dean.courtney@noaa.gov

Lee Hulbert

Alaska Department of Fish and Game 

Juneau, Alaska

Figure 1. A satellite-tagged 

Pacific sleeper shark being 

released.
27

Figure 3. Tracking records for some of the sleeper sharks originally tagged 

with sonic tags in the Chatham Strait.

Figure 2. An archival tag attached externally to the dorsal fin of a Pacific 

sleeper shark.
28

The purpose of this study is to explore failure (or conversely success) 

scenarios in pop-up satellite archival tags (PSATs) attached to pelagic 

fish, sharks, and turtles. As an example, of 121 PSATs attached to 

sharks, billfish, and tuna in Hawaii, 71 (or 60%, rounded) reported data 

with 40% of the tags listed as “nonreporters” (namely, nonreporting is 

not synonymous with mortality). Specifically, the study is designed 

to look for explanatory variables in the context of PSAT retention 

rates, percentage retrieved satellite data (i.e., depth, temperature, 

or geolocations), and tag failure. By examining several factors and 

information about PSATs attached to vastly different pelagic species, it 

is anticipated that certain patterns or commonalties may emerge to help 

improve our understanding of attachment methodologies, selection of 

target species, and experimental design. It is anticipated that this study 

will examine information from over 1,000 PSATs. Information derived 

from this study will allow an unprecedented and critical appraisal of 

the overall efficacy of the technology.

14

PSAT Performance and 

Metadata Analysis Project

Michael Musyl, Geoff Arnold,

Michael Domeier, Molly Lutcavage, 

Lianne McNaughton, Yonat Swimmer,

and Steve Wilson

Pacific Islands Fisheries Science Center

Joint Institute for Marine and Atmospheric 

Research

Honolulu, Hawaii

michael.musyl@noaa.gov

Richard W. Brill

Northeast Fisheries Science Center

Virginia Institute of Marine Science

Gloucester Point, Virginia
29

A primary focus of recovery efforts for depressed salmonid stocks has 

been assessing and improving fish passage conditions at hydroelectric 

projects and through their reservoirs. Since the listing of Columbia 

River basin salmonids under the Endangered Species Act, juvenile 

salmonid passage and survival studies at Lower Monumental, Ice 

Harbor, and McNary dams have been conducted to make informed 

decisions in the best interest of the stocks (Figure 1).

Over the course of the last 10 years, we have improved the detection 

efficiency of our telemetry receivers, thanks in large part to the 

designs created by RF Engineering (Lynnwood, Washington). Unlike 

other telemetry receivers currently being used to track fish, the 

NMFS 30 megahertz (MHz) multichannel receiver detects amplitude 

modulated (AM) pulse-coded carrier frequency signals on nine 

channels simultaneously without using digital signal processing (DSP) 

technology. Each channel is optimized for wide dynamic range and 

high adjacent channel rejection, and provides excellent sensitivity. 

Once a tag is detected, the receiver decodes the signal to determine 

which individual tag sent the signal. The receiver then records one line 

of data to a local file containing the time stamp of the detection, the 

channel and code that together uniquely identify the fish, and power 

(signal strength).

In 2003, we began to design a wireless network for data acquisition and 

management. The original network consisted of FreeWave 900-MHz 

Wireless Data Transceivers (FreeWave Technologies, Boulder, Colorado) 

that were connected to our telemetry receivers. This configuration 

allowed a single person to download more than 50 telemetry sites 

within the constraints of an 8-hour work day (approximately 140 miles 

of study area). However, the 900-MHz system had limited range and 

did not allow for automated downloading. During 2004 and 2005 we 

changed to the airBridge TOTAL 2.4-GHz client (SmartBridge, San Jose, 

California). Powered through the use of an Ethernet cable, this unit 

has higher receiver sensitivity and rugged weatherproof design, and 

provides error-free data transfer with auto-fallback data rate for longdistance communication in noisy environments.

15

Utilizing Radiotelemetry 

to Investigate Passage 

Behavior and Survival of 

Juvenile Salmonids in the 

Columbia River Basin

Gordon A. Axel, Eric E. Hockersmith, 

Byron L. Iverson, Samuel L. Rambo, 

Darren A. Ogden, and Douglas B. Dey

Northwest Fisheries Science Center

Seattle, Washington

gordon.axel@noaa.gov

Figure 1. Locations of the hydroelectric facilities on the Snake and Columbia rivers.
30

Currently, we are pursuing a smaller radio transmitter 

that will enable us to tag a larger portion of the total 

population. When we began tagging juveniles in 1997, 

we used a 1.8-g tag. In 2005, our tags weighed 0.9 g. 

Limitations on tag size include the overall output of 

the tag and the battery life required for such output. 

In order to provide complete detection of juvenile 

salmonids through the study area, we require a battery 

life of 10 days. We are examining the use of different 

potting substances to decrease the weight of the tag and 

ways to decrease the length of the antenna that trails 

behind the animal as it swims. In addition, we are also 

investigating a transition from an AM transmitter to a 

frequency modulated (FM) transmitter. With a slight 

modification to our current RF receiver board, we will 

be able to detect and code an FM tag. This modification 

will substantially increase the number of individual tag 

codes and reduce the power consumption of our current 

tag, thus allowing for a smaller, more efficient juvenile 

RF tag. Because FM tags would require less power to 

produce the same output and tag life that we currently 

need, we would be able to use a smaller battery and 

reduce the tag weight by one-third.

Our electronics technicians are developing quarterwave two and three element receiving antennas. These 

antennas will reduce antenna size by 50%, while keeping 

the antenna tuned to our carrier frequency of 30 MHz. 

This will increase antennas’ versatility and durability. 

For underwater applications, the electronics shop is 

developing a dual plane dipole antenna (Figure 2).

This antenna will increase the number of detections 

by allowing detections in both horizontal and vertical 

planes.

Figure 2. Diagram of the detection field of the antenna attached to 

the upstream face of the dam demonstrates the difference between 

radiation patterns of current antennas used for radiotelemetry work 

with salmonids and the new dipole antenna being developed.

While modifications to our antennas and receivers will 

be helpful, data communications efficiency is paramount 

to the success of the juvenile salmonid radiotelemetry 

studies. The current data communication is done via 

RS-232 serial port. We are investigating a transition from 

RS-232 to Ethernet that will provide a minimum of 10 

megabits per second of data transfer, thus improving 

network reliability and speed. This will allow us to 

download from receivers several times daily and receive 

site reports that will provide the electronics staff with 

the information necessary to keep the telemetry receivers 

running at their optimal capabilities.

With recent technological enhancements, radiotelemetry 

will continue to provide critical information on passage 

and survival for juvenile salmonids at hydroelectric 

dams and through their reservoirs. As we take 

advantage of these enhancements, we will be able to 

improve our assessments of the stocks and determine 

the best course of action to recover, conserve, and 

manage endangered and threatened salmonids and their 

habitats.
31

Whether using remotely sensed tags for small-scale animal movement 

studies or large-scale survival and behavioral analyses, data retrieval 

and organization are often the most time-consuming and technically 

challenging aspects of a telemetry research project. Furthermore, the 

complexity and quantity of telemetry data can make analysis and 

interpretation difficult. Using a radiotelemetry study of juvenile 

salmonid passage and survival as an example, we describe steps one 

can take to automate much of this process, increasing overall project 

productivity as well as data accuracy and retrieval reliability.

From 2 May to 15 July 2005, we radio-tagged and released almost 15,000 

juvenile salmonids in the Snake River and tracked their downstream 

migration through the hydropower system, generating over 4 gigabytes 

of raw data. Release locations ranged from the Ice Harbor Dam 

tailrace to the forebay of Lower Monumental Dam, a distance of about 

60 km. We collected positional data using an array of 74 stationary 

radiotelemetry receivers distributed within a 120-km reach of the lower 

Snake and mid-Columbia rivers (Figure 1).

We released tags on nine separate frequencies, and each of our 

stationary receivers was programmed to listen for all frequencies 

simultaneously. When a tag was detected, the receiver decoded the 

signal and recorded one line of data to a local file containing the 

time stamp of the detection, the channel and code (that together 

uniquely identify the fish), and power (signal strength) recorded in a 

hexadecimal format. This data collection sequence is common to most 

telemetry studies.

Receivers grouped in the same geographical area, such as a dam, were 

networked to a local computer using wireless Ethernet radios. The 

computer was connected to the Internet, allowing access to the receivers 

and their data from anywhere with an Internet connection (Figure 2).

Files were automatically downloaded from the receivers using a 

program called Tracker2. This program was produced via contract by 

the White Salmon Group (White Salmon, Washington) to help organize 

the downloading and maintenance of radiotelemetry receivers. On 

a preset schedule, Tracker2 contacted each receiver, downloaded the 

current file, reset the receiver’s clock (to maintain consistency between 

16

Automated Telemetry 

Data Retrieval and 

Organization

Brian J. Burke, Bruce F. Jonasson,

Eric E. Hockersmith, Kinsey E. Frick, 

Gordon A. Axel, Byron L. Iverson, 

Samuel L. Rambo, Mark A. Kaminski,

and Ron L. Helgeson

Northwest Fisheries Science Center

Seattle, Washington

brian.burke@noaa.gov

Figure 1. A typical stationary 

radiotelemetry site, near 

McNary Dam on the Columbia 

River. An antenna and two solar 

panels provide power to the 

radiotelemetry receiver located 

in the cabinet under the bottom 

solar panel.
32

receivers), and cleared the memory of the receiver. In 

addition to automated downloading, we were able 

to contact each receiver directly using Tracker2 for 

diagnostics.

Each morning, we collated all the files from the previous 

day and sent them to a local server via file transfer 

protocol (FTP). To help accomplish this task, we used 

an FTP program, FTPShell, which allowed 1) a script to 

send the appropriate files (using its own native scripting 

language) and 2) scheduling scripts so that file transfers 

could be done automatically.

Once all the files for a given day were stored on our FTP 

server (ftp.afsc.noaa.gov), we transferred them to the 

Linux server that runs our Oracle database. We used 

a script scheduling capability in Linux to deal with 

the files and the data. Each file was converted from 

hexadecimal format to ASCII text (using a C program) 

and loaded into a temporary table in Oracle using sqlldr, 

an Oracle bulk data loading program. Filters were 

then applied to the data with Procedural Language/

Structured Query Language (PL/SQL) code, which 

sorted out the potentially informational records from the 

obvious noise records, associated tag detections with the 

appropriate release record, and flagged any duplicate 

records. By using one piece of code stored in the 

database, we ensured that all data were treated equally 

(i.e., the exact same “rules” were applied to all data), 

increasing data quality. Furthermore, if we decided to 

change the rules, a simple alteration of the PL/SQL code 

and rerunning the PL/SQL program was all that was 

necessary.

We then summarized the data, again using PL/SQL, 

and generated reports specifying the content of the files 

received that day. These reports were sent via 

e-mail to a list of recipients specific to each type of data. 

For example, the reports associated with tagging and 

release events were sent to one group of researchers 

while a report describing receiver diagnostics was sent 

to another group of researchers. These e-mail lists were 

maintained on the server and used a script written in 

Perl. All processing, receiver diagnostics, and detection 

summary reports were complete and e-mailed by 7 AM

daily.

Occasionally difficulties arose with some of these 

automated tasks. Sometimes a server would be 

inadvertently shut down, or a script might encounter 

an error while running. When this occurred, we were 

alerted to the failure either by the contents of the reports 

we received or by specific system error e-mail reports. 

Sometimes an error simply meant rerunning a script; 

other times it meant checking a list of files or a receiver 

in the field for troubleshooting. However, the delays 

caused by these events were minor compared to the 

amount of time necessary to run a project of this size 

without the use of automation.

Figure 2. The wireless arrangement for one receiverantenna combination (not shown) installed on the 

on the deck of the McNary Dam. All of the receivers 

are connected to a local computer, which can be 

accessed through the Internet.

Automation of remote data retrieval, filtering, and 

summarization ensured that we addressed problems 

with receivers, such as a loss of power, in a timely 

manner and that abnormal fish behavior could be 

recognized in season. This timely supply of information 

can often drive the schedule for tagging additional 

fish or receiver maintenance and repair, reducing the 

downtime of receivers, and increasing the efficiency and 

success of the researchers’ efforts. Moreover, any or all 

of these steps can be modified to fit individual research 

projects, regardless of scope or tagging methodology. As 

with most aspects of research, some foresight and initial 

time investment can ultimately result in large savings of 

time and money, as well as an increase in data quality.
33

Most deployments of dorsal fin–mounted telemetry tags have not 

provided location information for their entire expected service life. 

However, the reasons for these premature failures could not be 

discerned because these problems could have been due to multiple 

factors. As a result, efforts to correct these problems have been 

confounded. Although several researchers have noted or alluded to 

causes of telemetry system failures, none designed their studies to 

attempt to determine the specific causes.

We assessed the failure modes of small cetacean telemetry tags 

by deploying paired tags, usually an Argos platform transmitter 

terminal (PTT) and a very high frequency (VHF) transmitter, and 

obtaining periodic opportunistic and dedicated resighting efforts of 

these animals to the extent possible. Tags were deployed on 7 Dall’s 

porpoises (Phocoenoides dalli), 18 harbor porpoises (Phocoena phocoena), 

28 bottlenose dolphins (Tursiops truncates), and 7 killer whales 

(Orcinus orca). We used results from these observations and other data 

to discern failure modes such that iterative modifications could be 

made to mitigate perceived telemetry problems to increase durations 

of monitoring (Figure 1). The iterative design modifications were 

intended to reduce tag-generated drag, reduce skin contact, increase 

fin cooling, and incorporate flotation material so the tag could be 

recovered to better assess system failures.

For 23 of 60 deployments, relocations or resightings allowed 

assessment of the attachment or hardware condition. Fourteen 

deployments could be monitored for the expected service life of at 

least one of the transmitters. Although many instances of attachment 

component failures were likely responsible for signal loss, multiple 

deployments had documented or diagnosed hardware component 

failures. Attachment component failures included breakage of the 

attachment pins or tag housing, and tissue breakdown resulting in pin 

outmigration. Hardware problems included faulty saltwater switches, 

antennas grounding out on the dorsal fins, and antenna breakage. 

For bottlenose dolphins and harbor porpoises, the two species with 

the most deployments and widest variety of tag designs, only in 

bottlenose dolphins did the signal contact duration consistently 

increase with tag system modifications. However, despite design 

modifications (Figure 2, upper photo), tag attachments for bottlenose 

dolphins continued to experience pin migration (Figure 2, lower 

photo). Although implementation of similar system modifications 

were made to harbor porpoise tags, durations of signal contact 

continued to be variable with some relatively short durations of 

contact and most durations not extending 6 months. Lack of resight 

data hampered assessment of latter harbor porpoise tag deployments.

Early signal loss is probably associated with attachment failures 

most likely due to rubbing behavior or antenna grounding problems. 

Signal loss mid-duration in the transmitter’s expected service life, 

while also possibly associated with attachment failures due to 

rubbing behavior, could also be due to pin outmigration or saltwater 

switch biofouling. Attachment failure due to rubbing has been, and 

likely continues to be, an issue for tag deployments in some species. 

Therefore in order to reduce rubbing behavior, tag attachments 

methods should try to minimize tag sensation. The trajectory of 

attachment pin migration in the dorsal fin tissue continues to indicate 

that additional efforts are needed to understand and mitigate the 

role of tag shape, position, or stability to minimize impact and dragrelated forces to reduce tissue breakdown. A complementary effort 

17

Failure Modes of Dorsal 

Fin-Mounted Small 

Cetacean Telemetry Tags

Aleta A. Hohn

Southeast Fisheries Science Center

Beaufort, North Carolina

aleta.hohn@noaa.gov

M. Bradley Hanson

Northwest Fisheries Science Center

Seattle, Washington

Forrest Townsend and Frank Deckert

TracPac

Fort Walton Beach, Florida

Tiu Similä

NORCA (Norwegian killer whale project)

Straumsjoen, Nordland, Norway

Broken

pins

Figure 1. Tag attachment 

failure due to broken pins on a 

bottlenose dolphin. Photo by K. 

Mazzarella, Nags Head Dolphin 

Watch.
34

to minimizing tag-related tissue damage should be 

developing a single point release system to reduce 

tissue damage associated with unsynchronized tag 

release.

Reductions in transmitter size are needed to decrease 

drag forces, attachment “footprint,” and therefore 

possibly associated sensation. However, because smaller 

tags will likely remain attached for longer durations, this 

size reduction cannot be made at a cost to the service life. 

On the contrary, service life will need to be increased. 

New generations of tags often require a significant 

redesign of various components. However, these 

redesigns sometimes result in reduced reliability of the 

transmitter or its components. More thorough testing 

of transmitters is required to mitigate this problem. 

In order to increase long-term reliability of saltwater 

switches and antennas, transmitter manufacturers 

need to make design modifications that will mitigate 

biofouling and increase the robustness of the antennas 

relative to the forces associated with drag and rubbing 

behavior.

As transmitter size is reduced and attachment duration 

increases, smaller batteries will be required to operate 

for extended time periods. This situation necessitates 

renewed efforts and new approaches to improve 

management of transmitter power and of signal 

transmission, reception, and processing to provide the 

highest accuracy locations with the fewest number of 

transmissions.

Only through a concerted effort to mitigate previously 

noted failure modes will the goal of consistent telemetry 

tag deployments lasting a year be achieved on small 

cetaceans.

Figure 2. A modified tag design where it was hoped that the more 

streamlined design would improve attachment (upper photo), but 

subsequent observations revealed that the pins still migrated with this 

design (lower photo).
35

Nearly all of the approximately 1,300 Hawaiian monk seals (HMSs, 

Monachus schauinslandi) inhabit the remote Northwestern Hawaiian 

Islands (NWHI) in six main subpopulations. Following substantial 

declines in abundance after the late 1950s, the species was listed as 

endangered under the Endangered Species Act in 1976. Perhaps 

because of the poor foraging success and subsequent poor survival 

of juveniles, their numbers are declining overall. A comprehensive 

understanding of the diet and foraging habitats and patterns has 

been identified as a key component for successful conservation of 

monk seals. Consequently, from 1996 through 2004, the movements 

and diving behaviors of 157 seals were documented throughout 

the Hawaiian Islands Archipelago (HIA) using satellite-linked 

depth recorders (SDRs, Wildlife Computers SDR-T16s, Redmond, 

Washington) attached to the dorsal pelage (Figure 1). The primary 

objectives of these studies were to characterize the marine and 

terrestrial habitat requirements of HMSs throughout their range and 

compare differences in foraging habitat and behavior between sex or 

age-classes and subpopulations to better understand how resource 

availability and foraging success may affect HMS demography. We 

summarize those data here and evaluate the null hypothesis that 

foraging patterns did not vary with age and sex of the seals or among 

colonies.

Seals in the NWHI foraged extensively within barrier reefs and on 

the slopes of reefs and islands at all colony sites, but their foraging 

habitats also ranged widely to seamounts and submerged reefs and 

banks along the HIA submarine ridge (Figure 2). Most dives were less 

than 150-m deep, though some exceeded 550 m. Foraging patterns 

varied substantially with age and sex of seals and among colonies. In 

the NWHI, foraging ranges of seals increased from the eastern colony 

at French Frigate Shoals to the colony at the western end of the HIA at 

Kure Atoll.

Seals in the Main Hawaiian Islands (MHI) foraged in shallow habitats 

closer to haul-out sites compared with seals in the NWHI. Most 

locations were within the 200-m bathymetry contour and most dives 

of all seals were less than 60 m, though some had deeper modes at 

between 80 and 160 m and two seals exceeded 200 m. Dive durations 

generally lasted between 6 and 10 minutes. These data suggest that 

there may be fundamental differences in prey abundance or community 

18

Foraging Studies of 

Hawaiian Monk Seals 

Using Satellite-Linked 

Depth Recorders

Charles L. Littnan

Pacific Islands Fisheries Science Center 

Honolulu, Hawaii

charles.littnan@noaa.gov

Brent S. Stewart

Hubbs-SeaWorld Research Institute

San Diego, California

Figure 1. Hawaiian monk seals were tagged with satellite-linked depth recorders to 

monitor their movements and diving behaviors. This photo shows an adult male monk seal 

with a satellite tag attached to its dorsal pelage.
36

dynamics among colonies but particularly between the 

NWHI and the MHI. These differences may be limiting 

population recovery of monk seals in the NWHI but 

are adequate to support population growth in the MHI 

(Figure 3).

The current SDR technology has provided valuable 

information on the foraging behavior of monk seals on 

a course scale (i.e., intra-atoll movement). However, 

there is a great need to develop and deploy instruments 

that can record foraging movements on a finer scale to 

better assess dive behavior, habitat use, and potential 

competition within and between sex and age-classes. 

Current technology relying on the estimation of location 

using the Argos satellite system is limited by the much 

reduced frequency of satellite passes near the equator 

as well as the behavior of the animals. Much of the 

bathymetric data being collected is at a resolution of 

5-m grid spacing. To make effective use of these maps 

for studying monk seal habitat use, we would need a 

location resolution of 10- to 25-m accuracy from the 

seals. It is likely that new GPS technology will be the 

most reliable way to monitor monk seal movements in 

the future.

Figure 3. The calculated 95% and 50% probability 

distributions representing the overall habitats used 

by three monks seals in the MHI. The age-classes 

were adult (A), juvenile (J), and weaner (W), and sex 

categories were male (M) and female (F). Results 

show that monk seals forage within the 200-m 

bathymetry contour and tend to have relatively 

small ranges.

Figure 2. Foraging locations of 147 monk seals from 

six subpopulations in the Northwestern Hawaiian 

Islands. Satellite tracking showed that monk seals 

used much of the benthic habitat, including atolls, 

slopes, and seamounts. Numbered areas indicate 

atolls, islands, or known seamounts.
37

The application of satellite telemetry to highly inaccessible species 

such as arctic marine mammals has revolutionized the study of their 

movement patterns and foraging behavior. We report on a unique 

approach that combines satellite telemetry and molecular genetic 

analysis to describe the movements, foraging ecology, dispersal 

patterns, and population structure of beluga whales (Delphinapterus 

leucas) in the Alaskan, Russian, and Canadian arctic. The polar 

environment limits tag deployment primarily to the summer months 

and typically curtails transmissions to much less than one year. Ice 

conditions also limit sampling opportunities for genetic analysis to a 

number of discrete coastal areas in spring and summer.

The genetic analysis of 1,200 tissue samples collected at the ice edge in 

spring and along the coast in summer resolved population structure 

and identified separate stocks of beluga whales in the western Nearctic, 

as well as reconstructing spring migration routes of these stocks 

(Figure 1). The deployment of satellite tags at a number of these same 

coastal sites in the summer months has added to our knowledge of 

movements and provided unique insights into beluga dive behavior 

and foraging ecology. Telemetry enabled us to reconstruct the 

remainder of the annual migration pathways of a number of stocks and 

revealed that distinct stocks often overlapped in space if not in time. 

The integration of the telemetry and genetic findings with traditional 

ecological knowledge and aerial and shore-based surveys is a powerful 

tool in designing effective management policies for this species.

Figure 1. To study movements and dispersal patterns of beluga whales in the Alaskan, 

Russian, and Canadian arctic, whales were tagged with satellite tags. The map shows the 

movements of the tagged whales.

19

Combination of Satellite 

Telemetry and Molecular 

Genetic Analysis in the 

Study of Beluga Whales in 

the Western Nearctic

Greg O’Corry-Crowe

Southwest Fisheries Science Center

La Jolla, California

greg.o’corry-crowe@noaa.gov

Robert Suydam

North Slope Borough

Department of Wildlife Management

Barrow, Alaska

Jack Orr

Department of Fisheries and Oceans Canada

Winnipeg, Manitoba

Lloyd Lowry and Kathy Frost

University of Alaska—Fairbanks

Fairbanks, Alaska

Dennis Litovka

ChukotTINRO

Anadyr, Chukotka, Russia

Rod Hobbs

Alaska Fisheries Science Center

Seattle, Washington
38

In 1989 we developed and tested a microprocessor event recorder 

to document long-distance marine animal migrations. The recorder 

contained 256 K of memory, a clock, and a control circuit to operate the 

recorder that recorded time, sea surface temperature (SST), sea surface 

light intensity, and pressure. The recorder was housed in a columnar, 

titanium pressure housing. We deployed these dive recorders on adult 

male northern elephant seals (Mirounga angustirostris) at the end of the 

breeding season and recovered the recorders 4 months later when the 

animals returned to land to molt. With the recorded data, we were able 

to obtain a single point estimate of animal location each day and chart 

the migration of animals from the California Channel Islands to the 

Northern Gulf of Alaska and their return to the Channel Islands

(Figure 1).

The derivation of animal location has been described. Essentially 

measurements of surface light intensity are used to construct the 

day length for each day the animal is at sea. From light-level 

measurements, estimates of civil twilight, day length, and local 

apparent noon are calculated; these data are used to estimate a 

latitude and longitude. The method does not work at high latitudes 

in conditions of continuous daylight or darkness. The method is 

also prone to errors during 15 days on either side of the vernal and 

autumnal equinox. During these periods we compared recorded sea 

surface temperatures to recorded SST summaries of blended analyses 

from satellite, shipboard, and buoy measurements to obtain the best 

estimate of animal location.

This same technology has been used to assess migration of other marine 

mammals and is now used on pop-up tags to track large pelagic fish.

20

Documenting Elephant 

Seal Movement with a 

Geographic Location, 

Time-Depth Recording 

Archival Tag

Robert L. DeLong and Sharon Melin

Alaska Fisheries Science Center

Seattle, Washington

robert.delong@noaa.gov

Brent S. Stewart

Hubbs-SeaWorld Research Institute

San Diego, California

Roger D. Hill

Wildlife Computers

Redmond, Washington

Figure 1. To document longdistance marine animal 

migrations, dive recorders 

were deployed on adult male 

northern elephant seals. Using 

this technology, researchers were 

able to monitor the locations 

of the tagged seals and show 

distinct double migrations for 

males and females.
39

Little is known about the behavior and distribution of central California 

coho salmon (Oncorhynchus kisutch) and steelhead (O. mykiss) during 

the ocean phase of their life histories. As both species are protected

by the Endangered Species Act, there is no targeted local ocean 

fishery and they are rarely collected by Chinook salmon 

(O. tschawytscha) fishery and research surveys. While this is due in part 

to the greater abundance of Chinook salmon and lower probability of 

capturing coho salmon or steelhead, it does not answer the question of 

ocean habitat use by these two species.

We have recently begun an archival tagging program at Scott Creek, 

a small central California coastal stream approximately 100 km south 

of San Francisco. The first phase of the program was to tag juvenile 

fish just prior to ocean entry. We selected one of the smallest archival 

loggers available (iBKrill, 13.2 × 25.4 mm, 3.2 g, Alpha Mach Inc., 

Mont-St.-Hilaire, Quebec), which collected temperature data in 0.5°C 

resolution. The tag can be applied with internal or external attachment 

methods. The external method currently requires a two-point 

attachment. Due to concerns about fish growth and drag, the tags were 

surgically implanted into the body cavity of juvenile fish greater than 

200-mm fork length and 100-g mass (Figure 1). While it was possible

to collect wild steelhead in this size range, juvenile coho salmon rarely 

exceed 140 mm prior to ocean entry. A small conservation hatchery 

in the watershed produces juvenile steelhead and coho salmon from 

wild broodstock. Here, growth rate of both species was accelerated 

so that hatchery fish of sufficient size were available for tagging. 

Approximately 150 archival temperature loggers were deployed on 

juvenile coho salmon and steelhead just prior to ocean entry for the 

purposes of studying movements (limited) and thermal preferences at 

sea. In addition, 35 short-term, high-resolution (1- or 5-minute data 

collection intervals) deployments of temperature loggers were made 

on steelhead smolts to study estuary usage patterns (Figure 2) during 

the summers of 2003 and 2004. In the spring of 2002 and 2004, we also 

deployed external tags (Figure 2) on adult female steelhead during their 

return migration to sea. To date, five short-term and four long-term 

21

Archival Tagging of 

Salmonids on the Central 

California Coast

Sean A. Hayes, Ellen V. Freund,

Chad V. Hanson, Morgan H. Bond,

and R. Bruce MacFarlane

Southwest Fisheries Science Center

Santa Cruz, California

sean.hayes@noaa.gov

Figure 1. Implanting iBKrill temperature logger into a 220-mm juvenile 

salmonid. Upper photo shows tag partially inserted; lower photo 

shows fish after implantation and closure with surgical staples.

Figure 2. External attachment of iBKrill tag on steelhead smolt (upper) 

and the larger iBCod tag on steelhead (lower).
40

deployment tags have been recovered, providing clear 

patterns of estuary and ocean thermal environments 

experienced by steelhead (Figure 3).

Several aspects of the study site make it ideal for archival 

tagging. The hatchery provides large juvenile fish and 

serves as a tagging laboratory. An adult fish trap and 

relatively small adult populations (approximately 350 

returning adults per species) increase the probability 

of data logger recovery and enable the collection of 

adult steelhead during their return migration to sea for 

external and internal tagging purposes.

The major challenge facing archival tagging research 

with salmonids relates to their typically poor survival 

rates between life history stages. In Scott Creek, 

approximately 3% of smolts entering the ocean survive 

to return as adults, and only 4% to 6% of adult steelhead 

are observed returning to spawn a second time. This 

translates into tag recovery probabilities of roughly 

1% to 5%, accounting for potential increased mortality 

rates associated with tagging, and probability of not 

recapturing the fish in the stream even if it survives to 

return. This drives the need for inexpensive tags since 

only a small percentage will ever be recovered (iBKrill 

is approximately $45 per tag). In addition, tags need 

to be small for use on juveniles and to avoid increasing 

mortality rates.

Currently, the most likely methods of tracking 

movement appear to be geolocation and comparing sea 

surface temperature (SST) data to tag temperature data 

from times when fish were known to be near the ocean 

surface (if depth or pressure data are recorded). The 

use of archival satellite tags is not a possibility due to 

the limited amount of time salmonids spend at or near 

the surface. At this point pop-up tags are not small 

enough for deployment on a 4-kg adult steelhead, much 

less a 100-g smolt. Alternatively the use of ultrasonic 

tags and large arrays of acoustic monitors could 

provide for data collection on multiple individuals. The 

limitations of these systems include the high cost of the 

arrays and limited coverage by the listening stations. 

Future plans include tagging juvenile coho salmon 

and steelhead with internal archival tags that record 

a time series of temperature and depth, and tagging 

adult steelhead with external archival tags that record a 

time series of temperature, depth, and light. As we are 

in the early stages of the project, data analysis efforts 

are preliminary. Clearly, a geographic information 

system (GIS) of representing the data will need to 

be implemented, one that can overlay satellite data 

such as SST and data collected from ships, including 

temperature, conductivity, salinity, chlorophyll, or depth 

profiles.

Figure 3. Upper plot shows partial tag records from a juvenile and 

an adult steelhead in the estuary just prior to and after ocean entry 

in March 2004. Estuary thermal data are overlayed for comparison. 

Lower plot shows a full year of ocean temperature environment 

experienced by adult steelhead.

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41

Data storage tags were deployed on Atka mackerel (Pleurogrammus 

monopterygius), Pacific cod (Gadus macrocephalus), and several flatfish 

species in the eastern Bering Sea and Gulf of Alaska between 2000 

and 2005. The tags, originally manufactured by Conservation Devices 

(model RL-42) and currently manufactured by Lotek Wireless (model 

LTD-1100, Newmarket, Ontario), recorded both pressure (depth) 

and temperature. Tags are flat sided, measuring 8 × 16 × 27 mm and 

weighing approximately 4.1 g. Tags were attached externally, beneath 

the anterior dorsal fin, using 0.5-mm stainless steel wire (Figure 1).

A total of 1,412 tags have been deployed, including 530 on Atka 

mackerel, 634 on Pacific cod, and 248 on flatfish. Tagged fish were 

captured in commercial trawl, pot, longline, and jig fisheries. A cash 

reward of $200 was provided as an incentive for returning tags. Thus 

far, recovered tags include 24 from Atka mackerel, 285 from Pacific cod, 

and 2 from northern rock sole (Lepidopsetta polyxystra).

The initial impetus for deployment of data storage tags was to 

determine whether the vertical movements of these species influenced 

their availability to resource assessment surveys. NMFS Alaska bottom 

trawl surveys are conducted during daylight hours only. Results from 

the Atka mackerel tags indicate clear diurnal movements with fish 

remaining on the bottom during nighttime and undergoing extensive 

vertical migrations during daytime (Figure 2). Vertical movements of 

Pacific cod were much more variable, although it appears individuals 

spend most of the time closely associated with the bottom during both 

daytime and nighttime.

22

Archival Tagging of Atka 

Mackerel, Pacific Cod, and 

Flatfish in the Aleutians, 

Gulf of Alaska, and 

Eastern Bering Sea

Dan Nichol

Alaska Fisheries Science Center

Seattle, Washington

dan.nichol@noaa.gov

Figure 2. Diurnal vertical movement pattern of Atka 

mackerel for a week period.

Figure 1. Archival tagging of 

Atka mackerel (left) and Pacific 

cod (right).

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42

More recent examination of the tag data from Pacific 

cod documents a recuperation period after tagging. 

Unlike Atka mackerel and flatfish species, Pacific cod 

have swim bladders that can rupture during capture. 

Although swim bladders can be sealed within 24 hours 

after capture, a recuperation process, characterized by 

a gradual descent back to the depth of capture, usually 

occurs. Gradual descents can take more than 2 weeks 

depending on the depth cod are returning to. These 

descents actually represent the neutrally buoyant 

descent of cod after they have lost gas from the rupture. 

Descents are slow because the physiological process of 

secretion of gas into the swim bladder is slow.
43

23

Application of Electronic 

Data Storage Tags in 

Studies of Black Sea Bass 

and Yellowtail Flounder in 

the Northwest Atlantic

Joshua Moser, Gary Shepherd,

Steve Cadrin, Azure Westwood,

and Stacy Kubis

Northeast Fisheries Science Center

Woods Hole, Massachusetts

joshua.moser@noaa.gov

Figure 1. Lotek 1100 data storage tag (left, shown to scale against a paper clip) and a 

pressure chamber used for predeployment testing (right, shown to scale against a ruler).

Electronic data storage tags (Lotek 1100, Figure 1, Lotek Wireless, 

Newmarket, Ontario) that record temperature and pressure have 

provided new insight into the behavior of black sea bass (Centropristis 

striata) and yellowtail flounder (Limanda ferruginea). Several hundred 

tags have been deployed in seasonal batches at predetermined 

locations.

Development of an experimental design is critical for a successful 

program. Prior to tag deployment, quality assurance testing in a 

pressurized container has reduced the likelihood of tag failure

(Figure 1). Recovery of archived data also depends on fishermen to 

recapture and report tagged fish. Consequently, reward incentives 

and outreach programs are a critical part of these tagging programs. 

We have experienced lower return rates in sea bass (3.7%) relative 

to internal anchor tags (14.3%), while flounder returns (8.1%) have 

exceeded traditional Petersen tags (5.6%). Differences in predation 

resulting from visibility of the tag (color, possible light flashes), taginduced mortality, tag loss, and differences in fisheries may contribute 

to the variable recovery rates between species (Figure 2). Results of 

the experiments have identified movement corridors in yellowtail 

flounder related to temperature, seasonal changes in temperature 

and depth along migratory routes in sea bass (Figure 3), and daily 

behaviors related to tidal cycles for both species (Figure 4). Availability 

of oceanographic data corresponding to the area used by tagged fish is 

critical for the interpretation of archived tagging data.

Suggested improvements in tag design may involve measurements of 

conductivity, longer battery life, and alternative attachment designs 

that are less invasive.
44

Figure 4. Depth records from an archival tag 

deployed on a yellowtail flounder on Georges 

Bank indicating time on bottom and reflecting the 

local tidal cycle. Distinct off-bottom movements 

(numbered 1–5) during late evening or early 

morning are also shown along with a substantial 

change in bottom depth associated with movement 

(number 3).

Figure 2. Areas of abrasion 

on black sea bass (left) and 

yellowtail flounder (right) 

resulting from tags. Time at 

large was 355 days for black 

sea bass and 723 days for 

yellowtail flounder. Tag-induced 

pathologies may lead to tag loss 

or mortality.

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Figure 3. Time series of data storage tag (DST) 

readings from tagged black sea bass released 

November 2003 in Rhode Island and recovered 

February 2004 in Hudson Canyon (179 miles

[288.1 km] southwest of release point). Results 

suggest a behavioral relationship between 

temperature and movement.

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45

Large areas of cold, oxygen-depleted (hypoxic) waters are permanent 

features of the eastern tropical Pacific and Atlantic oceans, a result of 

intense nutrient upwelling. Here we use electronic tags to show that 

these cold, hypoxic strata compress the acceptable physical habitat 

of marlin and sailfish into a shallow surface layer, with important 

ecological and fisheries consequences.

Very little data exist to characterize the habitat depths of tropical 

pelagic billfish and tuna, even though these features are critical for 

monitoring population abundance. We investigated habitat depth of 

marlin and sailfish using pop-up satellite archival tags (PSAT). We 

monitored 19 billfish for an aggregate of 801 days in western North 

Atlantic habitats where dissolved oxygen (DO) concentrations are not 

limiting, and 13 billfish for an aggregate of 429 days in the eastern 

tropical Pacific, where hypoxic conditions are often as shallow as 25 m 

(Figure 1). We stratified the amount of time spent by each fish, and its 

deepest dive during successive 6-hour periods, into strata of less than 

or equal to 50 m, greater than 50 m, greater than 100 m, and greater 

than 200 m. Pacific billfish remained within the shallowest strata, while 

Atlantic billfish were much more likely to venture deeper (Figure 2). 

Our analyses showed markedly different vertical habitat use (highly 

significant p < 0.001) in the two study areas.

The spatial extents of acceptable habitats for some estuarine and 

shallow demersal reef fishes are known to respond to variations in DO. 

Our findings show this phenomenon also exists at a much larger scale 

for pelagic fishes in the tropical oceans. In our Pacific study area, DO 

levels of 1.5 ml/l occur at about 75 m and this depth appears to form 

the lower threshold of habitat use for our Pacific billfish (Figure 3). 

Conversely, DO rarely declined below 3.5 ml/l and did not appear to 

constrain vertical habitat use of our Atlantic marlin or sailfish

(Figure 3). The extremely shallow depth of acceptable habitat in 

the Pacific study area arising from nutrient upwelling in the region 

also restricts this highly productive environment to the very near 

surface. We feel that this habitat compression facilitates closer physical 

proximity of predator and prey in the same habitat, which would 

provide enhanced foraging opportunities that may contribute to larger 

average sizes of apex predators.

24

Hypoxia-Based Habitat 

Compression of Tropical 

Pelagic Fishes

Eric D. Prince

Southeast Fisheries Science Center

Miami, Florida

eric.prince@noaa.gov

C. Phillip Goodyear

Niceville, Florida

Figure 1. Pacific basin (blue, 

A) and Atlantic basin (red, B) 

study areas and release sites 

(white stars). Areas encompass 

horizontal displacements where 

electronic tags deployed on 

billfish sent transmissions to the 

Argos satellite system.
46

Figure 3. (A) Temperature (°C), (B) dissolved oxygen 

(ml/l), (C) salinity (ppt), and (D) chlorophyll (μg/l), 

profiles derived from 1998 and 2001 World Ocean 

Atlas data for the Atlantic (red) and Pacific (blue) 

study areas. Temperature, dissolved oxygen, and 

salinity data are means, and horizontal error bars 

are ±1 standard deviation. Chlorophyll data are 

medians, and horizontal error bars are for the 10th 

and 90th percentiles of the distribution of values 

within included cells.

We have discovered strong quantitative evidence 

that the depth of the acceptable habitat for billfish is 

shallower in our eastern Pacific study area than the 

western North Atlantic. We contend that this difference 

is a consequence of the cold, hypoxic water underlying 

the shallow thermocline in the eastern Pacific, not 

present in the western North Atlantic. The same 

environmental features that limit acceptable habitat 

to a very shallow layer also make the fishes more 

vulnerable to exploitation, as evidenced by high catches 

of tropical pelagic tuna in these areas. Where the habitat 

is compressed into a shallow surface layer, fish are 

fully exposed to highly efficient surface gears such as 

purse seines—a combination that can threaten resource 

productivity and sustainability. Many of these species 

are already fully exploited or overfished.

Figure 2. Proportion of (A) time at depth and (B) 

proportion of records with dives to depth for four 

depth strata (≤50 m, >50 m, >100 m, and >200 m) 

in Atlantic (red) and Pacific (blue) basin study areas 

for sailfish (solid color) and marlins (hatched bars). 

Horizontal error bars for proportion of time at depth 

and proportion of records with dives at depth are 

±1 standard error.

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47

Satellite telemetry of 43 juvenile loggerhead sea turtles (Caretta 

caretta) in the western North Pacific together with satellite remotely 

sensed oceanographic data identified the Kuroshio Extension Current 

Bifurcation Region (KECBR) as a forage hotspot for these turtles

(Figure 1). Thirty-seven of the loggerhead turtles were 1- and 2-

year-olds that were hatched and reared at the Port of Nagoya Public 

Aquarium, while the other six were juveniles caught and released from 

commercial longline vessels in the central North Pacific. Argos-linked 

transmitters were attached to all turtles.

We used satellite remotely sensed sea surface height and ocean color 

data to examine the turtles’ ocean habitat. We tried several approaches 

to link oceanographic data with turtle position and movement data. To 

examine seasonal links, quarterly histograms of the latitude-frequency 

distribution of all turtles were combined with mean geostrophic 

velocity and surface chlorophyll as functions of latitude. To examine 

fine-scale use of habitat features, we used overlays of turtle tracks and 

satellite imagery.

The results indicated that in the KECBR juvenile loggerhead turtles 

resided in Kuroshio Extension Current (KEC) meanders and the 

associated anticyclonic (warm core) and cyclonic (cold core) eddies 

during the fall, winter, and spring when the KEC water contains 

high surface chlorophyll. Turtles often remained at a specific feature 

for several months. However, in the summer when the KEC waters 

become vertically stratified and surface chlorophyll levels were low, 

the turtles moved north up to 600 km from the main axis of KEC to the 

Transition Zone Chlorophyll Front (TZCF).

In some instances, the loggerhead sea turtles swam against geostrophic 

currents, and seasonally all turtles moved north and south across the 

strong zonal flow. Loggerhead sea turtles traveling westward in the 

KECBR had their directed westward movement reduced 50% by the 

opposing current, while those traveling eastward exhibited an increase 

in directed zonal movement. It appears, therefore, that these relatively 

weak-swimming juvenile loggerhead sea turtles are not passive drifters 

25

Kuroshio Extension 

Current Bifurcation 

Region: A Pelagic Hotspot 

for Juvenile Loggerhead 

Sea Turtles

Jeffrey J. Polovina, George Balazs,

and Evan Howell

Pacific Islands Fisheries Science Center

Honolulu, Hawaii

jeffrey.polovina@noaa.gov

Itaru Uchida

Port of Nagoya Public Aquarium

Minato-ku, Nagoya, Japan

Denise Parker

Pacific Islands Fisheries Science Center

Joint Institute for Marine and Atmospheric 

Research

University of Hawaii

Honolulu, Hawaii

Peter H. Dutton

Southwest Fisheries Science Center

La Jolla, California

Figure 1. Satellite-tagged juvenile loggerhead sea turtles.
48

in a major ocean current but are able to move east, 

west, north, and south through this very energetic and 

complex habitat (Figure 2).

These results indicate that oceanic regions, specifically 

the KECBR, represent an important juvenile forage 

habitat for this threatened species. Interannual and 

decadal changes in productivity of the KECBR may be 

important to the species’ population dynamics. Further, 

conservation efforts should focus on identifying and 

reducing threats to the survival of loggerhead sea turtles 

in the KECBR.

Figure 2. Overlays of migration records from (A) October 2003, (B) November 2003,

 (C) December 2003, and (D) January 2004 of satellite-tagged juvenile loggerhead sea 

turtles and satellite imagery show that the turtles were not drifting with the major ocean 

current, but actively swimming.
49

We report on the progress, advantages, and challenges of merging 

satellite telemetry, archival tag, and oceanographic data for ecosystem 

applications. Since 1990, the Alaska Ecosystems Program has 

used satellite transmitters or satellite dive recorders, sometimes in 

combination with archival tags (time-depth recorders), to record 

movements and diving patterns of 260 northern fur seals (Callorhinus 

ursinus) and 154 Steller sea lions (Eumetopias jubatus) (Figure 1).

Subsets of the movement and diving data have been merged with 

remotely sensed and directly observed environmental data. These 

efforts have advanced our understanding of the foraging ecology of 

these animals and have resulted in the identification of oceanographic 

processes that appear to influence at-sea behavior. However, locating, 

acquiring, formatting, processing, and merging environmental data 

with movement and diving data for analysis has been difficult. 

Some of the challenges include integration of environmental data that

differs between northern fur seals and Steller sea lions, Argos location

error problems when interpreting Steller sea lion movements compared 

to northern fur seal movements, long-term deployments (>1 year), 

and coordinating the efforts of multiple groups processing the 

same information without reinventing the wheel. Possible solutions 

include increased spatial and temporal overlap using autonomous 

underwater vehicles, drifter buoys, small-scale ship surveys, and 

onboard environmental sampling; evaluating both “constructive” and 

“destructive” Argos location filtering techniques; applying software 

modules for all filtering techniques; using GPS tags; experimenting 

with new adhesives, which may increase flexibility and durability and 

decrease application time; and utilizing remote-sensing or animaltracking users group to share processed remote-sensing data.

26

Merging Satellite 

Telemetry with 

Oceanographic and 

Archival Tag Data to 

Assess Foraging Ecology 

of Alaskan Pinnipeds

Jeremy T. Sterling, Rolf Ream,

Brian S. Fadely, and Tom Gelatt

Alaska Fisheries Science Center

Seattle, Washington

jeremy.sterling@noaa.gov

Figure 1. Steller seal lion foraging 

location, surface chlorophyll 

a, and geostrophic vectors. 

Results show merged altimetry 

data Colorado Center for 

Astrodynamics Research (CCAR) 

1⁄4°–geostrophic vectors and 

Moderate Resolution Imaging 

Spectroradiometer (MODIS)

4.89 km2 surface chlorophyll a.

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54°N

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56°N

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58°N

58°N

Kodiak Island

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50

The decline of the western stock of Steller sea lions (Eumetopias 

jubatus) has been attributed to juvenile mortality, which may have 

been exacerbated by environmental perturbations that altered the 

distribution or abundance of food resources. It is necessary, therefore, 

to assess how juvenile Steller sea lions alter their foraging strategies in 

response to spatial and temporal changes of oceanographic processes, 

which ultimately affect the distribution of prey. Although data on the 

foraging behavior of juvenile Steller sea lions have been fairly detailed, 

little is known about the relationship between foraging locations and 

their associated physical and biological characteristics. For this study, 

a combination of satellite telemetry, remote-sensing techniques, and a 

geographic information system (GIS) was used to assess the foraging 

ecology and habitat use of juvenile Steller sea lions with respect to 

patterns of oceanic features (sea surface temperature, or SST, and 

chlorophyll a), which possibly serve as proxies for environmental 

processes or prey.

Because archival tags such as time-depth recorders are difficult to 

retrieve from Steller sea lions due to logistics associated with recapturing 

the animals, 75 satellite-depth recorders (SDRs, Wildlife Computers, 

Redmond, Washington) and 23 satellite relay data loggers (SRDLs, Sea 

Mammal Research Unit, SMRU, St. Andrews, Scotland) were deployed 

on juvenile Steller sea lions in the Aleutian Islands, Gulf of Alaska, and 

Washington from 2000 to 2004. Location data collected by SDRs were 

decoded using Satpak software (Wildlife Computers), whereas location 

data collected by SRDLs were decoded in a marine mammal behavior 

visualization system (MAMVIS) by the SMRU. In addition to location 

data (latitude, longitude), SDRs provided information over specified 

time periods for all dives (depth, duration, and time at depth) within 

user-defined histogram bins. The SRDLs provided similar data but 

provided attributes of behavior and the environment (i.e., temperature 

at depth) with the corresponding time, enabling us to interpolate 

behaviors to specific locations.

Level 3 standard mapped images of SST and chlorophyll a, which 

were collected by the Moderate Resolution Imaging Spectroradiometer 

(MODIS) instrument aboard the Terra and Aqua satellites (NASA’s 

EOS-AM and EOS-PM, Earth Observing Systems crossing the equator 

in the morning and evening, respectively), were obtained from the 

Goddard Earth Sciences Distributed Active Archive Center and the 

Ocean Color Discipline Processing System. These data products had 

a spatial resolution of 4.88 km and were converted to raster data grids 

using ArcGIS 9.0 (ESRI, Redlands, California). Temperature data 

provided by SRDLs were useful for ground truthing remotely sensed 

images of SST, which often were missing data as a result of cloud cover. 

Additionally, geostatistical techniques and other geoprocessing tools 

(ArcGIS) were used to interpolate or enhance chlorophyll images that 

were missing data. Landscape metrics of composition and configuration 

were quantified for all images using a spatial pattern analysis program 

and examined with respect to the distribution and behavior of Steller sea 

lions.

Despite the advantages provided by SRDLs, only subsamples of data 

were transmitted by the instruments due to bandwidth restrictions. The 

ongoing development of a remote release platform (Figure 1, Advanced 

Telemetry Systems, Isanti, Minnesota), which is a device configured to 

release attached equipment from marine mammals on a signal from a 

command unit, will greatly improve our ability to collect the satellite 

tags and therefore obtain detailed dive data for Steller sea lions.

Figure 1. A prototype remote 

release platform that is being 

developed by Advanced 

Telemetry Systems.

27

Spatial Patterns of 

Juvenile Steller Sea Lions 

at Sea with Respect to 

Corresponding Patterns 

of Environmental 

Features

Michelle E. Lander, Jeremy T. Sterling, and 

Brian S. Fadely

Alaska Fisheries Science Center

Seattle, Washington

michelle.lander@noaa.gov
51

Scientists and resource managers seeking oceanographic data are 

often confronted with a bewildering array of data sets and formats. 

Even with the high-quality satellite data now supplied by NOAA, 

NASA, and their international partners, integration and dissemination 

of these data sets requires significant technical infrastructure and 

expertise. We have developed a system to demonstrate a method 

for the effective integration of information retrieved from electronic 

tags deployed with independently derived environmental data. The 

rapidly expanding suite of quality hydrographic data measured by 

a variety of commercially marketed tags provides a unique capacity 

to identify oceanic habitat, but these records are inherently unable to 

describe the larger-scale processes that may bias local measurements. 

In order to place the in situ (“at critter”) measurements within the 

context of changing oceanic conditions, we use a Live Access Server 

to combine the data measured by the electronic tag placed on the 

animal with available satellite data and model output at temporal and 

spatial scales commensurate with those of the predominant regional 

ocean dynamics. Projects have been initiated with several tagging 

teams (e.g., Pacific Islands Fisheries Science Center and the Census 

of Marine Life’s Tagging of Pacific Pelagics program). Preliminary 

results from each project are presented and discussed. The emphasis 

for current and future work is placed on improving the Internet-based 

interface to improve direct involvement in the analyses by all levels of 

investigators; the feedback from those investigators is expected to drive 

these efforts.

A research team at the Environmental Research Division of the 

Southwest Fisheries Science Center has developed an index of habitat 

potential that is based on the observed range of temperatures used 

by electronically tagged Chinook salmon (Oncorhynchus tshawytscha) 

and the distribution of sea surface temperatures (SSTs) that match this 

range. SST values from satellites are used to extrapolate (Figure 1, 

upper maps) over the entire range, offering insight into the impact of 

28

Critters in Context: 

A Method for Integrating 

Tag Data with Other 

Environmental 

Information

David G. Foley

Joint Institute for Marine and Atmospheric 

Research

Southwest Fisheries Science Center

Pacific Grove, California

dave.foley@noaa.gov

Lynn deWitt

Southwest Fisheries Science Center

La Jolla, California

Figure 1. Potential habitat 

for Chinook salmon based 

on temperature preferences 

measured with electronic tags 

shows significant interannual 

variability between years 

(upper maps). The lower graphs 

illustrate how dive behavior 

of the salmon changed when 

preferred surface habitat was 

no longer available due to 

anomalously warm surface water.

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52

ocean environmental parameters while also providing 

a useful diagnostic tool for examining behavior of the 

animals (Figure 1, lower graphs). In this case satellite 

ocean-color data were used also to examine the role 

of surface productivity in determining the seasonal 

patterns of vertical movement by Chinook salmon. This 

work lays the foundation for describing habitat on the 

basis of temperature and suggests a need to incorporate 

other variables in the analysis. Because the tags used 

included no mechanism for deriving geographic 

position, there was no way to compare the satellite 

measurements with those recorded on the tags.

The availability of geographic position fundamentally 

changes the approach one uses to analyze the data. In 

addition to displaying simple overlays of tracks on SST, 

bathymetry, sea surface height, surface chlorophyll 

concentration, surface currents, and surface winds, 

one can also view movies and actually extract various 

digital data along the track of the animal for each time 

period available. This technique is analogous to the 

“drill down” capability of many geographic information 

systems (GISs), but is more appropriate to the dynamic 

ocean environment as it allows the animal to essentially 

swim through the data as they did in the actual ocean.

Figure 2. Sample output from data extractions performed for a specific leatherback turtle 

(Dermochelys coriacea). Environmental values of (A) chlorophyll, (B) water depth, and (C) 

SST are shown in red for the track of the animal, with the background “available” values 

shown in green. (D) Bathymetry and track are shown. Clearly the turtle demonstrates 

a preference for low-chlorophyll, high-visibility waters, while showing no distinct 

preference for SST or water depth. This result is similar to the preferences of loggerhead 

sea turtles (Caretta caretta) in the subtropical convergence zone as observed elsewhere. 

Note: This was preliminary data, which differed significantly from the final analysis.

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As part of a NMFS-led effort to understand and 

eventually mitigate the take of olive ridley turtles 

(Lepidochelys olivacea) in mahi mahi (Coryphaena hippurus) 

longline fisheries near Costa Rica, a number of turtles 

were equipped with pop-up satellite archival tags 

(PSATs), which maintain a rough record of position 

based on measured light level and a fair amount 

of filtering and comparison with independently 

measured environmental parameters. These data 

were integrated with satellite data using the Pacific 

Fisheries Environmental Laboratory Live Access Server 

to determine what, if any, preferences could be found 

with respect to environmental conditions (Figure 2). 

A very strong preference for low chlorophyll water 

was discovered. The resulting probability distribution 

function can now be used to generate maps of likely 

turtle locations using satellite-based ocean-color 

measurements with possible application toward the 

mitigation of adverse interactions with the fisheries. The 

probability distribution function would entail a simple 

quantification of the relationships established in

Figure 2 (e.g., by regression) and then plugging in the 

values to the satellite data fields for use in fisheries 

management models.
53

Monitoring the long-term movements of small cetaceans with 

radiotelemetry has the potential to identify important seasonal habitat 

use patterns. This type of information is critical for improving stock 

assessments. Understanding the interactions between species and 

their environment is the cornerstone for assessing population viability. 

Determining the degree to which inherent environmental variability 

affects the distribution and abundance of populations compared 

to direct or indirect anthropogenic impacts is key to informed 

conservation actions.

Marine mammals, for at least some part if not all of the year, focus 

on foraging. In many cases their prey are highly mobile, as they 

respond to patchy productivity in the ocean environment. This 

productivity is in turn driven by complex interactions of bathymetric 

and hydrographic features that can cause marine habitats to vary 

dramatically on sometimes relatively short temporal and spatial scales.

In northern Washington and southern British Columbia, the primary 

static bathymetric features include five basins: 1) outer coast, 2) Strait 

of Juan de Fuca, 3) Haro Strait, 4) Georgia Strait, and 5) Puget Sound. 

Only the first four are relevant to this study on porpoise movements. 

Several prominent features of the 60-km wide outer coast shelf area 

adjacent to the entrance to the Strait of Juan de Fuca include the Juan de 

Fuca Canyon and La Perouse and Swiftsure banks. The Strait of Juan 

de Fuca, bounded by Vancouver Island and the Olympic Peninsula, 

links the ocean with the Georgia Strait basin (via Haro Strait) and Puget 

Sound. This strait gradually shallows from west to east with its most 

prominent feature being the north-south Victoria sill. Haro Strait/

Boundary Pass is the largest channel connecting the Strait of Juan de 

Fuca with the Georgia Strait, running north-northeast through the San 

Juan Islands to the east and Vancouver and Gulf Islands to the west. 

This channel is deep along the eastern shore shallowing to the west 

in Haro Strait, and the reverse bathymetry pattern exists in Boundary 

Pass. The bathymetric junction between Boundary Pass and Georgia 

Strait is the Boundary Pass sill. Georgia Strait runs northwest from 

the northern San Juan Islands and is bounded by the Gulf Islands and 

Washington State in the southern portion and Vancouver Island and the 

mainland in the northern portion. The southern portion is the widest 

region with a deep central basin that narrows to the west of the mouth 

of the Fraser River. This region has two major persistent features: the 

California Current on the outer coast and the Fraser River plume in 

Georgia Strait. Several prominent ephemeral features of the system 

include 1) prevailing southwest winter winds and northwest summer 

winds, 2) outer coast spring upwelling, 3) the Juan de Fuca eddy,

 4) Fraser River freshet, and 5) spring or neap tides.

In the early spring, a dramatic shift occurs in prevailing wind patterns 

from the winter southwesterly winds to the summer northwesterly 

winds. This results in coastal upwelling with cold, nutrient-rich water 

moving up the continental slope, including the Juan de Fuca Canyon. 

Some of this water mass rotates counterclockwise, creating the Juan 

de Fuca eddy, and some of this water mass continues moving up the 

Strait of Juan de Fuca until it reaches the Victoria sill. A combination of 

the spring freshet from the Fraser River and the spring and neap tides 

acts to pump this deep layer over the Victoria sill, up Haro Strait, and 

eventually over the Boundary Pass sill into the Strait of Georgia.

Seasonal movements of Dall’s and harbor porpoises (Phocoenoides dalli

and Phocoena phocoena) were determined from locations of individuals 

29

Seasonal Movements 

and Habitat Use of Dall’s 

and Harbor Porpoises in 

the Inland and Coastal 

Waters of Washington 

State as Determined by 

Radiotelemetry

M. Bradley Hanson

Northwest Fisheries Science Center

Seattle, Washington

brad.hanson@noaa.gov
54

tagged with satellite-linked or very high frequency 

(VHF) transmitters for 6–19 months from 1998 to 2005. 

Dall’s porpoises were tagged in Haro Strait, and harbor 

porpoises in both western Strait of Juan de Fuca and 

northern San Juan Islands. In most cases locations 

were obtained weekly. Satellite imagery for sea surface 

temperature (SST) and chlorophyll a were acquired from 

NOAA and NASA for the periods these animals were 

tracked.

For both species, multiseason residency was generally 

observed in Haro, Juan de Fuca, and southern Georgia 

straits, with only seasonal use of La Perouse and 

Swiftsure banks. For the harbor porpoise tagged in 

northern San Juan Islands, during the first 3 weeks after 

tagging, it moved between Presidents Channel and the 

deep basin in southern Georgia Strait. After mid-July it 

was only relocated in the area of this deep basin, until 

the last location in January when it was again relocated 

in northern Presidents Channel. No associations were 

readily apparent with large-scale features detectable 

from remote sensing, but occurrences adjacent with tidal 

fronts were commonly observed during tracking. For 

the three harbor porpoises tagged in the western and 

central Strait of Juan de Fuca, two moved to the

La Perouse and Swiftsure bank areas shortly after 

tagging, potentially associating with remnants of the 

Juan de Fuca eddy. Subsequently, all porpoises were 

located in the central Strait of Juan de Fuca, generally 

west of the Victoria sill, an area where a substantial 

cold-water feature develops in the fall (Figure 1). One 

of the Dall’s porpoises displayed the largest-scale shift 

between regions of any of the porpoises. The timing of 

these movements appeared to be in association with the 

development of the Juan de Fuca eddy in the spring of 

both 1999 and 2000. In October she was relocated in the 

central Strait of Juan de Fuca, in the same general area 

where the tagged harbor porpoises were located, but in 

early January she returned to Haro Strait.

Bathymetric and land features of this region, in 

combination with oceanographic features, likely serve 

to provide a consistently high state of productivity, 

supporting both species as year-round residents. In 

addition, these features and conditions also likely 

concentrate this productivity in many of these areas 

resulting in high site fidelity. Of particular note was the 

significant movement of a tagged Dall’s porpoise to the 

outer coast coincident with the timing of development 

of the Juan de Fuca eddy in two consecutive years. Its 

departure is consistent with the breakdown of this 

feature. The Juan de Fuca eddy is likely important 

to other marine mammal species, such as humpback 

whales (Megaptera novaeangliae), which are found there in 

large numbers only during the summer. Although some 

of the tagged harbor porpoises appear to associate with 

the Juan de Fuca eddy, their focus in the central Strait of 

Juan de Fuca (as was the fall seasonal use by the Dall’s 

porpoise) with the substantial and relatively persistent, 

but yet to be described, cold-water feature, deserves 

further investigation.

Figure 1. Fall locations in central 

Strait of Juan de Fuca (left) 

coincided with breakdown of 

Juan de Fuca eddy and Strait of 

Juan de Fuca cold-water features 

(right).
55

Traditionally, tracking the movements of aquatic organisms has been 

accomplished by active tracking in which an individual is fitted with an 

acoustic transmitter, followed, and position estimated (Figure 1). This 

method is costly and labor intensive because active manual tracking 

requires relocating or tracking the tagged animal continuously for 

long periods. Recent advances in acoustic technology using stationary 

omnidirectional hydrophone arrays have allowed the collection of longterm location data without the bias and costs of potentially “chasing” 

animals within the study site.

Because previously active tracking of sharks has resulted in few or 

no relocations, an array system was employed in a study on Atlantic 

sharpnose (Rhizopriondon terraenovae) and blacktip (Carcharhinus 

limbatus) sharks to gain better data on shark associations with 

environmental parameters and habitat use. In 2004, 12 hydrophones 

(Vemco VR1, Shad Bay, Nova Scotia) were deployed in a semienclosed 

bay (approximately 2 × 15 km, Figure 2) in northwest Florida, and 14 

sharks were tagged with ultrasonic transmitters (69.0 kilohertz) and 

monitored for 5 months (1 May to 30 September). Of the 153 days the 

array was present in the bay, Atlantic sharpnose (n = 9) and blacktip 

(n = 5) sharks were monitored for an average of 10.2 and 26.6 days, 

respectively.

Preliminary analysis using an algorithm for taking presence-absence 

data and converting them to averaged positions demonstrated that 

sharks do not respond to environmental factors (i.e., tidal or lunar 

phase, temperature, salinity, and dissolved oxygen) but appear to exit 

and enter the study site randomly. When sharks were present in the 

bay, spatial use varied by species. Atlantic sharpnose sharks occupied 

the center of the bay, adjacent to the opening, 53.3% of the time, while 

spending 24.8% and 21.9% at the shallower extremes, respectively. 

Conversely, blacktip sharks occupied the center of the bay 33.1% of 

the time, and the western and eastern extremes 46.1% and 20.8% of the 

time, respectively. These results differ from those previously obtained 

for blacktip sharks for a similarly sized bay where sharks spent over 

100 days in residence, and they contradict commonly held theory that 

sharks remain in distinct coastal areas throughout summer months. 

Future work will employ the use of continuous environmental data 

loggers that will allow for the better coupling of abiotic data and 

30

Assessing Habitat Use 

and Movements Patterns 

of Coastal Sharks with 

an Automated Acoustic 

Telemetry System

John K. Carlson

Southeast Fisheries Science Center

Panama City, Florida

john.carlson@noaa.gov

Michelle Heupel and Colin Simpfendorfer

Mote Marine Laboratory

Sarasota, Florida

Figure 1. An Atlantic sharpnose shark tagged with an ultrasonic transmitter.
56

Figure 2. Location of study site in Florida and VR1 

stations within the bay system.

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movement patterns. This platform will provide a 

window into shark ecosystem community dynamics not 

previously available.
57

One of the reasons for holding this workshop is to address ways of 

improving stock assessments. I reviewed the definition of a stock 

assessment, the components of stock assessment models such as natural 

mortality and annual recruitment rates, and the role of electronic tag 

data in improving those components (see Tables 1, 2, and 3).

31

Potential Role of 

Electronic Tags in Stock 

Assessments

Richard D. Methot

Northwest Fisheries Science Center

Seattle, Washington

rick.methot@noaa.gov

Table 1. Catch and electronic tags.

Catch and electronic tags

Element Data need Electronic tags?

Discard Percent survival Yes

Location Location of fishing VMS

effort and catch

Observer sampling Pr (find needle Yes

efficiency in haystack)

Table 3. Biology and electronic tags.

Biology and electronic tags

Element Data needed Electronic tags?

Movement Stock boundaries Yes

Movement Diffusivity Yes

Growth & maturation Biochemical sensor?

Natural mortality Predator-prey Maybe?

encounters 

I concluded that there is a significant, immediate opportunity to use 

tags to understand the effect of fish behavior on survey catchability. As 

well, information on scales of spatial mixing will be important as we 

move further into spatially explicit models. However, technology must 

be cheaper and more robust before statistically valid population-level 

studies can be designed.

Table 2. Surveys and electronic tags.

Surveys and electronic tags

Element Data need Electronic tags?

Direct abundance Statistically designed Yes, but mostly with

estimate tag-recapture program large N dumb tags

Catchability Response to sampling gear Yes

Diel vertical migration Yes

Response to environment Yes

(thermocline depth)

Habitat usage Yes
58

A mission of NOAA Fisheries Service is to manage ocean resources 

use through ecosystem-based management. In addition, the Marine 

Mammal Protection Act and the Endangered Species Act (ESA) require 

conservation of marine mammals. Satellite telemetry data have 

provided inferences of northern fur seal (Callorhinus ursinus) (Figure 1) 

and endangered Steller sea lion (Eumetopias jubatus) foraging behavior 

to evaluate potentially adverse competitive overlap with fisheries.

Sea lions and fur seals are sympatric over large portions of their 

Alaskan ranges and have declined substantially during the past 30 

years. Lactating fur seals segregate in Bering Sea foraging areas in 

summer, and both sexes undertake winter migrations into pelagic 

and coastal waters of the North Pacific Ocean. In contrast Steller 

sea lions tend to remain largely within continental shelf areas. Both 

species consume pollock (Theragra chalcogramma) of sizes important to 

commercial fisheries. Causes of recent fur seal declines are unknown, 

but may be among causes hypothesized for sea lion declines. Numerous 

consultations under ESA of federal fishery actions off Alaska have 

extensively used telemetry data to infer Steller sea lion foraging 

needs. Fishery actions and ESA-directed conservation measures are 

also subject to review for environmental and social concerns under the 

National Environmental Policy Act (NEPA).

Designation of sea lion critical habitat was based in part on telemetry 

deployments made prior to 1993. Analyses suggesting that decreased 

juvenile survivorship was a proximate cause of the decline directed 

recent research toward investigating juvenile foraging ecology. These 

data were combined with information on fisheries and fish stocks 

to implement conservation measures aimed at halting the decline 

of Steller sea lions (Figure 2). Analyses progressed from examining 

general location and diving data summaries to analysis of distancestratified frequencies of diving locations. Because data-logging 

instruments are difficult to retrieve, diving behavior was characterized 

using satellite-linked recorders that binned dives into 6-hour periods. 

The periods limited the spatial resolution to which foraging behavior 

could be inferred. And because recent telemetry studies addressed 

32

How Can Pinniped 

Telemetry Data Fit into 

Fisheries Management? 

Examples from Steller Sea 

Lions and Northern Fur 

Seals in Alaska

Brian S. Fadely, Lowell Fritz, 

Jeremy T. Sterling, and Rolf Ream

Alaska Fisheries Science Center

Seattle, Washington

brian.fadely@noaa.gov

Shane Capron

Alaska Regional Office

Juneau, Alaska

Figure 1. A northern fur seal with satellite tracking and dive recording instrument 

packages attached.
59

questions about juveniles, less than ideal age and 

geographic coverage was available during conservation 

measure development. Ultimately insufficient data exist 

to directly link behavior with foraging success, survival, 

or reproductive success.

Analyses of pollock catch and biomass distributions 

within each foraging area from 1982 to 2002 suggest 

that harvest rates within areas used by lactating fur 

seals from St. George Island averaged four times greater 

than in areas used by St. Paul Island seals. During 

this period, seal populations on St. George declined 

more rapidly than those on St. Paul, but it is unknown 

whether this decline was related to spatial differences 

in fishing intensity. However, analyses conducted 

under NEPA found that as sea lion protection measures 

were implemented to reduce fish removals from critical 

habitat, pollock trawl fishing effort expanded northward 

from the Eastern Aleutian Islands into the Bering Sea 

and may have shifted to fur seal foraging areas. The 

extent of overlap may also have been affected by pollock 

responses to interannual oceanographic variability in 

bottom temperature on the eastern Bering Sea shelf.

Figure 2. An adult female and 

yearling Steller sea lions.

Continuing advancements in technology and 

analytical methodology will improve our ability to 

utilize telemetry-derived pinniped data in fisheries 

management. Among these advancements are any 

combinations of technologies that provide more accurate 

and precise location fixes and that can deliver detailed 

dive profile data so as to better identify foraging trips 

and dive patterns, improved capture methods to deploy 

instruments on larger animals, and development of 

statistically appropriate models to evaluate foraging 

behavior on a population basis and to include varied 

data types and multiple species. Also needed are 

continuing discussions about how best to incorporate 

such models when designing or evaluating fisheries 

management actions. Current management structures 

require analyses under multiple legal processes to 

fully evaluate potential impacts of fisheries on marine 

mammal populations.
60

Several research projects in the northeast United States use various 

types of electronic tags to study fish behavior, and results from these 

research efforts contribute to fishery stock assessments. The primary 

use of electronic tags has been to track movements of individual 

animals, leading to inferences of stock structure, supporting the 

estimation of mixing rates between adjacent stocks, and potentially 

contributing to estimates of stock size. The application of electronic 

tagging for fisheries science has traditionally been to illustrate basic 

aspects of life history, such as juvenile and adult habitat, vertical and 

horizontal movements, and home range. Such descriptive information 

can be used to determine appropriate structure of population dynamics 

models and associated sampling designs.

Information from electronic tags can also be used more directly for 

stock assessment and fishery management. For example, in “roundtrip” movements across management boundaries (Figure 1), electronic 

tags have been used to evaluate mortality rates (Figure 2), effectiveness 

of marine protected areas, and the effect of environmental variables on 

seasonal movements.

One of the challenges of using electronic tags for stock assessment is 

the prohibitive cost of deploying tags on a representative sample of 

fish populations (Figure 3). As the technology advances and becomes 

more cost effective, we expect the role of electronic tagging in stock 

assessment to expand.

33

Using Information from 

Electronic Tags for Stock 

Assessment of Northeast 

Fishery Resources

Steven Cadrin, Gary Shepherd, 

Tim Sheehan, Stacy Kubis, Joshua Moser, 

and Azure Westwood

Northeast Fisheries Science Center

Woods Hole, Massachusetts

steve.cadrin@noaa.gov

Figure 1. Inferred trajectory of a yellowtail flounder (Limanda ferruginea) based on depth, 

tidal amplitude and time of high tide derived from archival tag data, local predictions 

from a tidal model, and a search algorithm with distance constraints. Release and 

recapture positions are indicated by green and red circles, respectively. Stock area 

boundaries are indicated in red, and fishing closure areas are indicated in pink.

From Gröger, J. P., R. Rountree, S. X. Cadrin, A. Westwood, and S. Kubis. In press. The use of digital 

storage tags and tidal information to study migration patterns of yellowtail flounder [Limanda 

ferruginea] off New England. Can. J. Fish Aquat. Sci.
61

Figure 2. Estimates of Atlantic salmon (Salmo salar) smolt survival 

derived from ultrasonic telemetry receiver arrays (Vemco VR2 units, 

Shad Bay, Nova Scotia) that monitored migration through the Dennys 

River (Maine) into the Bay of Fundy and Gulf of Maine. Hatcheryreared smolts with surgically inserted ultrasonic pingers were 

released into the Dennys River (open-filled circle) during 2001 (n = 

70), 2002 (n = 150), and 2003 (n = 150). VR2s units (solid circles) were 

placed throughout the system to monitor migratory dynamics and 

estimate migration success. Telemetry array sharing with a Canadian 

Department of Fisheries and Oceans telemetry study (Gilles LaCroix, St. 

Andrews, Canada) allowed for array coverage into the Bay of Fundy

(solid lines, 2001–2002). Lower boxes represent numbers and 

percentages of smolts assumed dead within each zone.

Figure 3. A comparison of recaptures of many traditional tags and 

several archival tags related to the population distribution. Density 

of black sea bass (Centropristis striata) was derived from catch data 

reported on vessel trip reports (2002–2004). Internal anchor tag and 

electronic data storage tag recapture locations are shown with three 

red lines connecting release and recapture locations of electronic tags.
62

Marine mammal stock assessments are a core mission for NMFS under 

the Marine Mammal Protection Act. Adequate stock assessments require 

accurate delineations of stock structure boundaries as well as robust 

estimates of population size and trends. It has been noted that many 

types of data can provide information on stock structure, including 

distribution, population response, morphology, genetics, life history, and 

contaminants, but each has inherent limitations. In some cases genetic data 

can provide information on where delineations in population structure 

occur, although in others it can only indicate that additional structure exists 

within the population. On the West Coast of the United States, several 

stocks of harbor porpoises (Phocoena phocoena) and one stock of Dall’s 

porpoise (Phocoenoides dalli) have been delineated from genetics data. In 

Washington State, two stocks of harbor porpoises are currently recognized: 

the Oregon/Washington coastal stock and the inland Washington stock, 

with the boundary arbitrarily set between Cape Flattery and Bonilla Point, 

Vancouver Island. However, recent genetic analyses suggest additional 

structure within the inland water stock exists but the boundaries cannot be 

delineated. This study used seasonal movements of individual porpoises 

tagged with telemetry devices to assess current boundaries and identify 

other potential stock boundaries. In addition, the movement of these 

tagged animals identified regions of higher densities where survey effort 

could be focused to improve stock estimates.

A combination of satellite-linked transmitter location data (latitude, 

longitude) and triangulations of very high frequency (VHF) transmitter 

signals allowed locations to be determined approximately weekly. 

Seventeen harbor porpoises were captured and tagged between 1998 and 

2003, one from the northern San Juan Islands, and 16 in the western Strait 

of Juan de Fuca. The porpoise tagged in the northern San Juan Islands 

was tagged in June and the western Strait of Juan de Fuca animals were all 

tagged in early fall. Monitoring durations that exceeded 6 months were 

available for the one porpoise from the northern San Juan Islands and 

three of the porpoises in the Strait of Juan de Fuca. Eight Dall’s porpoises 

were tagged between 1997 and 1999, all in Haro Strait in May. Two of the 

porpoises had monitoring durations that exceeded 6 months.

Based on location data from a tagged harbor porpoise (9802) and other 

porpoise observations in the northern San Juan Islands, boat-based line 

transect surveys were conducted in 1999 and 2002 in the San Juan Island 

section of the inland waters to improve on aerial survey estimates. Effort 

was increased (approximately 1,150 km) over the previous aerial line 

transect surveys (574 and 846 km). More important, effort was stratified to 

increase effort in the southern Strait of Georgia in the area the tagged animal 

had been tracked.

The harbor porpoise tagged in the northern San Juan Islands (9802) 

was relocated over a 215-day period. During this period, the porpoise’s 

movements were confined to a relatively small area that included only 

the northern San Juan Islands and the U.S. waters of the southern Strait of 

Georgia (Figure 1). Two harbor porpoises tagged the western Strait of Juan 

de Fuca were tracked for 6 months and one for 19 months. Although two 

of these porpoises (0103 and 0204) made initial movements to the west and 

northwest, by early winter all were residing in the central Strait of Juan de 

Fuca. The animal that was tracked for 19 months (0308) remained in the 

central strait region the entire time (Figure 1).

Two Dall’s porpoises tagged in Haro Strait were tracked for 180 and 378 

days, respectively. The subadult male porpoise that was tracked for 180 

days remained in the Haro Strait/Swanson Channel for almost the entire 

34

Using Location Data from 

Telemetry Tagged Marine 

Mammals to Improve 

Stock Assessments

M. Bradley Hanson

Northwest Fisheries Science Center

Seattle, Washington

brad.hanson@noaa.gov
63

period. The other porpoise, an adult female, only remained 

in the Haro Strait region for about a week before making 

an abrupt move to the outer coast off the entrance to the 

Strait of Juan de Fuca. She remained there until at least 

mid-August and by early October she was relocated in the 

central Strait of Juan de Fuca. In early January the animal 

shifted back to Haro Strait with occasional forays into the 

southern Strait of Georgia. The porpoise was last located off 

the entrance to the Strait of Juan de Fuca in mid-May 2000, 

within 2 weeks of the time it had moved there the year before.

Boat-based line transect surveys found large numbers 

of harbor porpoises concentrated in the southern Strait 

of Georgia, in the same general region as the locations 

of the tagged porpoise 9802 (Figure 2). The preliminary 

population estimates from the boat survey were greater 

than the estimate derived from aerial data, and the 

preliminary coefficient of variation (CV) estimates showed 

some reduction compared to the aerial surveys.

The small-scale movements of harbor porpoise 9802 and the 

consistent observation of other porpoises in the northern 

San Juan area during this period suggest limited seasonal 

movements for at least some porpoises in this region. In 

addition, the small-boat surveys confirmed the presence of 

a high density of porpoises in the southern Strait of Georgia.

Limited seasonal movements of the tagged harbor 

porpoises to the outer coast suggests that the current 

boundary for the inland waters and coastal stocks is 

accurate, but the lack of interchange between porpoises 

tagged in the Strait of Juan de Fuca and Strait of Georgia 

suggests there are potentially at least two stocks within 

inland waters. Although sample size is small, the locations 

of tagged Dall’s porpoises were consistent with the current 

stock definitions while their limited movements suggest 

additional structure.

Although sample size is limited, the movements of Dall’s 

porpoises are restricted to the boundaries of the stocks as 

defined by genetic studies. The seasonal movement of 

one Dall’s porpoise to coastal waters may explain why 

population estimates for inland waters varied widely 

between two consecutive surveys. In 1991 the population 

of Dall’s porpoises was estimated to be 3,745 (CV of 44.2%), 

whereas in 1996 the population estimate had decreased by 

over 50% to 1,545 (CV of 43.1%). While the large CVs likely 

account for some of the variation, some may be explained 

by a net movement of porpoises outside the survey area 

during the season these surveys are typically conducted 

(August). Consequently, future surveys that include some 

portion of the outer coast may provide more representative 

estimates for this species.

Data from tagged small cetaceans can assist with 

improving stock delineation by identifying boundaries 

from movements and by providing information to improve 

survey design to yield more accurate abundance and trend 

data.

Figure 2. Weekly locations of 

tagged porpoises in 1999.

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64

In the last decade, efforts have been made to incorporate information 

on animal movements and habitat use patterns into fish stock 

assessment models. These efforts are accomplished in numerous 

ways. First, hypotheses concerning stock structure are being tested 

using electronic tags. Based on electronic tag data, it is now believed 

that bluefin tuna (Thunnus thynnus) feeding in the Georges Bank area 

of the North Atlantic are from two separate stocks, each with different 

breeding grounds. Thus, stock assessments of Atlantic bluefin tuna 

are being developed to examine the North Atlantic population as two 

stocks. Second, catch-per-unit effort (CPUE) indices are standardized 

based on habitat models developed from information on the animals’ 

behaviors. For example, for a longline fishery, if details of effort are 

well documented and information is known about the preferences of 

the targeted animals, it is possible to distinguish between periods when 

fishing may be more effective depending on the time of day, the depth 

of the hooks, temperature of the water column, or a number of other 

environmental indices.

Behavior of pelagic fishes is difficult to observe; however, electronic 

tagging studies are increasingly providing information on thermal, 

depth, and geographic preferences of many pelagic species. Since 2001, 

we have been deploying implantable archival tags in juvenile north 

Pacific albacore tuna (Thunnus alalunga) off the west coast of the United 

States and northern Baja California, Mexico. The tags record water 

temperature, depth, light, and peritoneal temperature every minute 

while the fish is at liberty. Data recovered from 16 tags by the end of 

2005 demonstrated that North Pacific albacore tuna inhabit waters 

from the surface down to a depth of 250 m during the day, but remain 

almost exclusively in the top 50 m at night (Figure 1). In contrast, most 

of the hooks of a longline fishery operating southeast of Japan fish 

at depths between 50 and 300 m (Figure 2). These data will be used 

to standardize CPUE indices of abundance from the Hawaii-based 

longline fishery that overlaps with the areas used by these fish.

Effective fishing effort for a given time and area will be calculated 

as the product of the proportion of time albacore tuna spend at a 

particular depth stratum and the number of hooks fishing at that depth 

stratum summed over all depth strata. The proportion of time spent at 

any given depth stratum may be calculated as a function of the absolute 

water temperature at depth, mixed layer temperature and depth, sea 

surface to ambient water temperature differential, or dissolved oxygen. 

At this time, we do not yet have enough electronic data to determine 

which factors will be the most influential in the habitat model.

A number of things should be considered when designing an electronic 

tagging study for habitat-based models of highly migratory fish. It 

is important that fishery statistics of catch and effort be collected in 

sufficient detail to be able to describe the effective effort. For example, 

for a longline fishery it may be important to know at what depth the 

hooks are fishing because it may be a factor of the number of hooks 

between floats as well as the prevailing weather and oceanographic 

conditions. Tagging efforts should be focused on those individuals 

(i.e., size or age-classes) that are selected in the fishery for which 

a standardized index is being developed. Tagging efforts should 

also be spread out to cover the entire area over which the fishery 

operates. And finally, as tag technology improves and a larger suite of 

miniaturized sensors become available, it will be important to select the 

appropriate sensors based on the habitat preference assumptions for the 

animal being studied.

35

Using Archival Tagging to 

Better Understand Stock 

Structure and to Develop 

Habitat-Based Models for 

North Pacific Albacore

Suzanne Kohin and John Childers

Southwest Fisheries Science Center

La Jolla, California

suzanne.kohin@noaa.gov
65

Figure 1. Albacore tuna time-at-depth histograms, n = 2,072 days.

Figure 2. Albacore tuna combined depth distribution of numbers 1, 3, and 7 longline 

hooks. 

From Yano, K., H. Yamada, and T. Kosuge. 2004. Preliminary results of relationship between setting 

depth of tuna longline and swimming depth of Pacific bluefin tuna at the spawning grounds. Working 

document of the 3rd Pacific Bluefin Tuna Working Group meeting of the Interim Scientific Committee 

for Tuna and Tuna-like Species in the North Pacific, ISC/04/PBF-WG/06.

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Atlantic bluefin tuna (Thunnus thynnus) are managed through the 

International Commission for the Conservation of Atlantic Tuna 

(ICCAT). The populations in the eastern and western Atlantic have 

been managed separately since 1981. However, in 1993 ICCAT 

scientists developed a two-area virtual population analysis (VPA) 

that suggested small interchanges between the two populations could 

have important implications. The original two-area VPA assumed fish 

movement is diffusive, that is, fish moving across the ocean “forget” 

where they came from. An alternative is to assume the two populations 

overlap and that sojourning fish return home. Research published in 

2001 fitted the “diffusion” and “overlap” VPAs to conventional tagging 

data and estimated interchange rates on the order of a few percent. 

Recently, the results from several pop-up tagging experiments seem 

to suggest that up to 40% of western bluefin tuna move into eastern 

waters. This preliminary study explores this contention by fitting the 

VPA to published data from two such experiments.

The catch data, abundance indices, and VPA procedures employed 

are described in ICCAT’s Report of 2002 Atlantic Bluefin Tuna Stock 

Assessment Session. Release and recovery data for 22 platform 

transmitter terminal (PTT) and 19 pop-up archival transmitting (PAT) 

tags placed on bluefin tuna caught off New England appeared in 

two other studies. Tag recoveries were assumed to be multinomial 

distributed with negative loglikelihood:

where R is the number of bluefin tuna that were tagged, cky is the 

number of tagged bluefin tuna that were recaptured during year y in 

area k, and rk is the number of tagged bluefin tuna that survived to the 

end of the experiment and were located in area k at the time the tags 

reported to the satellite. The tag attrition model used to compute r and 

c is described in a previously published article.

The addition of the pop-up tags had little impact on the VPA in the 

absence of interchange (unsurprising considering there were only 

41 tags, most of which detached after a few months). The fit to the 

tagging data was significantly better when the interchange rates 

were estimated; Akaike’s Information Criterion corrected (AICc) 

values for the overlap, and diffusion models were 1,379 and 1,383, 

respectively (compared to 2,811 without interchange). The diffusion 

model estimated 12% of western bluefin tuna move east, whereas 

the overlap model estimated 2% of eastern bluefin tuna move west 

(i.e., the eastward moving tags had been placed on eastern bluefin 

tuna sojourning in the west). The overlap model provided a better fit 

than the diffusion model, but the difference in AICc values was not 

statistically compelling.

The appraisal for western bluefin tuna was less optimistic when 

interchange rates were estimated (Figure 1, East). The abundance 

of spawners (age 8 and older) in 2000 relative to the 1970 level was 

estimated to be 7% with the overlap model and 9% with the diffusion 

model (as compared to 12% with no interchange). The appraisal for 

eastern bluefin tuna was almost unchanged with the overlap model, 

but more optimistic with the diffusion model; the estimated abundance 

of age 8 and older group was higher for 2000 than for 1970

(Figure 1, West).

36

Virtual Population 

Analyses of Atlantic 

Bluefin Tuna that Include 

Information from 

Electronic Pop-up Tags

Clay E. Porch

Southeast Fisheries Science Center

Miami, Florida

clay.porch@noaa.gov

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67

There are several potential pitfalls in this analysis. 

One study found that tags that stayed attached to 

the fish remained in the west, whereas tags that 

detached prematurely often drifted east. Most of 

the tags used in the VPA that reported from the east 

were PTT tags, which have no means of detecting 

premature detachments, so it is unclear whether the 

tags were still attached when they reported. When the 

VPAs were rerun without the PTT tags the estimated 

interchange was much lower (about 3% eastward) and 

the abundance trends were similar to the case without 

interchange (Figure 2).

The limited coverage of the tagging data was 

problematic. Only adult bluefin tuna off New England 

were tagged. Longer deployments and extended 

geographic coverage would aid in identifying the most 

appropriate model (overlap, diffusion, or otherwise) and 

estimating the interchange rates. Another challenge is 

to reconcile the fine-scale spatiotemporal information 

available from the tags with the course spatiotemporal 

grid (two area, annual) used by the VPA. For example, 

should a tag that barely crosses into the east and avoids 

the main eastern fisheries be counted as having moved 

east?

In summary, the present study illustrates that even 

relatively few pop-up tags can provide statistically 

significant information on interchange rates, if not 

mortality. Inasmuch as the reporting rates with 

electronic tags tend to be high and to some extent fishery 

independent, interchange estimates are apt to be less 

biased than when obtained from conventional tagrecapture data. Wide geographic and temporal coverage 

is important when the data are used in assessment 

models. It would be useful to extend the VPA to use 

information from archival tags on the time spent in each 

management area.

Figure 2. Trends in abundance 

of spawning-age fish (age 8 and 

older) estimated by the diffusion 

VPAs with all tags (blue squares) 

and without the PTT tags (green 

circles). The black line refers to 

the no-interchange model. 

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estimated by the overlap (red triangles), diffusion (blue squares), and 

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68

Section 117 of the Marine Mammal Protection Act requires that NMFS 

develop stock assessment reports for all marine mammals present in 

U.S. waters. Since marine mammal stock assessment reports were first 

developed in 1995, the use of electronic tagging information in the 

stock assessment reports has increased. Data collected from a variety 

of electronic tag types, including radio and satellite, are now a critical 

component of many stock assessment reports. Electronic tagging 

data are most frequently used for correcting abundance estimates for 

animals not observed during surveys and are used to improve our 

understanding of animal distribution, to aid in stock identification, and 

for a variety of other reasons (Figure 1). Assessments updated most 

recently have included new information collected from satellite tags. 

In order to develop the next generation of stock assessments, it will be 

necessary to obtain additional information from electronic tags and 

further develop tag technology to allow the collection of different types 

of information.

37

Using Electronic Tags in 

Marine Mammal Stock 

Assessment Reports

Robyn P. Angliss and Ray Outlaw

Alaska Fisheries Science Center

Seattle, Washington

robyn.angliss@noaa.gov

Figure 1. Examples of electronic 

tag technologies that have been 

used to collect data for various 

components used to make stock 

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Background

Acoustic tags transmit their acoustic signal after receiving an interrogation pulse from 

a sonar source or are set to transmit their signals at a selected pulse rate. For most 

studies, acoustic tags are surgically inserted into the fish. Tag size depends on the size 

of the transducer, whose diameter is inversely proportional to frequency. Detection 

range is also inversely proportional to frequency; larger, low-frequency tags (e.g., 30 

kilohertz [kHz]) may have a detection range of around 1 km while smaller higherfrequency tags (e.g., 300 kHz) may have a detection range of less than 400 m.

Typically, the low-frequency tags are used to track larger pelagic fish and the higherfrequency tags are used in studies that require smaller tags. Acoustic tags are used in 

saltwater environments because sound transmits well through salt water compared 

to radio waves that quickly attenuate. Both portable and fixed hydrophones are used 

to receive the transmitted pulse signals to help determine the location of the tagged 

individuals. Besides location, data can be transmitted from internal sensors that 

record physiological parameters, depth, and swimming direction or speed.

Workgroup discussion

The first topic covered during the discussion was the type of problems that occurred 

with currently available acoustic-tag technologies. Researchers brought up that 

receiving systems are unable to decode tags from all of the different manufacturers, 

interference among tags was common when tracking fish in small or confined 

geographic areas, activation of the smaller tags was time consuming, and some tags 

failed to activate.

Because tags are expensive to purchase, attendees discussed having NOAA negotiate 

a bulk purchase price by combining the purchases for separate projects. They 

also raised the point that NOAA should hire an independent firm to test the tags 

and receivers and then write a document comparing the telemetry equipment. By 

combining forces, attendees hoped that they would have more power in getting the 

equipment manufacturers to develop features that worked better for fisheries research. 

These features would include a lower failure rate, specifically to reduce the number of 

tags that fail to activate or stop functioning shortly after activation.

In addition to discussing the pros and cons of different tag and receiving equipment, 

attendees discussed the importance of sharing information on attachment techniques. 

Attendees pointed out that it was as valuable to document what did not work as what 

did work for individual species. After sharing some of their experiences, attendees 

suggested a NOAA-sponsored Web site might be a good place for sharing tagattachment information.

Attendees talked about needing smaller or longer-lasting tags for their research. 

Suggested ways of achieving these improvements were miniaturization of the 

different types of sensors (e.g., inactivity, temperature, or electromyogram transmitters 

calibrated against swim speed), and development of new battery technologies. As 

with all of the other tags, researchers wanted smaller and longer lasting batteries. 

They also suggested that being able to remotely turn the tags on and off or change 

pulse rates would improve power management. In addition, they discussed the need 

for more streamlined batteries because often the shape of available batteries produces 

a tag shape that does not work well with all host species.

Attendees also considered how to improve tracking results. They wanted methods 

that would reduce interference when tracking tagged fish in confined geographic 

areas. They wanted more accurate approaches for recording the three-dimensional 

positions of all sizes of fish and suggested adding GPS and exploring fixed beacons for 

Breakout 

Session 

Summaries

Acoustic Tags
70

Pop-up Satellite 

Tags

triangulation. Some mentioned the need for improved time synchronization among 

receiving systems.

Finally, attendees discussed both data acquisition and database management. They 

wanted to be able to communicate remotely with receivers either through wireless 

or cell connections to download data. They also discussed developing standardized 

protocols for data processing so that databases for independent studies contained 

similar information (e.g., receiver locations, tag code format, user information, 

integration of sensor and environmental data, or protocols for data processing). One 

person suggested that maybe this database could be included within an already 

existing regional database system such as Pacific Coast Ocean Observing Systems 

(PaCOOS).

New features researchers would like to see with acoustic tag technology included 

an “I have been eaten” sensor, compass and magnetic georeferencing, and ways to 

activate the tags based on where a tag is or a specific time or set of times. In order to 

increase the number of species that could be monitored with miniature acoustic tags in 

different habitats, another feature needed was a broader range of acoustic frequencies.

Background

The development of the Argos Data Collection System, a joint venture between France 

and the United States, provides complete world coverage with receivers installed 

onboard NOAA satellites orbiting the Earth. With this system an electronic tag could 

transmit stored data to this satellite system without recovering the tag. Furthermore, 

location of the tag would be known whenever data were transmitted.

The initial sizes of satellite tags were large and therefore could only be used with 

large species. Furthermore, for tags to be effective, the species need to be on the 

surface long enough to be detected by a passing satellite and have time to transmit the 

stored data. Accuracy of determining the tag’s location improves with the number 

of successful “uplinks” during each satellite overpass and Service Argos classifies the 

quality of location (class 1, 2, or 3) achieved with each fix.

To expand the number of species that could be tagged and to enable tags to be at 

the surface long enough to be effective, tag manufacturers designed mechanisms for 

releasing the tags from the animals. These pop-up tags detach from the animal at 

a predetermined time and float to the surface, where they then transmit the stored 

data to the Argos satellite system. Many variants are currently available as tag 

manufacturers attempt to satisfy research needs.

Workgroup discussion

The first topic covered was the type of problems that occurred with the currently 

available satellite and pop-up tag technologies. Attendees noted that few tags report 

after 6 months, long-term tag attachment is an issue, biofouling causes problems with 

the saltwater switch, there is a need for a wider range of sensors, and tags release 

prematurely yet researchers are unable to identify why.

Because tags are expensive, attendees discussed having NOAA negotiate a bulk 

purchase price by combining the purchases for the separate projects. Because 

longevity is an issue, they advocated running a group of tags through extreme 

temperature and pressure cycles for 1–6 months to try to determine the cause of 

failure. If the vendors are unwilling to do these tests, then NOAA should conduct the 

necessary tests or issue a contract for the work. If the failures are due to batteries, the 
71

group recommended that vendors investigate alternative batteries or develop methods 

for recharging the batteries (e.g., using solar or current methods).

Attendees discussed, at length, premature release of tags. They suggested that in 

order to determine the cause of the premature releases, it would be useful to receive 

a detailed set of data (using a finer time scale than what is permanently stored) from 

the last few days before release instead of sending the initial set of stored data. They 

emphasized that this is important because often data are not completely uploaded 

by these prematurely released tags and consequently, these final critical data points 

are never received (or the data points are on a time scale too gross for determining 

what might have happened to cause the tag to release). The attendees also noted that 

prematurely released tags in northern latitudes keep transmitting the same data since 

there is only so much time for transmission. It would be useful if transmission did not 

always begin at the same point in the stored data.

The premature-release topic led naturally into a discussion of tag-attachment issues. 

The general consensus was that movement of the anchors was probably causing most 

of the tag losses. They commented that often an animal’s tissue was damaged by the 

moving anchor. Researchers then conveyed their different approaches for attaching 

tags (e.g., swivels or shock absorbers on the tethers). They concluded that it would be 

helpful if the tags were shaped more hydrodynamically and if researchers designed 

experiments to test attachment methods. Along these lines, they mentioned that 

alternatively shaped (e.g., more streamlined) batteries might make it possible to design 

more hydrodynamically shaped tags. Attendees also noted that smaller tags would 

offer more flexibility in tag-attachment techniques.

Attendees conveyed that biofouling is a problem with these long-acting tags. 

Biofouling interferes with tag attachment and causes problems by weighing down the 

pop-up tags. It also causes some tag failure as it affects the saltwater switch on some 

of the pop-up tags.

The group talked about alternatives for determining geolocation. The group proposed 

that the vendors investigate using magnetic anomalies, tidal flux, temperature at a set 

depth (e.g., 50 m), sea surface temperatures (SSTs), and GPS.

Software, the Argos Data Collection System, and data management were the last set 

of topics covered. The tag users recommended that the tag manufacturers maintain 

the format of outputted data spreadsheets because changes require alterations to 

data management tools that have already been developed. They recommended that 

any new information be added at the end of the data stream. They said they would 

like more data from Argos; one person related that often more location data were 

contained in the DI (or DIAG) messages than in the DS (or Dispose) messages. They 

wondered if more satellites would help produce more data. Finally, they conveyed 

the different data management tools that were available and discussed the strengths 

and weaknesses of applying different filters and algorithms. To avoid duplication of 

effort, they recommended getting NOAA support for granting permission so all of the 

satellite and pop-up tag researchers could use tools that are already available to some 

of the users.

The group also discussed new features they would like to see made available. These 

included a wider range of sensors. They listed recording salinity (as a measure of 

density), dissolved oxygen, and velocity. They also suggested for coastal species it 

would be useful to have a smaller tag that just transmitted its location, so it could be 

recovered easier. Attendees also wondered whether it was possible for the tags to only 

transmit when satellites were in view, which would conserve battery life.
72

Background

Radio tags transmit a simple pulsed signal at a selected pulse rate. Radio tags are 

ineffective in marine environments where the signal quickly attenuates, but they 

are an effective research tool in freshwater because physical obstacles, turbidity, 

turbulence, and thermal stratification do not affect radio waves. Furthermore, radio 

signals radiate through the water surface and can be detected at great distances 

because there is little loss of signal strength in air. Receivers can be fitted into listening 

stations on land, boats, or aircraft. Radio tags operate at high frequencies (20–250 

megahertz [MHz]) and thus, there is little signal drift.

Theoretically, large numbers of fish can be monitored simultaneously using multiple 

frequencies or pulse rates. In practice, however, it is very difficult to distinguish more 

than four or five pulse rates on an individual frequency. Radio tags are short-term tags 

with their longevity depending on size of battery and pulse rate.

NOAA researchers use radio tags to investigate the life history stages of anadromous 

species that occur in freshwater habitats. For example, salmonids are tagged with 

radio tags to learn how habitat modifications have affected different populations. 

Small radio tags used to monitor juvenile salmonids typically operate for 1–4 weeks 

while larger tags used to monitor adult salmonids can continue operating up to 12 

months. For salmonid research, radio tags are inserted surgically into the juveniles 

and inserted into the stomach of the adults. In both cases, antennas hang outside of 

the body.

Workgroup discussion

This workgroup included researchers working with satellite or platform transmitter 

terminal (PTT) tags that use radio signals to transmit their data as well as those 

working with traditional pulse radio tags. The first topic covered during the 

discussion was the type of problems encountered with the currently available tag 

technologies. Attendees noted that even the smallest tags are still too large for some 

research projects, two-way communication between the PTTs and satellites is needed, 

the cost of using Argos is too high, attachment of PTTs is an issue, and a standardized 

receiver system is needed.

Both the PTT and pulse radio tag users want tags that are smaller and last longer. 

They would like PTTs that are attached externally to be more hydrodynamically 

designed.

To improve data collection with the PTTs, the attendees discussed having the ability 

to remotely interrogate the tags both above water and underwater. Furthermore, they 

discussed the advantages of having tags with the ability for two-way communication 

between the PTTs and satellites, and how their research would benefit from higher 

resolution in position fixes. Not only would they like to see a reduction in the 

cost of using Argos, but they would also like access to the raw data since the data 

transmission is often prematurely terminated.

Background

Simple archival tags are data loggers that record depth, temperature, pressure, light, 

chemical, or physiological indicators at set intervals for months or years. More 

sophisticated archival tags are programmable and are capable of providing a direct 

estimate of geographical position for each individual fish at regular intervals over 

months or years. Theoretically, some of these tags could record data for up to 5 years 

and store this information for up to 20 years.

Radio Tags

Archival Tags
73

Archival tags have been produced in many shapes and are either inserted surgically 

or attached externally to species of interest. Because these are long-term tags, a large 

amount of data can potentially be generated from individual tags and therefore only 

small numbers of animals are usually tagged. However, the longer a tag is deployed, 

the more likely it is to become detached, so researchers often include experiments to 

monitor attachment success into their studies.

In order to retrieve the information, archival tags must be recovered from the 

individual. Recapture operations frequently rely on commercial or recreational 

fishermen and often use incentives (e.g., money or prizes) to improve the chances of 

recovering the tags. To facilitate identification of individuals carrying tags internally, 

an external mark or tag is commonly applied to the test animal.

Workgroup discussion

The first topic covered during the discussion was the types of problems that occurred 

with the currently available archival-tag technologies. Researchers relayed that tag life 

is frequently significantly less than what the manufacturers advertise (which makes 

it difficult to answer certain research questions), there is often a large difference in 

recovery among tagged species (sometimes it is impossible to determine why this is 

true), and the software for collecting and retrieving the data is inadequate.

Because archival tags are expensive, attendees discussed having NOAA negotiate 

a bulk purchase price by combining the purchases for the separate projects. They 

also raised the point that NOAA or some independent firm should test the tags for 

reliability and performance. Many researchers test each tag before it is deployed and 

they have seen failure rates as high as 50%; these rates do not include tags that fail 

after deployment. NOAA should use its collective power as a large user of these tags 

to work with the vendors to improve tag reliability by performing quality control 

testing before the tags are shipped to users; furthermore, vendors should replace tags 

that fail before deployment. NOAA should also use its collective power to negotiate 

with vendors to make certain that the software is updated before hardware updates 

are released and that any changes are documented.

Attendees also noted that NOAA researchers have been successful at communicating 

to the vendors the new features they want added to archival tags, but have not been 

successful at communicating the need for an inexpensive stable tag. Many types of 

research could be accomplished with a reliable archival tag.

Another point the attendees emphasized was the need for an honest appraisal of 

how these tags perform under realistic environmental conditions. In other words, 

vendors need to provide realistic estimates of tag life when the tag and its battery 

are frequently exposed to fluctuating or extreme pressures and temperatures. 

Furthermore, vendors need to provide the information on how the researchers should 

set up the tags in order to prolong battery life (e.g., give instructions on how to set up 

duty cycle settings to yield a longer tag life).

The attendees also identified a significant need for finding ways to extend battery life 

for archival tags because it is their longevity that makes them such a useful research 

tool. Researchers suggested making the batteries rechargeable, finding ways to use 

either water flow or the sun to recharge the batteries, and investigating whether there 

are batteries that would function better under cold-water conditions. If the vendors 

are unwilling to investigate this battery issue on their own, NOAA should offer to 

share the costs of this work. After all, the data being collected are greatly expanding 

our knowledge of populations and areas of high productivity, which contributes 

directly to NOAA’s ability to manage resources. Furthermore, in situations where 

good geolocation data can be obtained using electronic tags, they can be a costeffective way to get environmental samples compared to oceanographic sampling 

platforms.
74

The attendees also discussed the fact that some new sensors with archival tags have 

the potential to aid in providing other important information for NOAA. For example, 

light-level sensors could help measure chlorophyll and water flow sensors might help 

measure current velocity.

Because the software for collecting and retrieving the data is inadequate, attendees 

learned during this workshop that each group of NOAA researchers has been 

developing its own software. Consequently, researchers recommended that NOAA 

should eliminate this redundant effort and instead create a common database 

platform, which would include the ability to analyze the different data sets with 

various filters and models. Furthermore, this concentration of data would assist with 

the broader effort to integrate the electronic tag data with environmental and stock 

assessment data. Another software issue raised was a time stamp problem that needs 

to be resolved.

Along the lines of sharing a database, attendees discussed creating a Web-based 

working group where members could share information such as a vendor list, 

methods used, tag attachment protocols, tag-related requests for proposals, and tag 

testing results.
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79

Workshop 

Attendees

Kelly Andrews

Northwest Fisheries Science Center

Seattle, Washington

kelly.andrews@noaa.gov

Robyn P. Angliss

Alaska Fisheries Science Center

Seattle, Washington

robyn.angliss@noaa.gov

Stephen J. Auer

NOAA Office of Global Programs

Washington, DC

stephen.auer@noaa.gov

Gordon A. Axel

Northwest Fisheries Science Center

Pasco, Washington

gordon.axel@noaa.gov

Scott R. Benson

Southwest Fisheries Science Center

Moss Landing, California

scott.benson@noaa.gov

Steven Bograd

Southwest Fisheries Science Center

La Jolla, California

steven.bograd@noaa.gov

Richard W. Brill

Northeast Fisheries Science Center

Virginia Institute of Marine Science

Gloucester Point, Virginia

richard.brill@noaa.gov

Brian J. Burke

Northwest Fisheries Science Center

Seattle, Washington

brian.burke@noaa.gov

Steven Cadrin

Northeast Fisheries Science Center

Woods Hole, Massachusetts

steven.cadrin@noaa.gov

John K. Carlson

Southeast Fisheries Science Center

Panama City, Florida

john.carlson@noaa.gov

John Childers

Southwest Fisheries Science Center

La Jolla, California

john.childers@noaa.gov

Dan Cooper

Alaska Fisheries Science Center

Seattle, Washington

dan.cooper@noaa.gov

Dean L. Courtney

Alaska Fisheries Science Center

Seattle, Washington

dean.courtney@noaa.gov

Peter A. Cummiskey

Alaska Fisheries Science Center

Seattle, Washington

peter.a.cummiskey@noaa.gov

Nancy D. Davis

University of Washington

High Seas Salmon Research Program

Seattle, Washington

ncdd@u.washington.edu

Andrew Dittman

Northwest Fisheries Science Center

Seattle, Washington

andy.dittman@noaa.gov

Sandra L. Downing

Northwest Fisheries Science Center

Seattle, Washington

sandy.downing@noaa.gov

John W. Durban

Alaska Fisheries Science Center

Seattle, Washington

john.durban@noaa.gov

Peter H. Dutton

Southwest Fisheries Science Center

La Jolla, California

peter.dutton@noaa.gov

John Eiler

Alaska Fisheries Science Center

Seattle, Washington

john.eiler@noaa.gov

Sheryan Epperly

Southeast Fisheries Science Center

Miami, Florida

sheryan.epperly@noaa.gov

Brian S. Fadely

Alaska Fisheries Science Center

Seattle, Washington

brian.fadely@noaa.gov
80

John W. Ferguson

Northwest Fisheries Science Center

Seattle, Washington

john.w.ferguson@noaa.gov

David G. Foley

Southwest Fisheries Science Center 

Joint Institute for Marine and 

Atmospheric Research

Pacific Grove, California

dave.foley@noaa.gov

Kinsey E. Frick

Northwest Fisheries Science Center

Seattle, Washington

kinsey.frick@noaa.gov

Michael Goebel

Southwest Fisheries Science Center

La Jolla, California

mike.goebel@noaa.gov

M. Bradley Hanson

Northwest Fisheries Science Center

Seattle, Washington

brad.hanson@noaa.gov

Donald Hawn

Pacific Islands Fisheries Science Center

Honolulu, Hawaii

donald.hawn@noaa.gov

Sean A. Hayes

Southwest Fisheries Science Center

Santa Cruz, California

sean.hayes@noaa.gov

Gina K. Himes Boor 

Montana State University

Bozeman, Montana

gkhimesboor@montana.edu

Eric E. Hockersmith

Northwest Fisheries Science Center

Pasco, Washington 

eric.hockersmith@noaa.gov

Aleta A. Hohn

Southeast Fisheries Science Center

Beaufort, North Carolina

aleta.hohn@noaa.gov

Kim Holland

University of Hawaii

Hawaii Institute of Marine Biology

Kaneohe, Hawaii

kholland@hawaii.edu

Bob Iwamoto

Northwest Fisheries Science Center

Seattle, Washington

bob.iwamoto@noaa.gov

Bruce F. Jonasson

Northwest Fisheries Science Center

Seattle, Washington

bruce.jonasson@noaa.gov Véronique Koch

Southeast Fisheries Science Center, 

Miami, Florida

veronique.koch@noaa.gov

Suzanne Kohin

Southwest Fisheries Science Center

La Jolla, California

suzanne.kohin@noaa.gov

Stacy Kubis

Northeast Fisheries Science Center

Woods Hole, Massachusetts

stacy.kubis@noaa.gov

John Lamkin

Southeast Fisheries Science Center

Miami, Florida

john.lamkin@noaa.gov

Michelle E. Lander

Alaska Fisheries Science Center

Seattle, Washington

michelle.lander@noaa.gov

Mike Laurs

Southwest Fisheries Science Center

La Jolla, California

mike.laurs@noaa.gov

Steven T. Lindley

Southwest Fisheries Science Center

La Jolla, California

steve.lindley@noaa.gov

Charles L. Littnan

Pacific Islands Fisheries Science Center

Honolulu, Hawaii

charles.littnan@noaa.gov

Elizabeth A. Logerwell

Alaska Fisheries Science Center

Seattle, Washington

libby.logerwell@noaa.gov

R. Bruce MacFarlane

Southwest Fisheries Science Center

La Jolla, California

bruce.macfarlane@noaa.gov
81

Douglas M. Marsh

Northwest Fisheries Science Center

Seattle, Washington

doug.marsh@noaa.gov

Gene M. Matthews

Northwest Fisheries Science Center

Seattle, Washington

gene.matthews@noaa.gov

R. Lynn McComas

Northwest Fisheries Science Center

Pasco, Washington 

lynn.mccomas@noaa.gov

Susanne F. McDermott

Alaska Fisheries Science Center

Seattle, Washington

susanne.mcdermott@noaa.gov

Richard D. Methot

Northwest Fisheries Science Center

Seattle, Washington

richard.methot@noaa.gov

Joshua Moser

Northeast Fisheries Science Center

Woods Hole, Massachusetts

joshua.moser@noaa.gov

Mary L. Moser

Northwest Fisheries Science Center

Seattle, Washington

mary.moser@noaa.gov

Peter Munro

Alaska Fisheries Science Center

Seattle, Washington

peter.munro@noaa.gov

Michael Musyl

Pacific Islands Fisheries Science Center

Joint Institute for Marine and 

Atmospheric Research

Honolulu, Hawaii

michael.musyl@noaa.gov

Dan Nichol

Alaska Fisheries Science Center

Seattle, Washington

dan.nichol@noaa.gov

Greg O’Corry-Crowe

Southwest Fisheries Science Center

La Jolla, California

greg.o’corry-crowe@noaa.gov

Layla Osman Gallegos

Southwest Fisheries Science Center

La Jolla, California

laylaosman@uach.cl

Daniel Palacios

Southwest Fisheries Science Center

Pacific Grove, California

daniel.palacios@noaa.gov

John Payne

Northwest Fisheries Science Center

Seattle, Washington

jcpayne@u.washington.edu

Jeffrey J. Polovina

Pacific Islands Fisheries Science Center

Honolulu, Hawaii

jeffrey.polovina@noaa.gov

Clay E. Porch

Southeast Fisheries Science Center

Miami, Florida

clay.porch@noaa.gov

Earl F. Prentice

Northwest Fisheries Science Center

Seattle, Washington

earl.prentice@noaa.gov

Eric D. Prince

Southeast Fisheries Science Center

Miami, Florida

eric.prince@noaa.gov

Samuel L. Rambo

Northwest Fisheries Science Center

Pasco, Washington 

samuel.rambo@noaa.gov

Anne Richards

Northeast Fisheries Science Center

Woods Hole, Massachusetts

anne.richards@noaa.gov

Cheryl Ryder

Alaska Fisheries Science Center

Seattle, Washington

cheryl.ryder@noaa.gov

Benjamin Sandford

Northwest Fisheries Science Center

Seattle, Washington

ben.sandford@noaa.gov

Christopher R. Sasso

Southeast Fisheries Science Center

Miami, Florida

chris.sasso@noaa.gov
82

Peter F. Sheridan

Southeast Fisheries Science Center

Panama City Beach, Florida

pete.sheridan@noaa.gov

Yunbing Shi

Alaska Fisheries Science Center

Seattle, Washington

bing.shi@noaa.gov

David Somerton

Alaska Fisheries Science Center

Seattle, Washington

david.somerton@noaa.gov

Jim Stark

Alaska Fisheries Science Center

Seattle, Washington

jim.stark@noaa.gov

Jeremy T. Sterling

Alaska Fisheries Science Center

Seattle, Washington

jeremy.sterling@noaa.gov

Skip Tezak

Northwest Fisheries Science Center

Seattle, Washington

skip.tezak@noaa.gov

Robert V. Walker

University of Washington

High Seas Salmon Research Program

Seattle, Washington

rvwalker@u.washington.edu

Samantha Whitcraft

Southeast Fisheries Science Center

Cooperative Institute for Marine and 

Atmospheric Science

Miami, Florida

samantha.whitcraft@noaa.gov

John G. Williams

Northwest Fisheries Science Center

Seattle, Washington

john.g.williams@noaa.gov

Lisa Wooninck

Southwest Fisheries Science Center

Pacific Grove, California

lisa.wooninck@noaa.gov

Cynthia Yeung

Alaska Fisheries Science Center

Seattle, Washington

cynthia.yeung@noaa.gov