Life in the World’s Oceans 15

The population status and general oceanic movements of many species and guilds were virtually unknown in the eastern Pacifi c basin when Tagging of Pacifi c Predators TOPP was initiated

3 Environmental Research Division, National Oceanic and Atmospheric Administration, Southwest Fisheries Science

Center, Pacifi c Grove, California, USA

15.1 Large Pelagic Species

in the Marine Ecosystems of

the North Pacific

In the oceanic realm, species diversity, population

struc-ture, migrations, and gene fl ow in marine pelagic species

are poorly understood Large marine animals such as

whales, pinnipeds, seabirds, turtles, sharks, and tunas have

behaviors and life - history strategies that involve high

dis-persal movements and vagile populations Most of these

animals lack obvious geographic barriers in the marine

environment Obtaining baseline information about

sea-sonal movement patterns, regional habitat use, and location

of foraging and breeding grounds has remained elusive

The population status and general oceanic movements of

many species and guilds were virtually unknown in the

eastern Pacifi c basin when Tagging of Pacifi c Predators

(TOPP) was initiated as a fi eld program of the Census of

Marine Life Additionally, potential effects of global

climate change on species diversity, biomass, and

com-munity structure in pelagic environments remain largely

unexplored and diffi cult to assess or predict These are

alarming facts, given that many species face an

unprece-dented level of exploitation from both directed fi sheries

and bycatch, and ecosystem management is dependent upon a scientifi c understanding of habitat use

The lack of knowledge about large marine species is marily due to the challenges inherent in studying marine animals The sheer size of the Pacifi c Ocean makes it chal-lenging to use traditional techniques such as ship surveys In

pri-an effort to rectify this lack of knowledge the Census ated two Pacifi c tagging efforts, TOPP (see www.topp.org ), and the Pacifi c Ocean Shelf Tracking Project (POST) ( www.postcoml.org ; see Chapter 14 ) These programs proposed to use electronic tracking technology to study the movements

initi-of marine organisms in the North Pacifi c In the case initi-of TOPP, biotelemetry or biologging (use of electronic tags carried by the animal to measure its biology) became the major ecological tool of choice for advancing knowledge of multi - species habitat use We proposed combining elec-tronic tag technology data with oceanographic data acquired through remote sensing and, when possible, with foraging ecology and genetics We hypothesized that the primary physical forces that infl uence temporal distribution patterns were temperature and primary production We expected that by studying multiple species within an ecosystem such as the California Current, we could reveal common locations for feeding, migration highways, potential reproduction regions, and hot spots The principal factors acting on popu-lation dynamics might be revealed, and these would include seasonal variations in thermal regimes and the formation of prey - aggregating physical features, which were assumed

to cause variation in food supply, physiological ance, and predation pressures Understanding behavior of

perform-Part IV Oceans Present – Animal Movements

292

the tag deployments throughout the program (2006 – 2009) Large - scale deployments (approximately 3,000 tags) of existing and new technologies across multiple taxa in a synoptic seasonal pattern occurred Central to the TOPP plan was selection of approximately two dozen key target species that had distributions within the eastern and central North Pacifi c Ocean and were tractable for tagging and population studies The implementation plan built on the known tagging success of key species during the early years, to inform the selection of TOPP target species

The tag data would be combined with in situ and remotely

sensed oceanographic observations to build a decade - long survey of key species in the North Pacifi c Ocean As data began to be collected, TOPP scientists focused on the improvement of electronic tagging technology, implemen-tation of simultaneous large - scale tagging, development

of a data acquisition system capable of handling multiple tagging platforms, and integration and visualization of multiple data streams and initiation of four - dimensional display

Workshop deliberations and early tagging experiments generated a list of key animals that became the research subjects of TOPP (Box 15.2 , p 308) This included a diverse group of species with interesting ecological link-ages One key concept that emerged early in the program was the focus on tagging of guilds of closely related species The TOPP species guilds include sharks of the family Lam-

nidae (white, mako, and salmon), fi sh of the Thunnus guild

(yellowfi n, bluefi n, and albacore), albatrosses (black footed and Laysan), pinnipeds (elephant seals, California sea lions, and northern fur seals), rorqual whales (blue, fi n, and humpback whales), and sea turtles (loggerheads and leath-erbacks) The guild concept turned out to be among the most successful ideas in TOPP for exploration of the oceanic environment harnessing the evolutionary power for related species By using this classic comparative approach, we were able to examine how organisms of similar phylogeny have diverged in their niche use and foraging ecology and the physiological mechanisms used (Feder 1987 ; Costa & Sinervo 2004 ) Additionally, we found that tagging techniques could easily be passed on to multiple species, improving the trophic connections and comparative methodologies (Block 2005 ) Several addi-tional species that shared similar habitats complemented the original guild species These species included blue and thresher sharks that overlapped with the lamnid guild, molas that were common in the tuna guild ecosystem, and shearwaters that overlapped with the albatross guild The guild approach simplifi ed the logistics of the tagging efforts More than one species within a guild is often found in the same region at the same time of year, making it possible

to maximize the success of the tagging effort by using a single platform to tag multiple species Details of the types

of tag used, and how tag technology progressed during TOPP, are given below

organisms relative to the physical and biological forces they

experience was considered prerequisite to a study of multi

species community structure of large pelagic species in the

North Pacifi c Ocean

15.2 Tagging of Pacific

Predators, 2000 – 2008

15.2.1 Planning and i nitiation

of TOPP

TOPP scientists proposed a decade - long tagging campaign

to elucidate the distribution, movements, behavior, and

ecological niche of apex marine predators within the

oceanic ecosystems of the North Pacifi c Ocean To examine

whether it was possible to observe and monitor multiple

species in coastal and open - ocean habitats in the North

Pacifi c, a series of planning workshops was initiated Ninety

participants from the USA, Canada, Mexico, France, and

Japan met in Monterey, California, USA, for four days in

November 2000 to discuss the experimental tagging

approaches, selection of organisms, and together developed

the foundation deployments of the TOPP program This

workshop led to a formal TOPP plan to use biologging

techniques in concert with oceanographic data, feeding

studies, and molecular techniques to examine 23 top

preda-tors of the North Pacifi c Ocean (Block et al 2003 ) After

the initial TOPP workshop, ten working groups were

formed and met separately to plan the details of the program

and experiments, and coordinate the ocean - scale tagging

efforts (Box 15.1 ) The working groups were concentrated

around seven organismal teams (tunas, sharks, squid,

pin-nipeds, seabirds, cetaceans, and turtles), as well as

oceanog-raphy, tag development, data management, and education

and outreach As with any project of this size and

complex-ity the work reported here could not have been done

without the participation and dedication of many

individu-als to the TOPP program (Box 15.1 )

The workshop participants recommended a staged

implementation of the TOPP program, beginning with

species selection An emphasis was placed initially on the

use of current technologies that had a track record of

proven deployment success in large - scale experiments (for

example archival/TDR tags), on species that would most

likely yield quick data returns (elephant seals, Pacifi c

bluefi n tuna) Initiation of pilot studies to explore new

and potentially challenging species (for example squid and

swordfi sh), and to test large - scale deployments or new

technologies and attachment strategies were also initiated

(for example spot tags on shark dorsal fi ns, archival tags

on shearwaters) After the successful completion of this

testing and development phase (2003 – 2005), a second

round of fi eld efforts focused on increasing the scale of

Cetaceans

Bruce Mate a , Don Croll b , John Calambokidus c , Nick Gales d ,

Jim Harvey e , and Susan Chivers f

Seabirds

Scott Shaffer b , Yann Tremblay b , Bill Henry b , Henri

Weimer-skirch f , Dave Anderson g , Jill Awkerman g , Dan Costa b , Jim

Harvey e , and Don Croll b

Pinnipeds

Dan Costa b , Dan Crocker h , Burney Le Boeuf b , Juan Pablo

Gallo i , Jim Harvey e , Mike Weise b , Mike Fedak j , Carey Kuhn b ,

Sam Simmons b , Patrick Robinson b , Jason Hassrick b ,

Jeremy Sterling k , Sharon Melin k , and Bob DeLong k

Sea t urtles

Steven Bograd f , Scott Bensen f , Peter Dutton f , Scott Eckert l ,

Steve Morreale m , Frank Paladino n , Jeff Polovina f , Laura

Sarti f , James Spotila o , and George Shillinger r

Sharks

Scot Anderson p , Dave Holts f , Oscar Sosa - Nishizaki q ,

Barbara Block r , Aaron Carlise r , Peter Pyle s , Sal Jorgenson r ,

Ken Goldman t , Peter Klimley u , Chris Perle r John O ’ Sullivan v ,

Kevin Weng r , Suzanne Kohin f , Heidi Dewar f , and Sean Van

Sommeran r

Tuna

Barbara Block r , Kurt Schaefer w , John Childress x , Heidi

Dewar f , Suzanne Kohin f , Kevin Weng r , Steve Teo r , Chuck

Farwell r , Dan Fuller w , Chris Perle r , Dan Madigan r , Luis

Rodriguez r , Jake Noguiera r , and R Schallert r

m Cornell University

n Indiana University

o Drexel University

p Point Reyes Bird Observatory

q CICESE

r Stanford University

s Pelagic Shark Foundation

t Alaska Fish & Game

u University of California at Davis

v Monterey Bay Aquarium

w Inter - American Tropical Tuna Commission

x University of California at Santa Barbara

These individuals represent the members of the various organismal working

groups of TOPP Their work and perseverance in field tagging efforts and

dedication to the TOPP program made this ten - year effort possible

Box 15.1

Part IV Oceans Present – Animal Movements

294

methods to synthesize a vast array of disparate data streams (Teo et al 2004b ; Tremblay et al 2006, 2007, 2009 ;

Bailey et al 2008 ) Simply put, TOPP is the fi rst large - scale

tagging program to implement automation of the ARGOS and geolocation tag management, metadata delivery, and integration of online data display in near - real - time with oceanographic data information A public display in a browser format (las.pfeg.noaa.gov/TOPP) was developed for the TOPP team members and education and outreach Four broad classes of electronic tags were tested, refi ned and/or developed, and deployed as part of the TOPP program

In fi sh this tag can only be used on highly exploited species (tunas) where an enhanced reward is offered to recover the tag after capture Archival tags are also used with species that have a high probability of returning to the colony where they were initially tagged (that is, sea lion, elephant seal, albatross, and shearwater) Archival tags have provided tracks covering up to 1,000 days in northern

bluefi n tuna (Block et al 2001 ; Block 2005 ) and 1,160 days in yellowfi n tuna (Schaefer et al 2007 ) These tags

were a mainstay of the TOPP program, with over mately 1,600 light, temperature, depth (LTD) (Lotek) 2310

approxi-tags deployed, primarily on bluefi n (Kitagawa et al 2007 ;

Boustany et al 2010 ), yellowfi n (Schaefer et al 2007,

2009 ) and albacore tunas This archival tag (D - series) has

a pressure accuracy of ± 1% of the full - scale reading (up

to 2,000 m) The LTD temperature ranged from − 5 to

40 ° C, with an accuracy of 0.05 ° C The temperature response is less than 2 seconds, so that as an animal dives,

it provides a temperature profi le with depth (Simmons et

al 2009 ) In the TOPP program, archival tags were used

primarily on tunas that were juveniles (3 – 20 kg) and lescents (up to 55 kg) The smallest animal tagged was the

ado-sooty shearwater (Shaffer et al 2006 ), weighing

approxi-mately 800 g For this, we used the smallest archival tag the Lotek LTD 2410 that weighs only 5.5 g and is 11 mm

in diameter and 35 mm long

Archival tags often carry sensitive optical detectors that can measure variations in light level quite accurately The Lotek 2310 tag used by TOPP has a polystyrene light stalk that extends externally from an animal after it has been surgically implanted The wall of the stalk contains a fl uo-rescent dye that is sensitive to narrow band blue light

15.2.2 Developing t ag

t echnologies for m arine b iologging

Biologging technology allows researchers to take

measure-ments from free - swimming marine animals as they move

undisturbed through their environment Importantly, it

permits researchers to observe animals beyond the natural

reach of humans, and provides extensive data on both the

animals ’ behavior and their physical environment

Biolog-ging can be used for observational studies of animal

behavior, controlled experimental studies (translocation

experiments), oceanographic observations of the in situ

environment surrounding the animal, and ecological

research such as foraging dynamics

An early challenge for TOPP was to solve the many

technological issues associated with the tag platforms before

launching the major deployment phase For the fi rst three

years of TOPP deployments (2001 – 2004), the priority was

to develop effi cient deployment strategies of proven

tech-nologies, while simultaneously investing in and testing new

tags TOPP worked with four manufacturers of commercial

tags and advised signifi cant engineering decisions, which

over the course of a decade led to advancements in all

major tag types used Testing included a development phase

with new ARGOS transmitters, Fastloc GPS, novel sensors

with oceanographic capabilities, increased memory,

mini-aturization, new track fi ltering, and data compression

algo-rithms (Teo et al 2004a, 2009 ; Kuhn & Costa 2006 ;

Tremblay et al 2006, 2007, 2009 ; Biuw et al 2007 ; Bailey

et al 2008 ; Kuhn et al 2009 ; Costa et al 2010a ; Simmons

et al 2009 )

Stable and prototype electronic tags were both available

in 2000 They ranged from ARGOS tags to data storage

tags (archival) that could be attached or implanted

surgi-cally, and pop - up satellite archival tags designed to track

large - scale movements and behavior of animals for which

the use of real - time ARGOS satellite tags was not possible

The pop - up satellite tags jettisoned from the animal on a

pre - programmed date and transmitted data about depth,

ambient temperature, pressure, and light to ARGOS

satel-lites (Block et al 1998 ) Each generation of the tags had

technological issues that included the accuracy of sensors,

the resilience of tag components, pressure housing

prob-lems, and algorithm limitations In the fi rst phase of TOPP

we tested many of the tags on free - ranging animals to

ensure that they would be suffi ciently robust for the larger

scale deployments in the second phase

Tag attachment strategies were another early challenge

Strategies were shared among organismal working groups,

and the increased communication with multiple taxa

spe-cialists helped to facilitate the exchange of ideas and

tech-niques In addition, the increased memory capacity of the

new tags, and the scale of the TOPP deployments, resulted

in the need for investment in a novel data management

system, improved analytical and visualization tools, and

is less than a second over a 70% step in this range Further advances in the form of data compression have made it possible to get signifi cantly more data through the limitations of the ARGOS system, including detailed

oceanographic and behavioral information (Fedak et al

2001 ) ARGOS satellite tags are larger than archival tags, with the smallest unit weighing 30 g

15.2.2.3 GPS t ags

With funds from the National Oceanographic Partnership Program (NOPP), TOPP supported the development of a GPS tag for use on marine species (Decker & Reed 2009 ;

Costa et al 2010b ) The advantage of GPS tags is twofold

First, GPS tags provide an increase in the precision of animal movement data to within 10 m compared with the

1 – 10 km possible with ARGOS satellite tags Second, GPS tags provide a higher time resolution, with positions acquired every few minutes compared with a maximum of about eight to ten positions a day with ARGOS However, standard navigational GPS units do not work with diving species, as they require many seconds or even minutes of exposure to GPS satellites to calculate positions and the onboard processing consumes considerable power At the beginning of the TOPP project, two conceptual solutions

to this problem were identifi ed and resources invested in the development and testing of the Fastloc system devel-oped by Wildtrack Telemetry Systems (Leeds, UK) The Fastloc uses a novel intermediate solution that couples brief satellite reception with limited onboard processing to reduce the memory required to store or transmit the loca-tion This system captures the GPS satellite signals and identifi es the observed satellites, calculates their pseudo - ranges without the ephemeris or satellite almanac, and pro-duces a location estimate that can be transmitted by ARGOS Final locations are post - processed from the pseudo - ranges after the data are received using archived GPS constellation orbitography data accessed through the Internet Although this technology provides a major advance in our ability to monitor the movements and habitat use of marine animals (Fig 15.1 ), TOPP researchers have also used these tags to validate the error associated with ARGOS satellite locations

(Costa et al 2010a )

15.2.2.4 Conductivity, t emperature, and d epth t ags

A fundamental component of the TOPP program was a desire to further the development of using animals to collect oceanographic data This served two functions: the

fi rst was to acquire physical oceanographic data that were not otherwise available, and the second was to collect physical environmental data at a scale and resolution that matched the animal ’ s behavior As with the GPS tag, funds from the NOPP program allowed TOPP to support the development and testing of a reliable and commercially

(470 nm) passing through the side wall of this optical fi ber

When excited, it radiates light in the green wavelengths and

focuses the light down the base of the fi ber where it is

detected by a photodiode The photodiode is used to

convert the fl ow of photons into a fl ow of electrons that is

measured with an electrometer with about 9 decades of

range, allowing detection of sunrise and sunset while a tuna

is cruising at depths On board or post - processing

algo-rithms allow construction of light - level curves and the

cal-culation of local apparent noon to determine longitude

Estimates of time of sunrise and sunset are used to

deter-mine day length and latitude using threshold techniques

(Hill & Braun 2001 ; Ekstrom 2004 ) These locations can

be improved by using archival tag observed measurements

of sea surface temperature, and TOPP research with double

tag datasets provided a robust improvement for these

algo-rithms (Teo et al 2004a ) Archival tags have also been used

to estimate in situ chlorophyll concentrations (Teo et al

2009 )

15.2.2.2 ARGOS s atellite t ags

Satellite tags provide at - sea locations and have the

advan-tage that the data can be recovered in real time and

remotely without the need to recover the tag The

satel-lites are operated by CLS - ARGOS (Toulouse, France, or

Landover, Maryland, USA) and the data are acquired from

this service over the Internet Because the antenna on the

satellite transmitter must be out of the water to

com-municate with an orbiting ARGOS satellite, the technology

has mainly been used on air - breathing vertebrates that

surface regularly (McConnell et al 1992a, b ; Le Boeuf

et al 2000 ; Polovina et al 2000 ; Weimerskirch et al

2000 ; Shaffer & Costa 2006 ) A signifi cant innovation

of the TOPP program was the realization that satellite

tags could be effectively deployed on sharks (Weng et al

2005 ; Jorgensen et al 2010 ) For large fi sh, sharks, or

other animals that remain continuously submerged, the

ability to transmit to ARGOS at the surface is not

possible For these organisms, a pop - up satellite archival

tag (PSAT) was developed (Block et al 1998, 2001 ;

Lutcavage et al 1999 ; Boustany et al 2002 ) Pop - up

satellite archival tags combine data - storage tags with

satel-lite transmitters These tags are externally attached and

are programmed to release or pop off at a preprogrammed

time The pop - up satellite devices communicate with the

ARGOS satellites that serve both to uplink data and

cal-culate an end - point location Importantly, the tags are

fi sheries - independent in that they do not require recapture

of the fi sh for data acquisition The Mk10Pat model, the

most used in TOPP, has a pressure sensor with resolution

of about 0.5 dBar The temperature accuracy improved as

an external thermistor was tested and used to improve

acquisition of oceanographic quality data (temperature

accuracy is ± 0.1 ° C with 0.05 ° C accuracy from about − 5

to 40 ° C) (Simmons et al 2009 ) The temperature response

(B) 60˚ N

Humpback whale Fin whale Sperm whale Sooty shearwater California sea lion Northern fur seal Blue whale Northern elephant seal

Thresher shark Yellowfin tuna Albacore tuna Blue shark Mako shark White shark Loggerhead turtle

Mola mola

Pacific bluefin tuna Leatherback turtle Salmon shark Laysan albatross Black-footed albatross Humboldt squid

(A) 60˚ N

Fig 15.1

Basin - scale Pacific map showing all TOPP tracks

color - coded by species (A) shows salmon sharks

on the top layer, (B) shows elephant seals on the

top layer

Example of North Pacific conductivity (salinity) and temperature ( ° C) profiles derived from CTD tags deployed on seven elephant seals Each seal is

represented by a different color line on the top or surface of each track The curtain effect represents the integrated temperature or conductivity profile

available conductivity, temperature, and depth (CTD) tag

for animals, in collaboration with the Sea Mammal

Research Unit at St Andrew ’ s University, UK (SMRU;

www.smru.st-andrews.ac.uk ) A conductivity –

tempera-ture – depth satellite relay data logger (CTD - SRDL)

incor-porates a Valeport CTD sensor with pressure accuracy

± 5 dBar, temperature resolution of ± 0.001 ° C, with an

accuracy of 0.01 ° C and an inductive coil for measuring

conductivity with resolution of ± 0.003 mS cm − 1 The tag is

optimized to collect oceanographic data at the descent and

ascent speeds exhibited by seals (approximately 1 m s − 1 )

In addition to collecting data on an animal ’ s location and

diving behavior, it collects CTD profi les (Fig 15.2 ) The

tag looks for the deepest dive for a 1 - or 2 - hour interval

Every time a deeper dive is detected for that interval, the

tag begins rapidly sampling (2 Hz) temperature,

conductiv-ity, and depth from the bottom of the dive to the surface

These high - resolution data are then summarized into a set

of 20 depth points with corresponding temperatures and

conductivities These 20 depth points include 10

prede-fi ned depths and 10 infl ection points chosen by a “ broken

stick ” selection algorithm (Fedak et al 2002 ) These data

are then held in a buffer for transmission by ARGOS

Given the limitations of the ARGOS system, all records

cannot be transmitted; therefore a pseudo - random method

is used to transmit an unbiased sample of stored records

If the SRDLs are recovered, all data collected for

transmis-sion, whether or not it was successfully relayed, can be

recovered The use of these tags has led to insights into

both the animal ’ s behavior relative to its environment

(Biuw et al 2007 ) as well as the physical oceanography

(Boehme et al 2008a, b ; Charrassin et al 2008 ; Nicholls

et al 2008 ; Costa et al 2010b )

15.2.3 Top p redator d istributions and the d iscovery of b asin - s cale

m igrations

One of the principal results of the TOPP program was a new understanding of the distribution and migration pat-terns of a suite of apex marine predators Over the course

of the TOPP program, 4,306 animals, representing 23 species (Box 15.2 ), were equipped with a variety of sophis-ticated tags carrying high - resolution sensors (Figs 15.1 A and B) The predators recorded data on their position, the ocean environment, habitat use, and behaviors while traveling remarkable distances underwater The dataset yielded many surprises and demonstrated for the fi rst time seasonal patterns and fi delity to the eastern Pacifi c for many species tagged in TOPP and unlimited boundaries when roaming over vast reaches of the Pacifi c Ocean for others (Figs 15.3 , 15.4 , and 15.5 ) For example, white sharks show a coastal to offshore migration from California near-shore waters to offshore waters of Hawaii and back, result-

ing in homing behavior (Boustany et al 2002 ; Weng et al 2007a ; Jorgensen et al 2010 ) Salmon sharks move from

the Arctic to the sub - tropical reaches of the North Pacifi c Ocean and back to the foraging grounds in Prince William

Sound (Weng et al 2005 ), whereas bluefi n tuna and

log-gerhead turtles range across the North Pacifi c, breeding in the western Pacifi c but migrating as juveniles and adoles-cents to the eastern Pacifi c to take advantage of the highly

productive California Current (Peckham et al 2007 ; tany et al 2009 ) Leatherback turtles tagged on their nesting

Bous-beaches in Indonesia cross the Pacifi c basin to feed off central California, whereas sooty shearwaters use the entire

Part IV Oceans Present – Animal Movements

298

archival tags on juvenile Pacifi c bluefi n in the eastern Pacifi c Recovery rates ranged from 50% to 75%, indicative of high mortality on these juveniles The bluefi n tagged displayed

a cyclical pattern of movements on a seasonal scale that ranged annually from the southern tip of Baja California to

the coast of Oregon (Boustany et al 2010 ) This seasonal

signal was apparent and provided the fi rst clear signal that the California Current has a seasonality that many TOPP species (bluefi n, yellowfi n, and albacore tunas, blue whales, lamnid sharks, and shearwaters) were following Approxi-mately 5% of the recovered tagged bluefi n tuna migrated back into the western Pacifi c using the North Pacifi c Transi-tion Zone (Fig 15.3 ) Large adult Pacifi c bluefi n tuna were also tagged in the south Pacifi c off New Zealand during TOPP (Fig 15.1 ) The emerging story is of a Pacifi c bluefi n that travels across the entire North Pacifi c Ocean as a juve-nile and adolescent, and that is capable of post - spawning migrations from the North Pacifi c to the South Pacifi c Taken together, the electronic tag data on adolescents and adults demonstrate this tuna species encompasses one of the largest home ranges on the planet

Pacifi c Ocean from the Antarctic to the Bering Sea (Shaffer

et al 2006 ) These trans - oceanic journeys require

remark-able animal navigation, energetics, and philopatry The

TOPP species that best illustrate these trans - oceanic

migra-tions are the Pacifi c bluefi n tuna, the sooty shearwater, and

the leatherback turtle

15.2.3.1 Pacific b luefin t una

Pacifi c bluefi n tuna are one of three species of bluefi n tuna

that inhabit subtropical to subpolar seas throughout the

world ’ s oceans Among Thunnus , Pacifi c bluefi n tuna have

the largest individual home range, being found throughout

the North Pacifi c Ocean and ranging into the western South

Pacifi c (Collette & Nauen 1983 ) Pacifi c bluefi n tuna

remain in the western Pacifi c after being spawned (near the

Sea of Japan) but a proportion of the juveniles make

exten-sive migrations into the eastern Pacifi c late in the fi rst or

second year (Bayliff 1994 ; Inagake et al 2001 ) It has been

hypothesized that the trans - Pacifi c migrations from west to

east are linked to local sardine abundances off Japan

(Polovina 1996 ) TOPP researchers deployed over 600

Multiple trans - Pacific migrations of a single 15 kg

Pacific bluefin tuna that crossed the North Pacific

three times in 600 days Positions are from a Lotek

2310 tag with threshold geolocation for longitude

and sea surface temperature enhanced positions for

latitude

Equally impressive was the TOPP observation with archival

tags that sooty shearwaters that breed off the Southern

Islands of New Zealand cross the equator to feed in diverse

regions of the North Pacifi c Ocean, from Japan to Alaska

and California (Shaffer et al 2006, 2009 ) We were able

to document this trans - equatorial migration using newly

developed miniature archival tags that log data for

estimat-ing position, dive depth, and ambient temperature The

Pacifi c Ocean migration cycle had a fi gure - eight pattern

(Fig 15.4 ) while traveling, on average, 64,037 ± 9,779 km

round trip over 198 ± 17 days This is the longest migration

of any individual animal ever tracked Shearwaters foraged

in one of three discrete regions off Japan, Alaska, or

California before returning to New Zealand through a

relatively narrow corridor in the central Pacifi c Ocean

These migrations allow shearwaters to take advantage of

prey resources in both the Northern and Southern

hemi-spheres during the most productive periods; in other

words, they exist in an “ endless summer ”

15.2.3.3 Leatherback t urtles

Two distinct populations of leatherback turtles were tagged

during TOPP: one that breeds on the Indonesian islands of

the western Pacifi c and another that breeds on the beaches

of Costa Rica A portion of the tagged western Pacifi c

leatherbacks undergo remarkable trans - Pacifi c migrations,

arriving off the coast of California in late summer to forage

on dense aggregations of jellyfi sh The eastern Pacifi c

popu-lation, in contrast, undergoes a cross - equatorial migration that takes them into the oligotrophic waters of the eastern

subtropical South Pacifi c (Shillinger et al 2008 ) Nearly all

of the tagged eastern Pacifi c leatherbacks made this journey, traversing a relatively narrow migration corridor through the highly dynamic equatorial Pacifi c The apparently different migration and foraging strategies of these two populations of Pacifi c leatherbacks was another surprise result of TOPP

targeted fi sheries populations (Worm et al 2003 ; Sydeman

et al 2006 ) Although it is well known that top predators,

including large predatory fi shes, cetaceans, pinnipeds, sea turtles, marine birds, and human fi shers, congregate at loca-

tions of enhanced prey (Olson et al 1994 ; Polovina et al

2000 ), little is known about why particular regions or physical features are hot spots, how the animals locate and

Part IV Oceans Present – Animal Movements

300

throughout the eastern Pacifi c, including leatherback and loggerhead turtles, sooty shearwaters, Laysan and black - footed albatrosses, blue and humpback whales, sea lions, northern fur seals, elephant seals, bluefi n, yellowfi n and albacore tunas, white, makos, salmon, blue, and thresher sharks The CCS is a highly productive eastern boundary current system, driven by seasonal coastal upwelling, which maintains numerous economically important marine fi sher-ies This region is characterized by strong cross - shore gra-dients in physical and biological fi elds, is strongly modulated

by seasonal wind forcing and Ekman dynamics, and has a complex and energetic current structure (Hickey 1998 ;

Palacios et al 2006 ) These dynamics contribute to the

aggregation of prey and, hence, top predators Within the California Current, several areas have emerged as critical multi - species hot spots These include areas we have desig-nated as the California Marine Sanctuaries Hot Spot (CMHS), the Southern California Bight Hot Spot (SCBHS), and the Baja California Hot Spot (BCHS)

TOPP data have shown that the North Pacifi c Transition Zone (NPTZ) is equivalent to a major top predator highway across the North Pacifi c Ocean Bluefi n and albacore tunas, albatrosses, shearwaters, elephant seals, fur seals, and turtles all occur with great frequency in this region The NPTZ is a complex region encompassing an abrupt north

to south transition from subarctic to subtropical water masses, has an abundance of energetic mesoscale features (fronts and eddies), and is dominated by biological patchi-ness (Roden 1991 ) Interactions between eddies and the mean fl ow create transient jets and submesoscale vortices, resulting in up - and downwelling patches a few kilometers across that contribute to this biological patchiness (Woods

1988 ; Roden 1991 ) This large basin - scale frontal feature serves as a primary foraging area and migratory corridor for most of the TOPP predators that undergo trans - oceanic movements

The CCS and NPTZ hot spots support several important ecological functions for North Pacifi c top predators TOPP data has also revealed distinct niche separation among TOPP guilds that use these regions (Figs 15.1 , 15.3 , and 15.7 ) At the initiation of the Census we knew that there were differences in the thermal tolerances of marine preda-tors As a result of the TOPP program, we now know that the physiological tolerance of marine predators, their ener-getics, and physiological constraints on the cardiac system

(Weng et al 2005 ) determine the home range of many of

the TOPP species For example, endothermy enables birds, mammals, salmon sharks, and bluefi n tuna to range over vast regions of the North Pacifi c Ocean, including the colder temperate and subarctic oceans In contrast, species such as yellowfi n tuna, mako, and blue sharks are more constrained in their thermal tolerances to the warm temper-ate to subtropical waters of the North Pacifi c Ocean The clear separation in habitat between members of fi sh or shark guilds occurs primarily by thermal preferences, with

use these features, and what trophic interactions occur

within the hot spots The inaccessibility of open ocean hot

spots has precluded systematic fi eld studies that could

elu-cidate the physical characteristics and ecological function

of biological hot spots The TOPP dataset has provided a

unique view of North Pacifi c top predator hot spots,

allow-ing us to address several compellallow-ing questions What

condi-tions occur within hot spots to make these areas of

confl uence for a diverse set of species? What are the

physi-cal characteristics and spatial - temporal persistence of the

hot spots? What are the behavioral responses of different

species when they enter a hot spot? What trophic

interac-tions occur within hot spots? How can a better

understand-ing of critical habitat result in enhanced conservation and

management of these species?

Efforts at studying biological hot spots have relied on

two complementary approaches From a “ bottom - up ”

per-spective, standard oceanographic sampling (particularly

remote sensing) can be used to describe ocean features of

relevance to apex pelagic predators This approach has

several advantages: (1) it can provide global, near - real - time

views of the ocean surface; (2) it can identify regions of

enhanced biological activity (from ocean color); (3) it can

identify features that are persistent or recurrent in space

and time, which may be appealing areas for migratory

animals; and (4) it can describe the dominant scales of

ocean variability, from which hot spots can be classifi ed

(that is, based on their spatial - temporal scale, their degree

of persistence or recurrence, their forcing mechanisms, and

their potential biological impacts) (Palacios et al 2006 )

A more direct “ top - down ” approach is to let the animals

identify and describe hot spots through large - scale tagging

studies such as TOPP (Costa 1993 ; Block et al 2001, 2003 ;

Block 2005 ; Costa et al 2010b ) This approach allows

(1) a direct detection and observation of the preferred

habitats of the animals; (2) a matching of behavioral cues

to local oceanographic conditions; (3) a differentiation of

behavioral responses in relation to ocean features, allowing

a classifi cation of hot spots by their ecological function (for

example, aggregation, migration, foraging, diving, and

breeding); and (4) a differentiation between species - specifi c

hot spots and hot spots that are biologically diverse and

more universally occupied Understanding the

oceano-graphic, ecological, and physiological factors that are

important in attracting apex marine predators to these hot

spots, and determining how and why they remain retentive

to these species, is a continuing research aim of TOPP and

will likely be one of its primary legacies

Two oceanographic regions that have emerged as key

top predator hot spots in the North Pacifi c Ocean are the

California Current and the North Pacifi c Transition Zone,

which are described in detail below

The California Current ecosystem (CCS) has emerged as

a major hot spot for more than a dozen exploited,

pro-tected, threatened, or endangered predators that range