Bluefin Tunas: The State of the Science

8/3/2019 Bluefin Tunas: The State of the Science

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Bluefn TunaThe State o the Science

Ocean Science SerieS


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Bluen Tunas: The State o the Science b

Executive SummaryThe three species o bluen tunas can be ound throughout the worlds oceans rom the equator to

sub-polar seas. A suite o physiological adaptations has allowed bluen to range widely, exhibiting

some o the greatest individual ranges o any sh. Some sheries targeting bluen tunas have been

operating since ancient times, mainly supplying sh to small, local markets. Recent changes in the

globalization o sh markets, coupled with industrial-scale sheries and a high price in the global

sushi market, have driven exploitation o bluen tunas beyond sustainable levels. As a result, global

populations have declined considerably, in some cases to as low as 3 percent o unshed population

levels. The threat rom overshing is compounded by lie history traits, such as slowness to reachmaturity and a long lie span, which means rebuilding depleted populations will be a lengthy

process. Greater knowledge o the underlying biology o bluen will allow scientists to understand

how much shing pressure is sustainable and how ast populations can recover. Ultimately, the

recovery o bluen tuna populations depends on the willingness o managers to enact scientically

sound management measures and on the ability o governments to enorce agreed upon rules.


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Bluefn TunaThe State o the Science

Bluen Tunas: The State o the Science 1

Introductionamog th wolds tu sps, o s

lg s o s dvdully vlubl s th blu

tus. Blu omps th sps; atl-

t (Thunnus thynnus), P (T. orientalis),

d south (T. maccoyii). all th hghly

dsd o th ttol sush td d

ossttly mog th most xpsv sh thwold (colltt et al. 2011). Ths oom vlu

hs povdd shs woldwd wth th -

tv to xplot blu popultos t usust-

bl lvls. cutly, th th blu sps

mog th most ovxplotd tu sps

th wold. Ths doumt summzs th ut

st lttu o blu tu l hstoy,

gogph dstbuto, lyls, shg hstoy,

d mgmt.

The Biological Characteristics thatDistinguish Bluefn Tunasall blu sps sh my bologl h-

tsts, suh s lg sz, slowss to h

dulthood, d gt blty to kp th

bods wm ltv to oth tus. Howv,

lg ds lso xst mog th th blu-

sps, d v mog popultos wth

gv sps. Fo xmpl, md g o

mtuty (th g t whh th mjoty o sh

populto bl to podu) s stmtd

to g om 5 ys o st atlt blutu to 15 ys o wst atlt d south-

blu tu. Ths stmts ptully

mpott bus ds l hstoy

pmts hv lg mpts o th hlth

o popultos, d o th spos o popul-

tos to ov-xplotto.

Hlth o populto s dtmd by p-

od ssssmts odutd by ststs usg

th ltst dt o th ts, s wll s bolog-

l pmts o th sps bg ssssd.

Sps o popultos tht mtu l g-

lly btt bl to wthstd shg pssu

bus mo sh h spwg g bo

bg ptud (Jgs et al. 1999). Mtu

o dult sh tht podu dd to

mt populto lvls, d thg toomy mmtu o juvl sh wll lv dult

sh umbs dpltd too. ag o mtuty lso

fus popultos blty to ov om

ovxplotto. Sps d popultos wth

old g o st poduto hv mo ys

btw sussv gtos, d populto

gowth ous muh mo slowly th popul-

tos tht hv youg g o st poduto

(Huthgs d ryolds 2004).

Oth mpott bologl tos tht

qu ddtol sh lud spwglotos d tms, populto stutu, d

ssol movmt ptts. Udstdg

ths tos wll mpov stmts sstl o

buldg d mtg hlthy populto

lvls. Btt kowldg o populto stutu,

mgto ptts, d spwg s wll llow

mo stlly soud gol shg quots

to b st. Wthout kowldg o ths bs

bologl pmts, too muh shg ou

o o subpopulto o o spwg ggg-

tos, wh sh ptully t sk. althought s possbl to mg shy wthout ut

dt, mgmt msus must b mo p-

utoy to out o th utty th

ssssmts bsd o thos dt.

How podutv output, o th umb o

youg podud p dult sh, hgs wth g

lso mpts th blty o blu popultos

to ov om ovxplotto. Fo ll sps

Andre Boustany, Ph.D.*

* See back cover or biography.


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o blu, th oldst sh lkly to ply th

most mpott ol podutv output o th

populto s whol. as wth my m sh

sps, th umb o ggs podud s muh

gt th lgst sh, whh podu

bout 5 mllo ggs t 190 m (6 t 3 hs) to

bout 25 mllo ggs t 250 m (8 t 2 hs)

(Fly d Dvs 1998, Swd et al. 2005, ch

et al. 2006, Bgl 1982). Th bud o ggspodud ss wth sz d g o th sh;

tho, th mpt ths old, lg sh hv

o th totl podutv output o th popul-

to s v gt th th umbs wth th

populto would ld o to ssum.

Where Bluefn Are FoundBlu b oud ll th wolds os,

om th quto to sub-pol os (Byl

1994, Mthet al. 1995, Fly d Dvs 1998,

Blok et al. 2005) (Fgu 1). Th th tus ths sps omplxP, atlt, d

southhv th blty to mt body

tmptus bov suoudg wt tmp-

tus, tt mssg om most oth sh sps

(cy d Lwso 1973, Shp 1978, colltt

et al. 2011). Ths s possbl bus thy pos-

sss hghly dvlopd twok o splzd

blood vssls d tt gt sz ltv to

oth tu sps. as sult, thy ot s

gogphlly lmtd by suh vomtl

tos s wt tmptu d tho hv

th lgst vomtl gs o ll th tus.

a wd vty o sh mthodslud-

g tggg, gts, d msug hml

sgtus body ptshv b usd to bt-

t udstd blu dstbutos d movm

ptts. Th south blu gs om th

id O to th South O d to thSouth atlt; atlt blu w oud th

pst om Bzl to tl nowy th atlt;

d th P blu s oud thoughout th

noth P d to th South P to aust-

l d nw Zld (colltt d nu 1983,

Byl 1994, Mthet al. 1995, Fly d Dvs

1998) (Fgu 1). Lg dults o ll th blu

sps hv th blty to xpd th g

to ool wts; whl juvl tus my b

lmtd to wm tmptus d oud ov

muh smll gogph xps (itoh et al.2003b, Ktgw et al. 2004, Blok et al. 2005).

Atlantic bluefn tuna rangesi th atlt O, blu hv b oud

om th othst ost o Bzl to nw-

oudld, cd th wst, d noth a

to th tl ost o nowy th st (Mth

et al. 1995) (Fgu 2). Ths g hs ottd

t dds, s blu tu o log

PacificOcean

IndianOcean

Atlantic

Ocean

PacificOcean

Figure 1. BlueFin tuna od wods os.

Atlantic Bluen RangeAtlantic Bluen Spawning Area

Pacic Bluen RangePacic Bluen Spawning Area

Southern Bluen RangeSouthern Bluen Spawning Area


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oud o th ost o Bzl, o th noth S.

Th atlt blu (T. thynnus) s th oly sp-

s o blu tu kow to hv mo th o

spwg st th Mdt S d

th Gul o Mxo/Bhms (Mthet al. 1995).

Spwg ous th Mdt om My

to august d th Gul o Mxo om apl

to ly July (Dt d Ptt 1980, cot

d Lozou 1990, rhds 1990). Lv d

spwg dult sh hv b oud th Bh-

ms d th Stts o Flod, though ths s

my b xtso o th Gul o Mxo spw-

g go (rhds 1990). altt spw-

g sts hv b poposd outsd o ths

gos, but o lv o sh th l stgs

o spwg hv b oud to dt (Lutvg

et al. 1999, Goldst et al. 2007, Glud et al.

2010). rt gt studs hv omd

tht th Gul o Mxo d th Mdtblu tu gtlly dstt popultos

d tho, qu spt mgmt

(clsso et al. 2007, Bousty et al. 2008).

Mgg ths two popultos o blu

sptly psts dults wh mgto

ptts d dstbuto o th popultos

tk to out. although sh om th Md-

t S d Gul o Mxo do ot tmx

th spt spwg gouds, shs

hv vd tht th s hgh lvl o mx-

g btw popultos o th dg gouds

thoughout th noth atlt (Blok et al. 2001,

Blok et al. 2005, rooket al. 2008). Bus

shs optg ths gos my b th-

g sh om both popultos, sttg pop

th lvls o th populto boms mo

dult. rsh hs dtd tht lg

ptg, phps v th mjoty, o juvl

sh th wst noth atlt ogtd om

th Mdt populto (Blok et al. 2005,

Bousty et al. 2008, rooket al. 2008). Th

umb o sh om th Gul o Mxo popul-

to tht swm to th st atlt s lss

wll dtd, but svl tkd sh hv b

obsvd to tvl om wst to st m-

gmt zos (Mthet al. 1995, Lutvg et

al. 1999, Blok et al. 2005, Wll et al. 2009).Wth th wst noth atlt, smll sh

xt th Gul o Mxo t bg spwd d

glly m th wm ostl wts o

th est cost o th Utd Stts o th st

svl ys o l (Mthet al. 1995). Th

movmts glly ollow wm wt oth

th spg d summ d tu south th

wt (Blok et al. 2001, Glud et al. 2010).

IndianOcean

AtlanticOcean

PacificOcean

Figure 2. atlantic BlueFin tuna od oo a O d spw Md S d g o Mxo.

Atlantic Bluen RangeAtlantic Bluen Spawning Area


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as ths sh gow, thy bg to xpd th

g ot oly oth, but lso th osho

(Lutvg et al. 1999, Blok et al. 2005, Wll

et al. 2009, Glud et al. 2010). Th oldst

d lgst sh, whh hv th gtst blty

to mt lvtd body tmptus old

wts, hv th lgst g, d b oud

oth wt, splly th Gul o

St. Lw, cd, d out to th Flmsh

cp th tl noth atlt (Blok et al.

2005, Glud et al. 2010).

Som blu tu blvd to m

wth th Mdt o svl ys t

hvg b spwd (Mthet al. 1995). How-

v, som popoto o sh xt th Mdt-

d t th st noth atlt, mly

to th ostl wts o Sp d Potugl d

to th By o Bsy dug th st v ys

o l (rodguz-M et al. 2003). Sml toblu th wst noth atlt, blu

th st atlt xpd th g s thy

mtu, tg wts o nowy d ild

d to th tl noth atlt (Stoksbuy

et al. 2004, clsso et al. 2004, MKz d

Mys 2007, Fomt 2009). Mtu sh th

bg to mk tu mgtos to th spwg

gouds dug th sptv spwg ssos.

Pacifc bluefn tuna rangesP blu (T. orientalis) hv th lgst

hom g o th th blu sps (Fgu

3). P blu b oud thoughout th

noth P om th est ch S to th

P osts o th Utd Stts d Mxo

(colltt d nu 1983, Byl 1994). Spw-

g s td th est ch S d ryukyu

islds th spg d xtds to th S

o Jp th summ moths (Byl 1994,

igk 2001). although th pp to b d-

s th tmg, loto, d sz o sh

spwg th wst P, t s blvd

tht th s oly o populto o blu tu

th P (Byl 1994, rooket al. 2001).

Juvl sh mov oth log wth th s-

g tmptu d vtully om to sd

usy s th S o Jp d to th

Kuosho cut (igk et al. 2001, itoh etal. 2003). Most P blu tu m

th wst P, but smll poto jouy

oss th o d to th wts log th

wst osts o th Utd Stts d Mxo (By-

l 1994, igk et al. 2001). Th sh mgtg

to th st P hv b lkd to bu-

ds o sds th wst P (Polov-

1996, chvz et al. 2003). Ths mgtos

IndianOcean

AtlanticOcean

PacificOcean

Figure 3. PaciFic BlueFin tuna v s om o b sps.

Pacic Bluen RangePacic Bluen Spawning Area


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stwd usully md by juvl sh, d

th jouy oss th P ou lttl

ov two moths (itoh et al. 2003). O th

ostl wts o wst noth am, blu

mov up d dow th ost, ojuto wth

ssol pks lg d sd vlbl-

ty (Domet al. 2005, Ktgw et al. 2007,

Bousty et al. 2010). Ths sh wll m th st P o svl ys bo tu-

g to th wst s dults (Byl 1994, Bousty

et al. 2010). Most dult sh th m th

wst noth P, lthough smll poto

osolly tvls to th st noth P

o to th South P o th osts o austl

d nw Zld (Smth et al. 1994).

Southern bluefn tuna rangesSouth blu tu (T. maccoyii) oud t

th south xtts o th P, id, datlt os (colltt d nu 1983, com-

msso o th cosvto o South Blu

Tu [ccSBT] 2010) (Fgu 4). South blu

hv sgl kow spwg loto, btw

othwst austl d Jv, idos,

d blvd to omps sgl popul-

to (Potoet al. 1995, Yukw 1987, Fly

d Dvs 1998). Th vst mjoty o spwg

ous btw Sptmb d apl, wth som

low spwg lvls s ll moths xpt

July (Gw et al. 1997, Fly d Dvs 1998).

Juvl tu mgt, usully dug th

st y, to th South austl Bght, wh

movmt ptts blvd to ollow ssol

pks ood vlblty (Shgu 1967, Wd

et al. 2006). at bout g 5, south blu

spd lss tm th ostl wts to th southo austl d bg to g mo wdly

thoughout th P, id, d atlt

os (ccSBT 2010). Spwg bgs btw

gs 8 d 15, d south blu h g

42 (Fly d Dvs 1998, ccSBT 2010).

The Bluefn Tuna Lie Cycleall tus spw s wth wm su wt

(Sh 2001). i topl tu spssuh

s yllow, blk, d bgydults lv

o wts tht lso sutbl o spw-g, d s sult, spwg ths sps

ou thoughout th y thy hv ss

to sut sous (nshkw et al. 1985,

Fotu d Mll 1988, Sh 1998,

Sh 2001).

i otst, bus dult blu tu spd

th mjoty o th lvs om th wm

spwg s, thy mk log mgtos

btw wm d old wts. Th tmg

PacificOcean

IndianOcean

AtlanticOcean

PacificOcean

Figure 4. SOuthern BlueFin tuna od so xs o

P, id, d a Os.

Southern Bluen RangeSouthern Bluen Spawning Area


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d loto o spwg sks to mxmz th

lvl suvvl. Blu tu spw gos

wth low vblty o t-ul wt tm-

ptu to ds th sk o squtl ys

o low spwg suss d lolzd xtto

(roy d Fomt 2007). Ths low vblty

s ptully mpott o blu tus, whh

ly mssv umbs o ggs wth hgh motl-

ty t. Bus o ths, v smll vtos

th suvvl t o ggs d lv hv

lg mpts o th ovll populto umbs

(cushg 1968).

i ddto to tmptu, ddy tvty s

lso kow to hv mpott mpts o blu

tu spwg suss (G et al. 2005, To

et al. 2007b, igk, 2001). Spwg hs b

obsvd mo qutly gos wth mod-

t (24 o -27o c) s su tmptu, psum-

bly bus ths gos povd th ssyodtos o lvl suvvl wthout bg too

wm o dults (igk 2001, To et al. 2007b).

i ddto, modt ddy tvty, whh

pull d suspd lv gos sutbl

o suvvl, lso sm to b pd spwg

hbtt (G et al. 2005, igk 2001, To et

al. 2007b). rpoduto ous ov two wks

to svl moths o dvdul sh wth -

quy btw spwg vts oug vy

o to ou dys (Fly d Dvs 1998, Blok et

al. 2005, ch et al. 2006, To et al. 2007).

Atlantic bluefn tuna lie cyclei th atlt O th s wd g

th g t whh blu tu bg to spw. it

s blvd tht blu h dulthood s ly

s g 3 to 5 th Mdt, d ot utl

t g 8 th Gul o Mxo d Bhms

(rodguz-rod 1967, Dst et al. 1980,

Bgl 1982). i th Mdt, mmum

gs o spwg w stmtd by xmg

sh o th spwg goud dug th spwgsso d my udstmt th vg g o

dulthood o th t populto (rodguz-

rod 1967). Ths s bus my sh o ths

gs my ot hv tud to th spwg

gouds d tho ot smpld usg ths

mthodology. elto tggg dt, whh hs

ot obsvd sh youg th g 8 movg to

th Mdt om th noth atlt, would

suppot th hypothss tht som popoto o

th Mdt popultos do ot mtu

utl muh lt th g 5 (Blok et al. 2005).

Sz omposto o ths svl shs

th Mdt would lso suggst tht

my o ths sh bg spwg t g 8 to 9

(Hsh et al. 2008). Howv, gt lyss

shows tht th my b multpl popultos

wth th Mdt S, d t s pos-

sbl tht h populto hs dt g o

st spwg.

i th wst atlt, blu g o

mtuty s glly ogzd s bg gt

th th st atlt (Mthet al. 1995,

nmso et al. 2000). Bgl (1982) suggstd

tht w sh youg th g 8 w mtu but

dd ot stmt ull podutv shdul o

th populto s whol. Tht study xmd

smpls o sh 165 m (5 t. 5 .) d smll(youg th g 8) o th spwg gouds

d oud o to b mtu, whl sh wth

th Gul o Mxo w oud to b 205 m (6 t.

9 .) d log (m sz o 243 m [lmost 8

t.]), d ll w blvd to b mtu (Bgl

1982). Th sz dstbuto o th smpld sh

om th Bgl study wth th Gul o Mxo

mths up wll wth th dstbuto o logl

th d szs o ltolly tkd sh

tg th Gul o Mxo (nmso et al.

2000, Blok et al. 2005, Dz d Tu 2007,Glud et al. 2010). Ths, tk togth,

would suggst tht th g bov whh th

mjoty o th populto mtus (th g t

whh mo th 50 pt o th populto hs

sttd spwg) s hgh, old th 12 ys.

i ddto, w gowth t studs o wst

atlt blu hv show slow gowth ts,

mkg sh o gv sz old th ws pv-

ously ssumd (rstpo et al. 2010). Tkg ths

to out suggsts tht th lst spwg

th Gul o Mxo hpps oud g 8 to10, wth th mjoty o sh ot spwg utl

ppoxmtly g 15 (Dz 2011). i ddto

to hgh g o mtuty, wst atlt blu

tu log-lvd (stmtd t up to 32 ys,

wth mxmum szs o 320 m [10 t. 6 .] d

680 klogms [1,500 pouds]), sultg log

gtos o ths populto (Mthet al.

1995, nlso d cmpg 2008).


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Pacifc bluefn tuna lie cycleP blu tu blvd to mtu by gs

3 to 5, but ths stmts hv b md oly

by xmg sh o th spwg gouds (By-

l 1994, ch et al. 2006, Tk et al. 2006).

Tho, ths stmts do ot out o sh

old th 5 tht my ot hv hd mtuty,

ldg to pottl udstmto o th m

g o mtuty o th t populto. P

blu log-lvd d blvd to lv

up to g 26 d tt wghts o up to 450 kg

(990lbs.). Th mjoty o ths o th spwg

gouds om om sh log th 160 m (5 t.

3 .), suggstg tht g 5 should b osdd

mmum g o mtuty th th th g

t whh th mjoty o th populto bgs to

spw (colltt d nu 1983, Swd et al.

2005, itoh 2006, Shmos et al. 2009).

Southern bluefn tuna lie cycleSouth blu tu mtu t muh lt g

th do P blu (ccSBT 2010). el-

st stmts pl g o mtuty 8, whl

studs tht usd dt gg thqus hv

stmtd gs o mtuty t 11 to 15 ys (Gu

et al. 2008, ccSBT 2010). Th s som v-

d tht dvdul gowth ts d populto

pmts suh s vg g o mtuty hv

hgd spos to shg pssu. aly-

ss o tg tus d otolths dt tht shgowth ts hv sd om th 1960s to

2000 s th populto ws dud (Polhk

et al. 2004, ccSBT 2010). Ths ws ttbutd to

dsd omptto btw blu o py

sous. i ddto, th m g o south

blu o th spwg gouds dld om

ppoxmtly 19 to 21 ys old th 1990s

to 14 to 15 th st dd o th 21st tuy

(ccSBT 2010). Ths s ptully mpott

s sh om th oldst d lgst g lsss

glly hv muh gt mpt o ddgto utu gtos th do smll d youg

spwg sh (Sott et al. 1999). Fo south

blu, th mjoty o sh o th spwg

gouds w gs 15 to 25 ys wth logvty

up to g 40 (Fly et al. 2007, Gu et al. 2008,

ccSBT 2010). although south blu td

to hv smll mxmum szs th P o

atlt blu, thy h 245 m (8 t.) d

mo th 260 kg (573 lbs.) (nkmu 1990).

Bluefn Tuna Fisheries, Pastand PresentFshs o blu tu hv glly dvl-

opd th mjo pods. ely shs,

dtg bk thousds o ys, usd smll-sl

tsl ppohs suh s tps, hd-ls,

d ostl ts. Ths shs suppld sh,

smokd, o sltd sh to lol mkts. Bus

ths shs w glly lmtd to ostl

wts, ths w usully smll. Th xt

phs o th blu shy sw lg, mo

dustlzd shspus-s vssls d

bt bots, whh povdd sh o g op-

tos; d logls, whh povdd sh o th

oz sshm mkt Jp. although ths

shs stll xst, muh o th ot t

ys hs shtd. Th l stg o dvlop-

mt globl blu tu shs hs b

th xpso o pus-s fts supplyg lvsh o hg optos. rhg volvs

th ptu o youg sh to b pld o

ps, wh thy d d sd bo thy

klld. Ths sh supply th sh sshm

mkt, mly Jp but tly xpdg

oth outs. Bus th ps o blu

tu th sshm mkt muh hgh th

o d tu, th mg d globlzto

o ths mkt gtly hgd th ooms o

globl blu shs d ougd th ov-

xplotto o blu tu (issbg 2007).

Atlantic bluefn tuna fsheries

Eastern Atlantic Ocean and

Mediterranean Sea

Th st kow blu tu shs w

dvlopd th Mdt S. as ly s

4000 B.c., th s vd o blu ths

usg bh ts d hook d l (S 1980,

Fomt 2009). Ths shg mthods w

lt pld by xd tps, whh by 2000 B.c.llowd Pho d rom shg om-

muts to od ths o thousds o tos

o blu (Poh 2005). Th us o ths g

md ltvly uhgd thoughout th

Mdt S d djt atlt O

utl th dvt o mod shg mthods th

lt 1900s (Mthet al. 1995). although ths

fututd, psumbly ot wth vo-

mtl vblty, tps, d th ommuts


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tht bult up oud thm w mtd wll

to th 20th tuy (rv d Fomt 2004,

Fomt d Pows 2005).

By th 1950s, lg pus-s shs

hd dvlopd o blu tu th noth S,

pmly by nowg shs, d ths ths

soo bm th lgst shy th st

atlt d Mdt S (Myk et al.

2004) (Fgu 5). Pus-s shg s ptu-

lly tv bus ts dployd oud

t shools o sh. Up to 18,000 mt tos

o blu w ldd vy y th noth

S; howv, ths ths w ot sust-

bl, d by 1963 ths ollpsd d hv ot

ovd (Fomt d Pows, 2005, MK-

z d Mys 2007, Fomt 2009). Ovll

ths md ltvly low (lss th 15,000

mt) th st atlt d Mdt

thoughout th 1960s d to th ly 1970s(ittol commsso o th cosvto o

atlt Tus [iccaT] 2010) (Fgu 5).

i th 1980s d 90s, th mkt o blu

tu volvd om pmly lol osumpto

euop to lg xpot mkt to Jp. Th

out s pg optos, whh

llowd o btt mkt tmg d sd

ps, md th Mdt S shs

muh mo potbl (Fomt d Pows

2005, Fomt 2009). Ths lso stmultd

sgt llgl, ugultd, d upotd(iUU) shg o blu tu th Mdt-

. Th sd ths by pus-s fts

wth th Mdt pushd th totl st

atlt d Mdt ldgs om 11,000

mt 1970 to stmtd 60,000 mt 2006,

ll-tm hgh (Fgu 5). it s blvd tht

ths hv dld sgtly s 2006,

but poo potg om th mjo shs th

Mdt d ogog iUU shg mk y

stmt o ths ut (iccaT 2010).

Western Atlantic

Blu tu shs th wst atlt

O do ot dt bk ly s s thos

th st atlt. Th lst kow blu-

shs w smll-sl tp d hpoo

shs nw egld d cd th ly

20th tuy (Bglow d Shod 1953). By

th md 20th tuy, tol spot sh-

s hd dvlopd log th U.S. d cd

est costs (Fgto 1949). Th tol

blu shs th Stts o Flod/Bh-

ms w ptully otbl. Ths shs

tgtd lg blu s thy lt th Gul o

Mxo spwg goud, ddto to pusug

gt blu o th py-h summ dg

gouds o nov Sot, wh thy w t th

mxmum wghts (Fgto 1949). although

ths shs w smll tms o umbs

ught, thy otbutd to th hsto lo o

th sz, spd, d pow o blu tu. Fo

xmpl, t ws Bm th Bhms wh

est Hmgwy dsbd th p bttls

btw shm d blu tu, whh h

dld th kg o ll sh.

Th st lg-sl omml shs

o blu tu th wst atlt w th

Jps logl shy tht dvlopd o th

ost o Bzl d th U.S. pus-s shyo nw egld, both o whh dvlopd th

lt 1950s (Mthet al. 1995). Jps ths

o Bzl sd to mo th 12,000 mt

y by 1964, but by th d o th dd blu-

tu hd dsppd om ths d hv

yt to tu (Fomt 2009). cout wth

th dvlopmt o th shy o Bzl, th U.S.

pus-s shy o smll d mdum szd

blu (lss th 91 kg [200 lbs.]) dvlopd

nw egld, pkg 1962 t mo th

5,000 mt (Myk et al. 2004). Th hgh ld-gs ths two shs pushd totl wst

atlt ths los to 20,000 mt by 1964,

lvl thy hv ot ppohd s (Fomt

d Pows 2005, Poh 2005).

Th 1970s w tstol pod du-

g whh gs d shg outs hgd

(Fgu 5). Jps logls movd to th

Gul o Mxo d noth atlt, smll

pus-s shy md nw egld

d th od-d-l omml shy log

th est costs o th Utd Stts d cdbm mjo sou o ldgs (Mthet al.

2005). i ddto to hgs shg go

d g typ, t ws t ths tm tht th mkt

o blu tu shtd om dmd o d

tu to sshm xpot mkt Jp. Gtly

sd ps kpt shg pssu hgh, d

ldgs md btw 5,000 d 7,000 mt

y utl stt quots d b o tgtg

blu o th Gul o Mxo spwg gouds


11/20


th ly 1980s lmtd ths to 2,500 mt

o lss, wh thy m (Mthet al. 1995,Fomt d Pows 2005, iccaT 2010)

(Fgu 5).

Pacifc bluefn tuna fsheries

Eastern Pacifc Ocean

Whl muh hs b wtt gdg th log

hstoy btw hums d atlt blu

tu, blu tu shs th P O

hv stthd bk just s , ot uth.

i th st P, bos o lg (gtth 160 m [5 t. 3 ]) blu tu hv b

oud hologl sts o dgous om-

muts om Btsh columb, cd, d

oth Wshgto th Utd Stts. Ths

ms dt bk to t lst 3,000 B.c., d

tbl lds dsb tv shs o blu

though th md-19th tuy (cokod 1997).

Th lst spot shy o blu tu

lso b td bk to th st P. i th

lt 19th tuy, th st od-d-l ths o

lg blu tu (gt th 100 kg [220 lbs.])oud o th ost o South clos

ctl isld. Th m hsg ths sh soo

omd th st spot-shg lub th wold,

th ctl isld Tu club, outlg uls o

ply o gm shs.

i otst to ths ly pots o gul

blu tu pps th st P,

t outs wth lg blu tu hv

b spod d lss umous (Fom d

ishzuk 1990). comml shs, mly

pus ss, dvlopd th st Pby 1914 d xpdd gtly th lt 1950s

(Byl 1994). Ths shs w ousd

mly o smll sh (lss th 100 m [39 .]),

lthough lg sh w osolly tk wh

thy w vlbl (H 1983). cths

th st P, mly o South clo-

, Utd Stts d Bj clo, Mxo,

hd pk o los to 18,000 mt 1965

bo dlg th 1980s d ly 1990s

* Note: catches or southern bluefn tuna and Mediterranean Sea catches are believed to have been signifcantly underreported in recent decades.

Figure 5. rePOrteD BlueFin tuna lanDingS o o mm s s 1950.*

So B tP B t

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es a B t Ws a B t

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0

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12/20


(Byl 1994) (Fgu 5). Bus th vl-

blty o blu th st P dpds

o blu movg oss th o om th

wst, ths w hghly vbl thoughout

th 20th tuy, fututg by mo th 5,000

mt subsqut ys (H 1983) (Fgu5).

i th lt 1990s, blu ths bg to

s g th st P, hg

up to 10,000 mt 2007 (ittol S-

t commtt o Tu d Tu-lk Sps

th noth P O [iSc] 2008) (Fgu

5). ag, ths s oud ojuto

wth sht th mkt o blu tu om

podut ught o s to lv sh ptud

o pg optos Mxo to supply th

sh sshm mkt Jp (it-am

Topl Tu commsso [iaTTc] 2010). Mo

th 90 pt o th th th st P

ous o blu th sz g o 60 to 100m(24 to 40 .), sh tht ppoxmtly 1 to 3

ys o g (iaTTc 2010).

Western Pacifc Ocean

Sml to thos th st P, ths o

blu tu lkly stth bk to 6,000 ys

ostl ommuts o Jp (Muto et al. 2008).

Ths took th om o ostl hpoo d hd-

l shs, d ldgs pobbly w smll

bus shs w lmtd to ostl wts.

Mo dvd shs, usg tps, dt-tsd hd-ls dvlopd th lt 19 th tuy

Jp, russ, Ko, d Tw, Pov o

ch. although ths shs w d-

t om mod fts, t hs b stmtd

tht ldgs w 3,000 to 50,000 mt y,

wth th hghst ths oug 1935 d

th dlg sgtly th 1940s d 50s

(Muto et al. 2008).

at Wold W ii dd, Jps pus-

s d logl fts tgtg blu tu

th wst P xpdd gtly, d ldgsfututd btw 10,000 d 35,000 mt y

thoughout th ltt hl o th 20th tuy d

th st dd o th 21st (Myk et al. 2004)

(Fgu 5). Th lgst shy o blu tu

th P s th Jps pus-s shy,

whh hs ught 2,000 to 25,000 mt y s

1952 (iaTTc 2010). Ths ft tgts smll sh

(lss th 1 to 3 ys old) mly th S o

Jp d th est ch S (Myk et al. 2004).

i ddto, Jps d Tws logl-

s tgt lg sh thoughout th wst

P, ptully o th spwg gouds

(iaTTc 2010, Myk et al. 2004). Smll toll

d dt-t shs lso tgt blu tu

th wst P, lthough ldgs by ths

shs sgt ompd wth th

muh lg pus-s d logl shs.

Bus th lgst blu shs th wst-

P tgt smll sh, t s stmtd tht

up to 93 pt o totl sh ldd youg

th 3 ys old (itoh 2001).

Smll ths o P blu tu lso

odd th South P, ptully o

austl d nw Zld (Myk et al. 2004).

although th umb o sh ught ths

shs s smll, ths glly omposd

o vy lg, mtu sh (itoh 2006).

Southern bluefn tuna fsheriesSouth blu tu hv ot b shd s

log s th atlt o P blu, d

th s o ompbl od o ly tsl

shg hstoy. istd, th st shs o

south blu dvlopd th 1950s (Hys

1997, Shp 2001), wh Jps logl-

s bg tgtg dult south blu tu

o th spwg gouds btw idos

d austl; ths xpdd to los to

60,000 mt by 1961 (Myk et al. 2004) (Fgu5). Ths ths gdully dld, d th

Jps ft bg to xpd shg op-

tos to th south o austl, nw Zld, d

South a th 1970s d 80s (Shp 2001).

cths otud to dl thoughout th

1980s, vtully lmtd by stt quots put

pl th 1990s to stop th dl o th

populto (S 2001) (Fgu 5).

austl bt bot, toll, d pus s

shs lso dvlopd th go south o

austl th 1950s. Ths tgtd smllblu th dd th Jps logl shy,

wth most o th podut gog to g op-

tos austl. cths ths shs

sd, vtully hg mo th 20,000

mt 1982 (ccSBT 2010) (Fgu 5). Sml to

th Jps logl shy, ths th aus-

tl shy dld sgtly th 1990s

s quot msus m to pl. at th sm

tm, th mkt o blu wt om supplyg


13/20


s to povdg sh o tu hs

South austl (ccSBT 2010).

Totl ths o south blu md

ly low (ppoxmtly 14,000 mt y)

thoughout th 1990s s th m outs

tgtg blu tuaustl, Jp, d

nw Zldw lmtd by gmt o

quots (Hys 1997, ccSBT 2010) (Fgu 5).

Yt, ths by oth tos bg to s

th lt 1990s, pushg totl ldgs to mo

th 20,000 mt 1999 bo dlg g

th ly pt o th 21st tuy (Myk et

al. 2004). Howv, th s vd to suggst

tht ths ov th pst two dds my hv

b substtlly udpotd (ccSBT 2010).

compg th umbs potd by Jps

logl shg vssls to th umb o sh

dlvd to sh mkts, t s stmtd tht tu

ths w doubl wht ws potd to m-gmt gs (Polhk d Dvs 2007).

Management and Status oBluefn Tuna PopulationsBlu tu mgmt s omplx. as wth

most plg, o op o, sh, thy m-

gd ud th usps o gol shs

mgmt ogztos (rFMOs). rFMOs

povd th mwok by whh mmb Stts

om to gmt o osvto d m-

gmt msus, d th mplmttoo thos msus ous t th outy lvl.

Th rFMOs lso mhsm to moto

ompl by mmb Stts d to ollt

shy dt. Fou rFMOs sposbl o

th mgmt o blu tu shs; ths

md up o outs tht sh o blu

d oth plg sps gv o

d lud both ostl Stts d dstt

wt shg outs. Th ogzto o h

rFMO ds, but dsos usully md by

ossus. cosqutly, tg mjo hgsto shs mgmt s gdul d ot

dult poss.

i ddto to ds how th rFMOs

stutud, ds lso xst how

th s o populto ssssmts s o-

dutd d usd. Som rFMOs, suh s iaTTc,

mt pmt st o ststs tht

udtks muh o th sh d oduts

th populto ssssmts. Oths, suh s

iccaT, ly o mmb govmts to supply

sh omto d ststs to odut

populto ssssmts, d oly mt ull

tm dmsttv d thl st. Th com-

msso o th cosvto o South Blu

Tu (ccSBT) hs dpdt h o ts

st ommtt d pl o dpdt

ststs ddto to ststs om mmb

govmts. Ultmtly, dsos o tol

d ovll quots, sz lmts, d oth mg-

mt dsos ot md by th ststs,

but by psttvs o th mmb Stts who

mk up th rFMOs commsso. Glly,

th commsso sks th st ommtts

o sp dv, whh t ollow o dd

ot to.

as wth ll sh, th s glly

g o utty oud y bologl

pmt usd th populto ssssmt po-ss, d ths utty hv lg mpts

o th outom o th ssssmts. Fo xmpl,

th g o gs o mtuty my b stmtd

t 5 to 10 ys, dpdg o how th umb

ws lultd. Usg stmt o 5 wll sult

populto ssssmts tht show hgh

populto gowth ts th wll thos usg

stmt o 10. assumg g t st podu

to o 5 wll, ud most modls, povd mo

optmst sult d wll suggst tht hgh

th ts ould b llowd.Utty s v gt o bolog-

l pmts tht dult to msu but

mpt th sults o th populto ssssmt.

Fo xmpl, tul motltyo th umb

o sh tht d gv y sptv o

shgs xtmly hllgg to stmt, yt

th ssumptos hv lg mpt o modl

outputs, suh s th totl umb d wght

o sh stmtd to b th populto. as

sult, ststs wll ot pst mgs

wth g o pobblts pstg thsutty, s opposd to sgl totl llowbl

th. although govmts hv ll ommt-

td to th putoy ppl, whth o ot

mmb govmts g to st putoy

quots (t th low d o th g o stmts)

usully dpds mo o ooms d polts

th o th stgth o th udlyg s.

i ddto to hllgs suoudg th

s populto ssssmts d dg


14/20


ossus o ovll d tol th quots,

ompl wth d omt o ths quots

s lso hllgg. Ultmtly, mmb gov-

mts hv th sposblty to o gd-

upo uls o th ow fts. Wth wd g

poltl wll d pty o motog d

omt mog rFMO mmbs, ompl

wth uls vs gtly. i ddto, oom

tvs my tmpt Stts to tu bld y

to ovshg v thy do hv th ms to

otol t.

Atlantic bluefn tuna managementDlg ths atlt blu tu pp-

ttd omto o iccaT 1969 (iccaT 2006).

Th utly 48 mmb govmts

s wll s umb o o-ottg pts

(iccaT 2010). Du to dspt ths th

st d wst noth atlt, s wll sds l hstoy tts, iccaT ssumd

tht st atlt d wst atlt blu

blogd to dst popultos (ntol

rsh coul [nrc] 1994). Th boudy

btw popultos usd by iccaT s th

ctl atlt t ppoxmtly 45 dgs

wst logtud, d blu hv hstolly b

mgd ssumg low lvl o ovlp btw

popultosppoxmtly 2 to 4 pt

y (nrc 1994). although t gt stud-

s hv omd tht th st d wstatlt popultos podutvly soltd,

t s ow udstood tht th s gt lvl

o ovlp btw th two popultos, wth up

to 50 pt o th sh som gos o th

wst atlt hvg ogtd th st

atlt (Blok et al. 2005, rooket al. 2008,

Bousty et al. 2008). Ths t gtly mpts

th mgmt o wst atlt blu, s

th populto sz th st s stmtd to

b od o mgtud lg th tht th

wst, mg tht v smll hgs thumb o sh mgtg st to wst hv

lg ds th bud o wst

blu tu (iccaT 2010).

aoth o bout mxg d th

ssssmt poss s tht th st atlt

d Mdt S utly ssssd

s o populto, lthough gt dt sug-

gst tht two o mo dstt popultos spw

wth th Mdt (clsso et al. 2004,

Bousty et al. 2008, ro et al. 2010).

assssg multpl popultos th Mdt-

s o populto ss th possblty o

obsug dls mog smll popultos

ths om th lg popultos m hgh.

Sgt utts lso xst th

dt usd o th st atlt ssssmt

(advd Tu rhg Thologs [aTrT]

2010, iccaT 2008). Udpotg o both totl

ths d ths o sh blow th mmum

sz hs md t dult o ststs to pom

ut populto ssssmts d poj-

tos. Th gtst poblms th mgmt

o blu tu th st atlt, howv,

hv b ompl wth mgmt m-

sus. Du to ombto o mgs sttg

quots hgh th st gud d lk

o ompl wth thos quots, ths hv

xdd stlly ommdd lvls byup to 400 pt som ys (Huy et al. 2008).

i th wst atlt, hgs ssumptos

gdg th ltoshp btw umb o

dult d juvl sh hv usd iccaT to ol-

low mgmt sttgy tht ms to kp th

populto sz stbl th th tyg to gow

bk to lvls tht would suppot mo podu-

tv shs (S d Klg 2008).

Th st atlt populto s ssssd

t ppoxmtly 35 pt o dult bomss

(th wght o ll dult sh th populto)tht would llow o mxmum shy ylds, d

shg ts hv b mo th tw s hgh

s os tht would st th uth dl o

th populto (iccaT 2010) (Fgu 6). adult

bomss, whh shs mgs ot to

s spwg stok bomss (SSB), s ommo

wy to msu ltv hlth o blu tu

popultos ov tm. i th wst atlt,

SSB ws stmtd to hv dld 81 pt

om 1970 d hs md t thos low lvls

o mo th th dds wth lttl d-to o ss th populto (iccaT 2010)

(Fgu 6). Howv, bus th lgst ths

th wst atlt took pl bo 1970,

t s lkly tht dls om ushd popul-

to lvls muh gt th th 81 p-

t stmtd by iccaT (Mthet al. 1995,

Poh 2005).

Gv th mjo poblms th mg-

mt o atlt blu tu, wth ltg


15/20


dls populto sz th st d lk o

buldg ov 30 ys th wst, poposl

ws submttd to lud atlt blu tu

th appds o th covto o it-

tol Td edgd Sps (ciTeS),

whh would hv pohbtd ttol td

o omml puposs. as th mjoty o blu-

tu, d lmost ll o th hgh-pd tu

boud o globl sshm mkts, s tdd t-

tolly, suh lstg would hv sgtlydud th mkt os dvg ovxplot-

to. Th tht o ths lstg sd th ps-

su to bg llgl shg d lk o potg

ud otol. Whth th msus doptd

o ths gt omt o th ts hs

mpt o th hlth o blu tu popultos

th utu ms to b s.

a t suss stoy dos xst, howv,

wh osdg th buldg possblts o

ttolly mgd, lg plg sps:

th dplto d subsqut ovy o swod-sh th noth atlt. Du to ovshg,

lg ths o juvls d shg o spw-

g gouds, noth atlt swodsh populto

szs dsd osdbly btw 1980 d

2000 (iccaT 2010). Lowg ovll quots,

sg lgl mmum szs d tg

losd s to pott juvls d spwg

dults hv llowd swodsh popultos to

ov om ths l dls to th pot

wh thy ow osdd ully ovd.

By ollowg ths mwok o blu tu sp-

s, t ms possbl tht ths popultos

ould ov.

Pacifc bluefn tuna managementUtl tly, P blu tu ll though

th ks o mgmt th P rFMOs.

as tmpt tu, P blu do ot ll

ud th puvw o th two m rFMOs tht sposbl o oth mjo tu sps wth

sml gsiaTTc o th Wst d c-

tl P Fshs commsso (WcPFc). as

suh, oml mgmtludg ull popu-

lto ssssmts d stt th motog

d quot llotoshs ot b pl o

P blu s log s t hs o oth blu

sps. P blu tu populto ssss-

mts odutd by th iSc, d subsqut

mgmt ommdtos hdld by

iaTTc d WcPFc, o shs ud thsptv puvws.

P blu tu popultos w lst

ssssd to b btw 3 d 26 pt o

ushd bomss, dtg tht th P

blu ws ovshd (ihokw et al. 2010)

(Fgu 6). Howv, ths stmts ftd

hgh lvl o utty bus lttl ws

kow gdg o-shg sous o motl-

ty, whh hv lg ts o th outom

Figure 6. SPaWning StOck BiOMaSS (SSB), o d bomss, s fd ov m.

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Southern Bluefin TunaPacific Bluefin TunaEastern At lantic Bluefin Tuna Western Atlantic Bluefin Tuna


16/20


o th populto ssssmt modl sults (iSc

2008, iaTTc 2010). Muh s o oth blu

sps, th sgt ths tht oud

bo pop motog bg mks stmtg

vg populto sz xtmly dult (Myk

et al. 2004, Muto et al. 2008). Howv, v

ompd wth dult bomss stmts om th

pod ov whh good dt vlbl, 2007

bud ws stmtd to b blow 50 pt

o th pk odd 1960 (ihokw et al.

2010) (Fgu 6). O mjo sou o o

s th xtmly hgh ths o juvl sh

tht hv ot yt spwd; up to 93 pt o

sh ught th wst P, d ov 90

pt o th sh ught th st P

blow th lst szs d gs o mtuty

(itoh 2001, iaTTc 2010). rt ts o shg

motlty thought to hv b hgh th

sustbl lvls (iSc 2008).

Southern bluefn tuna managementDlg ths o south blu tu

th 1970s usd austl, nw Zld, d

Jp, th mjo shg Stts, to stblsh

quot systm 1982 (edwds 2001). i 1994,

ccSBT ws omlzd s stok sz otud to

dl d oth shg Stts bg to tgt

south blu (S 2001). although stt

quots w put to pl, ovhvstg by

mmb govmts d sd shg ps-su by o-mmbs lmtd y osvto

gs, d populto sz otud to dl

(ccSBT 2010).

i subsqut dds, South Ko d

idos jod th commsso d T-

w, Pov o ch, bm ptpt.

addtol outs w ddd s ooptg

ommbs. cooptg ommbs dh to

th mgmt msus but ot vot wth

th commsso (ccSBT 2010). Mgmt

o south blu tu hs b ptullyottous, ulmtg austl d nw

Zld bgg Jp bo tbul ud

th U.n. covto o th Lw o th S, llg-

g shg bov gd-upo quots (romo

2001). Subsqut udpotg o ths

by mmb govmts hs sultd uth

dls th dult bomss t dds.

Th ltst populto ssssmt showd tht

th south blu tu spwg stok hs

md t xtmly low lvls thoughout th

pst svl dds d s utly stmtd

t 3 to 7 pt o th lvl bo xplotto

bg (ccSBT 2010) (Fgu 6). rt m-

gmt tos d uth quot dutos,

ptully o mmb govmts tht hd

ovshd th pst, pdtd to llow

modst buldg o ths populto ov tm

(ccSBT 2010). Howv, th l hstoy tts o

south blu, splly log l sp d

lt podutv mtuty, m tht y buld

g o th sps s lkly to b slow.

ConclusionBlu tus my hllgs th ys

hd, lthough som postv mgmt

tos hv b tk. although th wolds

blu tu popultos m sgtly

dud om hstol lvls, ut mg-mt dsos hv mpovd wh ompd

wth pvous dds. Th ky s th tv

mplmtto d omt o thos d-

sos. ev o south blu d wst

atlt blu, hstolly som o th most

dpltd tus, populto dls blvd

to hv b std. i th s o wst

atlt blu, slght s populto

lvls hs b s t ys (iccaT

2010, ccSBT 2010). Fo st atlt blu

tu, th populto o whh ugultdshg hs oud most tly, mgs

ow bgg to ollow st om-

mdtos sttg quots. i 2010, th quot

o st atlt blu tu ws wth th

g o st dv. i ddto, o-

mt msus md t otollg llgl d

ugultd shg bg doptd th

st atlt d Mdt S. O

qusto ms: whth thos msus wll b

ompld wth d od, wth osqus

o o-ompl.Th ms utty suoudg both

th shy th dt s wll s th bs l

hstoy dt usd to omplt th ssssmts, so

y pvd mpovmt th sttus o th

stoks my pov to b ftg s dt qulty s

mpovd. Futh s o mpovmt th

mgmt o blu tus xst otollg

shg o juvl sh, ptully th P

d Mdt S, lmtg ths


17/20


o blu tu o th spwg gouds ll

popultos, d doptg d mplmtg

stog ompl msus.

i mgs bl to otu ths pos-

tv tds d vs gtv os, d ully

mplmt th putoy ppl o blu

tus, t ms possbl tht popultos

s to hlthy lvls g, s show by th

noth atlt swodsh xmpl. Fo blu

tus, whh hv v slow populto gowth

ts th swodsh, ths poss wll lkly ou

mo gdully, v ud th bst o um-

sts. Fo ths so, otud vgl s

dd to mk su tht y gs blu

popultos ot squdd th ds o

shot-tm pot.

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About the AuthorD. ad Bousty mjod eology d evolutoy Bology s udgdut t coll

Uvsty. a llog shm d o lov, h lwys gud h would d up wokg th ld

o m bology. at gdutg, ad hld umb o jobs hs tv clo, om wokg

o dy m to studyg dmogphs o spottd owls th S Bdo Mouts to svg s

obsv o plg dtt bots. it ws ths lst job tht todud ad to th vomt dmls o th op o, th tops h would go o to study. ad ompltd hs Ph.D. t Stod

Uvsty wh h usd lto tggg thologs d gts to study mgto ptts, hb-

tt utlzto, d populto stutu o blu tus d shks th P d atlt Os.

at gdutg, h movd to Duk Uvsty s postdotol sh, wh h hs otud to

study plg sh d shs, ptully wys to du byth d mpov shg y.

Suggested citation: Bousty, a. 2011.Bluefn Tuna: The State o the Science. O S

Dvso, Pw evomt Goup, Wshgto, Dc.

Credits: cov llustto by Stv rvst, sps llusttos by Phl Gb, d mps by

Gio ntwok.

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Bluefin Tunas: The State of the Science