Collapse of Bluefin Tuna in the Western Atlantic

Thanks to my friend Carl Safina for allowing us to reproduce this fine report.

The Atlantic bluefin tuna (Thunnus

thynnus) is one of theworld's largest

vertebrates, weighing up to 900 kg

(Fromentin & Powers 2005). It is an

extraordinary fish. It regularly makes

transoceanic migrations and uses its

elevated body temperatures to hunt

actively in frigid high latitudes (Block

et al. 2001). It also fetches astronomical

prices in the sushi market

(Associated Press 2001). This

last fact makes the bluefin a tragic

case because short-term economics

and politics have conspired against

the bluefin's survival. The Atlantic

bluefin tuna's western breeding population

is unprecedentedly low and

declining. Commercial catches off

the United States have fallen to 10%

of the quota, which suggests a population

collapse. Recent research findings

are not being incorporated into

management decisions. Although the

bluefin is a special fish, its problems

are just one instructive example of

how management can go off track if

the scientific part of the process is

corrupted by short-term economics

and political lobbying.

Two recognized populations inhabit

the Atlantic andMediterranean.

Mediterranean-spawning bluefin mature

by age 5 (Corriero et al. 2005),

whereas bluefin that spawn in the

Gulf of Mexico mature by about age

12 (Diaz & Turner 2006). Both populations

migrate extensively, mixing

throughout the North Atlantic, but

Paper submitted July 12, 2007; revised

manuscript accepted October 1, 2007. they do not interbreed (Lutcavage et

al. 1999; Nemerson et al. 2000; Block

et al. 2005; Carlsson et al. 2007).

Everywhere they swim, bluefin

tuna are fished heavily. The European

Commission (EC) recently moved to

reduce catch quotas for the eastern

Atlantic and Mediterranean, but the

quotas remain nearly double what

EC scientists recommend.We considered

the western-Atlantic breeding

population, which The World Conservation

Union lists as critically endangered.

Western Atlantic catches peaked

in 1964 at 18,679 t, declining to

1,523 t in 2005 (Fig. 1). From 1962

to 1967, Japanese boats annually

caught 5,000-12,000 t of mature

bluefin off Brazil. South Atlantic bluefin

now appear extirpated (Porch

2005). After Brazil's bluefin disappeared

and North Sea bluefin populations

crashed and did not recover

(MacKenzie & Myers 2007), concern

over the Atlantic bluefin tuna's future

prompted several nations to form

the International Commission for the

Conservation of Atlantic Tunas in

1966. The commission now has 43

members, but has never met its charter

mandate to maintain fish populations

at levels allowing "maximum

sustainable catches."

In 1981 the commission drew a

"management line" down the Atlantic's

center. Declines in the west

were already of sufficient concern

that the commission's scientific committee

that year recommended western

catches "be reduced to as near

zero as feasible" (ICCAT 1982). Consequently,

in 1982, commission managers

recommended an initial catch limit of 1160 t. But bowing to pressure,

the next year they raised it

to 2660 t (Safina 1993; Porch 2005;

Fig. 2). Continued decline followed.

By 1991 commission scientists estimated

spawning biomass at 22%

of the 1975 reference level (ICCAT

2006b).

In 1991 the commission faced a

proposed listing of the west Atlantic

bluefin by the Convention on International

Trade in Endangered Species

of Wild Fauna and Flora that would

have suspended international trade,

so they agreed to phase in a 50%

quota cut over several years (Safina

1993). In 1994 the commission reduced

the quota by 17%. When a

U.S. National Research Council review

recommended more research,

the commission abandoned quota

cutting, increasing the quota slightly

in 1995 and again in 1997. Population

decline resumed.

Reinterpreting Data to Raise

Fishing Quotas

In 1998 the commission's scientific

committee determined the annual

west-Atlantic catch of 2500 t could

not be sustained, 2000 t was likely

sustainable, and a quota near zero

was necessary to restore the population

to 1970s levels within 20 years

(ICCAT 1999).

A consultant hired by U.S. tuna exporters

and placed on the commission's

scientific committee suggested

the committee reassess the population

with a new model that omitted

1970s spawner-reproduction data.

The 1970s data showed that large breeding populations spawn occasional

large cohorts of juveniles, a

trend that has been widely observed

in other fisheries (Myers & Barrowman

1996). The new model, which

assumed the annual number of juvenile

fish entering the fishery could

not increase beyond the 1981-1994

average, implied that fewer adults

were needed to produce a lower estimated

potential yield, and this was

used to establish a lower recovery

goal. Supporters justified omitting

1970s spawner information by asserting

that the reproductive potential

of western bluefin tuna had changed

since the 1970s due to less favorable

environmental conditions; thus,

the 1970s spawner-reproduction relationship

was deemed no longer relevant (Porch 2005). The implication

was that lower catches of recent

years were equivalent to a new,

lower potential yield, and it was concluded

that no drastic management

changes would be needed.

No data indicated that the ocean's

bluefin carrying capacity had changed.

Populations of key bluefin prey

had recovered to high levels (NEFSC

2006; TRAC 2006), whereas bluefin

populations had declined. Bluefin

spawning success is better correlated

to population abundance than

any studied variable (ICCAT 2001a;

Brown et al. 2002; Ravier & Fromentin

2004). Nonetheless, and

despite unprecedented population

lows, in 1998 the commission chose

the new spawner-reproduction model and increased the catch quota to

2500 t (ICCAT 1999). Actual catches

in the western Atlantic were higher:

3200 t in 2002, well over the quota

(ICCAT 2004). In 2003 they raised it

again, to 2700 t.

In sum, in the 1980s through

1990s the commissioners implemented

much larger catch quotas than

the scientific committee recommended.

When the population continued

declining, they blamed environmental

change and implemented several

quota increases.

Since 2002 actual catches have

decreased annually. The allowed

western-area quota is 2700 t, and catches

from 2003 through 2005 were

2357 t, 2000 t, and 1523 t, respectively.

The U.S. commercial catch was only 27% of its quota in 2005

and around 10% in 2006 (McHale

2006, 2007b). As of September 2007

(the time of this writing), commercial

fishers caught only 63% of what

they caught by the same date in

2006 (McHale 2007a). Effort remains

strong; reduced catches result from

unavailability of fish. These trends

suggest U.S. bluefin may approach

widespread commercial unavailability

as early as 2008.

Continued Fishing Mortality of

the West Atlantic Breeders

The commission first highlighted the

desirability of ending fishing for bluefin

tuna in the Gulf of Mexico during

their spawning season (January-

June) in 1981 (ICCAT 1982). Not until

1998 did the U.S. National Oceanic

and Atmospheric Administration

Fisheries Service seek to specifically

limit the targeting of Gulf of Mexico

bluefin spawning aggregations

by limiting the take of bluefin to 1

fish/trip (50 C.F.R. 285.31 [a][30]).

In addition, boats targeting yellowfin

tuna (T. albacares) and swordfish

(Xiphias gladius) are still allowed

to fish in the spawning

areas of Gulf bluefin. New data indicate

that high water temperatures

and low oxygen levels kill the majority

of bluefin hooked on longlines

whether carcasses are retained or discarded

(Block et al. 2005).

Preventing Extinction of West

Atlantic Bluefin Tuna

Recent satellite-tagging studies and

genetic tests unequivocally show

that discrete western and eastern

bluefin populations mix during migrations

(e.g. Lutcavage et al. 1999;

Nemerson et al. 2000; Block et al.

2005; Carlsson et al. 2007). Migration

patterns also vary depending

on the age and size of tuna and

fluctuations in oceanographic conditions (Sibert et al. 2006). Many fish

counted against east or west catch

quotas originate on the other side of

themanagement line. Accounting for

mixing is especially critical for the

smaller western population (Magnuson

et al. 2001; ICCAT 2006c). Because

the population originating east

of the management line is substantially

larger, the quota is significantly

higher on that side of the line (29,000

t for the eastern Atlantic and Mediterranean)

than west of it. Furthermore,

fishing in the east is ineffectively

controlled, with rampant illegal fishing,

overcapacity, and catches often

significantly over the quota (Fromentin

& Powers 2005; Fromentin &

Ravier 2005; Fonteneau 2007). Eastern

catches of bluefin that originate

west of the management line could

be significant.

Overfishing and poor management

have caused collapse of the western

Atlantic bluefin tuna. Failing catches

indicate a fishery running out of time.

Based on the numbers and trends, we

believe the western Atlantic bluefin

tuna is now in danger of extinction.

Continued decline appears inevitable

unless catches are reduced to

near zero. We call for a 5-year moratorium

on possession of bluefin

tuna throughout the western Atlantic

and the closure of Gulf of Mexico

spawning areas to all gear capable

of catching bluefin tuna during

bluefin spawning season. Eastern

catches should be stopped until quotas

and management-area boundaries

adequately take into account the mixing

of western fish with eastern fish

and eastern regulations and enforcement

are improved. Eliminating all

fishing mortality may help western

bluefin recover from collapse.

Lessons Learned

The impending extinction of a key

population of a large, economically

valuable vertebrate is a tragedy in itself,

but the case of the western Atlantic

bluefin is only one of many instructional case studies in management

failure that highlights the need

for reform.When the advice of scientists

is not heeded, problems usually

worsen, sometimes catastrophically.

Fisheries managers are notorious for

ignoring scientific advice, and this

has caused problems for many fish

species in, for instance, the North Sea

(Rosenberg 2003). The reasons scientific

advice is ignored include industry

lobbying, inability of nations (or

other political divisions) to agree on

common goals for shared resources,

and interference by politicians, such

as congressional members who act

on behalf of their constituents but

in fact work against their constituent

communities' long-term interests.

Because so many people have interfered

with the scientific process in

order to keep catches high, the irony

is that the western Atlantic bluefin

population is crashing and thosewho

sought high catches are nowwitnessing

catches that are under 10% of the

quota, with the resulting loss of economic

activity. Sustainable catches

from a recovered population could

be much higher than current landings

(ICCAT 2006a). The wider problem

is that recovery may not be possible;

collapsed populations often do

not recover if relief comes too late

(Hutchings & Reynolds 2004).We do

not know whether it is already too

late for the western bluefin. It is likely

not too late for the Mediterranean

population. All of this points toward

the wisdom of temporarily ceasing

all fishing of Atlantic bluefin tuna, revamping

fisheries management commissions

such that scientific advice

is independent and insulated from

lobbying, and mandating managers

to limit fisheries catches to levels

recommended by those independent

scientists.

--Carl Safina%C3%A2%CB%86-%C3%A2%E2%82%AC%C2%A0%C3%A2%E2%82%AC%C2%A1 and Dane H. Klinger%C3%A2%CB%86-

%C3%A2%CB%86-Blue Ocean Institute, P.O. Box 250, East Norwich,

NY 11732, U.S.A.

%C3%A2%E2%82%AC%C2%A0Marine Science Research Center, Stony Brook

University, Stony Brook, NY 11794, U.S.A. Conservation Biology

Volume 22, No. 2, 2008