TUNA TALES
TUNA I
The World’s Tuna Fisheries
TUNA II
A Fishery Management Case Study:
Yellowfin Tuna and Dolphins
in the Eastern Tropical Pacific
TUNA III
The Mighty Bluefin
Table 7.1. Principal species of tuna involved in commercial fishing
Common name
Scientific name
Albacore
Thunnus alalunga
Bigeye
Thunnus obesus
Skipjack
Katsuwonus pelamis
Yellowfin
Thunnus aobacares
Atlantic bluefin
Thunnus thynnus
Pacific bluefin
Thunnus orientalis
Southern bluefin
Thunnus maccoyii
General Comments About Tuna
Tuna are neither warm blooded nor cold blooded. Their circulatory system
allows them to maintain their body temperature higher than their
surroundings, but they cannot maintain a constant body temperature.
The principal factors limiting the distribution of tuna are temperature and
oxygen concentration.
Because of their high metabolic rates, tuna are voracious predators. Daily
food consumption can be as high as 25-30% of their body weight.
Tuna are known to undertake very long migrations. Migrations across
entire ocean basins are not unusual. To some extent tuna may use ocean
currents to guide them on these migrations, but they also appear to have a
geomagnetic sense.
Skipjack, yellowfin, and bigeye tuna are generally considered to be tropical
tunas.
Albacore and bluefin tuna are found in more temperate latitudes
Some things to think about
Tuna enjoy:
The eastern sides of ocean basins have:
Warm Water
Shallow Thermocline
Lots of Oxygen
Shallow Oxygen Zone
Lots of Food
Nutrient-Rich Upwelling Zones
Some things to think about
Tuna enjoy:
The eastern sides of ocean basins have:
Warm Water
Shallow Thermocline
Lots of Oxygen
Shallow Oxygen Zone
Lots of Food
Nutrient-Rich Upwelling Zones
Along the west coasts of continents tuna can be found:
In Higher Concentrations
In Shallower Water
Closer to Shore
For Easier Fishing
Table 7.2. Pertinent information on commercially important tuna species
Species
Length
(cm)
Weight
(kg)
Age of sexual maturity
(years)
Lifespan
(years)
Albacore
60-90
10-20
5
10
Bigeye
80-180
15-20
4
10
Skipjack
30-80
8-10
2
12
Yellowfin
40-180
5-20
3
10
Atlantic
bluefin
45-450
135-680
4-8
15-30
Pacific bluefin
150-300
300-555
6
30
200
200
8-12
40
Southern
bluefin
Table 7.2. Pertinent information on commercially important tuna species
Species
Length
(cm)
Weight
(kg)
Age of sexual maturity
(years)
Lifespan
(years)
Albacore
60-90
10-20
5
10
Bigeye
80-180
15-20
4
10
Skipjack
30-80
8-10
2
12
Yellowfin
40-180
5-20
3
10
Atlantic
bluefin
45-450
135-680
4-8
15-30
Pacific bluefin
150-300
300-555
6
30
200
200
8-12
40
Southern
bluefin
Table 7.2. Pertinent information on commercially important tuna species
Species
Length
(cm)
Weight
(kg)
Age of sexual maturity
(years)
Lifespan
(years)
Albacore
60-90
10-20
5
10
Bigeye
80-180
15-20
4
10
Skipjack
30-80
8-10
2
12
Yellowfin
40-180
5-20
3
10
Atlantic
bluefin
45-450
135-680
4-8
15-30
Pacific bluefin
150-300
300-555
6
30
200
200
8-12
40
Southern
bluefin
Table 7.2. Pertinent information on commercially important tuna species
Species
Length
(cm)
Weight
(kg)
Age of sexual maturity
(years)
Lifespan
(years)
Albacore
60-90
10-20
5
10
Bigeye
80-180
15-20
4
10
Skipjack
30-80
8-10
2
12
Yellowfin
40-180
5-20
3
10
Atlantic
bluefin
45-450
135-680
4-8
15-30
Pacific bluefin
150-300
300-555
6
30
200
200
8-12
40
Southern
bluefin
Commercial catches of skipjack, yellowfin, bigeye, and albacore tuna
Skipjack tuna
Skipjack information
Virtually the entire catch occurs in the Pacific (70%) and Indian (24%)
oceans. The western Pacific accounts for 50% of the catch.
Skipjack are the smallest of the commercially important tunas and
have the largest surface-to-volume ratio. This makes
thermoregulation more difficult for skipjack than the other tuna
species.
Temperature range is 20-30oC.
Skipjack are also unique among the tunas in that the adults have no
swim bladder. Hence they must expend more energy in routine
swimming.
Skipjack information
Skipjack have a definite tendency to school, and most skipjack are
caught with purse seines. FADs have been a major impetus to the
skipjack fishery in the western Pacific.
Diet includes clupeids, crustaceans, and mollusks, but may also
include other skipjack. Peaks in foraging occur around dawn and
dusk. Predators on skipjack tuna include sharks, billfish, wahoo,
yellowfin tuna, and, in the case of small skipjack, even seabirds.
Spawning occurs throughout the year in tropical latitudes but is
confined to the summer months at higher latitudes.
Major market for skipjack tuna is canned tuna – “light-meat” tuna.
Skipjack information
Skipjack have a definite tendency to school, and most skipjack are
caught with purse seines. FADs have been a major impetus to the
skipjack fishery in the western Pacific.
Skipjack information
Skipjack have a definite tendency to school, and most skipjack are
caught with purse seines. FADs have been a major impetus to the
skipjack fishery in the western Pacific.
http://opinionator.blogs.nytimes.com/2011/09/20/time-to-boycott-tuna-again/?scp=2&sq=tuna&st=cse
FADs with location and biomass sensors
Purse Seines targeting Skipjack Tuna
Estimates of up to 20% of haul as bycatch
Much of that bycatch is immature Yellowfin and Bigeye
Fishing is done in unregulated “pockets” just outside
the EEZs of Pacific Island nations
Skipjack information
Skipjack have a definite tendency to school, and most skipjack are
caught with purse seines. FADs have been a major impetus to the
skipjack fishery in the western Pacific.
FAO Skipjack Tuna Catch Data
Table 7.3. Principal nations contributing to the catch of skipjack tuna in 2002.
Country
Principal fishing area(s)
% of catch
Japan
Northwest and west central Pacific
13.6
Indonesia
West central Pacific and eastern Indian
11.7
Taiwan
West central Pacific
11.5
South Korea
West central Pacific
8.6
Spain
Western Indian and east central Atlantic
6.9
Maldives
Western Indian
5.7
Philippines
West central Pacific
5.4
United States
West central Pacific
4.4
Yellowfin tuna
Yellowfin information
Geographical distribution, temperature range, and spawning behavior very
similar to skipjack.
Tend to associate with dolphins more than any other species. Yellowfin
have a keen sense of smell: dolphins have none. However, dolphins can
track prey using ultrasonic echolocation.
Pacific (67%) and Indian Ocean (22%) account for most of the catch.
Much of the fishing is done with purse seines. Canned tuna (light tuna) is
again the primary market.
Table 7.4. Principal nations contributing to the catch of yellowfin tuna in 2002.
Country
Principal fishing area(s)
% of catch
Mexico
East central Pacific
11.1
Indonesia
West central Pacific and eastern Indian Ocean
10.6
Venezuela
East central Pacific and southeastern Pacific
9.6
Philippines
West central Pacific
7.5
Japan
West central and northwest Pacific, western Indian
Ocean
7.4
Taiwan
West central Pacific and western Indian Ocean
7.2
Spain
Western Indian Ocean and east central Atlantic
6.7
France
Western Indian Ocean and east central Atlantic
5.1
Bigeye tuna
Bigeye information
Similar in appearance to yellowfin, but swim at greater depths and have a
higher fat content.
Catch distributed as follows: Pacific (50%), Indian (30%), Atlantic (20%).
Small bigeye are caught as bycatch of purse seining for skipjack and
yellowfin. The larger and more valuable bigeye are taken with long lines.
The meat of bigeye tuna turns light grey and sometimes darkish after
cooking or grilling, a characteristic that makes it less suited for canning
than skipjack, yellowfin, or albacore tuna. By far the most popular market
forms for bigeye tuna are fresh fillets (sashimi) and fresh whole fish. The
principal market is Japan, where bigeye sashimi is in high demand.
The principal fishing nations are Japan and Taiwan.
Not a great deal is known about the ecology of bigeye tuna, and scientists do
not agree on whether the stocks are being fully exploited. The bycatch of
bigeye associated with the skipjack and yellowfin fisheries is a concern, since
the fish in question are not sexually mature.
Table 7.5. Principal nations contributing to the catch of bigeye tuna in 2002.
Country
Principal fishing area(s)
% of catch
Taiwan
Indian Ocean, west central Pacific, southeastern Atlantic
24.2
Japan
Indian Ocean, central and southeastern Pacific
23.7
South Korea
East central Pacific
7.4
Spain
Western Indian Ocean, east central Atlantic
7.0
Ecuador
Southeastern Pacific
4.9
Indonesia
Eastern Indian Ocean
4.9
China
East central Pacific
4.3
USA
East central Pacific
2.9
FAO Bigeye Tuna Catch Data
Table 7.2. Pertinent information on commercially important tuna species
Species
Length
(cm)
Weight
(kg)
Age of sexual maturity
(years)
Lifespan
(years)
Albacore
60-90
10-20
5
10
Bigeye
80-180
15-20
4
10
Skipjack
30-80
8-10
2
12
Yellowfin
40-180
5-20
3
10
Atlantic
bluefin
45-450
135-680
4-8
15-30
Pacific bluefin
150-300
300-555
6
30
200
200
8-12
40
Southern
bluefin
Albacore
tuna
Albacore information
Albacore is a temperate water fish, and stocks in the northern and southern
hemisphere are disjoint. In the northeastern Pacific, for example, albacore are
not found in water with a temperature greater than 19oC.
The principal fishing areas are the western and central Pacific, which together
account for 58% of the catch.
Almost all albacore are caught either with pole-and-line, surface trolling, or long
lines. There is no purse seine fishery for albacore.
The principal market for albacore is canned tuna. Albacore is the only canned
tuna marketed as “white tuna”. Due to its unusual bone structure and the soft
consistency of its meat, albacore cannot be filleted.
As in the case of bigeye, Japan and Taiwan dominate the catch.
FAO Albacore Catch Data
Table 7.6. Principal nations contributing to the catch of albacore tuna in 2002.
Country
Principal fishing area(s)
% of catch
Japan
Northwest and west central Pacific
28.8
Taiwan
Southwest and central Pacific, southwest and west
central Atlantic, western Indian Ocean
24.6
USA
Northeast and southwest Pacific
7.4
Spain
Northeast Atlantic
4.5
Fiji
West central Pacific
3.4
South Africa
Southeast Atlantic
2.8
American Samoa
East central Pacific
2.5
New Zealand
Southwest Pacific
2.4
Bluefin tuna
Bluefin tuna being readied for auction at Tokyo’s Tsukiji Fish Market.
Commercial catches of bluefin tuna species
Atlantic bluefin information
Atlantic bluefin are found only in the North Atlantic and Mediterranean
and Black Sea. Bluefin in the South Atlantic are southern bluefin.
Atlantic bluefin are the largest of the tunas, with weights up to 680 kg and
a lifespan up to 30 years.
The fishery for Atlantic bluefin goes back literally thousands of years.
There are two spawning areas, one in the Gulf of Mexico between midApril and mid-June, and the second in the Mediterranean and Adriatic
Seas from June through August. There is controversy over whether the
stocks should be considered separate or not. Tagging studies have
shown that the tuna definitely make trans-Atlantic migrations.
Atlantic bluefin dive to depths of as much as 1,000 meters and feed on
fish such as mackerel, herring whiting, and squid.
The commercial value of Atlantic bluefin prior to 1970 was about $0.10 per kg.
Increasing demand for giant bluefin to supply the Japanese sushi and sashimi
markets changed this picture dramatically. With the development of air freight in
the early 1970s, giant Atlantic bluefin were being caught and immediately
shipped to Japan, where they were sold for more than $2 per kg.
n. b., Current prices are $20-$70 per kilogram.
Management
International Commission for the Conservation of Atlantic Tunas (ICCAT)
formed in 1969.
Western Atlantic stock of bluefin tuna continued to decline, and in 1981 ICCAT
set a quota of 1,160 tonnes for the western Atlantic.
This is based on the assumption by ICCAT that there were two separate stocks
–
western and eastern Atlantic.
The commercial value of Atlantic bluefin prior to 1970 was about $0.10 per kg.
Increasing demand for giant bluefin to supply the Japanese sushi and sashimi
markets changed this picture dramatically. With the development of air freight in
the early 1970s, giant Atlantic bluefin were being caught and immediately
shipped to Japan, where they were sold for more than $2 per kg.
n. b., Current prices are $20-$70 per kilogram.
Management
International Commission for the Conservation of Atlantic Tunas (ICCAT)
formed in 1969.
Western Atlantic stock of bluefin tuna continued to decline, and in 1981 ICCAT
set a quota of 1,160 tonnes for the western Atlantic.
This is based on the assumption by ICCAT that there were two separate stocks
–
western and eastern Atlantic.
Since 1982 the annual catches of bluefin tuna from the western Atlantic
have fluctuated around an average of about 2,200 tonnes. During the same
time catches of bluefin in the eastern Atlantic and Mediterranean increased
to roughly 40,000 tonnes, with most of the catch coming from the
Mediterranean Sea.
By the early 1990s the western Atlantic bluefin stock had declined by about
a factor of 10 from its level in 1975, and by 1993 the eastern Atlantic
population was estimated to be only 13% of its size in 1970.
Efforts by several countries (Sweden, Kenya) to list the western Atlantic
bluefin population in Appendix I of the Convention on International Trade in
Endangered Species (CITES). Proposals withdrawn as result of pressure
from Japan.
About 65% of the catch currently comes from the Mediterranean. Atlantic
bluefin are taken using pole-and-line, surface trolling, and long lines.
Table 7.7. Principal nations contributing to the catch of Atlantic bluefin tuna in 2002.
Country
Principal fishing area(s)
% of catch
France
Mediterranean
18.7
Spain
Northeast Atlantic, Mediterranean
17.9
Italy
Mediterranean
13.2
Japan
Northeast Atlantic
10.0
Morocco
East central Atlantic
8.5
Tunisia
Mediterranean
7.2
Turkey
Mediterranean
6.5
Algeria
Mediterranean
4.9
United States
Northwest Atlantic
3.4
Restrictions on fishing have apparently stopped the decline of the western Atlantic
bluefin stock in recent years.
However, the stock is either not recovering or is recovering very slowly. At its
1998 meeting, ICCAT adopted a rebuilding program for the western stock with a
goal of reaching the maximum sustainable yield in 20 years. The total allowable
catch (TAC) in the western Atlantic is currently 2,700 tonnes, with about 55% of
that quota being allocated to the United States. In the Mediterranean, about 30%
of the catches in 1993 were below the minimum size limit, an indication that the
nations involved in the fishery were not adhering to ICCAT recommendations.
Scientific evidence indicates that the catch in the eastern Atlantic/Mediterranean
must be reduced to no more than 25,000 tonnes before the stock can begin
rebuilding. The reported catch in the eastern Atlantic/Mediterranean in 2002 was
a little less than 33,000 tonnes.
Atlantic Bluefin: Enough Already
http://www.ens-newswire.com/ens/mar2008/2008-03-20-01.asp
http://panda.org/about_wwf/where_we_work/europe/what_we_do/
mediterranean/about/marine/bluefin_tuna/bluefin_tuna_news/
index.cfm?uNewsID=126820
http://www.iht.com/articles/ap/2007/09/19/europe/
EU-GEN-EU-Bluefin-Tuna.php
http://thelede.blogs.nytimes.com/2007/09/19/
ready-for-life-without-bluefin-tuna/
Pacific bluefin information
The Pacific bluefin fishery is the only unregulated bluefin fishery in
the world.
Japan currently accounts for about 64% of the catch, virtually all of
which is taken in the northwest Pacific. Taiwan (west central Pacific
and northwest Pacific) and Mexico (east central Pacific), account for
the remainder of the catch.
Unlike the Atlantic bluefin, there is clearly only one stock of Pacific
bluefin tuna. Adults are known to spawn between the Philippines
and southern Japan and in the Sea of Japan during the spring and
summer.
Tagging studies indicate that some Pacific bluefin remain in the
western Pacific for their entire lives. Others migrate to the eastern
Pacific, mostly during the first and second years of life, and remain
there for 1-2 years.
Pacific bluefin are caught on a variety of gear, and some are taken as bycatch of
longlines targeting tropical tuna. The fish caught using surface gear are often
juveniles, i.e., sexually immature. Almost all Pacific bluefin taken in the eastern
Pacific are sexually immature. Japanese catch Pacific bluefin less than one year
old by trolling. The fish are 15-30 cm in length.
Caught in warm, shallow water in the eastern Pacific, using purse seines.
Caught by trolling and longlines in other areas
Theoretical studies indicate that yield per recruit would be maximized if Pacific
bluefin were not recruited to the fishery until age 3-5.
Southern bluefin information
Southern bluefin are the most overexploited of the bluefin tuna.
There is only one known breeding ground, in the Indian Ocean southeast of
Java, Indonesia.
Juveniles migrate down the west coast of Australia. They may spend the first
few summers of their life in surface waters off the south coast of Australia,
but during the winter they move into deeper, temperate oceanic waters.
The fishery is dominated by Japan and Australia.
As is the case with other bluefin species, surface gear takes many sexually
immature fish.
Table 7.8. Principal nations contributing to the catch of Southern bluefin tuna in 2002.
Country
Principal fishing area(s)
% of catch
Japan
Indian Ocean, Pacific southwest, Atlantic southeast
38.2
Australia
Indian Ocean eastern
34.8
Indonesia
Indian Ocean eastern
9.7
Taiwan
Indian Ocean
7.2
South Korea
Indian Ocean
4.3
New Zealand
Pacific southwest
3.0
Since about 1990 a fishery has developed off the coast of South Australia for juvenile
fish that are transferred to floating enclosures and fattened to increase their market
value. Initially these farmed fish were caught with pole-and-line, but they are now taken
with purse seines. The fish are transferred to floating pens, which are towed to Port
Lincoln (South Australia). From there the tuna are transferred to moored farm pens.
In recent years 60-70% of the global catch of southern bluefin tuna has been longlined.
The recruitment of young fish declined substantially after 1980, and fisheries biologists
agree that the stock has been the victim of recruitment overfishing since that time.
Current estimates indicate that the spawning stock biomass is roughly 7-15% of the level
in 1960 (when substantial reductions had already occurred).
Recognizing that the southern bluefin stock was in trouble, Japan, Australia, and New
Zealand set informal catch quotas from 1989 to 1993, with Australia allocated 5,265
tonnes, Japan 6,065 tonnes, and New Zealand 420 tonnes. The three countries signed
an international convention in 1993 called the Commission for the Conservation of
Southern Bluefin Tuna (CCSBT) After 1994, the catch quotas were allocated by the
CCSBT.
South Korea and Taiwan joined the CCSBT in 2001 and 2002, respectively, and
Indonesia has become a cooperating non-member.
Under current management there is no evidence that the spawning stock is
recovering. The initial goal of the CCSBT was to rebuild the spawning stock to
the 1980 level by 2010, but that target has now been pushed back to 2020.
However, Australian and New Zealand scientists give the CCSBT little chance of
achieving that goal and feel that further reductions in the catch quotas will be
needed to give the stock a chance to recover.
The long time to reach sexual maturity makes this species particularly vulnerable
to overfishing.
TUNA TALES
TUNA I
The World’s Tuna Fisheries
TUNA II
A Fishery Management Case Study:
Yellowfin Tuna and Dolphins
in the Eastern Tropical Pacific
TUNA III
The Mighty Bluefin
Management
Western Pacific - Convention on the Conservation and Management of
Highly Migratory Fish Stocks in the Western and Central Pacific Ocean.
First meeting of the group in December, 2004.
Indian Ocean - Indian Ocean Tuna Commission (IOTC). Agreement came
into force in March 1997. Member nations who object to a decision by the
IOTC are not bound by it.
Eastern Pacific – Inter-American Tropical Tuna Commission (IATTC).
Originally (1950) USA and Costa Rica. Now 12 nations. Principal focus is
yellowfin tuna.
Management
Western Pacific - Convention on the Conservation and Management of
Highly Migratory Fish Stocks in the Western and Central Pacific Ocean.
First meeting of the group in December, 2004.
Indian Ocean - Indian Ocean Tuna Commission (IOTC). Agreement came
into force in March 1997. Member nations who object to a decision by the
IOTC are not bound by it.
Eastern Pacific – Inter-American Tropical Tuna Commission (IATTC).
Originally (1950) USA and Costa Rica. Now 12 nations. Principal focus is
yellowfin tuna.
Management:
IATTC and CYRA
Inter-American Tropical Tuna
Commission (IATTC). Formed
in 1950 by USA and Costa
Rica. Now includes 12
countries.
Purview is eastern tropical
Pacific to 140o west longitude.
Management has been almost
entirely concerned with
yellowfin tuna.
Commission’s Yellowfin
Regulatory Area (CYRA) is de
facto where the ITTAC is
regulating tuna catches
Geographical extent
of the CYRA.
Principal species of tuna involved in commercial fishing
Common name
Scientific name
Albacore
Thunnus alalunga
Bigeye
Thunnus obesus
Skipjack
Katsuwonus pelamis
Yellowfin
Thunnus aobacares
Atlantic bluefin
Thunnus thynnus
Pacific bluefin
Thunnus orientalis
Southern bluefin
Thunnus maccoyii
Yellowfin tuna
Commercial catches of yellowfin tuna
Background information on the tuna/dolphin problem
Problem is confined to the eastern tropical Pacific, where yellowfin tuna
tend to congregate under schools of certain species of dolphins
For many years fishing was done by chumming (pole and line) with no
impact on dolphins
Purse seining phased in during last few years of 1950s
Combination of fishing tuna located under schools of dolphins proved
deadly to dolphins and damaging to tuna stocks
Tuna can be found by several methods. “Porpoise” sets actually
account for less than half the purse seine sets during the 1970s. Log
sets a common alternative
Key strategies for releasing dolphins from net include backing down
procedure (1960) and Medina panels (1971)
A log used by tuna fishermen to attract schools of tuna
A floating board that has attracted some small fish
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
TUNA - DOLPHIN ASSOCIATION
TUNA
These animals have a sense of smell that works in the water
They are not known to be echo-locators
DOLPHINS
Their olfactory sense is not designed to work in the water
They have excellent sonar abilities
Might their combined sensory capabilities be
mutually beneficial?
Tuna boat in process of setting purse seine
Final stages of setting the purse seine
Tuna boat with purse seine encircling school of dolphins
Schematic Depiction of a “Porpoise Set”
Tuna caught in purse seine
Beginning job of
removing tuna from purse
seine with brail net
Schematic Depiction of a “Porpoise Set”
Initial stages of backing down operation
Dolphins escaping from purse seine during backing down operation
Dolphins escaped from tuna net
Schematic Depiction of a “Porpoise Set”
Marine Mammal Protection Act – 1972
“Certain species and population stocks of marine mammals are, or may
be, in danger of extinction or depletion as a result of man’s activities . . . .
They should not be permitted to diminish below their optimum sustainable
population . . . . Measures should be immediately taken to replenish any
species or population stock which has already diminished below [its
optimum sustainable] population.”
“In any event it shall be the immediate goal that the incidental kill or
incidental serious injury of marine mammals permitted in the course of
commercial fishing operations be reduced to insignificant levels
approaching a zero mortality and serious injury rate.”
NMFS permits voided by Judge Richey on grounds that NMFS had
inadequate information on which to base kill quotas
First and second status of porpoise workshops – 1976 and 1979
Optimum sustainable population defined to be any stock size between
65% and 80% of the virgin stock
NMFS Implementation of MMPA with respect to dolphin stocks
Determination of numbers of dolphins in various stocks (1976-1979)
Use of virtual population analysis to estimate size of virgin stocks
(assumed to be size of stocks in 1959)
Two stocks appear to be well below the OSP – eastern spinner and
northern offshore spotted
Sets on eastern spinners prohibited. 90% of subsequent sets are on
spotted dolphins
Judge Richey approves NMFS permits. Quotas steadily decline with time
Table 8.1. Status of dolphin stocks in the eastern tropical Pacifi c as of 1979 estim ated by
virtual population analysis
Stock
% of unexploited population
Coastal spott ed
97-100
Northern offshore spott ed
34-55
Southern offshore spott ed
93-98
Eastern spinner
16-21
Northern whitebell y spinner
62-81
Southern whitebelly spinner
85-94
Baja neritic and northern common
95-100
Central tropical common
74-99
Central tropical striped
99-100
Subsequent developments
Early 1980s – U.S. wants to put observers on all tuna boats. Observers on
fewer than 50% of U.S. boats and only a handful of foreign boat-trips.
Early 1980s – U.S. wants to ban sundown sets
Tuna boats start to drop out of U.S. fleet – 155 in 1976, 34 in 1987, 29 in
1990, 3 in 1991.
Late 1980s – dolphin kills start to increase
1988 Amendments to the MMPA
Must be 100% observer coverage of U.S.-registered boats
With some exceptions, U.S. boats cannot use sundown sets
Nations intending to export tuna to the United States must do the
following:
have a regulatory program comparable to that of the U.S.
(no sundown sets)
dolphin mortality must be no more than 1.25 the U.S. rate
no more than 15% of kill can be eastern spinners
participate in IATTC observer program
submit annual report concerning performance
To avoid laundering of tuna
Any nation exporting yellowfin tuna to the U.S. must identify the
harvesting nation
Such exporters must ban the entry of yellowfin tuna from any nation
that the U.S. embargoes
Sanctions will be imposed if harvesting and exporting nations fail to
comply with these requirements within six months.
Dolphin-safe tuna
1990 – Dolphin Protection Consumer Information Act establishes
standards for “dolphin-safe”
April 12, 1990 – Star-Kist, Bumble Bee, and Chicken of the Sea
announce that they will not buy tuna caught using porpoise sets
1991 – U.S. embargoes challenged by Mexico – General Agreement
on Tariffs and Trade (GATT)
Reported dolphin mortalities continue to drop. Kill has been less
than 2,000 animals per year since 1998
1997 – International Dolphin Conservation Program Act – amends
certain provisions of the MMPA.
Secretary of Commerce to make final finding concerning the dolphinsafe label and the impact of the fishery on dolphin stocks by 12/31/02.
12/31/02 – NMFS rules that use of porpoise sets is having “no
significant adverse impact on dolphin populations in the Eastern
Tropical Pacific Ocean.”
This finding effectively changes the definition of dolphin-safe to
include tuna caught with porpoise sets as long as no dolphins were
killed or seriously injured.
Table 8.2. Current estimates of status of depleted dolphin stocks. Source:
NMFS
Stock
Estimated population in
2000
% of virgin stock size
Northeastern offshore
spotted
641,153
20%
Eastern spinner
448,608
35%
Lessons Learned?
Pluses
Consumers, via their government, pushed effectively for the
implementation of management
Benefits to the fishery from accepting the management plan
1. Main markets didn’t want to buy dead dolphin
2. Spared dolphins live to help find tuna again
Minuses
Expenses to the industry have forced much of the fishing
fleet to jurisdictions where the management plan can
be evaded
A Tuna Management Case Study:
Good Idea, Poor Execution, and a Little Bit of Luck
Goal of management has been to keep catch per unit effort
above 2.7 tonnes per fishing day.
Problems associated with projecting the time when the
quota would be reached has often resulted in catches
exceeding quotas.
Poor judgement used in adjusting quotas.
Regime shift favoring yellowfin tuna seems to have occurred
in 1983-1985. There were very good recruitment years in
1998-2000.
Catch
(tonnes)
Goal of management has been to keep catch per unit effort above 2.7 tonnes per fishing day and
to base a given year’s quota largely on whether the preceding year’s quota resulted in an
increase or decrease in the CPUE.
2.7 tonnes of catch
1 day of effort
(Days)
A Tuna Management Case Study:
Good Idea, Poor Execution, and a Little Bit of Luck
A Pacific Basin Regime Shift and some following good
recruitment years did more good than the management
efforts in this case.
Think what would have happened to this fishery had the
regime shift not been a beneficial one!
TUNA TALES
TUNA I
The World’s Tuna Fisheries
TUNA II
A Fishery Management Case Study:
Yellowfin Tuna and Dolphins
in the Eastern Tropical Pacific
TUNA III
The Mighty Bluefin
ATLANTIC BLUEFIN
THUNNUS THYNNUS
Early History:
Caught in Mediterranean coastal
fisheries, using artisanal techniques Π
(Hand lines, and coastal traps, nets and
pounds)
A little more recently:
~1900 to ~1960.
Sport fishing, off the Atlantic coasts
of Canada and the U.S.
A Nova Scotia tournament recorded a
peak landingof 1,760 fish in 1949.
Fish caught in tournaments were sold
to pet food companies for pennies a
pound.
And then starting in the 1960s and
1970s:
Japanese demand for high-fat tuna;
The availability of airfreighting from
the Atlantic to Japan;
Made recreationally-caught Atlantic
Bluefin worth many dollars a pound.
Heavily capitali zed commercial fisheries
for Atlantic Bluefin we re developed.
These targeted both g iant adults (caught
by hook and line for sh ipment to Japan)
AND, small schooling bluefin (caught by
purse sei ne, for canning).
As values rose, purse seine technology
was applied to large Bluefins.
International Convention for the
Conservation of Atlantic Tunas
(ICCAT) Established in 1966
Two-Stock Hypothesis:
A Western Stock, spawning in the
Gulf of Mexico;
An Eastern Stock, spawning in the
Mediterranean and the Adriatic.
Western Stock much smaller than the
Eastern Stock.
The stocks donΥtmix.
Management Based on the TwoStock Hypothesis (1970s Π1990s):
Stock Management divided at 45
degrees longitude, down the middle
of the Atlantic.
Management Based on the TwoStock Hypothesis (1970s Π1990s):
Western Stock: reasonably wellmanaged, but stock continued to
decline.
Eastern Stock: not so well-managed,
and numerous non-ICCAT nations in
the fishery.
Fishers of the Western Stock upset by
the abuses of fishers of the Eastern
Stock and press for increased quotas
for themselves.
Science, 1995-2005:
Long term tagging study of Western
Stock tuna
Confirms the two-stock hypothesis,
with respect to breeding
Refutes the two-stock hypothesis
with respect to feeding
Science, 1995-2005:
Western Stock fish cross the Atlantic,
and vice-versa
The poorly managed and poorly
regulated European and African
fisheries are wiping out the Western
Stock.
Science, 1995-2005:
Western Stock fish cross the Atlantic,
and vice-versa
The poorly managed and poorly
regulated European and African
fisheries are wiping out the Western
Stock.
Western Stock Distribution
Block et al., 2005
5 years of tracking data for Tuna #603
Block et al., 2005
THE FUTURE FOR ATLANTIC BLUEFIN
CAPTURE FISHERIES:
BLEAK
FARMED FROM WILD STOCK:
WEAK
CLOSE THE LIFE CYCLE AND FARM:
HARD
WORK
Nature, 2005
The Economist, 2009
ICCAT
International Convention for the
Conservation of Atlantic Tunas
The Current Situation:
Vast Over-Capitalization in European
and African fisheries.
In 2008, catch potential of E&A
fisheries - > 54,000 tonnes.
In 2008, ICCAT catch limits of E&A
fisheries Π28,500 tonnes.
In 2008, fisheries scientists
recommended catch - 15,000 tonnes.
ICCAT
International Convention for the
Conservation of Atlantic Tunas
Also Known As
International Conspiracy to
Catch All Tunas
A Note on the Pacific Bluefin
Unlike the Atlantic bluefin, there is clearly only one stock of Pacific Bluefin tuna.
Adults are known to spawn between the Philippines and southern Japan and in
the Sea of Japan during the spring and summer.
Tagging studies indicate that some Pacific bluefin remain in the western Pacific
for their entire lives. Others migrate to the eastern Pacific, mostly during the first
and second years of life, and remain there for 1-2 years.
Pacific bluefin are caught on a variety of gear, and some are taken as bycatch of
longlines targeting tropical tuna. The fish caught using surface gear are often
juveniles, i.e., sexually immature. Almost all Pacific bluefin taken in the eastern
Pacific are sexually immature. Japanese catch Pacific bluefin less than one year
old by trolling. The fish are 15-30 cm in length.
Caught in warm, shallow water in the eastern Pacific, using purse seines.
Caught by trolling and longlines in other areas
Theoretical studies indicate that yield per recruit would be maximized if Pacific
bluefin were not recruited to the fishery until age 3-5.