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Status of the tuna stocks of the world


Juan Ignacio de Leiva & Jacek Majkowski
FAO Fisheries Department
Viale delle Terme di Caracalla
00100 Rome, Italy
E-mail: ignacio.deleivamoreno@fao.org; jacek.majkowski@fao.org

ABSTRACT

Tuna and tuna-like species are very important economically, and a significant source of food. Albacore, bigeye, Atlantic bluefin, Pacific bluefin, skipjack, southern bluefin and yellowfin are frequently referred to as the principal market tuna species. In 2002 their catch was approximately 4 million tonnes, which represents almost 65 percent of the total catch of all the tunas and tuna-like species.

The objective of this paper is to provide information on the status of 23 stocks of the principal market tuna species. This information was obtained mostly from publications and web sites, but also from direct communications with the tuna fishery bodies and other organizations significantly involved in research on tunas.

The maximum annual catches of 13 of the 23 stocks were taken before 1998. This may suggest that these stocks are deteriorating unless the reductions of catches in recent years are the result of economic or environmental conditions or restrictions on the fisheries.

Mostly on the basis of reference points, the sizes and the fishing mortalities of the tuna stocks were classified into the following categories to summarize their status on a global scale in a simple way:

If we consider only stock size, seven of the 13 stocks of tropical tunas (bigeye in the Indian Ocean (BET-IO), bigeye in the eastern Pacific (BET-EPO), bigeye in the western and central Pacific (BET-WCPO), yellowfin in the Atlantic (YFT-AO), skipjack in the western and central Pacific (SKJ-WCPO), yellowfin in the eastern Pacific (YFT-EPO) and yellowfin in the western and central Pacific (YFT-WCPO) are considered to be within their safe limits (above or near their reference points). Only three out of ten stocks of temperate tunas (albacore in the South Atlantic (ALB-SAO), albacore in the South Pacific (ALB-SPO) and Pacific bluefin (PBF-PO) are considered to be safe.

If we consider only fishing mortality, the situation is quite similar. The present fishing mortality of only three of the tropical stocks (bigeye in the Atlantic (BET-AO), bigeye in the eastern Pacific (BET-EPO) and bigeye in the western and central Pacific (BET-WCPO) cannot be regarded as sustainable. For temperate stocks the corresponding number is six (albacore in the North Atlantic (ALB-NAO), albacore in the North Pacific (ALB-NPO), Atlantic bluefin in the eastern Atlantic (BFT-EAO), Atlantic bluefin in the western Atlantic (BFT-WAO), Pacific bluefin (PBF-PO) and southern bluefin (SBF).

Little, if anything, is known about the stock sizes and fishing mortalities of eight of the 23 stocks (albacore in the Mediterranean Sea (ALB-MED), albacore in the Indian Ocean (ALB-IO), albacore in the North Pacific (ALB-NPO), skipjack in the eastern Atlantic (SKJ-EAO), skipjack in the eastern Pacific (SKJ-EPO), skipjack in the Indian Ocean (SKJ-IO), skipjack in the western Atlantic (SKJ-WAO) and yellowfin in the Indian Ocean (YFT-IO). This proportion is slightly higher for the tropical stocks than for the temperate stocks. There is significant uncertainty for four other stocks (albacore in the North Atlantic (ALB-NAO), bigeye in the Indian Ocean (BET-IO), bigeye in the western and central Pacific (BET-WCPO) and Pacific bluefin (PBF-PO), and if these are combined with the first eight stocks it can be said that information for more than half the stocks is considerably less than adequate. The least information on stock status is available for ALB and SKJ.

The status of the tuna stocks was presented across a bivariate system of references related to the stock size and fishing mortality. Seven stocks (ALB-SAO, ALB-SPO, BET-IO, SKJ-WCPO, YFT-AO, YFT-EPO and YFT-WCPO) could be considered to be within safe limits from the conservation perspective. For another eight stocks (ALB-NAO, BET-AO, BET-EPO, BET-WCPO, BFT-EAO, BFT-WAO, PBF-PO and SBF), the fishing mortality should be reduced, the stock size increased, or both, if they are to be brought to within safe limits. Only the stocks for which both reference points were available have been included in this analysis. However, other general information for SKJ-EPO and SKJ-IO indicates that they are within safe limits, while YFT-IO is fully exploited.

The case of the BET-IO deserves clarification. Despite the stock size and fishing mortality reference points suggesting that the stock is within safe limits, the present level of catches is regarded as not sustainable over the long-term, due to the fact that the stock is not in equilibrium.

Future large increases in the catches of the principal market tunas are neither expected nor recommended. In fact, the catches of the stocks that are fully exploited or overexploited may decline in a long-term unless they are properly managed. SKJ-EPO, SKJ-IO, SKJ-WCPO and ALB-SPO are the only stocks for which there are indications that there is still potential for increases in their catches. For SKJ, these increases should be accomplished in a way that would not lead to increases in the catches of stocks of other species, such as BET and YFT, which are currently fully exploited or overexploited. That would require development of methods to catch SKJ, but avoid small BET and YFT. Only gradual increases in the catches of ALB-SPO should be allowed, as it is not known whether large increases would be sustainable.

Presently, a quantitative determination of implications of stock status for the management of fishing capacity is difficult because of:

Even with the limited information on the status of tuna stocks on the global scale, some actions could be undertaken to prevent further increases in the present fishing capacity and, in some cases, reducing it gradually, while simultaneously carrying out further research to determine more precisely the desired extent of this reduction.

1. Introduction

1.1 Background information on tuna and their fisheries

The subfamily Scombrinae includes the tunas, bonitos, mackerels, seerfishes, and billfishes (Klawe 1977, Collette and Nauen 1983, Nakamura 1985, Collette 1999). These are among the largest and fastest fishes in the sea.

The tribe Thunnini, consisting of the genera Thunnus, Euthynnus, Katsuwonus, Auxis and Allothunnus, and a total of 15 species, includes the most economically important species, referred to as the principal market tunas because of their global economic importance and the extensive international trade in them for canning and for sashimi (raw fish, regarded as a delicacy in Japan and, increasingly, in many other countries). Because a tuna consists mostly of edible muscle tissue, they are relatively easy to process for human consumption.

The principal market tunas are albacore (ALB, Thunnus alalunga), bigeye tuna (BET, X obesus), Atlantic bluefin tuna (BFT, X thynnus), Pacific bluefin tuna (PBF, T. orientalis), southern bluefin tuna (SBF, X maccoyii), yellowfin tuna (YFT, X albacares) and skipjack tuna (SKJ, Katsuwonus pelamis). Their superbly efficient metabolic system includes a circulatory system that allows them to retain or dissipate heat as required for peak biological performance and efficiency. They occur in all oceans (see Appendix II), and are capable of long migrations or movements.

The principal market tunas are commonly classified as tropical and temperate species. In this paper, SKJ, YFT and BET are considered to be tropical species, and ALB, BFT, PBF and SBF to be temperate species.

The principal market tunas are divided into 23 stocks, based on their treatment for stock assessment purposes by the CCSBT, IATTC, ICCAT, IOTC, ISC and SPC. There are one, two or three stocks of ALB, BET, SKJ and YFT in each ocean, and these represent effective management units. BFT and PBF are each restricted to a single ocean, and SBF consists of a single stock occurring in the Atlantic, Indian and Pacific Oceans.

Because of the economic situation in Japan in recent years, the prices of BFT, PBF and SBF, the tuna species most valued for sashimi, although still high compared to those of other species, have decreased somewhat. For a whole fish, fishers may get between US $ 30 and US $ 40 per kg, with some getting closer to US $ 100 per kg. Not long ago, the price of a fish of exceptional quality was as high as US $ 500 per kg and, more recently, even higher. BET are also in demand for the production of sashimi, so the prices are high. Although YFT are also popular in these markets, the prices are much lower. For canning, ALB fetch the best prices due to their white meat, followed by YFT and SKJ. Fishers are paid less than US $ 1 per kg for YFT and SKJ. The relatively low prices for canning-quality fish are compensated for by the very large catches of these, especially SKJ and YFT. Longtail tuna (Thunnus tonggol) is becoming increasingly important for canning, and is a subject of substantial international trade. The consumption of tuna and tuna-like species in forms other than canned products or sashimi is increasing.

To manage tuna fisheries, the following tuna fishery bodies have been created:

In addition the following organizations:

also carry out or facilitate the assessment of tuna stocks in the North Pacific and South Pacific respectively, but they do not manage them. The WCPFC will soon undertake management responsibility for the tuna stocks in the area west of 150°W in the North Pacific and the area west of 120°W in the South Pacific.

Further information on tunas and their fisheries, trade and management on the global scale can be found in Allen (2002); Catarci (this collection); Joseph (2003 and this collection); Majkowski (1997 and this collection); Miyake, Miyabe and Nakano (2004); Miyake (this collection); and Reid et al. (this collection).

1.2 Objective of this paper

The objective of this paper is to provide information on the status of tuna stocks on a global scale that is of relevance to the management of tuna fishing capacity.

The information in this paper was collated for FAO's Project on the management of tuna fishing capacity, particularly for consideration at the 2nd Meeting of its Technical Advisory Committee (TAC), which was held in Madrid on 15-18 March 2004.

1.3 Background information on the related FAO project

The present tuna fishing capacity is excessive in respect to at least some tuna resources and the demand for some tuna products. This excess has led to overexploitation, and even depletion, of some tuna stocks. Also, in the recent past, excess capacity produced catches of some species, especially SKJ, which reduced the prices so much that fishing became unprofitable.

The ultimate objective of the FAO Project entitled "Management of tuna fishing capacity: conservation and socio-economics", which is funded by the Japanese government, is to improve the management of tuna fisheries on the global scale. Its immediate objectives are:

This is to be done on the global scale, taking into account conservation and socio-economic issues.

The Project's activities consist of:

The preparatory work includes:

The analyses and other studies consist of:

The Project is being implemented in close collaboration with tuna fishery bodies and other international organizations significantly involved in tuna fisheries research and management. Some further information on the Project can be found in Majkowski (2003).

1.4 Structure of the paper

The main body of the paper summarizes the information for tropical and temperate tunas, broken down by ocean, on:

These summaries are followed by a global summary, providing the numbers of stocks assigned by us into five categories, according to their status. The summaries were prepared on the basis of more detailed information on the same subjects, which is presented for each stock in Appendix I.

The abbreviations used in this paper are listed and explained at the beginning of the paper. References to papers and other sources of information cited in the main body of the paper are listed at its end. Additional sources of information cited in Appendix I are given there.

Appendix II provides some information on the structure of each stock and global maps showing the boundaries of the stocks and the distributions of the catches by the principal fishing gears.

2. Sources of information and methods

2.1 Catches

Information on the annual tuna catches in this paper is taken from the data base constructed for its public release through FAO's Fisheries Global Information System (FIGIS).[6] 2002 was the last year for which the data were available at the time of preparing this paper. Particularly, for this year the data may be reviewed in the future. The institutions from which these data were obtained are the CCSBT (December 2003), IATTC (November 2003), ICCAT (February 2004), IOTC (December 2003), ISC (December 2003) and SPC (November 2003). The dates in brackets indicate when the data were obtained. We provide data on the catches by longline, trolling, pole-and-line, purse-seine and "other" gears. Catches for which the gears are unknown are also included into the "other" category.

The maps in this paper were generated from another data base constructed for its public release through FAO's Fisheries Global Information System (FIGIS).[7] The organizations from which these data have been obtained are the Australian Fisheries Management Authority (AFMA, http://www.afma.gov.au, June 2003), IATTC (August 2002), ICCAT (February 2003), IOTC (May 2003), the U.S. National Marine Fisheries Service (NMFS, http://www.nmfs.noaa.gov, October 2002) and SPC (June 2003). Further information on the data available from FIGIS at the time of preparing this paper can be obtained from Carocci et al. (this collection).

Further information on tuna fisheries and their catches can be found in Miyake, Miyabe and Nakano (2004) and Miyake (this collection).

2.2 Stock structure, status and outlook for the catches

The information on the structure and status of the stocks and the outlook for future catches was obtained mostly from publications and the web sites of the tuna fishery bodies, ISC and SPC, and from direct communications with some of them. The exception is the classification of stock size of and fishing mortality for each stock into categories defined later in this section. All this information applies to the beginning of 2004. It is given in Appendix I, and summarized in the main body of the paper.

We recognize that the information compiled by us on the structure and status of the stocks and the outlook for the catches is uncertain and that this uncertainty varies among the stocks. These uncertainties are the result of deficiencies in the data and the methods applied to analyze the data, but it is very difficult to realistically evaluate these uncertainties. This is addressed further later in this paper.

Various reference points for the fishing mortality and the stock size are used by tuna fishery bodies, ISC and SPC. They include FMSY, FAMSY, Fmax, F30%, F40%, SSBMSY, BMSY, SBR, ratio of exploited to unexploited total biomass and slight modifications of the last reference point. In some cases, however, only qualitative information on the fishing mortality and the stock size is available (for example "the fishing mortality is low to moderate").

To summarize the status of stocks on a global scale in a simple way, on the basis of the information mentioned in the previous paragraphs, particularly the reference points, the sizes of and the fishing mortality for each tuna stock were classified into the following categories:

In cases for which the information on the stock status that we obtained from the tuna fishery bodies, ISC and SPC has been considered as substantially uncertain, we add "possibly" in front of categories (e.g. possibly above its reference point). The stock size and fishing mortality "near its reference point", depends on the age-composition of the catches, which is determined by the current combination of fishing gears and their current patterns of fishing.

When only qualitative information is available (i.e. BFT-EAO, BFT-WAO, ALB-SPO, PBF-PO, SKJ-WCPO, YFT-WCPO and SBF), the assignment of categories to the stock size and fishing mortality requires intuitive and subjective judgment. If the current fishing mortality or stock size is close to a reference point, also some subjectivity is involved into classifying them as "near its reference point". Due to significant uncertainties associated with the fishing mortality for ALB-NAO and SBF, we have created an "in-between" category ("near to above its reference point").

3. Tropical tunas

3.1 Atlantic Ocean

Stocks - The following stocks of tropical tunas are recognized in the Atlantic Ocean (AO):

Historical catches - The maximum combined annual catch of tropical tunas in the AO, 462 109 tonnes, was taken in 1994 (Figure 1). Since then, with some fluctuations, the catches have been decreasing, and in 2002 the catch was 324 923 (70 percent of that obtained in 1994). In 2002 most of the catches of tropical tunas in the AO were taken by purse-seine (56 percent), pole-and-line (23 percent) and longline (19 percent) gear.

In 2002 the principal countries or entities fishing for tropical tunas in the AO were as follows: purse seining, Spain, France and Ghana; pole-and-line fishing, Ghana and Brazil; longlining, Taiwan Province of China and Japan.

The maximum annual catches of tropical tunas (Figure 2) were as follows: BET, 129 506 tonnes (in 1994); SKJ, 203 173 tonnes (in 1991); YFT, 192 456 tonnes (in 1990). In 2002 the catches of BET, SKJ and YFT were 73 110 tonnes (56 percent of the maximum catch), 114 373 tonnes (56 percent of the maximum catch) and 137 440 tonnes (71 percent of the maximum catch), respectively.

FIGURE 1
Catches of the tropical species, by gear, in the AO


FIGURE 2
Catches of the tropical species in the AO


FIGURE 3
Catches of the tropical species, by gear, in the IO

Stock status - Reliable information on the stock size and fishing mortality is missing for two of the four stocks (SKJ-EAO and SKJ-WAO). For BET-AO, the stock size is below its reference point and the fishing mortality is above its reference point. For YFT-AO, both the stock size and fishing mortality are near their reference points.

Outlook - BET-AO is overexploited and YFT-AO is fully exploited, so sustained increases in their catches with the present pattern of exploitation (or, more specifically, the size-compositions of the catches) are not possible. However, if the catches of small BET and YFT could be reduced, sustained increases in their catches would be possible. The status of both SKJ-EAO and SKJ-WAO are unknown, so it is not known whether increases in their catches could be sustainable. However, in the light of the precautionary approach, such increases should not be considered until more reliable information on the status of these stocks is obtained.

3.2 Indian Ocean

Stocks - The following stocks of tropical tunas are recognized in the Indian Ocean (IO):

Historical catches - The combined annual catches of tropical tunas in the IO have been increasing since the 1980s (Figure 3). The maximum combined annual catch of these species, 913 564 tonnes, was taken in 2002. Of this, 43 percent was taken by purse seiners, 20 percent by longliners, 15 percent by pole-and-line gear, and 20 percent by other gears.

In 2002 the principal countries or entities fishing for tropical tunas in the IO were as follows: purse seining, France, Spain and the Seychelles; longlining, the Taiwan Province of China, Indonesia and Japan; pole-and-line fishing, the Maldives; other gears, Sri Lanka, Indonesia and Iran.

The maximum annual BET catch of 150 122 tonnes was taken in 1999 (Figure 4). Since then the BET catches have decreased, and the catch of 2002 was 122 842 tonnes (82 percent of the maximum catch). The SKJ catches have been increasing relatively steadily, reaching a maximum of 482 245 tonnes in 2002. The maximum annual YFT catch of 386 056 tonnes was taken in 1993. Since then the YFT catches have decreased, and the catch of 2002 was 308 477 tonnes (80 percent of the 1993 catch).

Stock status - The stock size of BET-IO is possibly above its reference point and the fishing mortality is possibly below its reference point. It has not been possible to estimate reference points for the stock sizes and fishing mortalities of SKJ-IO and YFT-IO. However, information presented at the 2003 meeting of the Working Party on Tropical Tunas (WPTT) of the IOTC indicates that there should be no immediate concern about the status of SKJ-IO. On the other hand, it appears that the catches of YFT are close to or above the MSY level, so the stock is considered to be fully exploited.

FIGURE 4
Catches of the tropical species in the IO


FIGURE 5
Catches of the tropical species, by gear, in the PO

Outlook - For the present pattern of fishing (or, more specifically, the size-compositions of the catches), BET-IO and YFT-IO catches have possibly reached the upper limits of their sustainable catches and, consequently, attempts to further increase the catches are not advisable. However, if the catches of small BET and YFT could be reduced, sustained increases in their catches might be possible. Sustainable increases in the catches of SKJ may be possible, but their extent is unknown. However, because SKJ is caught with juvenile BET and YFT, increasing the catches of SKJ catches should not be attempted unless ways to reduce the accompanying catches of juvenile BET and YFT can be found.

3.3 Pacific Ocean

Stocks - The following stocks of tropical tunas are recognized in the Pacific Ocean (PO):[8]

Historical catches - With some fluctuations, the combined annual catches of tropical tunas in the PO have been increasing since the 1950s (Figure 5). The maximum annual combined catch of these species in the PO, 2 552 547 tonnes, was taken in 2002. Of this, 68 percent was taken by purse seiners, 12 percent by pole-and-line gear, 8 percent by longliners, and 12 percent by other gears.

In 2002 the principal countries or entities fishing for tropical tunas in the PO were as follows: purse seining, the Taiwan Province of China, Japan, the Republic of Korea, Mexico, Ecuador, the United States, Venezuela, Papua New Guinea and the Philippines; longlining, Japan, the Taiwan Province of China, the Republic of Korea, China and Indonesia; pole-and-line fishing, Indonesia and Japan; other gears, Indonesia and the Philippines.

Recently, the BET catches have been quite stable (Figure 6). The maximum annual BET catch, 222 732 tonnes, was taken in 2000. The 2002 BET catch, 197 523 tonnes, was 89 percent of its maximum catch. The SKJ catches have been increasing steadily, reaching the maximum annual catch of 1 479 603 tonnes in 2002. The maximum annual catch of YFT, 901 037 tonnes, was taken in 2001. In 2002 the catch of YFT decreased slightly to 875 421 tonnes (97 percent of the 2001 catch).

TABLE 1
2002 and maximum annual catches for tropical tuna stocks and their status

OCEAN


Atlantic (AO)

Indian (IO)

Pacific (PO)

STOCKS

BET-AO

SKJ-EAO

SKJ-WAO

YFT-AO

BET-IO

SKJ-IO

YFT-IO

BET-EPO

BET-WCPO

SKJ-EPO

SKJ-WCPO

YFT-EPO

YFT-WCPO

2002 catch (tonnes)

Total

73 110

92 945

21 428

13 440

122 842

482 245

308 477

73 416

124 107

158 911

1 320 692

429 299

446 122

%1

56%

55%

53%

71%

82%

100%

00%

60%

100%

60%

100%

100%

89%

LL

43 774

26

61

17 202

94 283

75

82 119

37 786

81 701

39

4 200

10 091

80 039

PL

11 640

24 074

18 737

20 172

958

113 658

20 544

-

2 927

592

280 37

928

17 815

PS

16 193

68 634

2 116

95 436

27 542

235 609

142 271

35 60

21 072

158 280

931 105

2158 280

170 492

TROLL



58

13

12

4 208

4 524

-

277

-

217


595

OTHER

1 503

211

456

4 617

47

128 695

59 019

-

18 130

-

104 793

-

177 181

Maximum annual catch (tonnes)

Total

129 506

169 771

40 272

192 456

140 272

482 245

386 056

109 596

124 107

265 598

1 320 692

429 299

501 438

Year2

1994

19941

1985

1999200

1999

2002

1993

200220

2002

1999

2002

2002

1998

LL

78 296

5

24

29 104

111 015

-

203 104

39 443

-

96

-

-

65 967

PL

20 285

41 612

28 490

24 278

604

-

9 275

-

-

2 109

-

-

17 256

PS

29 952

126 264

11 191

134 473

38 319

-

128 634

70 153

-

262 040



266 148

TROLL

34

19

-

330

39

-

3 898

-

-

-

-

-

1 173

OTHER

939

1 871

567

4 271

145

-

4 145

-

-

1 353

-

-

1 50 894

Catch-related reference point (tonnes)

79 000 to 105 000

Unknown

Unknown

137 500 to 161 300

102 000

Unknown

280 000 to 350 000

77 000 (PS = 48 000 LL = 29 000)

40 000 to 80 000

Unknown

1 600 000

250 000

381 000 to 554 000

Stock size

Below its reference point

Unknown

Unknown

Near its reference point

Possibly point

Unknown

Unknown

Above its reference point

Possibly point

Unknown

Above its reference point

Near its reference point

Above its reference point

Fishing mortality

Above its reference point

Unknown

Unknown

Near its reference point

Possibly below its point

Unknown

Unknown

Above its reference point

Possibly above its point

Unknown

Below its reference point

Near its reference point

Near its reference point

1 Ratio between the 2002 catch and the maximum historical annual catch.
2 Year in which the total maximum historical annual catch was taken for the stock.

FIGURE 6
Catches of the tropical species in the PO

Stock status - The stock size of BET-EPO and its fishing mortality are above their reference points. However, it was forecast that its size will decrease to below its reference point. The stock size of BET-WCPO is possibly near its reference point and the fishing mortality is possibly above its reference point. No reference points were estimated for the stock size and fishing mortality of the SKJ-EPO stock, but other general information suggests that the stock is well within its safe limits. The stock size of SKJ-WCPO is above its reference point and its fishing mortality is below its reference point. The stock size of YFT-EPO and its fishing mortality are both near their reference points. The stock size of YFT-WCPO is above its reference point, and the fishing mortality is near its reference point.

Outlook - With the present pattern of fishing (or, more specifically, the size-compositions of the catches) for BET-EPO, BET-WCPO and YFT-EPO, the catches should not be increased. Increases in the sustainable catches of these stocks might be possible if the catches of juvenile fish could be reduced.

Increases in the sustainable catches of SKJ-EPO could be possible. However, since the purse seiners that target SKJ catch also juvenile BET, the catches of SKJ-EPO should not be increased unless methods can be found to reduce the amounts of juvenile BET in the catches.

Increases in the sustainable catches of SKJ-WCPO could be possible.

4. Temperate tunas

4.1 Atlantic Ocean

Stocks - The following stocks of temperate tunas are recognized in the Atlantic Ocean (AO):

Historical catches - Since 1964, when the maximum annual catch of 125 566 tonnes was taken, the catch of temperate tunas in the AO has been fluctuating without a clear trend (Figure 7). The third-largest catch, 119 693 tonnes, was taken in 1994, and since then the catches have been decreasing. The 2002 catch, 95 823 tonnes, was 76 percent of the 1964 catch.

In 2002 approximately 39 percent of combined catches of temperate tunas in the AO were taken by longlining, 21 percent by purse seining, 20 percent by pole-and-line fishing, 4 percent by trolling, and 16 percent by other gears (Figure 7).

In 2002 the principal countries or entities fishing for temperate tunas in the AO were as follows: longlining, the Taiwan Province of China; purse seining, France and Italy; pole-and-line fishing, Spain and South Africa; trolling, Spain; other gears, France (mid-water trawling) and Morocco (traps).

FIGURE 7
Catches of the temperate species, by gear, in the AO


FIGURE 8
Catches of the temperate species in the AO

The maximum annual catch of ALB, 90 732 tonnes, was taken in 1965; since then the catches have fluctuated, with a decreasing trend (Figure 8). In 2002 the catch was 59 510 tonnes (66 percent of the 1965 catch). The maximum annual catch of BFT (53 163 tonnes) was taken in 1996. Since then the catches have decreased, and the 2002 catch was 36 313 tonnes (68 percent of the 1996 catch). The catches of ALB and BFT are currently limited by TACs.

Stock status - No information on the stock size and fishing mortality is available for ALB-MED. Stock size of ALB-NAO is below its reference point, and fishing mortality is near or above its reference point, but there are significant uncertainties in regard to these conclusions. Stock size of ALB-SAO is above its reference point, and its fishing mortality is below its reference point. For both BFT-EAO and BFT-WAO, the stock sizes are below their reference points, and the fishing mortalities are above their reference points.

Outlook - Insufficient information is available to predict the future catches of ALB-MED. TACs of 34 500 tonnes for ALB-NAO, 29 200 tonnes for ALB-SAO, 32 000 tonnes for BFT-EAO and 2 700 tonnes for BFT-WAO are currently in effect.

4.2 Indian Ocean

Stocks - Only one stock of temperate tuna, ALB-IO, is recognized in the Indian Ocean (IO).

Historical catches - The ALB catches fluctuated between 11 000 and 31 000 tonnes between 1962 and 1997, without showing a clear trend (Figures 9 and 10). Since then the catches have been increasing. The maximum annual catch, 42 749 tonnes, was taken in 2002. In that year 98 percent of the catch was taken by longliners.

The longline catches of ALB in the IO were taken principally by vessels of the Taiwan Province of China, Japan, Indonesia and Belize.

Stock status - There is no information about the status of ALB-IO.

Outlook - Because of the lack of information on ALB-IO, the outlook for future catches is unknown.

4.3 Pacific Ocean

Stocks - The following stocks of temperate tunas are recognized in the Pacific Ocean (PO):

Historical catches - The combined annual catch of temperate tunas in the PO increased greatly during the 1991-1999 period (Figure 11), and the maximum annual catch of 183 397 tonnes was taken in 1999. The annual catches have decreased since then, and 148 712 tonnes (81 percent of the 1999 catch) were caught in 2002. The estimates of the 2001 and 2002 catches are still preliminary.

In 2002 the catches of temperate tunas in the PO were taken by longlining (58 percent), pole-and-line fishing 21 percent), trolling (11 percent), purse seining (8 percent) and other gears (3 percent). In 2002 the principal countries or entities fishing for tropical tunas in the PO were as follows: longlining, Japan and the Taiwan Province of China; pole-and-line fishing and purse seining, Japan; trolling, the United States, Canada, New Zealand and Japan.

The catches of ALB have increased in recent years (Figure 12). The maximum annual catch, 159 057 tonnes, was taken in 1999. In 2002 the ALB catch was 133 094 tonnes (84 percent of 1999 catch). The catch of BFT has declined since the early 1980s. The maximum annual catch, 32 769 tonnes, was taken in 1981. The 2002 catch, 15 618 tonnes, was 48 percent of the maximum catch. (As mentioned above, the data for 2001 and 2002 are preliminary.)

Stock status - It was not possible to estimate reference points for the stock size and fishing mortality of ALB-NPO, but information compiled by the Interim Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean (ISC) suggests that the stock is fully to overexploited. The stock size of ALB-SPO is above its reference point, and its fishing mortality is below its reference point. The stock size of PBF-PO is possibly near its reference point, but its fishing mortality is above its reference point.

Outlook - The catches of ALB-NPO should not be increased, and it may be necessary to reduce them to ensure that the stock size is at the level corresponding to MSY. ALB-SPO catches are likely to increase with further increases in the fishing effort, but the extent to which the fishing effort and catches can be increased is unknown. PBF-PO is considered to be overexploited by the ISC, so the catches should be reduced. However, if the catches of age-0 and age-1 fish are reduced, it is likely that increased sustainable overall catches are possible.

FIGURE 9
Catches of the temperate species, by gear, in the IO


FIGURE 10
Catches of the temperate species in the IO


FIGURE 11
Catches of the temperate species, by gear, in the PO


FIGURE 12
Catches of the temperate species in the PO

TABLE 2
2002 and maximum annual catches for temperate tuna stocks and their status

OCEAN

Atlantic (AO)

Indian (IO)

Pacific (PO)

All

STOCKS

ALB-MED

ALB-NAO

ALB-SAO

BFT-EAO

BFT-WAO

ALB-IO

ALB-NPO

ALB-NPO

PBF-PO

SBF

2002 catch (tonnes)

Total

5 608

22 496

31 406

33 093

3 220

42 749

82 236

5 618

15 618

16 096

%1

100%

35%

77%

68%

77%

100%

65%

97%

48%

20%

LL

3 706

6 006

21 506

5 160

802

41 948

37 476

45 969

2 138

-

PL

29

6 639

9 539

2 569

-

-

29 987

262

518

-

PS

1 305

118

38

18 341

208

735

856

-

10 446

-

TROLL

117

4 007

-

12

-

4

10 663

4 477

982

-

OTHER

451

5 726

323

7 011

2 210

62

3 254

150

1 534

-

Maximum annual catch (tonnes)

Total

5 608

64 354

40 630

50 762

18 679

42 749

125 622

52 576

32 769

81 605

Year2

2002

1964

1987

1996

1964

2002

1976

1989

1981

1961

LL

-

15 868

30 964

12 959

12 410

-

17 958

22 238

977

-

PL


20 428

8 181

5 362



88 041

-

754

-

PS

-

-

948

26 344

5 158

-

1 381

-

24 304

-

TROLL


28 058





16 183

8 370

2 456

-

OTHER

-

-

537

6 097

1 111

-

2 059

2 968

4 278

-

Catch-related reference point (tonnes)

Unknown

32 600

30 915

Unknown

3 500 and 7 200

Unknown

Unknown

Unknown

Unknown

Unknown

Stock size

Unknown

Possibly below its reference point

Above its reference point

Below its reference point

Below its reference point

Unknown

Unknown

Above its reference point

Possibly near its reference point

Below its reference point

Fishing mortality

Unknown

Possibly near to above its reference point

Below its reference point

Above its reference point

Above its reference point

Unknown

Possibly above its reference point

Below its reference point

Above its reference point

Near to above its reference point

1 Ratio between the last year catch and the maximum historical annual catch.
2 Year in which the total maximum historical annual catch was taken for the stock.

4.4 Southern bluefin (SBF)

FIGURE 13
Catches of SBF by gear


FIGURE 14
Catches of SBF

Stocks - SBF consists of a single stock distributed throughout all the oceans of the Southern Hemisphere, mainly in waters between 30°S and 50°S, but only rarely in the AO and the EPO.

Historical catches - After a rapid increase in the catches during the 1950s, a maximum catch, 81 605 tonnes, was taken in 1961 (Figures 13 and 14). After that the catches declined precipitously until 1990. During the 1990-2001 period the catches fluctuated between 13 500 and 19 500 tonnes.

Stock status - The stock size of SBF is below its reference point and the fishing mortality is near to above its reference point.

Outlook - The catches of SBF should be decreased to allow the heavily-exploited stock to rebuild. The members of the CCSBT agreed to TAC of 14 030 tonnes for its members, plus an additional global allocation of 900 tonnes for cooperating non-members during the 2003-2004 season.

5. Global summary

Historical catches - Generally, the combined global catch of the principal market tunas has been increasing (Figure 15). The maximum annual catch of approximately 4 078 000 tonnes was taken in 2002.

In 2002 66 percent of the catches of the principal market species came from the Pacific Ocean, 24 percent from the Indian Ocean, and 10 percent from the Atlantic Ocean and Mediterranean Sea.

In 2002 58 percent of catch was taken by purse seiners, 15 percent by longliners, 14 percent by pole-and-line gear, 1 percent by trolling gear, and 13 percent by other gears.

The principal countries or entities fishing for tunas in 2002 were Japan, Indonesia, the Taiwan Province of China, the European Union (chiefly France and Spain), the Philippines, the Republic of Korea, the United States, Mexico, Venezuela, Ecuador, the Maldives and Papua New Guinea.

The global annual catches, by species, are shown in Figure 16. The catches of both SKJ and YFT have been increasing, and their maximum annual catches were both taken in 2002. In 2002 the catch of SKJ was 2 076 000 tonnes (51 percent of the total catch) and that of YFT was 1 321 000 tonnes (32 percent of the total catch).

In 2002 BET accounted for 10 percent of total catch. The catches of BET increased until 1997, when the maximum annual catch, 462 000 tonnes, was taken. After that the catches declined, and the BET catch in 2002 was 393 000 tonnes, about 85 percent of the maximum catch.

FIGURE 15
Global tuna catches by gear


FIGURE 16
Global tuna catches by species

In 2002 ALB accounted for 6 percent of total catch. ALB catches were approximately constant from the mid-1960s to the late 1990s, without large fluctuations. The maximum annual catch of ALB, 265 000 tonnes, was taken in 1999. In 2002 235 000 tonnes of ALB were caught (89 percent of the 1999 catch). The estimate for the 2002 catch of ALB should be interpreted with caution, however, since the catch data for the NPO are still preliminary.

The catches of Atlantic bluefin, Pacific bluefin and southern bluefin have been stable or decreasing, at much lower levels than those of the other principal tunas.

The maximum annual catch of BFT, 53 200 tonnes, was taken in 1996. The 2002 catch, 36 300 tonnes, was 68 percent of 1996 catch.

The maximum annual catch of PBF, 32 700 tonnes, was taken in 1981. The 2002 catch, 15 600 tonnes, was 48 percent of the 1981 catch. However, as is the case for ALB, the 2002 catch data are preliminary.

The maximum annual catch of SBF, 81 600 tonnes, was taken in 1961. After that the catches declined precipitously until 1990. During the 1990-2001 period the catches fluctuated between 13 500 and 19 500 tonnes. The 2002 catch, 16 000 tonnes, was approximately 20 percent of the maximum annual catch.

The combined catches of BFT, PBF and SBF account for only slightly more than 1 percent of the total catches of the principal market species.

Analysis of the catches - For eight out of the 13 tropical tuna stocks (BET-IO, SKJ-IO, BET-EPO, BET-WCPO, SKJ-EPO, SKJ-WCPO, YFT-EPO and YFT-WCPO), the maximum annual catch has been taken after 1998. All these stocks occur in the IO and the PO. The sizes of these eight stocks are classified by us as either above their reference points (four stocks), near their reference points (two stocks) or unknown (two stocks). The only stock in these oceans for which the maximum annual catch was taken before 1998 (in 1993) is YFT-IO. The maximum annual catches for the four tropical tuna stocks in the AO (BET-AO, SKJ-EAO, SKJ-WAO and YFT-AO) were taken before 1995, and the sizes of these stocks are classified by us as either below their reference points (one stock), near their reference points (one stock) or unknown (two stocks).

The maximum annual catches of only two of the ten temperate tuna stocks, ALB-MED and ALB-IO, have been taken in recent years (after 1997). The stock sizes and fishing mortalities of these two stocks are unknown. For the remaining eight temperate stocks, ALB-NAO, ALB-SAO, BFT-EAO, BFT-WAO, ALB-NPO, ALB-SPO, PBF-PO and SBF, the maximum annual catches were taken before 1996. With the exception of ALB-SAO and ALB-SPO, the sizes of these temperate stocks are classified by us as below their reference points (four stocks), near their reference points (one stock) or unknown (one stock), and their fishing mortalities as above their reference points (three stocks), near to above their reference points (two stocks) or unknown (one stock).

These observations should be interpreted with caution, however, because the catches depend not only on the status of the stocks, but also on socio-economic factors, management measures and environmental conditions.

Stock status - The numbers of stocks assigned to various stock size and fishing mortality categories are shown in Table 3.

The information in Table 3 suggests that the tropical stocks are, in general, in a better condition than the temperate stocks. If we consider only the stock size, seven of the 13 tuna tropical stocks (BET-IO, BET-EPO, BET-WCPO, YFT-AO, SKJ-WCPO, YFT-EPO and YFT-WCPO) are within their safe limits (above or near their reference points), and only one of them (BET-AO) is below its safe limit. However, only three of the ten temperate tuna stocks (ALB-SAO, ALB-SPO and PBF-PO) are within their safe limits, and four of them (ALB-NAO, BFT-EAO, BFT-WAO and SBF) are below their safe limits. For the fishing mortality, the situation is similar. Five of the 13 tropical stocks (YFT-AO, BET-IO, SKJ-WCPO, YFT-EPO and YFT-WCPO) are within their safe limits, and only three of them (BET-AO, BET-EPO and BET-WCPO) are above their safe limits. Only two of the ten temperate stocks (ALB-SAO and ALB-SPO) are within their safe limits, and six of them (ALB-NAO, ALB-NPO, BFT-EAO, BFT-WAO, PBF-PO and SBF) above those limits.

TABLE 3
Numbers of stocks assigned to the various stock size and fishing mortality categories

STOCK STATUS

Stock size


Above

Above-Near

Near

Near-Below

Below

Unknown

Tropical stocks

4 (1)

-

3 (1)

-

1

5

Temperate stocks

2

-

1 (1


4(1)

3

Total

6 (1)

-

4 (2)

-

5(1)

8

Fishing mortality

Below

Below-Near

Near

Near-Above

Above

Unknown

Tropical stocks

2 (1)

-

3


3(1)

5

Temperate stocks

2

-

0

2 (1)

4(1)

2

Total

4 (1)

-

3

2 (1)

7(2)

7

Note: The numbers in brackets indicate the numbers of stocks for which there is substantial uncertainty (e.g. the stock sizes of four tropical stocks are considered to be above the reference points, but there is substantial uncertainty about one of them).

No estimates of either the stock size or fishing mortality have been obtained for five of the 13 tropical stocks (SKJ-EAO, SKJ-EPO, SKJ-IO, SKJ-WAO and YFT-IO) and three of the ten temperate stocks (ALB-IO, ALB-MED, ALB-NPO). This proportion of the stocks for which this information is lacking is slightly higher for the tropical stocks than for the temperate stocks. If the number of stocks for which their status is significantly uncertain is added (ALB-NAO, BET-IO, BET-WCPO and PBF-PO), information is lacking for seven of the 13 tropical stocks and five of the ten temperate stocks. ALB and SKJ are the species for which the stock status is least known.

The status of the tuna stocks across a bivariate system of references related to the stock size and fishing mortality is presented in Figure 17. The representation is qualitative, since not enough information is available for a quantitative presentation. In accordance with the precautionary approach (FAO 1995), when the stock size or fishing mortality category assigned by us in Tables 1 and 2 was uncertain the more conservative category has been adopted in the figure.

Seven of the stocks (ALB-SAO, ALB-SPO, BET-IO, SKJ-WCPO, YFT-AO, YFT-EPO and YFT-WCPO) could be considered within safe limits from the conservation perspective (white area). However, the three stocks for which the levels of fishing mortality are near the reference points (YFT-AO, YFT-EPO and YFT-WCPO) should be and are closely monitored, so that, if necessary, management action can be undertaken. For instance, the IATTC has closely monitored YFT-EPO for many years, and there have been restrictions on the fishery since 1998.

FIGURE 17
Status of tuna stocks across a bivariate system of references

The case of the BET-IO requires a further clarification. Despite the stock size and fishing mortality categories suggesting that the stock is within safe limits, the present level of catches is regarded as not sustainable in the long-term. This is a consequence of the stock not being in equilibrium. In addition, the estimates for both BMSY and FMSY were considered to be substantially uncertain by the WPTT of the IOTC.

The remaining eight stocks (ALB-NAO, BET-AO, BET-EPO, BET-WCPO, BFT-EAO, BFT-WAO, PBF-PO and SBF) in the upper row of Figure 17 may be overfished (grey area). Their fishing mortalities should be reduced and their stock sizes should be increased, or both, if these stocks are to be brought to within safe limits. Of these stocks, the stock size of only one, BET-EPO, was above its reference point in 2002 (the last year for which stock size estimates were available at the time that this paper was prepared). However, assessments by the IATTC staff indicate that its stock size will decrease below its reference point.

The eight principal market tuna stocks for which the stock size and fishing mortality categories were not assigned (ALB-IO, ALB-MED, ALB-NPO, SKJ-EAO, SKJ-EPO, SKJ-IO, SKJ-WAO and YFT-IO) are not included in Figure 17.

Outlook - Future large increases in the catches of the principal market tunas are neither expected nor recommended. Several stocks are already fully exploited, overexploited (or depleted), and their catches should be limited to their current levels, or even decreased to permit the stock sizes to increase toward the levels corresponding to their MSYs. If this is not done, the catches may, in fact, decrease over the long-term. The information for several stocks is very limited and/or uncertain, so, in accordance with the precautionary approach, further research should be carried out before increases in catches are allowed.

SKJ-EPO, SKJ-IO, SKJ-WCPO and ALB-SPO are the only stocks for which there are indications that there is still potential for some increase in their catches. SKJ are caught mostly by purse seining, and sets that include SKJ usually also include small BET and YFT. Accordingly, increased fishing effort for SKJ should not be encouraged unless methods can be found for reducing the incidental catches of BET and YFT. Increases in the catches of ALB-SPO should be allowed only in small increments, as there is insufficient knowledge of the status of this stock to know to what extent they can be allowed.

It appears, from the information in Figure 17, that increases in the catches for BET-IO and ALB-SAO could be also be sustainable. This is not the case with BET-IO, however, for reasons stated in the previous subsection. For ALB-SAO, the stock size is currently above its reference point, and the fishing mortality is currently below its reference point. However, the catches have been above or close to those corresponding to the MSY since 1988, so ICCAT has adopted TACs to prevent overfishing.

The catches of some stocks other than SKJ-EPO, SKJ-IO, SKJ-WCPO and ALB-SPO could be increased if the catches of small fish could be reduced. This applies particularly to all stocks of BET, all stocks of YFT, BFT and PBF. The increased catches of some of these stocks might not be significant, but their SSBs would definitely increase. Also, the total market value of the fish would increase, because the market value per kilogram is greater for larger fish.

6. Discussion

The tuna fishery bodies, ISC and SPC and their member countries carry out substantial research to evaluate the status of stocks of principal market species of tunas. These evaluations are difficult for many reasons. In some cases the stock structure is uncertain. For example, the degree of independence of the BFT of the EAO from those in the WAO has been under investigation for many years. Each stock, especially PBF and SBF, has a very wide geographical distribution, so different individuals from the same stock are affected differently by oceanographic conditions in different parts of these areas. Fishing is carried out by vessels of many nations, with many different types of gear, and different species of fish are caught by the same gear. This makes collection of catch and fishing effort data, sampling of the catches, and analysis of the data very difficult. In some cases, data that are needed are not available or not made available to scientists. Surveys by research vessels are, for the most part, impractical because of the wide distributions of even single stocks.

Regardless of the difficulties and uncertainties described in the previous paragraph, substantial information has been obtained on the status of the tuna stocks. However, a uniform and consistent classification of tuna stocks in accordance with some simple, pre-determined criteria is quite difficult on a global scale because reference points for many of the stocks have not been determined. For some stocks for which reference points have not been determined, only qualitative information on the stock sizes and fishing mortality exists. Regardless of the problems with such information, we believe that it should be included in a review such as this one, as it indicates what further research should be conducted.

Different methods have been used to estimate the reference points for the different stocks, which makes it difficult to compare their statuses, particularly when the assessments have been carried out by different organizations. Consultations among these organizations might reduce or eliminate this problem. According to the United Nations Agreement for the Implementation of the Provisions of the United Nations Convention on the Law of the Sea of 10 December 1982 Relating to the Conservation and Management of Straddling Fish Stocks and Highly Migratory Fish Stocks (1995), both target and limit reference points should be established and estimated for each stock. At presently, there is no distinction between these two types of reference points.

Even if the types of reference points were standardized, comparisons of the different stocks would be difficult because estimates of the reference points are based on the age compositions of the catches, and these may differ for different stocks of the same species. Nevertheless, we regard the classification presented in this paper as a useful summary of the status of the tuna stocks of the world on a global scale.

There is insufficient information to evaluate the status of some tuna stocks, and other evaluations are highly uncertain. For these stocks, further research is required. For some other stocks, the uncertainties as to their status may appear to be less serious, but nevertheless it is important that additional data be collected and further analyses be made.

Presently, a quantitative determination of implications of stock status for the management of fishing capacity is difficult because of:

For the same reasons, combining the information on the desired reductions or possible increases in the fishing capacity on a global scale is even more complex. The Technical Advisory Committee (TAC) of the FAO Project "Management of tuna fishing capacity: conservation and socio-Economics", at its second meeting in Madrid, Spain, on 15-18 March 2004, was of the opinion that significant additional research is needed to address it. It was recommended that a multi-disciplinary working group for resolving the problem be created (FAO 2004).

Even with the limited information on the status of tuna stocks on a global scale presently available, some fisheries management actions could be undertaken to prevent further increases in the present fishing capacity and, subsequently, reducing it gradually, while simultaneously carrying out further research to determine more precisely the desired extent of this reduction. In fact, on the basis of all the information presented to the second meeting of TAC (including that from this paper), in its Statement (FAO 2004), it was recommended "that a moratorium on the entry of additional large scale tuna vessels be implemented, until an efficient, equitable and transparent management system of fishing capacity is achieved".

Acknowledgements

The information on the structure and the status of the tuna stocks and the outlook for their catches was obtained mostly from publications and web sites of, and from direct communications from, the following tuna bodies and international organizations:

The authors thank these institutions for their assistance in the preparation of this paper.

Particularly, the authors are grateful to Robin Allen (IATTC), Alejandro Anganuzzi (IOTC), John Annala (Ministry of Fisheries, New Zealand), John Hampton (SPC), Shelton Harley (IATTC), Brian MacDonald (CCSBT), Mark Maunder (IATTC), Talbot Murray (Ministry of Fisheries, New Zealand), Miki Ogura (National Research Institute of Far Seas Fisheries, NRIFSF, Japan), Victor Restrepo (ICCAT) and Ziro Suzuki (NRIFSF) for their assistance and valuable comments during the preparation of this paper. We have tried to account for them, but we take the full responsibility for the content of the paper, remaining grateful for their suggestions.

Also, we would like to thank Fabio Carocci (FAO) for the preparation of the maps.

References

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[6] These data or their updates can be obtained presently from: http://www.fao.org/figis/servlet//FiRefServlet?ds=staticXML&xml=webapps/figis/wwwroot/fi/figis/tseries/index.xml&xsl=webapps/figis/staticXML/format/webpage.xs
[7] These data or their updates and information about their collation and processing can be obtained presently from: http://www.fao.org/figis/servlet/TabSelector?tb_ds=TunaAtlas&tb_act=ACTION&tb_grp=RESET&tb_mode=MAP
[8] Even if there is no clear evidence of two stocks existing in PO (see the Stock Structure section of BET-PO in Appendix 1), stock assessments of BET for EPO and WCPO are currently undertaken separately. In this paper, therefore it has been considered appropriate to differentiate between BET-EPO and BET-WCPO.

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