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5. The purse-seine fisheries for tunas in the Indian Ocean and the Atlantic Ocean


For the Indian and Atlantic Oceans we consider the Russell (1985) measure because of its ease of estimation, and impose variable returns to scale.

5.1 Data and methodology

Data was sought from around the world on fishing activity for the Atlantic and Indian Ocean purse-seine fisheries for tuna. Contacts were also made with ICCAT and the IOTC to obtain data. The data were determined to be inadequate for estimating capacity. Subsequently, data were obtained from Pallares et al. (2003) and Pianet et al. (2003) on the Indian and Atlantic Ocean fisheries, respectively. These data, however, were highly aggregated and inadequate for estimating capacity on a nation-by-nation basis or by fishing mode (e.g. sets on floating objects vs. sets on unassociated schools). It was subsequently decided to estimate capacity using aggregate annual data on the catches of yellowfin, skipjack, bigeye, albacore and all other species combined, numbers of vessels, fishing days, searching days, carrying capacity, a weighted mean of GRT, using the mid-point of vessel tonnage classes, and number of sets. Data were then converted to a per-vessel basis by dividing by the number of vessels in each year. Data on the Atlantic fishery and Indian Ocean fisheries were available for 1991-2002 and 1981-2002, respectively (Tables 5.1 and 5.2).

Unfortunately, the data were extremely limited in number of observations and detail, which might be important variables for estimating capacity (e.g. fishing days and searching days on schools associated with floating objects and unassociated schools, or activities and summary statistics by nation). The number of observations was, in fact, too few to consider all inputs. Unlike statistics in which the required degrees of freedom are well established, there are no specific required degrees of freedom. It has been well established, however, that too few observations leads to problems in DEA because of its orientation to relative efficiency. A rough rule of thumb offered by Cooper, Seiford and Tone (2000) is that the degrees of freedom (n) for DEA should be as follows: n $ max {m × s, 3(m + s)}, where n is the number of observations; m is the number of outputs; and s is the number of inputs. For the two data sets on the Atlantic and Indian Ocean purse-seine fisheries, we have five outputs and up to five inputs (average GRT, fishing days, searching days, carrying capacity and number of sets). We should, thus, have a minimum of 30 observations (m × s = 25, and 3(5+5) = 30). It was subsequently decided to use only average GRT per vessel per year and fishing and searching days per vessel per year. The GRT was considered as a fixed factor (i.e. could not be easily changed), and fishing and searching days were considered to be variable factors.

TABLE 5.1
Data used to estimate capacity in the Atlantic tuna fishery

Year

Average GRT

Number of vessels

Days of fishing

Days of searching

Carrying capacity

Number of sets

Landings (tonnes)

YFT

SKJ

BET

ALB

Others

Total

1991

783

71

15 633

13 709

41 978

8 195

92 475

125 536

14 188

416

1 735

234 350

1992

804

65

17 454

15 886

44 091

6 975

96 705

87 243

18 230

2 518

1 254

205 950

1993

829

64

16 425

14 674

41 119

7 877

90 101

124 875

30 857

1 450

1 246

248 529

1994

800

59

15 904

14 231

40 833

7 663

88 062

105 633

32 378

1 079

2 239

229 391

1995

784

55

14 786

13 086

38 149

8 129

84 684

99 208

25 095

412

2 302

211 701

1996

775

54

14 671

13 116

35 641

7 705

82 476

83 928

25 006

258

3 799

195 467

1997

770

52

12 781

11 551

30 832

5 614

68 311

60 204

15 918

118

2 733

147 284

1998

1 005

44

12 585

11 215

29 784

5 898

73 338

56 438

12 622

434

3 065

145 897

1999

762

41

11 731

10 578

25 877

4 861

58 289

76 852

15 545

264

2 004

152 954

2000

730

41

10 576

9 394

27 385

5 122

64 047

64 625

13 752

32

1 741

144 197

2001

812

44

11 344

10 121

30 714

5 198

77 097

60 891

14 002

24

2 460

154 474

2002

801

41

9 823

8 816

25 036

4 324

74 094

47 900

14 230

39

1 008

137 271

Annual average

805

53

13 643

12 198

34 287

6 463

79 140

82 778

19 319

587

2 132

183 955

Source: Pianet et al. (2003)

TABLE 5.2
Data used to estimate capacity in the Indian Ocean tuna fishery

Year

Average GRT

Number of vessels

Days of fishing

Days of searching

Carrying capacity

Number of sets

Landings (tonnes)

YFT

SKJ

BET

ALB

Others

Total

1981

613

2

84

0

129

33

199

163

10

0

0

372

1982

681

4

256

221

02 0

105

1 028

1 027

8

0

0

2 063

1983

685

12

1 461

1 142

3 729

766

10 505

9 366

218

0

0

20 089

1984

847

47

8 041

6 502

23 642

3 491

56 4356

41 884

3 561

558

0

102 459

1985

886

48

9 929

8 302

29 209

4 289

65 772

55 266

6 160

726

0

127 924

1986

863

35

8 597

6 907

25 562

3 904

68 610

60 483

9 951

179

0

139 223

1987

935

35

8 246

6 484

25 942

4 940

78 335

68 22

12 682

239

0

159 548

1988

973

40

9 135

7 244

31 550

5 638

112 780

82 822

13812

266

0

209 680

1989

982

44

10 880

9 030

37 204

5 590

81 15 18

115 181

9 997

6

0

209 242

1990

1 015

46

10 628

8 880

34 525

5 9321

101 070

87 932

170 199

317

0

199 808

1991

1 041

39

9 767

7 985

33 781

5 493

94 087

91 9853

12 994

2 243

40

201 347

1992

1 095

39

9 944

8 162

35 061

6 227

91 172

102 569

8 326

3 256

0

205 323

1993

1 140

42

11 109

9 342

39 521

6 350

102 814

116 850

12 365

1 289

0

233 318

1994

1 133

492

11 061

9 228

40 113

7 051

98 623

144 492

13 767

2 574

1

2 57

1995

1 133

42

11 848

10 004

42 153

7 343

124 098

140 546

22 916

1 254

0

288 814

1996

1 174

47

12 380

10 510

45 384

7 733

112 501

124 998

21 755

1 526

1 286

262 066

1997

1 250

58

14 883

12 930

56 796

8 509

116 875

123 418

30 744

1 961

208

273 206

1998

1 226

53

14 648

12 667

54 669

8 300

89 193

132 073

24 945

1 376

0

247 587

1999

1 240

52

13 339

11 363

51 875

8 062

120 179

168 950

35 587

542

829

35 587

2000

1 267

50

12 635

10 657

52 740

8 132

130 7

170 793

25 519

1 162

2 779

330 970

2001

1 261

50

12 911

10 978

53 519

7 845

114439

156 929

19 482

1 230

525

292 605

2002

1 284

49

12 864

10 851

55 410

8 356

130 187

212 173

26 943

703

5 379

375 385

Annual average

1 033

40

9 757

8 154

35 152

5 639

86 532

100 372

14 647

973

502

203 026

Source: Pallares et al. (2003)

TABLE 5.3
Reported and estimated capacity output (tonnes) for the Atlantic Ocean purse-seine fishery

Year

Observed

Capacity

YFT

SKJ

BET

ALB

Others

Total

YFT

SKJ

BET

ALB

Others

Total

1991

92 475

125 536

14 188

416

1 735

234 350

96 705

125 536

32 378

2 518

3 799

260 936

1992

96 705

87 243

18 230

2 518

1 254

205 950

96 705

124 969

32 378

2 518

3 799

260 369

1993

90 101

124 875

30 857

1 450

1 246

248 529

95 771

124 875

32 378

2 424

3 799

259 247

1994

88 062

105 633

32 378

1 079

2 239

229 391

91 103

114 435

32 378

1 955

3 799

243 669

1995

84 684

99 208

25 095

412

2 302

211 701

87 368

106 083

28 637

1 579

3 799

227 466

1996

82 476

83 928

25 006

258

3 799

195 467

86 434

103 995

27 702

1 485

3 799

223 416

1997

68 311

60 204

15 918

118

2 733

147 284

84 567

99 820

25 832

1 297

3 652

215 167

1998

73 338

56 438

12 622

434

3 065

145 897

77 097

83 116

18 351

546

3 065

182 174

1999

58 289

76 852

15 545

264

2 004

152 954

74 094

76 852

15 545

264

2 004

168 759

2000

64 047

64 625

13 752

32

1 741

144 197

74 094

76 852

15 545

264

2 004

168 759

2001

77 097

60 891

14 002

24

2 460

154 474

77 097

83 116

18 351

546

3 065

182 174

2002

74 094

47 900

14 230

39

1 008

137 271

74 094

76 852

15 545

264

2 004

168 759

Annual average

79 140

82 778

19 319

587

2 132

183 955

84 594

99 708

24 585

1 305

3 216

213 408

In actuality, the DEA problem used to estimate capacity has only one factor of production (GRT). This is because capacity can be estimated without including the variable factors. The constraint introduced by 8 ensures unrestricted use of the variable factors, which is equivalent to excluding the variable factors from Problems [1] or [2]. We, nevertheless, have a potential problem with degrees of freedom relative to estimating capacity for the Atlantic Ocean purse-seine fishery.

Capacity on a per-vessel basis was estimated for both the Atlantic and Indian Ocean fleets and subsequently converted to total fleet activity by multiplying the per-vessel estimates of capacity by the number of vessels in each year. We stress that because of the limited degrees of freedom and the paucity of the data relative to detailed activities of the various nations and the modes of fishing, our estimates represent extreme lower-bound estimates of capacity for the Atlantic and Indian Ocean purse-seine fisheries.

5.2 Results

5.2.1 Overall levels of capacity in the tuna purse-seine fisheries of the Atlantic and Indian Oceans

Estimates of capacity output on a per vessel basis for the Atlantic and Indian Ocean purse-seine fisheries suggest that both fisheries have some degree of excess capacity for all species (Tables 5.3 and 5.4). The highest degree of excess capacity (i.e. capacity output minus observed output per vessel) occurred for skipjack and yellowfin for both fisheries, which also had the greatest landings of all four of the tuna species.

TABLE 5.4
Reported and estimated capacity output (tonnes) for the Indian Ocean purse-seine fishery

Year

Reported

Capacity

YFT

SKJ

BET

ALB

Others

Total

YFT

SKJ

BET

ALB

Others

Total

1981

199

163

10

0

0

372

199

163

10

0

0

372

1982

1 028

1 027

8

0

0

2 063

3 324

2 962

327

0

0

6 613

1983

10 505

9 366

218

0

0

20 089

10 505

9 366

1 036

0

0

20 907

1984

56 456

41 884

3 561

558

0

102 459

92 568

83 765

12 549

1 911

0

190 793

1985

65 772

55 266

6 160

726

0

127 924

107 057

97 010

14 845

2 272

0

221 184

1986

68 610

60 483

9 951

179

0

139 223

72 604

65 739

9 951

1 517

0

149 811

1987

78 335

68 292

12 682

239

0

159 548

89 665

81 360

12 682

1 954

0

185 660

1988

112 780

82 822

13 812

266

0

209 680

112 780

102 418

16 102

2 497

0

233 797

1989

84 058

115 181

9 997

6

0

209 242

124 402

115 181

18 142

2 817

0

260 542

1990

101 070

87 932

10 489

317

0

199 808

131 331

129 000

20 559

3 206

0

284 096

1991

94 087

91 983

12 994

2 243

40

201 347

112 196

115 090

18 492

2 893

2 734

251 404

1992

91 172

102 569

8 326

3 256

0

205 323

113 968

127 024

20 706

3 256

0

264 954

1993

102 814

116 850

12 365

1 289

0

233 318

124 098

147 683

24 319

3 507

0

299 606

1994

98 623

144 492

13 767

2 574

1

259 457

124 098

145 976

24 002

3 507

3 578

301 160

1995

124 098

140 546

22 916

1 254

0

288 814

124 098

145 976

24 002

3 507

0

297 582

1996

112 501

124 998

21 755

1 526

1 286

262 066

138 871

174 343

28 899

3 924

4 320

350 358

1997

116 875

123 418

30 744

1 961

208

273 206

171 373

240 045

39 693

4 842

6 048

462 001

1998

89 193

132 073

24 945

1 376

0

247 587

156 600

212 248

35 491

4 425

0

408 764

1999

120 179

168 950

35 587

542

829

326 087

153 645

212 369

35 587

4 341

5 340

411 283

2000

130 717

170 793

25 519

1 162

2 779

330 970

147 736

211 624

34 219

4 175

5 349

403 101

2001

114 439

156 929

19 482

1 230

525

292 605

147 736

209 919

34 219

4 175

5 300

401 347

2002

130 187

212 173

26 943

703

5 379

375 385

144 781

212 173

33 534

4 091

5 379

399 958

Annual average

86 532

100 372

14 647

973

502

203 026

109 256

129 156

20 880

2 855

1 729

263 877


FIGURE 5.1
Annual and average annual excess capacity relative to all species caught in the Atlantic Ocean purse-seine fishery

For the Atlantic Ocean fishery during 1991-2002 the highest level of excess capacity relative to all species occurred in 1997 (Figure 5.1); the highest level of excess capacity for the Indian Ocean fishery also occurred in 1997 (Figure 5.2). The reason for this is unknown, but it may be a result of management or environmental conditions.

The Atlantic Ocean purse-seine fishery had the capability of harvesting 84 596 tonnes of yellowfin, 99 708 tonnes of skipjack, 24 585 tonnes of bigeye, 1 305 tonnes of albacore and 3 216 tonnes of other species per year (Table 5.3). Alternatively, the fleet had the capability to harvest 213 408 tonnes of all species combined. In comparison, the fleet had a reported average annual harvest of 79 140 tonnes of yellowfin, 82 778 tonnes of skipjack, 19 319 tonnes of bigeye, 587 tonnes of albacore and 2 132 tonnes of other species; the reported average annual harvest between 1991 and 2002 was 183 955 tonnes of all species combined. There was not, however, excess capacity for all species in all years. There was no excess capacity for yellowfin in 1992, 2001 and 2002; none for skipjack in 1991, 1993 and 1999; none for bigeye in 1994 and 1999; none for albacore in 1992 and 1999; and none for other species in 1996, 1998 and 1999.

The overall greatest level of excess capacity occurred in the Indian Ocean purse-seine fishery (Table 5.4). The estimated average annual capacity output between 1981 and 2002 for the Indian Ocean fishery was 109 256 tonnes of yellowfin, 129 156 tonnes of skipjack, 20 880 tonnes of bigeye, 2 855 tonnes of albacore and 1 729 tonnes of other species; the reported average annual landings were, respectively, 86 532 tonnes of yellowfin, 100 372 tonnes of skipjack, 14 647 tonnes of bigeye, 973 tonnes of albacore and 502 tonnes of other species. The average annual capacity output for all species was estimated to equal 263 877 tonnes, whereas the reported average annual total output was 203 026 tonnes. There was no excess capacity for yellowfin in 1981, 1983, 1988 and 1995; none for skipjack in 1981, 1983, 1989 and 2002; none for bigeye in 1981, 1986, 1987 and 1999; none for albacore for 1981-1983 and 1992; and none for other species in all years except 1991, 1994, 1996-1997 and 1999-2001.

TABLE 5.5
Excess capacity and full-utilization levels of variable inputs per vessel in the Atlantic Ocean purse-seine fishery

Year

Number of vessels

Observed

Full-utilization

Excess Capacity (tonnes)

Fishing days

Searching days

Fishing days

Searching days

YFT

SKJ

BET

ALB

Others

Total

1991

71

220

193

246

224

60

0

256

30

29

374

1992

65

269

244

269

244

0

580

218

0

39

837

1993

64

257

229

269

245

89

0

24

15

40

167

1994

59

270

241

2702

247

52

149

0

15

26

242

1995

55

269

238

274

249

49

125

64

21

27

287

1996

54

272

243

275

249

73

372

50

23

0

518

1997

52

246

222

276

250

313

762

191

23

18

1305

1998

44

286

255

286

255

85

606

130

3

0

824

1999

41

286

258

286

258

385

0

0

0

0

385

2000

41

258

229

286

258

245

298

44

6

6

599

2001

44

258

230

286

255

0

505

99

12

14

630

2002

41

240

215

286

258

0

706

32

5

24

768

Annual average

53

259

232

274

248

104

322

100

14

21

560


FIGURE 5.2
Annual and average annual excess capacity relative to all species caught in the Indian Ocean purse-seine fishery

5.2.2 The Atlantic Ocean fishery

In the Atlantic Ocean fishery, a vessel had, on average, the capability to harvest an additional 322 tonnes of skipjack and 104 tonnes of yellowfin per year (Table 5.5). The total average annual excess capacity per vessel between 1991 and 2002 was 560 tonnes. They could do this by operating efficiently and making small increases in their fishing and searching days (the average annual number of fishing and searching days per vessel for the Atlantic fleet between 1991 and 2002 were, respectively, 259 and 232 days; the average annual level of fishing and searching days per vessel required to produce the capacity output were, respectively, 274 and 248 days). In general, the Atlantic Ocean purse-seine fleet could realize capacity output mostly by improving its efficiency (Table 5.6). The measure of CU adjusted for TE is quite close to one for most species and years, which indicates that gains in output could come mostly from operating more efficiently. The non-parametric Kruskal-Wallis test was conducted to determine the equality of observed and full-utilization levels of fishing and searching days; the equality was rejected at the 5-percent level of significance for both fishing and searching days, which implies that producing the capacity output would require an increase in fishing and searching days. The CU values were quite low for other species and albacore, which is the likely reason why the observed number of fishing and searching days were not equivalent to the levels required to produce the capacity output.

TABLE 5.6
Capacity utilization in terms of ratio of observed and technically-efficient output levels to capacity output levels in the Atlantic Ocean purse-seine fishery

Year

Capacity utilization - Observed/Reported output

Capacity utilization - Technically-efficient output

YFT

SKJ

BET

ALB

Others

YFT

SKJ

BET

ALB

Others

1991

0.96

1.00

0.44

0.17

0.46

0.96

1.00

0.95

0.70

1.00

1992

1.00

0.70

0.56

1.00

0.33

1.00

1.00

1.00

1.00

1.00

1993

0.94

1.00

0.95

1.00

0.33

0.98

1.00

1.00

0.86

1.00

1994

0.97

0.92

1.00

0.55

0.59

1.00

1.00

1.00

0.98

1.00

1995

0.97

0.94

0.88

0.26

0.61

1.00

1.00

0.99

0.95

1.00

1996

0.95

0.81

0.950

0.17

1.00

1.00

1.00

1.00

0.97

1.00

1997

0.81

0.60

0.62

0.09

0.75

0.98

0.91

0.89

0.77

0.86

1998

0.95

0.68

0.69

0.680

1.00

1.00

1.00

1.00

0.99

1.00

1999

0.79

1.00

1.00

1.00

1.00

1.00

1.00

1.00

1.00

1.00

2000

0.86

0.84

0.8

0.12

0.87

1.00

0.84

0.94

0.43

0.87

2001

1.00

0.73

0.76

0.04

0.80

1.00

0.88

0.96

0.74

0.80

2002

1.00

0.62

0.92

0.15

0.50

1.00

0.62

0.92

0.15

0.50

Annual average

0.93

0.82

0.80

0.41

0.99

0.9

0.94

0.97

0.80

0.92

TABLE 5.7
Observed and full utilization fishing and searching days required to produce the capacity output in the Atlantic Ocean purse-seine fishery

Year

Number of vessels

Observed Levels

Full-utilization levels

Fishing days

Searching days

Fishing days

Searching days

1991

71

15 633

13 709

17 454

15 886

1992

65

17 454

15 886

17 454

15 886

1993

64

16 425

14 674

17 216

15 665

1994

59

15 904

14 231

16 023

14 559

1995

55

14 786

13 086

15 069

13 674

1996

54

14 671

13 116

14 831

13 453

1997

52

12 781

13 011

14 354

13 011

1998

44

12 585

11 215

12 585

11 242

1999

41

11 731

10 578

11 731

10 578

2000

41

10 576

9 394

11 731

10 578

2001

44

11 344

10 121

12 585

11 242

2002

41

9 823

8 816

11 731

10 578

Annual average

53

13 643

12 198

14 397

13 029

In addition to improved efficiency in operations, the average annual capacity output for the fleet could be realized with only a very modest increase in fishing and searching days (Table 5.7). The analysis suggests that fishing days should be increased by a meagre 5.5 percent to realize the capacity output, and the number of days spent searching by the fleet should be increased by only 6.8 percent.

5.2.3 The Indian Ocean fishery

In the Indian Ocean fishery, a vessel had, on average, the capability to harvest an additional 504 tonnes of skipjack and 616 tonnes of yellowfin per year (Table 5.8), both of which are considerably greater than the levels of excess capacity for these two species in the Atlantic Ocean fishery. The total average annual excess capacity per vessel for 1981-2002 was 1 327 tonnes. Vessels could realize the capacity output mostly by operating efficiently and making small increases in their fishing and searching days (the average annual numbers of fishing and searching days per vessel for the Indian Ocean fleet for 1981-2002 were, respectively, 224 and 185 days; the average annual level of fishing and searching days per vessel required to produce the capacity output were, respectively, 242 and 199 days). In general, the Indian Ocean purse-seine fleet could realize capacity output mostly by improving its efficiency (Table 5.9). The measure of CU adjusted for TE is quite close to one for most species and years, which indicates that gains in output could come mostly from operating more efficiently. The Kruskal-Wallis test was again conducted to determine the equality of observed and full-utilization levels of fishing and search days in the Indian Ocean fishery; results of the test could not reject the equality of reported and full utilization fishing and searching days. In other words, based on the non-parametric analysis, we conclude that the number of fishing and searching days required to produce the capacity output is equal to the reported or actual number of fishing and searching days. The exception is 1982, when the CU values were extremely low for yellowfin (0.51) and skipjack (0.68). The number of fishing and searching days would have had to increase 83.2 and 62.4 percent, respectively. Alternatively, we conclude that the capacity output could be realized mostly by improvements in TE only. In contrast to the Atlantic Ocean fishery, the CU values were quite high for other species and albacore.

TABLE 5.8
Excess capacity and full-utilization levels of variable inputs per vessel in the Indian Ocean purse-seine fishery

Year

Number of vessels

Observed levels

Full-utilization

Excess capacity (tonnes)

Fishing days

Searching days

Fishing days

Searching days

YFT

SKJ

BET

ALB

Others

Total

1981

2

42

0

42

0

0

0

NA

0

NA

0

1982

4

64

55

117

90

574

484

80

0

0

1 138

1983

12

122

95

122

95

0

0

68

0

0

68

1984

47

471

138

233

185

768

891

191

29

0

1 879

1985

48

207

173

242

193

860

870

181

32

0

1 943

1986

35

246

197

246

197

114

150

0

38

0

303

1987

35

236

185

236

188

324

373

0

49

0

746

1988

40

228

181

243

202

0

490

57

56

0

603

1989

44

247

205

247

205

917

0

185

64

0

1 166

1990

46

231

193

249

207

658

893

219

63

0

1 832

1991

39

250

205

251

208

464

592

141

17

69

1 284

1992

39

255

209

269

224

585

627

317

0

0

1 529

1993

42

265

222

282

238

507

734

285

53

0

1 578

1994

42

263

220

282

238

607

35

244

22

85

993

1995

42

282

238

282

238

0

129

26

54

0

209

1996

47

263

224

282

238

561

1 050

152

51

65

1 879

1997

58

257

223

282

238

940

2 011

154

50

101

3 255

1998

53

276

239

282

238

1 272

1 513

199

58

0

3 041

1999

52

257

219

282

238

644

835

0

73

87

1 638

2000

50

253

213

282

238

340

817

174

60

51

1 443

2001

50

258

220

282

238

666

1 060

295

59

95

2 175

2002

49

263

221

282

238

298

0

135

69

0

501

Annual average

40

224

185

242

199

504

616

141

41

25

1 327

TABLE 5.9
Capacity utilization in terms of ratio of observed and technically-efficient output levels to capacity output levels in the Indian Ocean purse-seine fishery

Year

Capacity utilization - Observed/Report output

Capacity utilization - Technically-efficient output

YFT

SKJ

BET

ALB

Others

YFT

SKJ

BET

ALB

Others

1981

1.00

1.00

1.00

NA

NA

1.00

1.00

1.00

NA

NA

1982

0.31

0.35

0.02

NA

NA

0.51

0.68

0.91

NA

NA

1983

1.00

1.00

0.21

NA

NA

1.00

1.00

1.00

NA

NA

1984

0.61

0.50

0.28

0.9

NA

0.97

0.98

0.99

1.00

NA

1985

0.61

0.57

0.41

0.32

NA

1.00

1.00

1.00

1.00

NA

1986

0.94

0.92

1.00

0.12

NA

1.00

1.00

1.00

1.00

NA

1987

0.87

0.84

1.00

0.12

NA

1.00

1.00

1.00

1.00

NA

1988

1.00

0.81

0.86

0.11

NA

1.00

0.99

1.00

1.00

NA

1989

0.68

1.00

0.55

01.00

NA

1.00

1.00

1.00

1.00

NA

1990

0.77

0.68

0.51

1.00

NA

0.99

0.99

1.00

1.00

NA

1991

0.84

0.840

0.70

0.78

001

1.00

1.00

1.00

1.00

1.00

1992

0.80

0.81

0.40

1.00

NA

0.99

1.00

1.00

1.00

NA

1993

0.83

0.79

0.51

0.37

NA

0.99

1.00

1.00

1.00

NA

1994

0.79

0.99

0.57

0.73

01.00

0.98

1.00

1.00

1.00

1.00

1995

1.00

0.96

0.95

0.36

NA

1.00

1.00

1.00

1.00

NA

1996

0.81

0.72

0.75

0.39

0.390

0.98

1.00

1.00

1.00

1.00

1997

0.68

0.51

0.77

0.40

0.03

0.98

1.00

1.00

1.00

1.00

1998

0.57

0.62

0.570

0.31

NA

1.00

1.00

1.00

1.00

NA

1999

0.78

0.780

1.00

0.12

0.16

0.98

1.00

1.00

1.00

1.00

2000

0.88

0.81

0.75

0.28

0.52

0.97

0.98

0.98

0.99

0.98

2001

0.77

0.75

0.57

0.29

01.00

0.98

1.00

1.00

1.00

1.00

2002

0.90

1.00

0.80

0.17

1.00

0.98

1.00

1.00

1.00

1.00

Annual average

0.79

0.78

0.65

0.28

1.00

0.97

0.98

0.99

1.00

1.00

TABLE 5.10
Observed and full-utilization fishing and searching days required to produce the capacity output in the Indian Ocean purse-seine fishery

Year

Number of vessels

Observed levels

Full-utilization levels

Fishing days

Searching days

Fishing days

Searching days

1981

2

84

0

84

0

1982

4

256

221

469

359

1983

12

1 461

1 142

1 461

1 142

1984

47

8 041

6 502

10 951

8 700

1985

48

9 929

8 302

11 636

9 287

1986

35

8 597

6 907

8 597

6 907

1987

35

8 246

6 484

8 246

6 568

1988

40

9 135

7 244

9 734

8 072

1989

44

10 880

9 030

10 880

9 030

1990

46

10 628

8 880

11 451

9 522

1991

39

9 767

7 985

9 795

8 127

1992

39

9 944

8 162

10 499

8 755

1993

42

11 109

9 342

11 848

10 004

1994

42

11 061

9 228

11 848

10 004

1995

42

11 848

10 004

11 848

10 004

1996

47

12 380

10 510

13 259

11 195

1997

58

14 883

12 930

16 362

13 815

1998

53

14 648

12 667

14 951

12 624

1999

52

13 339

11 363

14 669

12 386

2000

50

12 635

10 657

14 105

11 910

2001

50

12 911

10 978

14 105

11 910

2002

49

12 864

10 851

13 823

11 671

Annual average

40

9 757

8 154

10 483

8 727

Although results from the Kruskal-Wallis test suggest that realizing the capacity output requires only improvements in TE, there is still the possibility that gains could be realized by very small increases in fishing and searching days (Table 5.10). The analyses suggest that fishing days should be increased by a meagre 7.4 percent to realize the capacity output, and the number of days spent searching by the fleet should be increased by only seven percent.

5.3 Summary and conclusions

Overall, it appears that there is excess capacity in the Atlantic and Indian Ocean purse-seine fisheries for tuna. The more serious level of excess capacity exists for the Indian Ocean fishery. It was determined that, on an annual basis, there was approximately 61 000 tonnes of excess capacity in the Indian Ocean fishery. In comparison, the Atlantic Ocean fishery had approximately 29 500 tonnes of excess harvesting capacity. Alternatively, if Indian and Atlantic Ocean vessels operated efficiently, fully utilized their variable inputs and harvested the average annual reported level of landings, fleet sizes could be reduced, respectively, from 40 to 31 (22.5 percent) in the Indian Ocean fishery and from 53 to 46 (13.2 percent) in the Atlantic Ocean fishery.

FIGURE 6.1
Skipjack in the global purse-seine fishery - Excess fishing capacity


FIGURE 6.2
Skipjack in the global purse-seine fishery - Observed catch, fishing capacity and fishing capacity purged for technical efficiency


FIGURE 6.3
Yellowfin and bigeye combined in the global purse-seine fishery - Excess fishing capacity

We stress that the estimates presented in this paper are extreme lower-bound estimates of capacity. The limited number of observations and inadequate information for considering different modes and nations' fishing activities limits the estimation of the frontier or piece-wise technology. Alternatively, if there are few observations for estimating the frontier, DEA will tend to recognize each firm as being technically efficient and operating at full capacity. In this case, the observed or reported output will equal the technically-efficient output level and the capacity output level.


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