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3. The purse-seine fishery for tunas in the Eastern Pacific Ocean


In this section we focus attention on the purse-seine fishery for tunas in the EPO. We find that excess capacity exists for the EPO fishery with respect to yellowfin (YFT), skipjack (SKJ) and bigeye (BET) tunas caught in sets on dolphins, sets on floating objects and sets on unassociated schools.

3.1 Data and methodology

Capacity output, capacity output adjusted for TE and CU rates (observed output divided by CU or observed output divided by capacity output adjusted for TE) are estimated by DEA. We attempted to estimate the output-oriented non-radial method of Russell (1985), but the results were unsatisfactory. We instead estimated the output-oriented radial expansion approach, whereby all outputs were kept in fixed proportions as they were expanded, holding fixed factors constant and with full utilization of variable inputs. The CU rates are thus ray measures (Segerson and Squires, 1990).

The set- and vessel-level purse-seine data from the EPO tuna fishery were provided by the Inter-American Tropical Tuna Commission (IATTC) for 1980-2002. These data, by set and vessel, included landings of yellowfin, bigeye and skipjack tunas, vessel GRT and other measures of vessel size (cubic meters, net weight, or length, weight and depth in metres), trip lengths (days, arrival date minus departure date for trip), number of sets. Total is catch in tonnes, and is derived from observer data (or logbook data when observer date not available) raised to unloaded weight. All of these data were differentiated by mode of fishing, i.e. sets on fish associated with dolphins, sets on floating objects and sets on unassociated schools. The data were also differentiated by vessel size class (carrying capacity in tonnes) as follows: (1) 0-45 tonnes; (2) 45-91 tonnes; (3) 92-181 tonnes; (4) 182-272 tonnes; (5) 273-363 tonnes; (6) >363 tonnes. Biomass estimates for yellowfin, bigeye and skipjack tunas were provided by the IATTC (Maunder, 2003 personal communication; also see Maunder, 2002; Harley and Maunder, 2004 and Maunder and Harley, 2004).[19] Monthly sea-surface temperature data were obtained from Rayner et al. (2003) for 5°N to 20°N between the coast of the Americas and 120°W to try to capture environmental influences.

Estimates of capacity outputs, allowing for variable returns to scale[20], were made at the set and vessel level by mode of fishing (dolphin, unassociated or floating object). Data for yellowfin and bigeye tunas were combined to reduce the number of zero-valued observations of bigeye (which is troublesome to the operation of the DEA program). Output or retained catches in the analysis was specified by species and method of harvest per set as follows: (1) yellowfin and bigeye tuna caught in sets made on dolphins; (2) yellowfin and bigeye tuna caught in sets made on unassociated schools; (3) yellowfin and bigeye tuna caught in sets made on floating objects; (4) skipjack tuna caught in sets made on dolphins; (5) skipjack caught in sets made on unassociated schools; and (6) skipjack caught in sets made on floating objects. The retained catches of other fish were negligible, and hence not considered in the analysis. The analysis estimated capacity output for all six outputs and three types of fishing, specifying a common harvesting frontier (i.e. the DEA models were run with all six outputs at once, rather than separately for each of the three types of fishing). To be able to accurately estimate capacity output by individual vessel for each of the different types of fishing, each of the six outputs in the DEA model were specified as average landings per vessel per set per year.

Biomass estimates for yellowfin and skipjack were used to specify stock conditions, with sea-surface temperature used to account for environmental conditions. Both of these variables were specified as non-discretionary or fixed (constrained) inputs. The capital stock or capacity base of an individual vessel was captured by the GRT to allow for consistency with specifications for the other tuna purse-seine fisheries.

Although data were provided for 1980-2002, capacity output estimates were made only for 1998-2002. Limiting the analysis to the five most recent years captures more recent fleet configurations, cost conditions and fishing patterns, and also helps to control for the potential shifts in capacity output due to technical change. Limiting the number of years of analysis thus leaves differences in TE and variable input usage as the determinants of differences in observed output from capacity output (Färe, Grosskopf and Kokkelenberg, 1989). In addition, the technological-economic approach to capacity output is predicated on "normal practice" or "normal operating conditions" among the vessels, which is better given when the number of years is limited (cf. Corrado and Mattey, 1997).

Capacity output and TE were estimated separately for each of the following vessel size groupings: (i) classes 2 and 3 with 28 vessels; (ii) classes 4 and 5 with 43 vessels and (iii) class 6 with 188 vessels. There were no class-1 vessels in the data set. Classes 2 and 3 and classes 4 and 5 were combined to provide an acceptable minimum level of observations in each grouping.[21] The full five years of data were available for only 50 vessels.

The technological-economic measure of capacity output specifies full utilization of variable inputs. However, estimates of TE by DEA were made using the number of sets per vessel by each type of fishing by year as the variable input.

Estimates of ray CU, in which deviations from full CU are due to either low variable input usage or technical inefficiency, are given by q in problem [1]. Estimates of ray CU purged for the effects of TE were given by the ratio q2/q1, where q2 is derived from problem [1], allowing for variable inputs that are not necessarily fully utilized and q1 is the q in problem [1] when variable inputs are fully utilized (Färe, Grosskopf and Kokkelenberg, 1989). Thus, estimates of ray CU purged for the effects of TE are due to low variable input usage. As noted above, we have attempted to control for deviations from full ray CU due to technical change in the later years by limiting the analysis to the last five years. We also attempted to control for deviations from full ray CU due to fluctuations in resource abundance and environmental conditions (which shift the capacity output frontier in or out) by specifying biomass and sea-surface temperature.

TABLE 3.1
Data used to estimate capacity for Class-2 and -3 vessels in the tuna purse-seine fishery of the EPO

Year

Set type

GRT

No. of vessels

Trip length (days)

Total no. of sets

Total landing (tonnes)

Yellowfin and bigeye

Skipjack

Total

By year

1998

All

148

68

10 608

2 907

8 260

6 663

14 923

1999

All

152

63

10 397

2 655

17 678

10 796

28 474

2000

All

146

64

11 939

3 233

10 028

13 564

23 591

2001

All

161

51

10 410

2 481

13 759

7 500

21 258

2002

All

167

53

7 918

1 625

5 920

6 325

12 245

By year and set type

2000

Dolphin

68

1

250

1

0

18

18

1998

Unassociated

153

25

5 539

2 370

6 839

4 271

11 110

1999

Unassociated

150

32

5 667

2 405

15 548

8 269

23 817

2000

Unassociated

153

32

6 336

2 946

9 115

10 590

19 705

2001

Unassociated

168

26

5 537

1 880

8 376

3 778

12 154

2002

Unassociated

172

25

4 178

1 248

4 853

5 045

9 898

1998

Floating object

158

19

4 323

537

1 421

2 392

3 813

1999

Floating object

161

23

4 259

250

2 131

2 527

4 658

2000

Floating object

148

25

5 134

286

913

2 955

3 868

2001

Floating object

154

21

4 724

601

5 383

3 722

9 104

2002

Floating object

169

22

3 527

377

1 067

1 279

2 347

Source: Inter-American Tropical Tuna Commission.
Note: There were no reported dolphin sets by Class-2 and -3 vessels in 1998, 1999, 2001 or 2002.

TABLE 3.2
Data used to estimate capacity for Class-4 and -5 vessels in the tuna purse-seine fishery of the EPO

Year

Set type

GRT

No. of vessels

Trip length (days)

Total no. of sets

Total landing (tonnes)

Yellowfin and bigeye

Skipjack

Total

By year

1998

All

374

47

9 869

2 742

11 686

12 100

23 786

1999

All

350

50

8 560

2 655

22 858

17 153

40 011

2000

All

319

53

10 059

3 162

13 780

21 089

34 869

2001

All

377

63

11 749

3 100

26 301

10 722

37 022

2002

All

406

73

13 805

4 450

30 295

16 764

47 058

By year and set type

2002

Dolphin

454

1

217

11

0

160

160

1998

Unassociated

366

23

5 075

2 269

7 659

9 588

17 248

1999

Unassociated

343

27

4 995

2 433

13 464

20 395

33 859

2000

Unassociated

318

27

5 739

2 867

16 824

12 015

28 839

2001

Unassociated

383

33

6 557

2 629

7 724

20 862

28 587

2002

Unassociated

410

38

7 633

3 850

12 363

26 513

38 876

1998

Floating object

401

20

4 369

473

4 440

2 098

6 538

1999

Floating object

387

18

3 237

222

3 689

2 463

6 152

2000

Floating object

334

21

4 287

295

4 265

1 765

6 030

2001

Floating object

388

25

5 081

471

2 997

5 439

8 436

2002

Floating object

429

30

5 913

589

4 400

3 622

8 023

Source: Inter-American Tropical Tuna Commission.
Note: There were no reported dolphin sets by Class-4 or -5 vessels between 1998 and 2001.

TABLE 3.3
Data used to estimate capacity for Class-6 vessels in the tuna purse-seine fishery of the EPO

Year

Set type

GRT

No. of vessels

Trip length (days)

Total no. of sets

Total landing (tonnes)

Yellowfin and bigeye

Skipjack

Total

By year

1998

All

1 036

362

88 984

21 211

279 749

119 093

398 842

1999

All

1 081

366

78 845

1 7528 2

296 782

231 517

528 299

2000

All

1 116

366

80 958

18 198

320 733

169 121

489 854

2001

All

1 119

323

71 755

17 477

376 226

116 751

492 977

2002

All

1 179

333

77 196

20 37719

395 408

134 087

529 495

By year and set type

1998

Dolphin

1 025

81

10 942

19 863

1 58 868

5 044

163 912

1999

Dolphin

1 060

91

8 709

20 456

143 775

1 758

145 533

2000

Dolphin

1 136

91

8 876

20 033

1 50 934

387

151 321

2001

Dolphin

1 018

73

9 130

14 438

221 481

1 668

223 149

2002

Dolphin

1 073

77

11 169

15 761

278 318

2 841

281 159

1998

Unassociated

1 053

127

4 742

30 789

60 188

13 596

73 784

1999

Unassociated

1 087

133

6 063

28 039

60 794

52 819

113 613

2000

Unassociated

1 113

134

5 597

29 294

49 656

54 908

104 564

2001

Unassociated

1 141

127

3 041

28 904

49 476

7 834

57 310

2002

Unassociated

1 182

130

3 235

30 747

41 343

16 658

58 002

1998

Floating object

1 054

122

5 476

30 098

60 005

100 277

160 282

1999

Floating object

1 102

128

4 934

27 230

91 898

176 791

268 689

2000

Floating object

1 127

125

3 703

28 207

119 971

113 076

233 047

2001

Floating object

1 178

132

5 296

26 268

104 908

107 224

212 132

2002

Floating object

1 202

110

5 960

27 497

75 410

114 491

189 901

Source: Inter-American Tropical Tuna Commission.

Annual capacity output on a per-set and per-vessel basis was estimated and subsequently converted to total annual fleet activity for each vessel size class by multiplying the per-vessel and per-set estimates of capacity output by the number of vessels and sets in each year for each vessel size class.

Technological change can also increase fishing capacity. To begin to evaluate the effects of technical change, we estimate a Malmquist index of technological change for the Class-6 vessels, which gives us balanced panel data set of nine years with total number of data for 128 vessels for all three set types. We estimate the Malmquist index DEA model with constant-returns-to-scale, which basically uses the same output-oriented DEA model as that in our capacity estimation, with number of sets as variable input and the interaction term of number of sets and gross weight of the vessel added as another input. This gives a flow measure of capital services for the vessel, engine and gear. Four CU rates (also called output distance in this methodology) are calculated. We provide annual year-to-year estimates and chain or cumulative indices over the nine years.

3.2 Results

3.2.1 Overall levels of capacity in the tuna purse-seine fishery of the eastern Pacific Ocean

The results of the analysis indicates that substantial excess fishing capacity, defined as fishing capacity output minus observed output (retained catches), when measured as: (1) potential catch minus actual catch or (2) potential catch, purged for TE, minus actual catch exists for:

FIGURE 3.1
Excess fishing capacity and excess fishing capacity purged for technical efficiency for the purse-seine fishery for skipjack in the EPO


FIGURE 3.2
Observed catch, fishing capacity and fishing capacity purged for technical efficiency for the purse-seine fishery for skipjack in the EPO


FIGURE 3.3
Excess fishing capacity and excess fishing capacity purged for technical efficiency for the purse-seine fishery for yellowfin and bigeye combined in the EPO

In short, tuna purse-seine vessels had the capacity to catch substantially more of all species during 1998-2002 than they actually caught. The greatest contributor, by far, to excess capacity was Class-6 vessels, although there was excess capacity for Classes 2-3 and 4-5 vessels as well (Table 3.5). Excess capacity for all species combined, purged for TE, fluctuated from a minimum of 120 420 tonnes in 1998 to a maximum of 208 162 tonnes in 1999, dipping in 2000 and steadily rising to 193 199 tonnes in 2001 and to 196 178 tonnes in 2002 (Figures 3.5 and 3.6). Across all vessels it is estimated, after accounting for TE, that during 1998-2002 the combined catches of yellowfin and bigeye could have been 33 percent greater (Table 3.5, Figures 3.3 and 3.4) while those of skipjack could have been be 29 percent greater (Table 3.5, Figures 3.1 and 3.2).

The CU rates for all species combined also indicate substantial excess capacity, defined as capacity output minus observed output, regardless of whether TE is purged (Table 3.7). (CU is defined as observed output divided by capacity output. CU ranges from 0 to 1, where 0 indicates no observed output and 1 indicates that observed output equals capacity output.) The CU for Class 2-3 vessels, purging TE from capacity output, averaged 67 percent, i.e. on average a vessel caught about two-thirds of its potential catch. Across all Class 2-3 vessels it is estimated, after accounting for TE, that the combined catches of yellowfin and bigeye could have been 51 percent greater, while those of skipjack could have been 39 percent greater (Table 3.5). The CU for Class 4-5 vessels, purging TE from capacity output, averaged 72 percent; i.e. on average a vessel caught slightly less than three-quarters of its potential catch. Across all Class 4-5 vessels it is estimated, after accounting for TE combined, that the combined catches of yellowfin and bigeye could have been 10 percent greater, while those of skipjack could have been 28 percent greater (Table 3.5). The CU for Class-6 vessels, purging TE from capacity output, averaged 75 percent, i.e. on average a vessel caught about three-quarters of its potential catch. Across all Class-6 vessels it is estimated, after accounting for TE, that the combined catches of yellowfin and bigeye could have been 34 percent greater, while those of skipjack could have been 29 percent greater (Table 3.5).

FIGURE 3.4
Observed catch, fishing capacity and fishing capacity purged for technical efficiency for the purse-seine fishery for yellowfin and bigeye combined in the EPO


FIGURE 3.5
Excess fishing capacity and excess fishing capacity purged for technical efficiency for the purse-seine fishery for all species combined in the EPO


FIGURE 3.6
Observed catch, fishing capacity and fishing capacity purged for technical efficiency for the purse-seine fishery for all species combined in the EPO

Excess capacity exists for all vessel size classes combined for all set types for yellowfin and bigeye tuna when measured as either: (1) potential catch, purged for TE, minus actual catch (Table 3.5, Figure 3.3), or as (2) potential catch, purged for TE, minus the combined AMSYs for both yellowfin and bigeye (Tables 3.6, Figure 3.7). Excess capacity for yellowfin and bigeye tuna vis-à-vis their combined AMSY was relatively small in 1998 at 37 167 tonnes, i.e. capacity output, purged for TE, was 37 167 tonnes, or almost 11 percent more than the combined AMSYs. Capacity output, purged for TE, rose to 92 518 tonnes, or almost 27 percent more than the combined AMSY in 1999. In 2000, capacity output, purged for TE, decreased slightly to 89 704 tonnes, or almost 26 percent more than the combined AMSYs. By 2001, however, capacity output, purged for TE, rose to 210 915 tonnes, or almost 61 percent more than the combined AMSYs. In 2002, capacity output, purged for TE, rose to 241 835 tonnes, or almost 70 percent more than the combined AMSYs. In all cases, Class-6 vessels contributed the lion's share of the excess capacity.

In summary, by 2002 tuna purse-seine vessels had the capacity to harvest almost 70 percent more than the AMSYs for yellowfin and bigeye combined.

TABLE 3.4
Reported catch, estimated capacity and capacity purged for technical efficiency for the purse-seine fishery in the EPO.

Vessel class

Year

Reported catch (tonnes)

Skipjack

Yellowfin and bigeye

Dolphin

Unassociated

Floating objects

Dolphin

Unassociated

Floating objects

Classes 2 and 3

1998


6 012

2 201

---

7 663

2 126

1999


6 444

1 992

---

7 303

1 361

2000

18

5 817

2 317

0

9 664

2 041

2001


6 467

1 696

---

10 230

779

2002


5 934

1 415

---

8 306

1 567

Av.

18

6 135

1 924

0

8 633

1 575

Classes 4 and 5

1998


7 659

4 440

---

9 588

2 098

1999


13 464

5 172

---

20 395

3 076

2000


16 824

4 265

---

12 015

1 765

2001


7 724

2 997

---

20 862

5 439

2002

0

12 330

4 272

160

26 431

3 622

Av.

0

11 600

4 229

160

17 858

3 200

Class 6

1998

5 044

13 596

100 277

158 868

60 188

60 005

1999

1 758

52 819

175 308

143 775

60 794

91 285

2000

387

54 908

113 076

150 934

49 656

119 971

2001

1 585

7 673

105 875

216 583

48 180

103 634

2002

2 763

15 893

113 021

272 926

40 211

74 840

Av.

2 307

28 978

121 511

188 617

51 806

89 947


Vessel class

Year

Fishing capacity (tonnes)

Skipjack

Yellowfin and bigeye

Dolphin

Unassociated

Floating objects

Dolphin

Unassociated

Floating objects

Classes 2 and 3

1998

---

11 801

4 977

---

21 322

5 394

1999

---

14 715

4 360

---

18 065

4 948

2000

18

13 347

4 725

0

22 024

4 638

2001

---

11 200

4 100

---

16 981

2 471

2002

---

12 619

3 959

---

16 493

4 507

Av.

18

12 736

4 424

0

18 977

4 392

Classes 4 and 5

1998

---

16 858

8 167

---

20 140

4 395

1999

---

18 775

6 334

---

26 523

3 517

2000

---

23 603

5 690

---

13 006

2 017

2001

---

11 933

4 578

---

27 631

7 499

2002

0

15 861

6 168

160

28 525

4 406

Av.

0

17 406

6 188

160

23 165

4 367

Class 6

1998

8 341

27 241

215 115

300 663

110 248

127 811

1999

2 364

75 097

283 217

207 942

86 925

149 876

2000

525

79 842

151 329

222 651

75 926

158 323

2001

2 593

10 843

161 598

347 537

72 673

160 706

2002

4 241

22 619

160 512

451 035

61 137

104 007

Av.

3 613

43 128

194 354

305 965

81 382

140 145


Vessel class

Year

Fishing capacity purged for technical efficiency (tonnes)

Skipjack

Yellowfin and bigeye

Dolphin

Unassociated

Floating objects

Dolphin

Unassociated

Floating objects

Classes 2 and 3

1998

---

8 348

4 266

---

15 749

7 465

1999

---

9 768

2 470

---

11 580

5 096

2000

18

8 475

2 674

0

13 150

5 652

2001

---

7 759

1 615

---

12 494

4 356

2002

---

7 756

2 168

---

10 682

4 538

Av.

18

8 421

2 638

0

12 731

5 421

Classes 4 and 5

1998

---

9 915

6 159

---

11 682

2 886

1999

---

17 945

6 125

---

23 937

3 366

2000

---

21 242

5 380

---

11 768

1 878

2001

---

10 448

4 023

---

24 616

6 373

2002

0

14 622

5 467

160

25 242

4 059

Av.

0

14 834

5 431

160

19 449

3 713

Class 6

1998

6 287

17 281

125 844

200 974

73 840

73 756

1999

2 205

66 485

249 450

187 020

76 618

133 513

2000

499

71 140

132 170

200 407

66 451

139 363

2001

2 255

9 674

139 122

307 197

64 133

140 473

2002

3 796

19 520

138 517

399 297

53 821

92 393

Av.

3 008

36 820

157 020

258 979

66 973

115 900

 

Note: Actual output (retained catches in tonnes) from Inter-American Tropical Tuna Commission.

TABLE 3.5
Reported catch, estimated excess capacity and excess capacity purged for technical efficiency for the purse-seine fishery of the EPO

Vessel class

Year

Reported catch

Excess fishing capacity

Excess fishing capacity purged for technical efficiency

Skipjack

Yellowfin and bigeye

Skipjack

Yellowfin and bigeye

Skipjack

Yellowfin and bigeye

tonnes

tonnes

tonnes

%

tonnes

%

tonnes

%

tonnes

%

Classes 2 and 3

1998

8 213

9 789

8 565

(104)

16 927

(173)

3 335

(41)

10 225

(104)

1999

8 436

8 664

10 639

(126)

14 350

(166)

3 957

(47)

5 386

(62)

2000

8 152

11 705

9 938

(122)

14 958

(128)

3 318

(41)

4 120

(35)

2001

8 163

11 009

7 137

(87)

8 443

(77)

2 337

(29)

3 101

(28)

2002

7 349

9 873

9 229

(126)

11 127

(113)

2 778

(38)

2 976

(30)

Average

8 077

10 208

9 102

(113)

13 161

(129)

3 145

(39)

5 161

(51)


Classes 4 and 5

1998

12 099

11 686

12 926

(107)

12 849

(110)

3 974

(33)

2 882

(25)

1999

18 636

23 471

6 473

(35)

6 569

(28)

5 434

(29)

3 833

(16)

2000

21 089

13 780

8 204

(39)

1 244

(9)

5 532

(26)

-134

-(1)

2001

10 721

26 301

5 789

(54)

8 829

(34)

3 749

(35)

4 688

(18)

2002

16 602

30 213

5 427

(33)

2 878

(10)

3 487

(21)

-752

-(2)

Average

15 829

21 218

7 764

(49)

6 474

(31)

4 435

(28)

2 103

(10)


Class 6

1998

118 917

279 061

131 781

(111)

259 661

(93)

30 495

(26)

69 509

(25)

1999

229 885

295 854

130 793

(57)

148 890

(50)

88 255

(38)

101 298

(34)

2000

168 371

320 561

63 325

(38)

136 339

(43)

35 438

(21)

85 659

(27)

2001

115 133

368 397

59 900

(52)

212 519

(58)

35 918

(31)

143 406

(39)

2002

131 677

387 977

55 695

(42)

228 201

(59)

30 155

(23)

157 534

(41)

Average

152 796

330 370

88 299

(58)

197 122

(60)

44 052

(29)

111 481

(34)


All vesselsa

1998

139 229

300 536

153 272

(110)

289 437

(96)

37 804

(27)

82 616

(27)

1999

256 957

327 989

147 905

(58)

169 809

(52)

97 646

(38)

110 517

(34)

2000

197 612

346 046

81 467

(41)

152 541

(44)

44 288

(22)

89 645

(26)

2001

134 017

405 707

72 826

(54)

229 791

(57)

42 004

(31)

151 195

(37)

2002

155 628

428 063

70 351

(45)

242 206

(57)

36 420

(23)

159 758

(37)

Average

176 702

361 796

105 165

(60)

216 757

(60)

51 632

(29)

118 745

(33)

Notes: Excess capacity output is defined as capacity output less observed output (landings) in tonnes. Actual output (landings in tonnes) from Inter-American Tropical Tuna Commission.

3.2.2 The fishery by class-2 and -3 vessels

FIGURE 3.7
Combined AMSYs vs. fishing capacity purged for technical efficiency for the purse-seine fishery for yellowfin and bigeye in the EPO

Potential catch exceeds actual catch for sets on unassociated schools and on floating objects for Class-2 and -3 vessels, i.e. there is excess capacity, regardless of whether capacity output is purged for TE (Table 3.4). (There were no dolphin sets for Class-2 or -3 vessels.) When TE is purged from capacity output for yellowfin and bigeye, this excess capacity is comparatively greater for sets on unassociated schools than for sets on floating objects, with an annual average about four times greater. Excess capacity for all set types for Class-2 and -3 vessels has been declined steadily during 1998-2002.

FIGURE 3.8
Annual year-to-year technical change class 6 vessels, all set types and species, 1994-2002


FIGURE 3.9
Cumulative (chained) technical change class 6 vessels, all set types and species, 1994-2002

3.2.3 The fishery by class-4 and -5 vessels

Potential catch exceeds actual catch for sets on unassociated schools and on floating objects for Class-4 and -5 vessels, i.e. there is excess capacity, regardless of whether capacity output is purged for TE (Table 3.4). (There was a negligible number of dolphin sets for this size category.) When capacity output is purged for TE for yellowfin and bigeye, this excess capacity is comparatively greater for sets on unassociated schools than for sets on floating objects, with an annual average about three times greater. For skipjack, this excess capacity also averages three times greater for sets on unassociated schools than for sets on floating objects. Excess capacity over all set types averages about three times greater for sets on unassociated schools than for sets on floating objects. The trend for excess capacity for all set types has been roughly downward during 1998-2002, but with considerable variability.

3.2.4 The fishery by class-6 vessels

Potential catch exceeds actual catch for sets on unassociated schools and on floating objects for Class-6 vessels, i.e. there is excess capacity, regardless of whether capacity output is purged for TE (Table 3.4). When capacity output is purged for TE for yellowfin and bigeye, this excess capacity can be ranked by set type, from most to least excess capacity as: dolphin sets, sets on floating objects and unassociated school sets. For skipjack, this excess capacity is greatest for floating-object sets, intermediate for sets on unassociated schools sets and least for dolphin sets. Average excess capacity, purged for TE, is greatest for dolphin sets at 71 063 tonnes per year, intermediate for sets on floating objects at 61 462 tonnes per year and least for sets on unassociated schools at 23 009 tonnes per year. Excess capacity for all set types has been roughly upward over 1998-2002, but with considerable variability.

3.2.5 Technical change

Technical change on a cumulative basis for Class 6 vessels increased by about 60 percent for all set types, species during 1998-2002 (Figure 3.9). Thus "fishing power" or the state of technology increased considerably, and was an important factor in the exhibited increase in fishing capacity and excess capacity over this time period.

3.3 Summary and conclusions

Excess capacity for all species combined, defined as capacity output minus observed output (retained catches), exists for all vessel size classes individually and combined for all set types (dolphin, unassociated, floating objects) for yellowfin and bigeye tuna when measured as: (1) potential catch minus actual catch or (2) potential catch, purged for TE, minus actual catch. Excess capacity, purged for TE, for all vessel size classes has increased from about 120 000 tonnes in 1998 to close to 200 000 tonnes in 2002, an increase approaching 63 percent in five years. The largest contributor, by far, to excess capacity was Class-6 vessels, although there was excess capacity for Classes 2-3 and 4-5 vessels.

TABLE 3.6
Excess capacity for yellowfin and bigeye: capacity output purged for technical efficiency minus combined average maximum sustainable yield of yellowfin and bigeye for all vessels in the EPO

Year

Capacity output purged for technical
(tonnes)

efficiency

AMSY (YFT + BET) (2)
(tonnes)

Excess capacity (1-2)
(tonnes)

Ratio
(1/2)

Classes 2-3

Classes 4-5

Class 6

All vessels (1)

1998

20 014

14 568

348 570

383 153

345 986

37 167

1.107

1999

14 049

27 303

397 151

438 504

345 986

92 518

1.267

2000

15 824

13 646

406 220

435 690

345 986

89 704

1.259

2001

14 109

30 989

511 802

556 901

345 986

210 915

1.610

2002

12 849

29 461

545 510

587 821

345 986

21 345

1.699

Annual average

15 369

23 194

441 851

480 414

345 986

134 428

1.389

Notes: Excess capacity output is defined as capacity output, purged for technical efficiency, less combined AMSY for yellowfin and bigeye in tonnes. AMSYs from Inter-American Tropical Tuna Commission.

TABLE 3.7
Average vessel capacity utilisation and technical efficiency by vessel class

Vessel Class

Year

Capacity utilisation

Technical efficiencya

Capital utilisation without technical efficiency

Classes 2 and 3

1998

0.40

0.70

0.59

1999

0.41

0.62

0.63

2000

0.49

0.65

0.74

2001

0.50

0.70

0.68

2002

0.46

0.63

0.69

All years

0.45

0.66

0.67

Classes 4 and 5

1998

0.46

0.61

0.76

1999

0.71

0.92

0.71

2000

0.72

0.92

0.73

2001

0.60

0.89

0.65

2002

0.72

0.91

0.74

All years

0.64

0.85

0.72

Class 6

1998

0.52

0.65

0.78

1999

0.67

0.89

0.75

2000

0.68

0.89

0.76

2001

0.63

0.88

0.71

2002

0.65

0.88

0.72

All years

0.63

0.84

0.75

Notes: a. Output-oriented technical efficiency for a vessel size class is measured relative to that vessel size class's own vessels' best-practice production frontier. Vessel size, biomass and sea-surface temperature are held fixed.

Excess capacity exists for all vessel size classes combined for all set types for yellowfin and bigeye tuna when measured as either: (1) potential catch, purged for TE, minus actual catch, or as (2) potential catch, purged for TE, minus the combined AMSYs for both yellowfin and bigeye.

For yellowfin and bigeye, combining over all set types and vessel size classes, excess capacity (defined as capacity output, purged for TE, minus combined AMSY) climbed from an excess of about 11 percent in 1998 to an excess of almost 70 percent by 2002. In all cases, Class-6 vessels contributed the lion's share of the excess capacity.

Technical change on a cumulative basis increased by about 60 percent for all set types, species and vessel size classes during 1998-2002. Thus "fishing power" or the state of technology increased considerably, and was an important factor in the exhibited increase in fishing capacity and excess capacity over this period.

In short, there is considerable excess capacity, whether measured relative to existing catches or AMSY. There is also considerable technical inefficiency and considerable increases in "fishing power" or the state of technology due to technical change, which, in turn, is an important factor in increases in fishing capacity.


[19] The estimates of biomass are for age 1 year and older. The 2003 assessments for which the yellowfin biomass comes from is at http://www.iattc.org/IATTC4thMeetingoftheScientificWorkingGroupENG.htm. The skipjack biomass is from stock assessment report 3. Bigeye is not from the assessment report 4, but from an updated assessment which the results are presented in the IATTC status of the stocks.
[20] Variable returns to scale were allowed by imposing the constraint 3 zj = 1.0 in problem [1].
[21] An "insufficient" number of observations gives an estimated piece-wise linear frontier with more and/or longer linear segments and a less accurate measure of capacity output. Without enough "kinks" (from shorter and a larger number of segments) in the piece-wise linear frontier, the distance from an observed output to the frontier, where the observed frontier gives the capacity output, is reduced.

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