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Yellowfin tuna - Eastern Pacific
Marine Resource  Fact Sheet
Stock status report 2018
Yellowfin tuna - Eastern Pacific
Fact Sheet Citation  
Yellow fin, Eastern Pacific Ocean (EPO)
Owned byInter-American Tropical Tuna Commission (IATTC) – More
Related observationsLocate in inventorydisplay tree map
 
Species:
FAO Names: en - Yellowfin tuna, fr - Albacore, es - Rabil, ru - Тунец желтоперый
Geographic extent of Yellowfin tuna - Eastern Pacific
Main Descriptors
Considered a single stock: Yes        Spatial Scale: Regional
Reference year: 2017
 
 
Biological State and Trend
State & Trend Descriptors
PartnerFIRMS
Exploitation rateModerate fishing mortality, close to that corresponding to MSYModerate fishing mortalityGreen
Abundance levelIntermediate abundanceIntermediate abundance
Aq Res State Trend
Exploitation stateFully exploited
Habitat and Biology
Bottom type: Unspecified.   Depth zone: Abyssal ( >1000m).   Horizontal distribution: Oceanic.   Vertical distribution: Pelagic.  

Geographical Distribution
Jurisdictional distribution: Highly migratory

Water Area Overview
Spatial Scale: Regional

Geo References
Resource Structure
Considered a single stock: Yes
Exploitation
 

The annual catches of yellowfin during 1988-2017 are shown in (Table A-1). The EPO totals for 1993-2017 include discards from purse-seine vessels with carrying capacities greater than 363 t. The El Niño event of 1982-1983 led to a reduction in the catches in those years, whereas the catches in the WCPO were apparently not affected. Although the El Niño episode of 1997-1998 was greater in scope, it did not have the same effect on the yellowfin catches in the EPO. In the EPO, catches increased steadily to a high of 443 thousand t in 2002; they decreased substantially in 2004, reaching their lowest level during 2006-2008, at only 44% of the highest catches of the 2001-2003 period. The 2017 catch of 212 thousand t is less than the average for the previous 5-year period (239 thousand t). In the WCPO, the catches of yellowfin reached a new high of 642 thousand t in 2017, surpassing the previous record of 607 thousand t in 2012.

The annual retained catches of yellowfin in the EPO by purse-seine and pole-and-line vessels during 1988-2017 are shown in (
  Yellowfin Skipjack Bigeye
  PS Ret. PS Dis. LP LL OTR + NK Total PS Ret. PS Dis. LP LL OTR + NK Total PS Ret. PS Dis. LP LL OTR + NK Total
1988 277,293 - 3,723 14,660 752 296,428 87,113 - 4,325 26 663 92,127 1,535 - 5 72,758 15 74,313
1989 277,996 - 4,145 17,032 263 299,436 94,934 - 2,940 28 1,019 98,921 2,030 - - 70,963 1 72,994
1990 263,253 - 2,676 34,633 960 301,522 74,369 - 823 41 1,874 77,107 5,921 - - 98,871 59 104,851
1991 231,257 - 2,856 30,899 958 265,970 62,228 - 1,717 36 1,909 65,890 4,870 - 31 104,195 25 109,121
1992 228,121 - 3,789 18,646 1,958 252,514 84,283 - 1,957 24 1,030 87,294 7,179 - - 84,808 13 92,000
1993 219,492 4,713 4,951 24,009 3,034 256,199 83,830 10,515 3,772 61 2,256 100,434 9,657 653 - 72,498 35 82,843
1994 208,408 4,525 3,625 30,026 1,487 248,071 70,126 10,491 3,240 73 731 84,661 34,899 2,266 - 71,360 806 109,331
1995 215,434 5,275 1,268 20,596 2,066 244,639 127,047 16,373 5,253 77 1,911 150,661 45,321 3,251 - 58,269 1,369 108,210
1996 238,607 6,312 3,762 16,608 1,639 266,928 103,973 24,494 2,555 52 1,261 132,335 61,311 5,689 - 46,958 748 114,706
1997 244,878 5,516 4,418 22,163 600 277,575 153,456 31,338 3,260 135 96 188,285 64,272 5,402 - 52,580 20 122,274
1998 253,959 4,697 5,085 15,336 1,529 280,606 140,631 22,643 1,684 294 237 165,489 44,129 2,822 - 46,375 628 93,954
1999 281,920 6,547 1,783 11,682 2,706 304,638 261,565 26,046 2,044 201 1,393 291,249 51,158 4,932 - 36,450 538 93,078
2000 253,263 6,205 2,431 23,855 1,109 286,863 205,647 24,467 231 68 66 230,479 95,282 5,417 - 47,605 253 148,557
2001 383,936 7,028 3,916 29,608 520 425,008 143,165 12,815 448 1,214 34 157,676 60,518 1,254 - 68,755 19 130,546
2002 412,286 4,140 950 25,531 551 443,458 153,546 12,506 616 261 119 167,048 57,421 949 - 74,424 12 132,806
2003 383,279 5,865 470 25,174 1,145 415,933 273,968 22,453 638 634 2,777 300,470 53,052 2,326 - 59,776 21 115,175
2004 272,557 3,000 1,884 18,779 627 296,847 197,824 17,078 528 713 1,106 217,249 65,471 1,574 - 43,483 194 110,722
2005 268,101 2,771 1,822 11,946 1,852 286,492 263,229 16,915 1,299 231 1,779 283,453 67,895 1,900 - 40,694 25 110,514
2006 166,631 1,534 686 10,210 1,458 180,519 296,268 11,177 435 224 986 309,090 83,838 1,680 - 31,770 40 117,328
2007 170,016 1,725 894 8,067 1,439 182,141 208,295 6,450 276 238 1,065 216,324 63,450 890 - 29,876 44 94,260
2008 185,057 696 814 9,820 941 197,328 296,603 8,249 499 1,185 1,163 307,699 75,028 2,086 - 26,208 28 103,350
2009 236,757 1,262 709 10,444 1,241 250,413 230,523 6,064 151 1,584 1,086 239,408 76,799 1,019 - 31,422 15 109,255
2010 251,009 1,031 460 8,339 1,032 261,871 147,192 2,769 47 1,815 1,269 153,092 57,752 564 - 37,090 2 95,408
2011 206,851 415 276 8,048 1,130 216,720 276,035 5,215 24 1,384 851 283,509 56,512 631 - 32,317 - 89,460
2012 198,017 451 400 12,954 1,488 213,310 266,215 3,511 303 2,381 1,109 273,519 66,020 473 - 36,167 27 102,687
2013 218,187 207 759 10,783 1,234 231,170 278,560 2,254 164 2,024 1,041 284,043 49,487 273 - 36,204 99 86,063
2014 234,066 517 C 8,646 3,549 246,778 261,469 2,596 C 194 1,231 265,490 60,445 83 - 35,340 177 96,045
2015 245,727 334 C 10,787 3,568 260,416 328,907 3,699 C 205 1,255 334,066 62,913 177 - 41,644 21 104,755
2016 242,095 404 - 9,402 2,883 254,784 337,562 4,086 - 191 718 342,557 56,713 541 - 35,525 22 92,801
2017 209,699 418 - 1,782* * 211,899 326,120 1,859 - * * 327,979 66,192 189 - 31,138 * 97,519
  Pacific bluefin Albacore Black skipjack
  PS Ret. PS Dis. LP LL OTR+NK Total PS Ret. PS Dis. LP LL OTR + NK Total PS Ret. PS Dis. LP LL OTR + NK Total
1988 1,379 - - 2 52 1,433 17 - 271 9,934 5,549 15,771 956 - - - 311 1,267
1989 1,103 - 5 4 91 1,203 1 - 21 6,784 2,695 9,501 803 - - - - 803
1990 1,430 - 61 12 103 1,606 39 - 170 6,536 4,105 10,850 787 - - - 4 791
1991 419 - - 5 55 479 - - 834 7,893 2,754 11,481 421 - - - 25 446
1992 1,928 - - 21 147 2,096 - - 255 17,080 5,740 23,075 105 - - 3 - 108
1993 580 - - 11 316 907 - - 1 11,194 4,410 15,605 104 3,925 - 31 - 4,060
1994 969 - - 12 116 1,097 - - 85 10,390 10,154 20,629 188 857 - 40 - 1,085
1995 659 - - 25 264 948 - - 465 6,185 7,427 14,077 202 1,448 - - - 1,650
1996 8,333 - - 19 83 8,435 11 - 72 7,631 8,398 16,112 704 2,304 - 12 - 3,020
1997 2,608 3 2 14 235 2,862 1 - 59 9,678 7,540 17,278 100 2,512 - 11 - 2,623
1998 1,772 - - 95 516 2,383 42 - 81 12,635 13,158 25,916 489 1,876 39 - - 2,404
1999 2,553 54 5 151 514 3,277 47 - 227 11,633 14,510 26,417 171 3,404 - - - 3,575
2000 3,712 - 61 46 349 4,168 71 - 86 9,663 13,453 23,273 294 1,995 - - - 2,289
2001 1,155 3 1 148 378 1,685 3 - 157 19,410 13,727 33,297 2,258 1,019 - - - 3,277
2002 1,758 1 3 71 620 2,453 31 - 381 15,289 14,433 30,134 1,459 2,283 8 - - 3,750
2003 3,233 - 3 87 369 3,692 34 - 59 24,901 20,397 45,391 433 1,535 6 13 117 2,104
2004 8,880 19 - 15 59 8,973 105 - 126 18,444 22,011 40,686 884 387 - 27 862 2,160
2005 4,743 15 - - 80 4,838 2 - 66 9,350 15,668 25,086 1,472 2,124 - - 22 3,618
2006 9,928 - - - 93 10,021 109 - 1 13,831 18,980 32,921 1,999 1,972 - - - 3,971
2007 4,189 - - - 14 4,203 187 - 21 11,107 19,261 30,576 2,307 1,625 - 2 54 3,988
2008 4,392 14 15 - 63 4,484 49 - 1,050 9,218 16,505 26,822 3,624 2,251 - - 8 5,883
2009 3,428 24 - - 161 3,613 50 2 C 12,072 19,090 31,214 4,256 1,020 - 2 - 5,278
2010 7,746 - - 3 89 7,838 25 - C 14,256 19,363 33,644 3,425 1,079 - 8 184 4,696
2011 2,829 4 - 1 244 3,078 10 - C 16,191 16,074 32,275 2,317 719 - 6 - 3,042
2012 6,705 - - 1 405 7,111 - - C 24,198 18,100 42,298 4,504 440 - 5 7 4,956
2013 3,154 - - 1 819 3,974 - - C 25,401 18,513 43,914 3,580 805 - 10 24 4,419
2014 5,263 66 - - 442 5,771 - - C 29,231 19,437 48,668 4,153 486 - 11 81 4,731
2015 3,168 - - 26 387 3,581 - - C 28,957 17,099 46,056 3,763 356 - 1 111 4,231
2016 3,025 - - 30 308 3,363 2 - - 28,537 14,502 43,041 6,606 792 - - 178 7,576
2017 4,109 - - * 14 4,123 - - - * * * 5,006 397 - * * 5,403
  Bonitos Unidentified tunas Total
  PS Ret. PS Dis. LP LL OTR+NK Total PS Ret. PS Dis. LP LL OTR + NK Total PS Ret. PS Dis. LP LL OTR + NK Total
1988 8,811 - 739 - 947 10,497 79 - - - 2,939 3,018 377,183 - 9,063 97,380 11,227 494,853
1989 11,278 - 818 - 465 12,561 36 - - - 626 662 388,181 - 7,928 94,812 5,161 496,082
1990 13,641 - 215 - 371 14,227 200 - - 3 692 895 359,640 - 3,946 140,096 8,167 511,850
1991 1,207 - 82 - 242 1,531 4 - - 29 192 225 300,406 - 5,520 143,057 6,161 455,144
1992 977 - - - 318 1,295 24 - - 27 1,071 1,122 322,617 - 6,001 120,610 10,276 459,504
1993 599 12 1 - 436 1,048 9 1,975 - 10 4,082 6,076 314,271 21,793 8,725 107,814 14,570 467,173
1994 8,331 147 362 - 185 9,025 9 498 - 1 464 972 322,930 18,784 7,311 111,901 13,943 474,870
1995 7,929 55 81 - 54 8,119 11 626 - - 1,004 1,641 396,603 27,028 7,066 85,152 14,096 529,945
1996 647 1 7 - 16 671 37 1,028 - - 1,038 2,103 413,623 39,828 6,395 71,283 13,183 544,312
1997 1,097 4 8 - 34 1,143 71 3,383 - 7 1,437 4,898 466,483 48,158 7,747 84,588 9,962 616,937
1998 1,330 4 7 - 588 1,929 13 1,233 - 24 18,158 19,428 442,365 33,275 6,897 74,758 34,815 592,109
1999 1,719 - - 24 369 2,112 27 3,092 - 2,113 4,279 9,511 599,160 44,075 4,059 62,254 24,310 733,858
2000 636 - - 75 56 767 190 1,410 - 1,992 1,468 5,060 559,095 39,497 2,809 83,305 16,756 701,462
2001 17 - - 34 19 70 191 679 - 2,448 55 3,373 591,243 22,798 4,523 121,616 14,755 754,934
2002 - - - - 1 1 576 1,863 - 482 1,422 4,343 627,077 21,742 1,958 116,057 17,158 783,992
2003 - - 1 - 25 26 80 1,238 - 215 750 2,283 714,079 33,417 1,177 110,799 25,600 885,072
2004 15 35 1 8 3 62 256 973 - 349 258 1,836 545,992 23,066 2,539 81,818 25,120 678,535
2005 313 18 - - 11 342 190 1,922 - 363 427 2,902 605,945 25,665 3,187 62,585 19,865 717,248
2006 3,507 80 12 - 3 3,602 50 1,910 - 29 193 2,182 562,330 18,353 1,134 56,066 21,754 659,636
2007 15,906 628 107 2 - 16,643 598 1,221 - 2,197 301 4,317 464,948 12,539 1,298 51,488 22,179 552,451
2008 7,874 37 9 6 26 7,952 136 1,380 1 727 883 3,127 572,763 14,713 2,388 47,164 19,617 656,645
2009 9,720 15 - 8 77 9,820 162 469 - 1,933 74 2,638 561,695 9,875 860 57,466 21,743 651,640
2010 2,820 19 4 2 70 2,915 136 709 - 1,770 36 2,651 470,105 6,171 511 63,279 22,045 562,112
2011 7,969 45 18 10 11 8,053 108 784 - 3,178 - 4,070 552,631 7,813 318 61,136 18,311 640,209
2012 8,191 156 - 1 64 8,412 41 354 - 196 221 812 549,693 5,385 704 75,900 21,419 653,101
2013 2,067 9 - 13 27 2,116 53 461 - - 529 1,043 555,088 4,009 923 74,439 22,286 656,745
2014 2,821 38 - - 154 3,013 113 328 - 269 392 1,102 568,330 4,114 - 73,692 25,463 671,599
2015 789 28 - - - 817 85 242 - - 1,232 1,559 645,352 4,836 - 81,620 23,673 755,481
2016 3,801 15 - - 1 3,817 123 212 - - 270 605 649,927 6,050 - 73,685 18,882 748,544
2017 3,357 37 - * * 3,394 231 256 - * * 487 614,714 3,156 - 32,920 14 650,804



). The average annual retained catch during 2002-2016 was 247 thousand t (range: 167 to 413 thousand t). The preliminary estimate of the retained catch in 2017, 210 thousand t, was 13% less than that of 2016, and 15% less than the average for 2002-2016. The average amount of yellowfin discarded at sea during 2002-2016 was about 0.7% of the total purse-seine catch (retained catch plus discards) of yellowfin (range: 0.1 to 1.5%) shown in Table A-2a.

The annual retained catches of yellowfin in the EPO by longliners during 1987-2016 are shown in Table A-2a. During 1990-2003 catches averaged about 23 thousand t (range: 12 to 35 thousand t), or about 8% of the total retained catches of yellowfin. Longline catches declined sharply beginning in 2005, averaging 10 thousand t per year (range: 8 to 13 thousand t), or about 4% of the total retained catches, through 2016. Yellowfin are also caught by recreational vessels, as incidental catch in gillnets, and by artisanal fisheries. Estimates of these catches are shown in Table A-2a, under “Other gears” (OTR); during 2002-2016 they averaged about 1 thousand t.

See also fishery fact sheet:EPO Tunas and billfishes fishery
Total catches (retained catches plus discards) for the purse-seine fisheries, and retained catches for the pole-and-line and longline fisheries, of yellowfin tuna in the eastern Pacific Ocean, 1975-2017. The purse-seine catches are adjusted to the species composition estimate obtained from sampling the catches. The 2017 catch data are preliminary.
Assessment
 
Assessment Model
Type:  Age-structured
An integrated statistical age-structured stock assessment model, Stock Synthesis

This report presents the most current stock assessment of yellowfin tuna (Thunnus albacares) in the eastern Pacific Ocean (EPO). An integrated statistical age-structured stock assessment model (Stock Synthesis Version 3.23b) was used in the assessment, which is based on the assumption that there is a single stock of yellowfin in the EPO.
Assumption

Yellowfin are distributed across the Pacific Ocean, but the bulk of the catch is made in the eastern and western regions. Purse-seine catches of yellowfin are relatively low in the vicinity of the western boundary of the EPO at 150ºW (Figure A-1a and A-1b).
Average annual distributions of the purse-seine catches of yellowfin, by set type, 2012-2016. The sizes of the circles are proportional to the amounts of yellowfin caught in those 5° by 5° areas.
Annual distributions of the purse-seine catches of yellowfin, by set type, 2017. The sizes of the circles are proportional to the amounts of yellowfin caught in those 5° by 5° areas.

The majority of the catch in the EPO is taken in purse-seine sets on yellowfin associated with dolphins, and floating objects (Figure B-1).
Figure B-1: Total catches (retained catches plus discards) for the purse-seine fisheries, and retained catches for the pole-and-line and longline fisheries, of yellowfin tuna in the eastern Pacific Ocean, 1975-2017. The purse-seine catches are adjusted to the species composition estimate obtained from sampling the catches. The 2017 catch data are preliminary.

Tagging studies of yellowfin throughout the Pacific indicate that the fish tend to stay within 1800 km of their release positions. This regional fidelity, along with the geographic variation in phenotypic and genotypic characteristics of yellowfin shown in some studies, suggests that there might be multiple stocks of yellowfin in the EPO and throughout the Pacific Ocean. This is consistent with the fact that longline catch-per-unit-of-effort (CPUE) trends differ among areas in the EPO. However, movement rates between these putative stocks, as well as across the 150°W meridian, cannot be estimated with currently-available tagging data.
Data

The assessment of yellowfin tuna in the eastern Pacific Ocean in 2017 is similar to the previous assessment, with the addition of new and updated data, catches shown in Figure B-1.

As noted in Document SAC-07-05b, these interpretations are uncertain, and highly sensitive to the assumptions made about the steepness parameter (h) of the stock-recruitment relationship, the average size of the oldest fish (L2), and the assumed levels of natural mortality (M). The results are more pessimistic if a stock-recruitment relationship is assumed, if a higher value is assumed for L2, and if lower rates of M are assumed for adult yellowfin. Previous assessments reported that the data components diverge on their information about abundance levels: results are more pessimistic if the weighting assigned to length-frequency data is decreased, and more optimistic if the model is fitted more closely to the index of relative abundance based on the catch per unit of effort (CPUE) of the northern dolphin-associated purse-seine fishery rather than of the southern longline fishery.
Results
Assessment Indicator
Type: Recruitment

There is uncertainty about recent and future levels of recruitment (Figure B-2) and biomass (Figure B-5).
Figure B-2: Estimated annual recruitment at age zero of yellowfin tuna to the fisheries of the EPO. The estimates are scaled so that the average recruitment is equal to 1.0 (dashed horizontal line). The solid line illustrates the maximum likelihood estimates of recruitment, and the shaded area indicates the approximate 95% confidence intervals around those estimates.
Figure B-5: Spawning biomass ratios (SBRs) for yellowfin tuna in the EPO, including projections for 2018-2028 based on average fishing mortality rates during 2015-2017, from the base case (top) and the sensitivity analysis that assumes a stock-recruitment relationship (h = 0.75, bottom). The dashed horizontal line (at 0.27 and 0.35, respectively) identifies the SBR at MSY. The solid curve illustrates the maximum likelihood estimates, and the estimates after 2018 (the large dot) indicate the SBR predicted to occur if fishing mortality rates continue at the average of that observed during 2015-2017, and average environmental conditions occur during the next 10 years. The shaded area indicates the approximate 95% confidence intervals around those estimates.



There have possible been three different productivity regimes since 1975, and the levels of maximum sustainable yield (MSY) and the biomasses corresponding to the MSY may differ among the regimes.

The recruitment was below average until 1982, mostly above average from 1983 to 2002, and then mostly below average until 2014. The most recent annual recruitments (2015-2017) were estimated to be at or above average, because of high quarterly recruitments in 2015 (quarters 3 and 4), 2016 (quarters 2 and 4) and 2017 (quarter 1), but these estimates are highly uncertain. The recruitment estimates for 2017 might be upwardly biased, because of a retrospective pattern already noticed in previous assessments.


Results
Assessment Indicator
Type: Fishing mortality

The highest fishing mortality (F) has been on fish aged 11-20 quarters (2.75-5 years), and lowest for the younger fish (< 10 quarters/2.5 years). The average annual F has been increasing for all age classes since 2009, but has shown a slight decline for the 11-20 quarter age group since 2014. (Figure B-3).
Figure B-3: Average annual fishing mortality (F) by age groups, by all gears, of yellowfin tuna recruited to the fisheries of the EPO. The age groups are defined by age in quarters.

Historically, the dolphin-associated and unassociated purse-seine fisheries have the greatest impact on the spawning biomass of yellowfin, followed by the floating-object fisheries (Figure B-4).
Figure B-4: Biomass trajectory of a simulated population of yellowfin tuna that was never exploited (dashed line) and that predicted by the stock assessment model (solid line). The shaded areas between the two lines show the portions of the fishery impact attributed to each fishing method.

In more recent years, the impact of the floating-object fisheries has been greater than that of the unassociated fisheries. The impacts of the longline and purse-seine discard fisheries are much less, and have decreased in recent years. Increasing the average weight of the yellowfin caught could increase the MSY.


Results
Assessment Indicator
Type: SSB

The spawning biomass ratio (SBR) has been average or below average since 2005, except during 2008-2010. However, the SBR at the start of 2018 was estimated to be 0.29, above the MSY level (0.27), due to the above-average recruitments of 2015 and 2016, which coincided with the 2014-2016 El Niño event. Under the current (2015-2017 average) fishing mortality, the SBR is predicted to increase in the next two years because of the large recent recruitments, and level off at about MSY level if recruitment is average.

The recent fishing mortality (F) is slightly below the MSY level (F multiplier = 0.99), and the current spawning biomass (S) is estimated to be above that level (S(recent)/S(MSY) = 1.08) (Table B-1).

and,



The recent biomass of fish aged 3 quarters and older (B), however, is higher than that corresponding to the MSY level (B(recent)/B(MSY) = 1.32), because of the high recruitments. The catches are also predicted to increase in the near future (Figure B-7).
Figure B-7: Historic and projected annual catches of yellowfin tuna by surface (top panel) and longline (bottom panel) fisheries from the base case while fishing with the current effort, the base case while fishing at the fishing mortality corresponding to MSY (FMSY), and the analysis of sensitivity to steepness (h = 0.75) of the stock-recruitment relationship while fishing with the current effort. The large dot indicates the most recent catch (2017).


Source of information
 
Inter-American Tropical Tuna Commission (IATTC).  “"Tunas and billfishes in the eastern Pacific Ocean in 2017. Inter-American Tropical Tuna Commission." Fishery Status Report. IATTC 2018.” Click to openhttps://www.iattc.org/PDFFiles/FisheryStatusReports/_English/No-16-2018_Tunas%20billfishes%20and%20other%20pelagic%20species%20in%20the%20eastern%20Pacific%20Ocean%20in%202017.pdf
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