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82fishing mortality are expected to subsequently reduce the SBR and catches. Under current effort levels, the population is unlikely toremain at levels that support MSY unless fishing mortality levels are greatly reduced or recruitment is above average for severalconsecutive years. These simulations are based on the assumption that selectivity and catchability patterns will not change in thefuture. Changes in targeting practices or increasing catchability of bigeye as abundance declines (e.g. density-dependent catchability)could result in differences from the outcomes predicted here.Recent catches are estimated to have been 19% higher than the MSY level (Table D-1). If fishing mortality (F) is proportional tofishing effort, and the current patterns of age-specific selectivity are maintained, the level of fishing effort corresponding to the MSYis about 81% of the current (2006-2008) level of effort. The MSY of bigeye in the EPO could be maximized if the age-specific selectivitypattern were similar to that for the longline fishery that operates south of 15N because it catches larger individuals that areclose to the critical weight. Before the expansion of the floating-object fishery that began in 1993, the MSY was greater than thecurrent MSY and the fishing mortality was less than F MSY (Figure D-8). The base case stock assessment results indicate that thebigeye stock in the EPO is overfished (S < S MSY ) and that overfishing is taking place (F>F MSY ) (Figure D-9).Analyses were carried out to assess the sensitivity of the stock assessment results to: 1) a stock-recruitment relationship; 2) use of aRichards growth curve fit to age at length data derived from otolith data; 3) extending the assumed western limit of the bigeye stockdistribution from 150°W to 170°E.The estimates of biomass are moderately sensitive to the steepness of the stock-recruitment relationship, but the trends are very similarto the base case. The recruitment time series is similar to the base case.When a Richards growth curve was used, the biomasses were lower than those obtained by base case model which assumes avon Bertalanffy growth function. However, the trends in the biomasses were very similar. The recruitment estimates were alsovery similar between the two models. The Richards growth curve provided a better fit to the fishery data when compared to thebase case model.When the assumed western limit of the bigeye stock distribution was extended from 150°W to 170°E, and the additional catch takenin the WCPO were included in the model, the recruitments and biomasses were greater than those estimated by the base case. However,the biomass estimates for most years became lower than the base case when the model was also fit to the additional CPUE andsize composition data from the WCPO.All four scenarios considered suggest that, at the beginning of 2009, the spawning biomass (S) was below S MSY . MSY and the Fmultiplier are sensitive to how the assessment model is parameterized, the data that are included in the assessment, and the periodsassumed to represent average fishing mortality, but under all scenarios considered, fishing mortality is well above F MSY . The managementquantities derived from the base case model were the less pessimistic among all scenarios.Key results1. The results of this assessment are similar to the previous assessments;2. There is uncertainty about recent and future recruitment and biomass levels;3. The recent fishing mortality rates are well above those corresponding to the MSY and this result is consistent across variousmodeling scenarios;4. The recent SBR levels are below those corresponding to the MSY and this result is consistent across various modelingscenarios;5. The results from the base case model are the more optimistic among the various modeling scenarios investigated;6. The results are more pessimistic if a stock-recruitment relationship is assumed;7. Assuming a more flexible Richards growth curve improved the model fit to the fishery data. This alternative model couldpotentially be considered as the base case model in future assessments;8. The assessment results are more pessimistic if the western limit of the bigeye stock distribution is extended from 150°Wto 170°E.
83FIGURE D-1. Movements of more than 1000 nm by tagged bigeye tuna in the Pacific Ocean.FIGURA D-1. Desplazamientos de más de 1000 mn de atunes patudo marcados en el Océano Pacífico.FIGURE D-2. Total catches (retained catches plus discards) of bigeye tuna by the purse-seine fisheries, and retained catches for thelongline fisheries, in the eastern Pacific Ocean, 1975-2008. The purse-seine catches are adjusted to the species composition estimate.The 2008 catch data are provisional.FIGURA D-2. Capturas totales (capturas retenidas más descartes) de atún patudo por las pesquerías de cerco, y capturas retenidasde las pesquerías palangreras en el Océano Pacífico oriental, 1975-2008. Las capturas cerqueras están ajustadas a la estimación de lacomposición por especie. Los datos de captura de 2008 son provisionales.
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COVER PHOTOGRAPH BY WAYNE PERRYMANF
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3FISHERY STATUS REPORT 7TUNAS AND B
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5INFORME DE LA SITUACIÓN DE LA PES
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7A. THE FISHERY FOR TUNAS AND BILLF
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10fisheries, and have been reported
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12line vessels.The estimated size c
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14Figure 2. Carrying capacity, in c
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16FIGURE A-2a. Average annual distr
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18.FIGURE A-4. Distributions of the
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20FIGURE A-6a. Estimated size compo
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Page 26 and 27:
Page 28 and 29:
26FIGURE A-9. Estimated catches of
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28FIGURE A-11. Estimated size compo
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30TABLE A-2a. Estimated retained ca
Page 34 and 35: 32TABLE A-2a. (continued)TABLA A-2a
Page 36 and 37: 34TABLE A-2b. (continued)TABLA A-2b
Page 38 and 39: 36TABLE A-3a. Catches of yellowfin
Page 40 and 41: 381TABLE A-3c. Catches of skipjack
Page 42 and 43: 40TABLE A-3e. Annual catches of big
Page 44 and 45: 42TABLE A-4b. Preliminary estimates
Page 46 and 47: 44TABLE A-6a. Annual retained catch
Page 48 and 49: 46TABLE A-7. Estimated numbers of s
Page 50 and 51: 48TABLE A-8. Types of floating obje
Page 52 and 53: 50TABLE A-10. Numbers and well volu
Page 54 and 55: 52TABLE A-11b. Estimates of the num
Page 56 and 57: 54A. LA PESQUERÍA DE ATUNES Y PECE
Page 58 and 59: 56En la Tabla A-2a se presentan las
Page 60 and 61: 581.3. Composición por tamaño de
Page 62 and 63: 601.5. Descargas de atunes y bonito
Page 64 and 65: 62bodega en el mar (VEM), en miles
Page 66 and 67: 64when the true dynamics includes a
Page 68 and 69: 66FIGURE B-2. Estimated recruitment
Page 70 and 71: 68FIGURE B-4. Spawning biomass traj
Page 72 and 73: 70FIGURE B-6. Catches of yellowfin
Page 74 and 75: 72FIGURE B-8. Phase plot of the tim
Page 76 and 77: 74TABLE B-1. Estimates of the MSY o
Page 78 and 79: 76Es importante señalar que la cur
Page 80 and 81: 78FIGURE C-1. Total catches (retain
Page 82 and 83: 80C. ATÚN BARRILETESe ha usado un
Page 86 and 87: 84FIGURE D-3. Average annual fishin
Page 88 and 89: 86FIGURE D-5. Trajectory of the spa
Page 90 and 91: 88FIGURE D-7. Catches for 1975-2008
Page 92 and 93: 90FIGURE D-9. Phase plot of the tim
Page 94 and 95: 92D. ATÚN PATUDOEn la presente eva
Page 96 and 97: 946. Los resultados son más pesimi
Page 98 and 99: 96FIGURE E-1. Retained catches of P
Page 100 and 101: 98F. ALBACORE TUNAThere are two sto
Page 102 and 103: 100300 000250 000200 000t150 000100
Page 104 and 105: 102fue aproximadamente 0.75, nivel
Page 106 and 107: 104FIGURE G-1. Retained catches of
Page 108 and 109: 106H. BLUE MARLINThe best knowledge
Page 110 and 111: 108H. MARLÍN AZULLa mejor informac
Page 112 and 113: 110FIGURE I-1. Retained catches of
Page 114 and 115: 112J. ECOSYSTEM CONSIDERATIONS1. In
Page 116 and 117: 114have been identified (by presenc
Page 118 and 119: 116Some marine mammals are adversel
Page 120 and 121: 118tors of stress, and removing liv
Page 122 and 123: 120Knowledge of the trophic ecology
Page 124 and 125: 1226. AGGREGATE INDICATORSRecogniti
Page 126 and 127: 124b. The incidental mortalities of
Page 128 and 129: 126FIGURE J-1. Simplified food-web
Page 130 and 131: 128FIGURE J-4. Trophic level estima
Page 132 and 133: 130cual no es incluida en los anál
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132Especie y poblaciónMortalidad i
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1342.7. Tiburones y otros peces gra
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136condición de la población del
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1387‰ con respecto a la línea de
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140entre índices de asociación de
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142b. En junio de 2003, la CIAT ado
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